I Am Large

Filed under: — Bravus @ 8:23 am

Never fear, not another weight-loss post (which my Facebook friends have seen from me ad nauseum)! My title is drawn from a line I love:

Do I contradict myself? Very well then, I contradict myself. I am large, I contain multitudes.

Walt Whitman

People on Facebook and Twitter have mentioned occasionally (and, I suspect, thought more than occasionally) that I’m difficult to pin down. It’s not entirely clear what I believe on a whole range of issues.

Sometimes that is ‘read’ as being dishonest or strategic. I don’t think it is: if someone wishes to ask a straight question about what I believe, I’m always willing to give a straight answer. That answer itself might be ‘it’s complicated’… and might then spin out into something like a blog post. That’s because I’m very comfortable with ambiguity and complexity, so what I really think about something is often not easy to communicate in a sentence.

I guess the other thing is that I’m happy to talk to other people in their own register, not in mine. I recently wrote a piece, which will be published in Adventist Today in a month or so, about climate change. I clearly outlined the science, but also made the point that it is the most vulnerable people on Earth who will be most harmed. I quoted the book of Revelation, which says that at the Second Coming Christ will return to ‘destroy those who destroy the Earth’, and I quoted Matthew 25 where Jesus talks about what his followers have done for ‘the least of these’.

For myself, I don’t necessarily believe that there will be a Second Coming. It seems wildly improbable to me. But I’m not being dishonest, I don’t think, in speaking to Christians in the language of their own wisdom literature, to motivate them to act in a way that is simply humane and human. To clarify for them that, despite the ‘prosperity gospel’ and all the deeply evil shit some of their ‘leaders’ espouse, if you actually look at what Jesus (is reported to have) said in the Bible, it’s generally a decent guide to life.

One of my atheist friends immediately commented one of the less lovely things Jesus (is reported to have) said, about creating division between families, and used that to dismiss everything Jesus (is reported to have) said. I see that approach pretty often, but I don’t necessarily see it as a way of having a connected human conversation with people.

I try to apply the same approach to other belief systems, unless and until they’re harmful. Taking the vitamin and herbal supplements your naturopath prescribes is, to me, a silly way of creating very expensive urine (because with a balanced diet, most supplements go straight through us), but I’m happy to leave you to it… until s/he prescribes bicarb soda instead of chemo for your cancer (because s/he believes it’s fungal) and significantly shortens your life.

So yes, I’ll engage with Christians on their own terms – until they’re opposing same-sex marriage in Australia or working toward the death penalty for gay people in Uganda: then I’ll resist them as hard as I can.

I guess there’s the danger of seeming condescending with this approach: “Oh well, I have this ascended understanding, so I can talk to all these deluded people in their own language to try to enlighten them.”

I don’t think it’s that, though. I think it’s an attempt to make a genuinely human connection ‘across the aisle’ with everyone. To hold no person in contempt… but to support and advocate for ideas that lead to human flourishing, and challenge ideas that do harm.

So, if you’re confused by who I am and what I stand for (a) I hope this little chat has been helpful and (b) so am I, a lot of the time and (c) ask!


A Range of Possibilities

Filed under: — Bravus @ 2:46 pm

Returning to the creationism well one more time, and then I really will leave it alone and talk about something else for a while!

Human groups around the world have a wide range of different creation and origin stories for Earth and life. For the purposes of this, I’ll only talk about Christian creation stories. But I do encourage you to read widely and get a sense of the range. There’s an interesting list here: http://www.gly.uga.edu/railsback/CS/CSIndex.html

Basically, the two (slightly different) creation stories in the first and chapters of Genesis, the first book of the Bible, have been interpreted in a range of ways. And each interpreter will loudly and repeatedly tell you that their particular interpretation is the simple, clear, plain and literal reading of the text, and all other interpretations are heretical or worse.

If we consider ‘young’ to mean something like ‘less than 20,000 years old’ and ‘old’ to mean something like ‘more than 10 million years old’ (because almost no-one believes that any of the things we’re about to talk about happened in the space between those periods. No-one things Earth is middle-aged, apparently. It’s a bimodal distribution.

So there is a range of possible views, within that scheme:

  1. Universe, Earth and life is young
  2. Universe is old, Earth and life is young
  3. Universe and Earth are old, life is young
  4. Universe, Earth and life is old

The interesting thing is that of these, only 4 does not require any kind of supernatural intervention – but 4 is still completely consistent with the possibility of supernatural intervention. That is to say, only 4 allows sufficient time for natural processes to create everything we see around us.

When I say ‘Earth’ above, it’s probably worth noting that that might mean ‘Earth and our Solar System’. The relevant texts in Genesis 1 talk about the creation of the Sun and Moon:

14 And God said, Let there be lights in the firmament of the heaven to divide the day from the night; and let them be for signs, and for seasons, and for days, and years:

15 And let them be for lights in the firmament of the heaven to give light upon the earth: and it was so.

16 And God made two great lights; the greater light to rule the day, and the lesser light to rule the night: he made the stars also.

17 And God set them in the firmament of the heaven to give light upon the earth,

18 And to rule over the day and over the night, and to divide the light from the darkness: and God saw that it was good.

This occurs after the creation of plants, and some folks like to make a ‘gotcha’ of that, but I don’t have a lot of appetite for that kind of frame-shift argument.

A lot tends to hinge, in arguments between proponents of the various positions in the numbered list (1-4) above, on the few words I’ve bolded above in Verse 16: “he made the stars also”. If their positioning with the creation of the sun and moon means they were created at the same time, the universe must be young, and only position 1 is tenable. Many interpret it as a parenthetical comment that allows the possibility that God made the stars, but some considerable time earlier.

To some extent these are accommodations between science and religion, but they are also readings of an ancient text through modern eyes. Terry Pratchett captured it nicely “the stars began to come out, like pinholes in the curtain of night. Or like enormous exploding balls of gas, as some people would say. But some people will say anything.”

The distinction between Earth, solar system, galaxy and universe is not something that would have been a commonplace for people almost 3000 years ago: they’re not even necessary commonplaces for many people now.

I believe that conflict between science and religion is not inevitable, but that conflict between science and certain simplistic readings of religious texts is much more common. Once a religion has become organised, there is systematic pressure to preserve particular interpretations.

I do always find it interesting to observe the passionate arguments between people who believe very strongly that a particular text is sacred and infallible, but read it very slightly differently.


Science and Authority

Filed under: — Bravus @ 8:54 am

Every couple of months this year I’ve written a short piece on the relationship between science and religious faith for a site called ‘Adventist Today’. (Searching my name in the search bar in the page will easily bring up all of the pieces published so far.)

The most recent has just appeared, so I thought I’d share it here, since it addresses similar concerns to some of of the recent posts here. I don’t think I’ve repeated myself too much…

Hope you find it interesting and useful. There’s a link at the bottom to the Adventist Today Facebook page where discussion usually ensues. (If your background is not Seventh-day Adventist some of the discussion may require a little interpretation…)


Climate Change

Filed under: — Bravus @ 10:53 pm

A short and simple explanation


Complexity – irreducible and otherwise

Filed under: — Bravus @ 7:47 am

This is the final post in this short series. It is the 12th, and a dozen seems like a reasonable tally. The sequence, as a set, is meant to allow someone who encounters a particular claim or meme to quickly access a clear, accurate response, written for a smart non-specialist. It’s by no means sufficient in terms of evidence, but hopefully it frames up the issues in a way that is helpful when someone goes looking for further evidence.

While I’m talking in this ‘meta’ way, can I encourage everyone, including myself, to always seek ‘disconfirming evidence’ and ‘discrepant cases’? Confirmation bias is real, and oh so tempting: to seek the evidence that confirms us in our existing views, and discount any that challenges them. The only approach that works, though, for anyone who values a life founded in truth, is to be always looking for the evidence that makes us change our minds.

This final topic is related to the earlier one on probability, but the focus is slightly different.

Complexity science is a fascinating and genuine area of study… but also one that is susceptible to being used as a ‘handwave’ in ways that are not scientific. Much like Deepak Chopra and his self-help ilk talk about ‘quantum indeterminacy’ to support their woo, “It appears complex therefore science supports the explanation I support” is not really an argument.

There are a number of different ways to think about complexity, and no definition is particularly universal. There isn’t a real convention. After having spent a fair bit of time reading, the following is just my best understanding, which reflects a number of influential perspectives in the field, but remains controversial.

In brief, the distinction – and it’s a philosophical one – is between things that are complicated and things that are complex. Lots of things are complicated: the internet, as a network of wires and a web of communications protocols, is complicated. Cells are complicated. Economics is complicated. In this definition, though, things that are complicated are able to be reductively analysed by breaking them down into simpler bits. While the complication is insane, it’s possible to understand each of the cables in a server farmer and what it does… and many server farms build a network. It’s possible to look at a data packet and know whether it’s organised with the ftp or http protocol.

Complex systems, on the other hand, exhibit emergent behaviours that are not able to be explained in terms of reduction to simpler components. We could argue that human brains are complex in this sense, for example: self-consciousness is not easy to explain in terms of neurons and neurotransmitters and potentials and neuroplasticity.

The question of whether a particular system is complicated or complex in this sense is not simple to determine in any final sense. It may just be that we haven’t yet thrown sufficient computational resources or smart enough algorithms at our reductive analysis. If resources short of infinity could analyse a system, it can be argued that it is merely complicated, not complex… and the case needs to remain open for a lot of things.

That approach is different from the concept of ‘irreducible complexity’ that tends to be used by the Intelligent Design advocates. They tend to launch from comments such as the ones Darwin himself made in ‘Origin’, about how difficult it is to imagine a process by which the eye could evolve. Darwin does not despair of it, however, and plausible sequences have been outlined. Eyes tend not to fossilise, so hard evidence is challenging to find, but there are numerous kinds of different eyes, and it appears as though eyes may have evolved multiple different times independently.

The key issue in their approach is assuming that an eye is ‘irreducibly complex’ – that unless there is an eye in pretty much its current form, with eyelids, muscles to turn it, a lens, an iris, a retina and optic nerves, rods and cones for black-and-white and colour vision, it is not an eye at all, and conveys no survival advantage. But much simpler eyes exist, right down to simple light-sensitive spots, and convey survival advantages significant enough to lead to selection. The notion of irreducible complexity is built on the misconception that complex systems must spring into existence in pretty much their current form from essentially nothing. But refuting something evolution does not predict does not refute evolution.

They have moved on from the eye, and things like the flagella that bacteria use to propel themselves, to DNA and the processes of cell division and replication – the most fundamental processes of life itself.

They are right to say that these processes are complex in a way Darwin couldn’t have known or imagined 150 years ago, and indeed, we have learned much more in just the past few decades. It’s quite amazing that our DNA has multiple independent self-repair mechanisms: when things go wrong they are often corrected, or the process aborted. Cancer would be far more common if these processes were not in place. They’re nothing we can yet reliably build in to our code, let alone to our material machines.

While fully accepting the complexity of the cell – which is wondrous – the argument that it could not have evolved, because it needs to exist in pretty much its current form to work at all, recapitulates many of the arguments about the eye and the flagellum, and is wrong for the same reasons.

There are plausible, but still quite early, proposals for simpler RNA-only replicating sequences that may have pre-dated, and evolved to form, the current very complex systems.

Life is, indeed, complex. Whether irreducibly so is a philosophical question. But arguments from that complexity for a divine Creator – by fiat ex nihilo or by tinkering at the edges – are not strong arguments.

For ease of navigation I will include links to each of the other posts in this series at the bottom of each post.

Why I think it’s important to understand evolution
Cosmogenesis, abiogenesis and evolution
Evolution and entropy
Facts, Theories and Laws
Radiocarbon dating
Radiometric dating and deep time
Four Forces of the Universe
Probability and evolution
Species and ‘baramin’, macro- and micro-evolution
Mitochondrial Eve and Y-chromosomal Adam
Transitional fossils


Transitional fossils

Filed under: — Bravus @ 8:11 am

In a way, this is more of a philosophical post than a paleontological one. From slightly different perspectives, either there are many ‘transitional fossils’, or there is no such thing. And both those views are consistent with the fossil record!

I’ve certainly said “There’s no such thing as a transitional fossil” before. What did I mean by that? Well, no species of living thing is ever ‘on the way’ to a different species, ‘in transition’ from one thing to another. Each living thing – and each population of living things, which is the unit evolution works on – is simply living. Simply being as well adapted to its particular ecological niche as it can possibly be, in order to live, move, breed and pass on its genes.

So a fossil of a living thing is, in a very real sense, not ‘between’ two other species. It is simply itself.

At the same time, in retrospect, we can reconstruct the ‘tree of life’ – the sequence from simpler to more complex organisms over time. (It’s worth noting that, more recently, this reconstruction is a dynamic process that includes DNA evidence as well as the fossil record.) That sequence is not linear: it is branching, and has many, many dead ends. The fact that there are more complex organisms doesn’t mean the simpler ones go away: bacteria, viruses and archaea are still with us today.

So, in the sense that we can reconstruct the sequence, in a sense any fossil that is not the fossil of a present-day species can be thought of as a transitional fossil, since that species had both ancestor species and successor species.

What is usually thought of as a transitional fossil, of course, is something that has obvious features of both its ancestors and its successors. Archaeopteryx, for example, is a bird-like dinosaur with teeth and feathers. It seems likely now that it was more of a dead-end than a transitional species, but it is the kind of thing we think of. (It is also believed now that many more dinosaurs had feathers than first thought: they’re just less easily fossilised than bones.)

There are fossils of limbed species that we believe are ancestors of modern whales, and modern whales have vestigial hips that suggested their ancestors had limbs. We could even argue that whales are ‘transitional’ to future ocean-going species in which those vestiges have completely disappeared.

As usual with these little posts of mine, checking out the Wikipedia page on ‘transitional fossils’ will add a lot more detail and a lot of examples, and googling the term will… well, frankly, lead you to a lot of examples but also a lot of ill-informed claims that such things have never been observed.

For ease of navigation I will include links to each of the other posts in this series at the bottom of each post.

Why I think it’s important to understand evolution
Cosmogenesis, abiogenesis and evolution
Evolution and entropy
Facts, Theories and Laws
Radiocarbon dating
Radiometric dating and deep time
Four Forces of the Universe
Probability and evolution
Species and ‘baramin’, macro- and micro-evolution
Mitochondrial Eve and Y-chromosomal Adam
Complexity – irreducible and otherwise


Mitochondrial Eve and Y-chromosomal Adam

Filed under: — Bravus @ 10:12 pm

Recent discoveries in genetics have led to the publication of some interesting work that has suggested that all currently living human beings can be traced back to a single human female on the order of 120,000 to 150,000 years ago. In the 1980s this individual was dubbed ‘Mitochondrial Eve’. Similarly, all modern humans can have their ancestry traced back to a common male ancestor, dubbed ‘Y-chromosomal Adam’, who lived a similar time span, or perhaps 20-30,000 years longer, ago.

While this is not 6,000 years, or even the fewer-than-20,000 often accepted by creationists, misconceptions about these concepts led to considerable excitement in creationist circles. Many assumed that these two individuals were married to each other, and were the single married couple of humans from whom all modern human beings descended.

It mightn’t be 6,000, but it wasn’t millions, and with their related misconceptions about dating, the dates could be set aside. The key was the ability to link it to the Genesis story of a First Couple, and to claim that humans have not evolved, but have always and only descended from humans.

These are misconceptions, though, and the purpose of this post is to very briefly explain why. Obviously it’s a short and simple explanation: there are more detailed ones out there, and the Wikipedia explanations of both are good and detailed.

First, in both cases, saying that all of us can trace our lineage back to an individual does not mean that that individual was the only person alive at that time!

We all have a vast number of ancestors. There’s a conundrum here. I have two parents, 4 grandparents, 8 great-grandparents, 16 great-great-grandparents and so on. It’s a sequence going up in powers of 2: I’m 20, my parents 21, grandparents 22, great-grandparents 23 and so on.

If we assume a human generation is about 20 years, that’s 5 generations a century, 50 a millennium. Perhaps 50 x 150 = 7,500 in 150,000 years. But the thing is, 27500 is 5.3 x 102257. There are only about 7.5 x 109 people on Earth right now, and that’s the most there’ve ever been: certainly not that other outlandish number.

The solution is that some of our ancestors were the same people. Quite a lot of them, as it happens. That is, given slightly older and younger child-bearing and other things, my 6-greats-grandfather on my father’s side might also be my 7-greats-grandfather on my mother’s side… or even take on more roles across generations.

And, of course, we don’t simply multiply the number of my ancestors by the number of people in the world to found out how many ancestors there were in the world, because some of my ancestors are also the ancestors of other people. Most trivially, my parents are also the parents of my siblings. My dad in particular is from large families going back generations, so some of my great-grandparents are ancestors of an enormous number of people, not just of me.

Mitochondrial Eve and Y-chromosomal Adam are simply the two individuals – probably living in Africa, but almost certainly not close together, in either space or time – who in each case are the most recent ancestor shared by all modern living humans when traced back using particular genetic techniques. And they are probably not unique.There may be multiple people fulfilling that criterion, although conceptual only one individual can be the most recent.

It’s also important to note that, in both cases, these are theoretical concepts, not actual individual people with names and addresses who have been identified.

So, to take ‘Eve’ first, mitochondria are the little ‘energy factories’ in our cells. They have different DNA in them than the DNA in the remainder of our cells. (They may well have arisen as bacteria that were symbiotic with other cells and then were incorporated, but that’s a whole separate fascinating story.)

Mitochondrial DNA is matrilineal (passed down via our mothers), and we can look at shared characteristics and their changes over time to calculate a ‘clock’ back in time until we have a common female ancestor. This is what is meant by the time back to the ‘Mitochondrial Eve’ theoretical concept.

Being able to make this calculation is an important and very interesting development in our understanding of genetics, but it does not mean that there was only a single human woman, 120,000 to 150,000 years ago, who was mother to us all.

The story for ‘Adam’ is very similar, but Y chromosomes tend to be passed down patrilinearly, from fathers to sons. The tracking back is essentially by a similar process of genetic reconstruction.

Exciting, very interesting science… but, when properly understood, no particular comfort to those who want all human beings to have descended from a single divinely created couple in Eden.

For ease of navigation I will include links to each of the other posts in this series at the bottom of each post.

Why I think it’s important to understand evolution
Cosmogenesis, abiogenesis and evolution
Evolution and entropy
Facts, Theories and Laws
Radiocarbon dating
Radiometric dating and deep time
Four Forces of the Universe
Probability and evolution
Species and ‘baramin’, macro- and micro-evolution
Transitional fossils
Complexity – irreducible and otherwise


2019 Nobel Prize in Physics

Filed under: — Bravus @ 11:44 am

Something a little different today. I thought I’d share a video, rather than a block of text. Depending on your interest level, there’s a sub-2 minute version and a roughly 13 minute version. If you watch the latter, you’ll see that one of the affordances of video over text is the ability to do hand-waves!

This doesn’t really fit within the current sequence on addressing objections to evolution… except that perhaps it kinda does…

If your interest level or tolerance for my waffling is a bit higher…

Thanks to Griffith University for use of the video suite: I’m sure science communication is part of my job, right?


Species and ‘baramin’, macro- and micro-evolution

Filed under: — Bravus @ 9:24 am

In the face of the claim that all forms of life were recently divinely created in something much like their current form, there is abundant evidence of new species forming right now, all around us.

The definition of the term ‘species’ is a relatively complex, and somewhat contested, matter in biology. A quick rule of thumb is that members of different species can’t reproduce sexually with one another in a sustainable way. It’s probably not a full and accurate definition, but it works for most cases.

That last distinction, about sustainability, addresses situations like mules: the offspring of a horse and a donkey, which are different species, is bred by humans for our purposes but is itself barren and unable to reproduce. If humans stopped breeding mules, they’d die out in a generation (I guess aside from random liaisons between wild horses and donkeys).

We see new species of plants, birds, insects, fish, amphibians and other species with relatively short lifespans arise regularly: I won’t link here, but just google ‘observed speciation’ for plenty of examples.

(If I were a real biologist I’d spend more time on all the layers of kingdoms and genera and phyla and families and such, but I’m not, so I won’t: there are very good Wikipedia guides if you’re interested.)

The common creationist response is the one that was parodied with ‘crocoduck’ memes: “We have never seen a fish turn into a cat: the new species you talk about look exactly like the thing they evolved from”. This is related to the claim that there are no ‘intermediate species’ in the fossil record: what they are looking for is something that is very obviously partly one recognisable modern species and partly another.

When faced with evidence of the ways in which species adapt to their environment – including things like the development of antibiotic-resistant bacteria – the creationist response is often “Well yes, God designed in adaptability to help life survive, but that’s only micro-evolution within species. Macro-evolution that creates new species (that are visibly and noticeably different) doesn’t and can’t happen.”

One of the quasi-scriptural notions used to support this distinction between micro- and macro-evolution is ‘baramin’. It’s not a real Hebrew word, it’s a recently-coined (well, 1941) term that (ungrammatically) combines the Hebrew words ‘bara’ (created) and ‘min’ (kind).

The scriptural creation account includes these phrases:

Genesis 1: 11-12, 20-21, 24-25 (King James version)

11 Then God said, “Let the land produce vegetation: seed-bearing plants and trees on the land that bear fruit with seed in it, according to their various kinds.” And it was so. 12 The land produced vegetation: plants bearing seed according to their kinds and trees bearing fruit with seed in it according to their kinds. And God saw that it was good.

20 And God said, “Let the water teem with living creatures, and let birds fly above the earth across the vault of the sky.” 21 So God created the great creatures of the sea and every living thing with which the water teems and that moves about in it, according to their kinds, and every winged bird according to its kind. And God saw that it was good.

24 And God said, “Let the land produce living creatures according to their kinds: the livestock, the creatures that move along the ground, and the wild animals, each according to its kind.” And it was so. 25 God made the wild animals according to their kinds, the livestock according to their kinds, and all the creatures that move along the ground according to their kinds. And God saw that it was good.

The phrase ‘according to their kinds’ is interpreted to mean something roughly analogous to the notion of ‘visibly different organisms’. It doesn’t really translate neatly to any level of the biological taxonomy.

In biology, there is essentially no mechanism that would prevent successive small changes in a population accumulating to produce larger changes: for many micro-evolutions to add up to macro-evolutions. This requires many generations: more generations than occur within a human lifespan, even for small organisms with short lifespans.

That’s why evolutionary theory does not predict that we would see large visible changes from one kind of living being into another on the scale of human lives, and we don’t. The fact that we don’t does not refute evolutionary theory, because it is not a prediction that evolutionary theory makes.

The concept of transitional fossils is related, but it probably deserves its own post.

For ease of navigation I will include links to each of the other posts in this series at the bottom of each post.

Why I think it’s important to understand evolution
Cosmogenesis, abiogenesis and evolution
Evolution and entropy
Facts, Theories and Laws
Radiocarbon dating
Radiometric dating and deep time
Four Forces of the Universe
Probability and evolution
Mitochondrial Eve and Y-chromosomal Adam
Transitional fossils
Complexity – irreducible and otherwise


Probability and evolution

Filed under: — Bravus @ 8:39 am

There are a range of arguments against evolution that rely on the notion that it is inherently so improbable as to be impossible. They date right back to William Paley, who published his ‘watchmaker argument’ in 1802, predating Darwin’s ‘Origin of Species’ by more than 50 years.

Essentially, this is the notion that the appearance of design implies the existence of a Designer. It’s also linked to the analogy of ‘a tornado in a junkyard creating a functional Boeing 747 aircraft’, and to the ‘infinite number of typing monkeys creating the complete works of Shakespeare if given an infinite amount of time’.

I’ve tried to avoid linking out to things elsewhere in this series and to make them self-contained, but this paper from 1971 in American Biology Teacher has a perfect example of the kind of thing I’m talking about, in the section entitled “How Many Genes Could Exist?”

Using the usual approach used in these kinds of arguments, that piece comes up with a probability of 1:10600 for the random evolution of all possible genes. That’s a genuinely outlandish number: to give you a sense, the number of atoms in the known universe is on the order of 1080. If that number were correct, then indeed it would seem wildly improbable that life could evolve.

This short post is just about explaining why it is not.

First, that assumes entirely random processes without a step-wise process of natural selection. It assumes that it is necessary (to mangle a metaphor) to arrive at the Boeing 747 without passing via the Wright Flyer and successive improvements.

Second, it assumes that a specific outcome is the goal, whereas biology has a very large range of possible ways to solve the same problems. There are different kinds of wings and eyes and different types of legs and different models of fish locomotion and… Again, to play with metaphors, it’s not inevitable that the monkeys will arrive at the complete works of Shakespeare: they might end up with Stephen King or Iain M Banks or S T Colleridge instead.

These two objections may not sound like much, but together they essentially mean that the statistical and probability claims against the evolution of life do not hold water. Statistical models are only valid when they accurately model the phenomenon of interest… and these simply don’t.

For ease of navigation I will include links to each of the other posts in this series at the bottom of each post.

Why I think it’s important to understand evolution
Cosmogenesis, abiogenesis and evolution
Evolution and entropy
Facts, Theories and Laws
Radiocarbon dating
Radiometric dating and deep time
Four Forces of the Universe
Species and ‘baramin’, macro- and micro-evolution
Mitochondrial Eve and Y-chromosomal Adam
Transitional fossils
Complexity – irreducible and otherwise


Four Forces of the Universe

Filed under: — Bravus @ 5:51 am

(This piece is a bit of a digression from the recent focus on evolution and its discontents, and moves back closer to my own comfort zone in physics. It is also at a high school physics level – the water gets much deeper than I’ve presented here very quickly, but this is a useful place to start.)

In discussions of the universe at the larger scale of cosmology and astrophysics – the formation and motion of stars and galaxies – I’ve recently begun encountering people who claim that ‘it’s all magnetism’, that every force in the end can be reduced to magnetism.

No doubt these voices have been around forever, and it’s just that I’ve started hearing them, but it’s a fascinating phenomenon. These people tend to be skeptics about General Relativity, and sometimes even about whether gravity exists at all. Certainly dark matter and dark energy are rejected passionately – it’s all magnetism!

I’m not sure what motivates it. Perhaps magnetism is the force that seems realest and most tangible. Most of us have played with magnets, and felt that real force, of both attraction and repulsion. It feels quite like the force of gravity holding us down – at least the attractive element does. And imagining a repulsive gravitational force is exciting! No heavy rockets needed to get to space if you’ve got anti-gravity!

As a bit of an antidote, I thought I might talk for a moment about the four fundamental forces that act in our universe. I might include a couple of equations for comparative purposes, but it should be quite easy to understand this post even if you ignore them.

The four forces are gravity, electromagnetism, the strong nuclear force and the weak nuclear force. (Newer physics links electromagnetism and the weak nuclear force together as the ‘electroweak interaction’, but that’s past where we want to go for the moment.)

The nuclear forces govern what happens inside the nucleus: the strong force is what holds the nucleus together in spite of the electrostatic repulsive forces between the protons, and the weak force governs radioactive decay. We won’t say too much more about them, except to note that the balance between the strong nuclear force and the electromagnetic force is what allows stable nuclei – and hence us – to form. Slightly different values of either would not allow matter to form. This has implications for whether divine fiddling with the speed of light or the rate of radioactive decay could happen, but that’s another story for another day.

Electromagnetism can be thought about as two things, although they are tightly tied together – electricity and magnetism.

We’ll take magnetism first. It’s fascinating, because it acts only on a moving charge. If a charged particle remains perfectly still in a magnetic field, no force acts on it. The formula is F = qvBsin(theta), where F is the force (newton), B is the magnetic field strength, q is the charge (coloumb), v is the velocity (metre per second) and theta is the angle (degrees or radians). As you can see, if v is 0, the force will be 0. The calculation is actually a ‘vector cross product’, and that tells us the direction the force will act in, but that’s also probably further than we need to go.

OK, we have enough already to reject the idea that gravity can be reduced to magnetism. We saw that if v is 0, F is 0, but also, if q – the net electrical charge on an object – is 0, the force will be 0. I don’t have a net electric charge on my body, neither do you, and neither does Earth. That means that the gravitational force holding me down on my chair as I type this is not a magnetic force.

(It’s possible the objection will be raised that the protons and electrons in my body have charge and are moving relative to those in the Earth, but again, there is not a net overall charge on an atom, and the directions of motion would all cancel one another out. And, of course, we now tend not to think of the motion of electrons in terms of the ‘orbit’ metaphor anyway…)

The other manifestation of the electromagnetic force is electrostatic attraction and repulsion, and this gets interesting. The formula is F=(kq1q2)/r2 where F is the force, k is a constant, 9 x 109 , q1 and q2 are the charges on the two objects and r is the distance between them.

The reason I said it gets interesting is that this has a direct mirror in the equation for gravitational force, F=(Gm1m2)/r2 where G is a different constant, 6.67 x 10-11 and m1 and m2 are the masses of two objects.

While the similarities are striking, there are also two important differences:

  1. There are both attractive and repulsive electrostatic forces. Professor Paula Abdul had it right: opposites attract! And same charges repel. On the other hand, there is only an attractive force of gravity, not a repulsive one. Objects with mass always pull one another closer, never push one another away.
  2. The relative strength of the forces. I haven’t included the units, but in terms of the normal SI unit conventions the constant for the gravitation force is about 1/1020 or 0.00000000000000000001 times as large as that for the electrostatic force. Inducing a very small charge in a party balloon, for example, will allow it to stick to a wall in defiance of gravity.

So there you have it: a brief rundown of the four fundamental forces, and – in simple terms at least – some discussion of why we still need four, and can’t boil them all down to one.

For ease of navigation I will include links to each of the other posts in this series at the bottom of each post.

Why I think it’s important to understand evolution
Cosmogenesis, abiogenesis and evolution
Evolution and entropy
Facts, Theories and Laws
Radiocarbon dating
Radiometric dating and deep time
Probability and evolution
Species and ‘baramin’, macro- and micro-evolution
Mitochondrial Eve and Y-chromosomal Adam
Transitional fossils
Complexity – irreducible and otherwise


Radiometric dating and deep time

Filed under: — Bravus @ 6:28 am

If you haven’t yet read the Radiocarbon dating post, and if you’re not already au fait with the elements of half-lives and radiometric dating, it’s probably worth clicking on the link and reading that post first, then coming back to this one.

Radiocarbon dating can only take us back on the order of a few tens of thousands of years. Humans and proto-humans are believed to have been around for a couple of million years, the last dinosaurs to have become extinct about 65 million years ago, and the Cambrian to be about half a billion years ago. Earth itself is believed to be about 4.5 billion years old.

That means we need some other dating methods, and some of those also rely on radioactive decay. Carbon-14 has a half-life of 5730 years, but other radioactive elements have much, much shorter half-lives – on the order of nanoseconds or even femtoseconds – and some have much, much longer half-lives.

A few different methods and decays are used:

DecayHalf-life (years)
Postassium-Argon1.3 billion
Uranium-Lead*4.5 billion
Rubidium-Strontium50 billion
Samarium-Neodymium106 billion

*This is the U-238 to Pb-206 decay, but there is also a U-235 to Pb-207 decay with a half-life of 700 million years that runs in parallel and can be used as an extra check.

The method is as for radiocarbon dating, but in most of these cases the ‘daughter nuclide’ – the second name in each of the pairs in the table, the thing that the first-name element decays into – is solid and stays around, unlike the nitrogen that is the product of radiocarbon dating. This means that the age is usually calculated in terms of the ratio of the parent and the daughter nuclide in the sample.

There are similar ‘gotcha’ examples sometimes used for these dates, but since many creationists are also proponents of a very short age of the Earth – some 6000 years in accordance with Bishop Ussher’s chronology based on the Biblical genealogies, some a little longer but not much. Most would suggest that the planet (or life: beliefs differ, but even those who believe the planet has been around longer believe it was ‘without form and void’, so there were not features capable of being dated) is younger than even the 80,000 years of a single half-life of the Uranium-Thorium decay.

That means that a common theme is “But you assume that the rates of radioactive decay has always been constant. Maybe it was different in the past. Some suggest that at the time of Noah’s flood there was also a dramatic increase in the rate of radioactive decay.

The thing is, every radioactive decay reaction also releases heat. If there had been sufficient acceleration to fit 4.5 billion years worth of decay into 40 days and 40 nights (while it was raining (in the account)) or even a year (before the floodwaters subsided), the heat released would have been sufficient to melt the entire planet, many times over.

The response I’ve sometimes received when raising that issue is “God has infinite power and could shield the Earth from the heat”. Well, I guess so, but that just piles ad hoc intervention on top of ad hoc intervention. If God wanted to do that, perhaps it would have been simpler just to specifically set the isotope ratios… and also do things like create the polonium halos in granite that certainly suggest radioactive decay occurred over a very long period.

My goal in these posts is really not to pick fights, but to enhance understanding of the relevant science. Occasionally, though, enhancing understanding involves addressing common misunderstandings.

For ease of navigation I will include links to each of the other posts in this series at the bottom of each post.

Why I think it’s important to understand evolution
Cosmogenesis, abiogenesis and evolution
Evolution and entropy
Facts, Theories and Laws
Radiocarbon dating
Four Forces of the Universe
Probability and evolution
Species and ‘baramin’, macro- and micro-evolution
Mitochondrial Eve and Y-chromosomal Adam
Transitional fossils
Complexity – irreducible and otherwise


Radiocarbon dating

Filed under: — Bravus @ 6:51 am

A friend, in a discussion of the age of the Earth, recently said “I remember a study where there were some bones that were known to be only a few years old but they were carbon dated as being 8 or 9,000 years old”.

It helps to illustrate the problem: it’s someone’s recollection of something someone else told them some time ago, so there’s no citation, and few details. It’s difficult to check what actually happened. I found it then but can’t now, but there are a number of similar articles around, and we’ll get to the issues with them.

I thought today I’d talk a little bit about radiocarbon dating specifically (more on other forms of radioactive dating in coming days): how it works, what it can and cannot do, and why some of the common objections to it don’t really hold water.

Radioactive decay is a fascinating process. Unlike physical decay, it is not influenced by how hot, wet, pressured or otherwise its environment is. It is a process that appears random at the level of individual decays – it’s impossible to accurately predict when one will occur – but is highly predictable at a statistical level, when many decays are combined.

If a sample of a substance has, say, 1000 atoms of a radioactive chemical element in it, the meaning of the term ‘half-life’ is the amount of time taken for half of those atoms to undergo decay. The half-life for a particular type of decay to occur is constant. Say in our example the element has a half-life of 2 days. After 2 days, there are 500 atoms left (half the original amount). After 2 more days, there are 250 left (half as many as 2 days ago, quarter as many as were there originally, 4 days ago). After 6 days in total there are 125, after 8 days there are 62.5 (there are not really 0.5 atoms, so it would likely be 62 or 63). It will keep halving, each 2 days, until there are no atoms left.

The great majority of the carbon in our environment is carbon-12. It has 6 protons and 6 neutrons in its nucleus, for a total of 12 ‘nucleons’. Carbon-12 is stable and does not undergo radioactive decay. A very small amount of the carbon has an extra neutron for a total of 13. It’s called carbon-13 and is sometimes important in MRI scanning. Carbon-13 is also stable.

When neutrons in incoming solar radiation strike nitrogen-14 in the upper atmosphere it sometimes undergoes a tranformation into carbon-14, and carbon-14 is radioactive.

It later undergoes radioactive decay to release a beta particle and returns to being nitrogen-14. The half-life of this decay is 5730 years.

(An electron anti-neutrino is also released, and this equation isn’t properly charge balanced, and there’s an interesting reason for the minus sign for atomic number on the beta ( ? ) particle, but perhaps that’s too much detail for here.)

The carbon-14 in the upper atmosphere is distributed through the whole environment. Plants take it in when they use energy from sunlight to power photosynthesis, changing carbon dioxide and water into glucose and releasing oxygen. Living things either eat plants or eat things that eat plants, so all living things have carbon-14 in them. As long as they’re alive, they keep replenishing their stores of carbon-14, and so the amount in their bodies is stable. There are radioactive decays going on, but the supply is being replaced.

Once something dies, though, it stops breathing, stops eating, stops interacting with the environment. No new carbon-14 is added to its body, and what is there decays in a predictable way.

This is why radiocarbon dating can only be used on things that were formerly alive. It is not useful for dating rocks, or fossils (which are rock that’s replaced something that was formerly alive), or buildings, tools and other artifacts. Something had to be living, breathing, eating and drinking at some point in history to be able to be radiocarbon dated. There are other methods of dating other materials, that I’ll talk about in a different post.

The period of time that radiocarbon dating can stretch back is also limited. With a half-life of 5730 years, it’s very convenient for dating things that are low multiples of that, back to 25,000 years or so, but even at that point you’re 4 half-lives in and there’s only 1/16th of the original amount remaining. If you have a larger sample, so that the remnant is larger even after multiple halvings, radiocarbon dating can get you back 50,000 years or so, but not much further than that.

As a matter of perspective, there are artifacts of Aboriginal settlement in Australia that are older than that.

Radiocarbon dating is generally reliable. It makes some assumptions, but they are generally valid, or else able to be calibrated for. So, for example, if additional volcanic activity, or nuclear testing or other influences changed the amount of carbon-14 in the atmosphere at the period in which the formerly-living thing being dated was alive, that’s relevant: and can be taken into account. If additional carbon-14 has leached in or out of the sample, that’s relevant.

There are a few claims made by creationists, that are usually of the ‘gotcha’ type. They will have sent a sample to a lab with no information about what it is or where it comes from, requested dating, and then triumphantly revealed that the real known age is different. In all of these cases I have seen, including the one with which I started this piece, there is a clear, simple scientific explanation for the apparent disparity, which does not invalidate the method of radiocarbon dating for age determinations.

Often, the issue is that the organisms being dated were not in contact with the atmosphere in a ‘normal’ way. Examples include shells that grew in water from underground caves, where the carbon dissolved in the water in which they and their food grew had in many cases spent a very long period as part of limestone. The carbon-14 in it had long ago decayed already, so the carbon these shells were absorbing was depleted in carbon-14 relative to the ‘norm’ in other places. When comparing these shells to similar ones grown in fresher water, they appeared ‘older’ because they had lower levels of carbon-14.

When the science is done properly, the sample is tagged with the location where it is found, and these kinds of anomalies can be calibrated for. The ‘gotcha’ examples might give those seeking to impugn the method something to crow about, but they’re not good science.

For ease of navigation I will include links to each of the other posts in this series at the bottom of each post.

Why I think it’s important to understand evolution
Cosmogenesis, abiogenesis and evolution
Evolution and entropy
Facts, Theories and Laws
Radiometric dating and deep time
Four Forces of the Universe
Probability and evolution
Species and ‘baramin’, macro- and micro-evolution
Mitochondrial Eve and Y-chromosomal Adam
Transitional fossils
Complexity – irreducible and otherwise


Facts, Theories and Laws

Filed under: — Bravus @ 6:42 am

(This piece is slightly modified from one originally published on the Adventist Today web page – apologies to those who have already ready it in other fora. More brand new words tomorrow!)

“Evolution is a fact” is something we tend to hear from one side in debates about origins. I’d argue that this statement reflects a misunderstanding of the roles of facts, theories and laws in science.

At the same time, from the other side of those same debates, we tend to hear “evolution is (just) a theory”, which is equally unfortunate as a way of thinking about what ‘theory’ means in science.

I want to, as clearly as I can, briefly outline the meanings in science of the terms ‘fact’, ‘theory’ and ‘law’, and to explain why a theory, no matter how well supported by evidence, never turns into a fact.

Evolution is, in some circles, a controversial theory, and therefore a bit awkward to use as an example for this discussion, since it brings in strong emotions and strongly held views on the part of readers. (And, just quietly, I’m a physics guy, not a biology guy.) So, instead, I’ll use the example of gravity.

Here is a fact about gravity: close to the surface of the earth, if any object (that has mass) is unsupported, it will accelerate toward the centre of the earth with an acceleration of about 32 feet per second per second, or about 9.8 metres per second per second. If you have an object and a stopwatch handy right now (and your phone probably has a stopwatch function), and have done a little high school physics, you can test this fact.

In science, ‘fact’ is used to refer to a single piece of data, the result of a measurement. Other facts about gravity include the fact that it decreases in strength as we move away from the centre of the earth, and that every object that has mass exerts a gravitational force on every other object that has mass. With sophisticated-enough instrumentation, all these facts can be measured and expressed in numbers.

Not all of science is physics, though, as my students often remind me. It’s a fact in chemistry that sodium chloride (table salt) has a cubic lattice structure between its atoms, and a fact in biology that living things contain DNA, and a fact in geology that most rocks contain a lot of silicon dioxide.

Let’s leave ‘theory’ on the side of our plate for the moment, because it’s the most complicated, and talk about ‘law’. In science, a law is a mathematical relationship between quantities. The most famous law in science is probably Einstein’s E = mc2, which describes the relationship between matter and energy.

The key law in gravity, which was formulated by Isaac Newton (and I do apologise for those who find equations challenging!), is F = (Gm1m2)/r2 In words, it says that if there are two masses, m1 and m2, a distance r apart, the force F between them is given by this law, where G is called the ‘universal gravitational constant’.

A law is powerful because it makes a relationship clearer. A couple of paragraphs ago I said that the force decreases with distance, but the law gives more detail. It shows that the force decreases with the square of distance: if the objects are 2 times as far apart, the force is only ¼ as great.

A theory is a human mental creation that explains facts and has withstood the test of experiment. This view of the nature of science and of theory is owed to philosopher of science Karl Popper. A theory in science has descriptive, predictive and explanatory power. That is, a theory describes the world as we see it and experience it. It allows us to reliably predict how the world will behave in future in a particular set of circumstances, and it explains why the world is as it is. If we make a prediction using a theory, and then conduct the experiment and the prediction fails – the world does not behave as the theory leads us to expect – then Popper would say the theory has been ‘falsified’ and should be discarded. The theories that make up science at any given moment are the ones that have been tested many times and have never been falsified. Einstein neatly summed up Popper’s perspective: “No amount of experimentation can ever prove me right; a single experiment can prove me wrong”.

A theory is not held to be ‘true’ in any final sense under this view: at best, it is the most powerful theory available, that explains the greatest number of facts, and has not been falsified. A new experiment may yet be conducted that will falsify it, and if that occurs the theory will need to be discarded and replaced with a better one.

The first – and longest-lived – theory used to explain our experience of gravity was proposed by Aristotle. He suggested that things in the universe have their ‘natural station’, the place where they belong. Things mostly belong on the ground – even birds – so when we lift them above the ground they are being lifted out of their natural state, and if they are not prevented from doing so, they will return to it. If we lift a book from the floor to a table, it is out of its natural place, and if the table were not there to prevent it doing so, the book would return to its natural place on the floor.

Aristotle’s theory of gravitation applied only on Earth, since he also believed that the heavens were a different domain from Earth, with different rules and processes. The contribution of the next great theorist of gravity, Isaac Newton, was to apply the same rule to objects in space like the moon and the planets that was used to explain how things move on Earth.

Johannes Kepler had created rules that described the motion of the planets in purely mathematical terms, but did not explain why the planets moved the way they did. Most times laws are derived from theories, but we could argue that Kepler’s laws were not drawn from a theory. They had descriptive and predictive power – Kepler could tell you when the next eclipse would come – but not explanatory power. Newton developed the theory that any two objects with mass exert a force on each other, and – crucially – that this is true in the heavens as well as on Earth. The same force that caused his (probably apocryphal) apple to fall from the tree to the ground explained the motions of the heavenly bodies. Newton had a theory, not just a law, because in addition to description and prediction, it was capable of explanation. Newton’s theory of gravity still works well for everything we encounter in everyday life, but for much more extreme environments, such as near the event horizon of a black hole, it breaks down. For those specialised contexts, it has been replaced by the theory of General Relativity proposed by Albert Einstein. The mathematics gets very complex very quickly, but in words, Einstein’s theory can be stated as ‘matter tells space how to curve, space tells matter how to move’. Gravity is explained, not as a force between objects, but as mass causing curvature in the local space, which then causes mass to move differently.

Einstein’s theory is considered ‘better’ than Newton’s because it is more universal – it can be applied everywhere in the universe, whereas Newton’s theory breaks down in some situations.

All three of the theories described – Aristotle’s, Newton’s and Einstein’s – explain the fact that a dropped book or apple will fall toward the ground. Aristotle’s does not have an associated law – a mathematical statement about how rapidly the apple will fall – while Newton’s theory does include a law. Einstein’s theory also includes laws, but the mathematics are too complex to go into here.

I hope these examples have helped to explain why a theory can never turn into a fact or a law, no matter how much evidence it has behind it. These are three different things with different qualities, each important in science.

I suspect that when someone says “evolution is a fact”, they are using the word ‘fact’, not as a scientist would, but in the everyday sense of ‘not fiction’. They mean that a textbook on evolutionary theory in the library would not be placed with the novels and short stories, but with the other books that contain true information about the world. It’s probably still an unfortunate usage, though, since the claim being made falls within science, so the language used ought to be the careful language of science.

Evolution is a theory. It is one that explains, not one fact, but an enormous variety of facts about the diversity and the characteristics of life on Earth. It is a theory that was proposed more than 150 years ago, and it has been tested in a wide variety of ways. The fundamental concepts have not been falsified, but significant elements have been changed and updated. Darwin did not know about genes when he wrote ‘On The Origin Of Species’, for example, or DNA. He did not have access to the vast array of data about living things that modern scientists can draw on. The modern evolutionary synthesis includes the recognition that gene transfer plays a much greater role than previously thought, for example, so that less of the ‘heavy lifting’ of generating new characteristics must be borne by mutations.

When people say “evolution is (just) a theory”, they are drawing on the common, everyday use of the word, rather than the scientific use. We say “I have a theory” when we mean a guess, a hunch, an untested brainwave. Saying “evolution is a theory” is thought of as a way of saying that it is unsupported, held without evidence, untested. These same people would tend not to say “gravity is (just) a theory”, although in scientific terms, gravity is indeed a theory. Or, at least, there are multiple theories of gravity that explain the facts of gravity, some of which provide mathematical laws, and Einstein’s is currently the best theory we have.

Theories do change, and Einstein’s theory may well be replaced by an even more powerful one in the future. There are interesting problems at the boundaries between General Relativity and quantum theory, for example, that may revolutionise our understanding in the future. But a book will still fall from a table, and an apple from a tree. A change to the theory of gravity will not enable us to suddenly, unaided by technology, safely walk off the roof of a tall building and just float. The facts of gravity will remain the same if the theory used to explain them changes.

The same is true of evolutionary theory. It has changed in the past and is likely to continue to change. Alternative candidate theories, including special creation and intelligent design, already exist, and already claim to explain the same facts. When the theory changes, the facts will not change. The DNA that forms the genetic blueprint for a jellyfish will not suddenly begin to produce a lion instead.

It’s probably a discussion for another article, but to date the alternative candidate theories – special creation and intelligent design – have not demonstrated descriptive, predictive and explanatory power in the same ways and to the same extent as the modern evolutionary synthesis. There are efforts to make these demonstrations, which will continue to be tested against the facts of biology.

I hope this brief discussion has been helped you to understand the meanings of the terms ‘fact’, ‘theory’ and ‘law’ in science, and to be aware when these terms are being used confusingly in discussions around origins as well as other scientific topics such as vaccination, genetic modification and climate change. If we can communicate clearly and accurately, and go forward together in good faith, we have more chance of finding our common ground.

For ease of navigation I will include links to each of the other posts in this series at the bottom of each post.

Why I think it’s important to understand evolution
Cosmogenesis, abiogenesis and evolution
Evolution and entropy
Radiocarbon dating
Radiometric dating and deep time
Four Forces of the Universe
Probability and evolution
Species and ‘baramin’, macro- and micro-evolution
Mitochondrial Eve and Y-chromosomal Adam
Transitional fossils
Complexity – irreducible and otherwise


Cosmogenesis, abiogenesis and evolution

Filed under: — Bravus @ 7:30 am

A common response to evolution is “It cannot account for how life first arose from non-life”. But that’s not the ‘job’ of evolutionary theory. Evolution is a theory that explains how, given life with the ability to self-replicate, we get from a few forms of simple life to the enormous variety of life on Earth.

Two other theories – or rather, domains of theory – are required to account for, respectively, the origin of the universe itself and the original origin of life.

I should take a small digression, because what I should have said in the previous sentence was ‘are required in the absence of miracles to account for…’ Science deals in ‘methodological naturalism’. I might go into that in more detail later, but in brief terms it means that, in science, miracles are not invoked as explanations. Things are explained in terms of natural causes and natural effects, not supernatural actions.

The implication of that is that, in the presence of miracles, all bets are off. If a Divine Creator created the universe in a miraculous supernatural act, no scientific theory of cosmogenesis is required. If such a Creator sparked off the beginning of life, no theory of abiogenesis is required. If She created life in pretty much its current form, no theory of evolution is required. (In each of these cases, though, a theological theory of why the Creator chose to make the universe look as though these processes took place might be required…)

OK, returning to the main theme, sometimes people are frustrated by the distinctions between cosmogenesis, abiogenesis and evolution: “It’s all evolution!” But these discussions take place in the domain of science. Even if the claims are religiously motivated, they are being presented as though they are scientific claims. In that domain, how words are used is important.

So cosmogenesis is the domain of theories that seek to explain the origins of the whole universe. The currently dominant such theory is the Big Bang, which is unfortunately named in that the word makes people think of an explosion in space, when it really describes an expansion of space-time itself. There are other candidate theories, including that the universe is in a ‘steady state’ and/or has always existed. Theories of cosmogenesis need to account for stars and galaxies and how they are distributed, for the ‘red shift’ that shows all galaxies are receding from us and the Cosmic Background Radiation.

Abiogenesis is the domain of theories about how life first arose from non-life. There exists life and, unless it has eternally existed, there must have been a point at which there was only non-living matter in the (natural – scientific theories don’t account for supernatural life) universe, and therefore some moment at which the first life existed.

Scientists acknowledge that, of the three domains, abiogenesis is the most difficult to engage with. For cosmogenesis we have the ancient light from the stars, and even from the beginning of the universe, that can be analysed and studied. For evolution, there is all of life, the fossil record and DNA to study. But the very first single-celled organisms were not the kinds of things that leave fossils or any consistent record. Abiogenesis is much more difficult to study.

Indeed, it is likely that we cannot ever confirm exactly how that first event went. About the best we can achieve is demonstrating possible mechanisms by which life can arise from non-life. There are interesting theories – about the surfaces of certain clays acting as templates, for example, or about lipid bubbles forming elementary cell walls – but there is a lot of work still to be done.

There are different candidate theories for the evolution of life and the ‘tree of life’ – the relationships between existing species, and between existing and extinct species, and between different extinct species. The most strongly supported by evidence, right now, is the ‘modern evolutionary synthesis’. Other posts in this series will outline that theory in more detail.

So, really, perhaps the main point of this piece is very simple: you will be recognised by others as knowing what you’re talking about if you recognise that different domains of theory are relevant for explaining different elements of how we get from nothing to here.

For ease of navigation I will include links to each of the other posts in this series at the bottom of each post.

Why I think it’s important to understand evolution
Evolution and entropy
Facts, Theories and Laws
Radiocarbon dating
Radiometric dating and deep time
Four Forces of the Universe
Probability and evolution
Species and ‘baramin’, macro- and micro-evolution
Mitochondrial Eve and Y-chromosomal Adam
Transitional fossils
Complexity – irreducible and otherwise


How do we decide who is, and is not, a Christian?

Filed under: — Bravus @ 3:13 pm

“That’s not very Christian!” is something we tend to hear when someone does something unkind or unloving. There’s an enormous range of shapes that Christianity takes in the world now, and the question in the title is a perplexing one for me. (I could replace that final word with Buddhist, Muslim, Mormon, Mason, Metalhead… but except on the last, I simply don’t know enough to speak, so I’ll stick with considering Christians.)

On the one hand, I tend to find ‘Is it _____ ?’ discussions tedious, where the gap is filled by ‘science’ or ‘art’ or ‘black metal’ or whatever. They turn on people’s individual definitions of those things, which can be quite divergent, so the debates tend to go around and around without reaching any worthwhile conclusions.

On the other hand, how we respond to people who claim to be Christians is coloured by our view of what it means to be Christian, and whose version of that we consider to be definitive – or, at least, most influential.

A complexifying factor is the ‘No True Scotsman’ fallacy. Very briefly, it stems from a story in which a newspaper report says that a Scotsman did something very bad, and a reader says ‘No true Scotsman’ would do such a thing. If a Christian does something evil, it’s much too convenient to simply define that person out: no ‘true Christian’ would do such a thing. The history of child sexual abuse by clergy uncovered in the recent Australian Royal Commission is just one example of bad things done by Christians, including pastors and priests.

If Christianity can never be represented by its worst adherents, but only by its charitable works and the best examples, it’s impossible to have a fair accounting of its net impact in the world.

At the other end of the spectrum, opponents of Christianity like Richard Dawkins might exclude or ignore all positive influences and impacts, and characterise Christianity only by its worst features and examples. Dawkins pays some lip service to more sophisticated theologies early in his book, but then defaults to treating all of Christianity as though it represented by its most literal and fundamentalist fringes.

There is a huge range of political views and beliefs in the church, from Christians like Jarrod McKenna, who builds homes for the homeless and refugees, and Father Rod Bowers who advocates for more humane policies, to the Michelle Bachmans of the world, who say that Donald Trump is the most godly president of our generation. Indeed, American evangelicalism has entirely embraced capitalism and wealth.

For most of these kinds of ‘club membership’ discussions I would be happy to accept people’s own self-identification as ‘in or out’. If someone decides they are a Christian, then they are, and I don’t have the right to gainsay them.

In this case, though, I’m going to suggest an alternative definition. It’s linked to something I think I’ve talked about in the past, either here on the blog or on Facebook, and certainly in conversations. While I think ‘What Would Jesus Do?’ (as represented on bracelets in the 90s) is dangerous because it is far too prone to projection, so that it becomes ‘What would I do?’ or ‘What would my pastor and the members of my church do?’, I think ‘What Did Jesus Do?’ is a pretty decent guide for living.

After all, Jesus is described as the ‘Christ’, and ‘Christian’ literally just means ‘follower of the Christ’. So, if someone claims to be a Christian, the test is simply ‘Do they do what Jesus did?’ And, I guess, do they refrain from doing what He did not?

Now, some of my atheist friends – and some of my theologian friends too, for that matter – might interject that the Gospels may have been subject to later tampering and interpolations, and were certainly a selection from among a range of documents at the time. They were also written some time after Jesus’ death, largely based on other accounts, both written and verbal. I acknowledge this, and yet… if we simply take what we have, and take it as a wisdom literature that informs our moral reasoning, not a creed that dictates it, the Jesus described in the four Gospels offers a way of life.

There are controversial sections where He says that he comes to bring division, and other difficult passages, but this is the story of a man who owned nothing more than the clothes he stood up in, and went around ministering to the poor and vulnerable and excluded in society. He reserved anger for the powerful, the wealthy and oppressors, and comforted those who were rejected by others in their society.

Read the Beatitudes, in Matthew 5, and the parable of the sheep and the goats in Matthew 25. In fact, read all the Gospels… it doesn’t take all that long.

Then, if someone claims to be a Christian – and particularly if they want to make you do something or stop you from doing something because they are a Christian – just run the ‘What did Jesus do?’ ruler over them.


Peter Achinstein and Explaining As An Activity

Filed under: — Bravus @ 5:58 pm

Achinstein notes that most accounts of scientific explanation have focused on the ‘product’ – the explanation itself, whether spoken or written – rather than on the act of explaining. He sets out to analyse explanation from the perspective of what human beings are doing when we explain.

An explanation is given by someone, with the purpose of helping someone else to understand. Achinstein explains it in slightly more technical language, but in brief he says that the purpose of an explanation is to have the audience know the correct answer to a question and know that it is a correct answer. We’ll leave aside the kinds of questions for which there is no correct answer, or many correct answers.

Achinstein describes explaining as an ‘illocutionary’ act. This is from a framework by Austin. Wikipedia sez: “In Austin’s framework, locution is what was said, illocution is what was meant, and perlocution is what happened as a result.”

Achinstein notes that the exact same sentence can be said with different intentions. An example he uses (I’ll paraphrase somewhat) is that when Dr Jones says “Bill ate spoiled meat”, he is giving an explanation of Bill’s stomach ache, and therefore the kind of illocutionary act he is undertaking is ‘explanation’. When Bill’s wife Jane says “Bill ate spoiled meat”, she is criticizing Bill’s dietary choices, so she is undertaking an illucutionary act of the kind ‘criticism’. This is true even though both people said the exact same words.

Achinstein suggests an ‘ordered pair’ approach, which can be described as (p, explaining q). ‘p’ is the explanation product itself – a sentence or proposition, and the second part of the brackets clarifies that someone said (or wrote) p in order to explain something, ‘q’. Dr Jones’ response might then be written as (“The reason that Bill has a stomach ache is that Bill ate spoiled meat”, explaining why Bill had a stomach ache).

By identifying what is going on in the explaining process, the explanation ‘product’ is clearer.

He considers the issue of evaluating explanations: a correct explanation may not be a good explanation in general terms, or it may not be a good explanation for a particular audience or a particular purpose. Achinstein talks about ‘instructions’ for explaining in a particular context.

Achinstein proposes the following criteria for the good-ness of an explanation:

  1. The audience does not already understand it
  2. There is a way to explain it that will allow the audience to know the correct answer and that it is a correct answer
  3. The audience is interested in the explanation
  4. It will be valuable for the audience to understand the explanation

There are a lot more details and issues, but the two key takeaways for me are (1) this approach is closer to my concerns with science teaching explanations than those of Hempel and Salmon because it centrally includes the explainer and the audience and (2) the challenges of teaching are with ensuring conditions (c) and (d) above – that our students are interested in the explanations we offer, and that the explanations we offer will be valuable for our students.

Note that (d) is not ‘the audience knows that it will be valuable to understand’. While that’s desirable, it is not essential, as long as the explainer knows it. But I would argue that it must be authentically in the interests of the audience (students, learners) to understand the explanation if we are to justify teaching it, and ‘valuable’ needs to mean something much more than passing an exam. The explanations we give in science teaching should transform worldviews and offer tangible benefits.


Eine Kleine Achinstein

Filed under: — Bravus @ 5:54 pm

Just a little taste for you of the kind of stuff I’m reading at the moment. The sauv blanc helps, at least in moderation. 😉

If Q is an explanation-seeking question (e.g. ‘Why did Nero fiddle?’), and q is the indirect form of the question (e.g. ‘The reason that Nero fiddled is that______’), and if a person A is seeking to understand q, and if qI is the answer to q under a specific set of instructions, I (so, for example, it might be ‘Explain why Nero fiddled in terms of his mental state’ or ‘Explain why Nero fiddled in terms of historical factors obtaining in Rome at the time…’ and so on), then:

A understands qI only if (∃p)(p is an answer to Q that satisfies I, and A knows of p that it is a correct answer to Q, and p is a complete content-giving proposition with respect to Q). (Achinstein, 1983, p. 57)

∃ is the ‘existential quantifier, which means ‘there exists’, so ∃p means ‘there exists a proposition p such that…’

A ‘complete content-giving proposition’ is complex, but basically it means it contains everything relevant and nothing irrelevant to explaining Q.

Wesley Salmon, Statistical Relevance and Causal/Mechanical Explanation

Filed under: — Bravus @ 2:49 pm

As you’ll know if you’ve been following along in this series of posts1 on the philosophy of explanation, or if you decide to go back and read them in chronological order before continuing to read this one, Wesley Salmon is a realist who has been working on the problems of explanation for some considerable time. He first advanced and then withdrew a ‘statistical-relevance (SR)’ approach to explanation, and later adopted what he called a ‘causal/mechanical’ approach. My aim here is to briefly explore both of these approaches and what they offer.

You’ll remember that Hempel advanced the ‘deductive-nomological (D-N)’ model for explanations when the causal laws that govern the scientific phenomena are deterministic: ‘if X happens then Y will definitely happen’. He also introduced the ‘inductive-statistical (I-S) model for when the laws are probabilistic (e.g. in quantum mechanics): ‘if A happens there is a 78% chance that B will happen’. Hempel insisted on a high probablity (close to 100% or 1.0) for explanations under the I-S approach. The main reason for this is that, if the probability is lower, A could presumably explain both the occurrence and non-occurrence of B. Say the probability is of B given A is .5, and A occurs, if B occurs we say ‘B happened because A’, but if B does not occur in some sense it also makes sense to explain this in terms of A, since there is a 50% chance that A will not lead to B.

There are also other helpful counter-examples. Jim (who is biologically male) did not become pregnant last year. Jim faithfully took birth control pills all year. Logically, we could say that Jim did not become pregnant because he took birth control pills, but our intuition tells us this is not a valid explanation. The birth control pills are not relevant to explaining the phenomenon. Similarly, being a lifelong smoker only yields about a 20% chance (probability of .2) of getting lung cancer, yet we consider that the smoking explains the cancer.

Similarly, the probability arguments can be complex. Someone who has pneumonia and is treated with penicillin has a higher probability of recovering than someone who does not have pneumonia. We would argue that the penicillin caused the recovery, or at least that it did so in conjunction with the immune system of the patient. (On the other hand, if we observe that taking Vitamin C correlates with recovering from the common cold after about a week we might consider that it is causal… until we realise that most people, Vitamin C or not, recover from the common cold in about a week.

Salmon suggested, therefore, that relevance is important in statistical cases. He also noted, as in the smoking example, that explanations for events with low probabilities can be explained, whereas Hempel’s approach insists on high probabilities.

Let’s go back the pneumonia patient, but add the information that there are penicillin-resistant strains of pneumonia. The simple argument that penicillin improves the odds of recovery is complicated by this new information, and the two classes of pneumonia patients initially – those treated with penicillin and those not – become four classes – those untreated who have the non-resistant strain, those treated who have the non-resistant strain, those untreated who have the resistant strain and those treated who have the resistant strain. In considering an individual patient’s likelihood of recovery, which of these quadrants s/he falls in is statistically relevant.

Salmon adds the additional criteria that (a) all relevant factors must be included and no irrelevant ones and (b) we must divide up our whole population of cases so that we look at an ‘objectively homogeneous’ class in trying to explain something. For example, in the case of our pneumonia patient, we can divde the population into four with two factors, and each of those four groups will be somewhat homogeneous (all members having the same characteristics). But there are potentially other relevant factors, like age, sex, obesity… the list is almost endless. In the end, while Salmon described objective homogeneity is an ideal, he conceded that practical problems mean it is unlikely to be actually useful in constructing and evaluating real explanations. He moved on to consider the important role of causality:

I no longer believe that the assemblage of relevant factors provides a complete explanation—or much of anything in the way of an explanation. We do, I believe, have a bona fide explanation of an event if we have a complete set of statistically relevant factors, the pertinent probability values, and causal explanations of the relevance relations. (Salmon, 1978)

His discussion of causation and explanation gets into Reichenbach’s ‘screening off principle’, conjunctive forks, interactive forks and other complexities that don’t really concern me for the moment.

The big contribution from Salmon to my project is (a) the very thorough overview his book ‘Four Decades of Scientific Explanation’ offers of Hempel’s work and the responses to it up until the late 1980s, (b) his realist approach in contrast to Hempel’s anti-realist approach and (c) the ways in which the statistical-relevance approach, despite shortcomings of its own, fixed some of the shortcomings of Hempel’s approach and led to other interesting work. He also enabled me to think carefully about which philosophers working in this field will need to be considered in depth in my book, for my purposes, and which can be mentioned in brief but not analysed in depth.

Next cab off the rank is Peter Achinstein, whose approach is less rigidly logical-philosophical and more directly focused on what human beings do when we explain. He calls it an ‘illocutionary’ approach, which is just a longer word for the process of giving and explanation and the ‘product’ of that explanation, whether it be written, spoken, animated etc. I’ll be reading Achinstein’s book over the next few days and will report in when I’ve done that.

  1. As you may have guessed, this series is in part a way of sharing the stuff I’m interested in and excited about with others, partly a way of taking notes for myself to remind me of some of the broader themes of what I’m reading… and partly just procrastination from writing the book I’m supposed to be writing about this stuff! I feel as though it’s worthwhile procrastination, though, because if I can explain it for a smart lay audience of my friends it will help me to better understand it for when I write about it more formally.


Salmon, W. (1978). “Why Ask ‘Why?’? An Inquiry Concerning Scientific Explanation”, Proceedings and Addresses of the American Philosophical Association, 51(6): 683–705. Reprinted in Salmon 1998: 125–141. doi:10.2307/3129654

Salmon, W. (1998).Causality and Explanation, New York: Oxford University Press. doi:10.1093/0195108647.001.0001

Realism and Anti-Realism in Philosophy of Science

Filed under: — Bravus @ 9:40 am

There’ll be a much more detailed post shortly about Wesley Salmon’s ‘statistical-relevance’ theory of scientific explanation (a response and extension from Hempel’s ‘deductive-nomological’ and ‘inductive-stastical’ approaches, discussed in an earlier post). In the mean time, though, a quick discussion on realism and anti-realism.

The distinction is that realists accept that the unobservable entities that we use in our scientific explanations such as fields, atoms, electrons, photons and so on are real features of the universe. Anti-realists – and one prominent school within this camp is the instrumentalists – claim that these entities are useful rather than true. They serve their purpose in that they help us to provide explanations that work and theories that allow us to describe and predict observable phenomena, but they are not considered to be in any sense ‘real’. Hempel is an anti-realist, and constructs scientific explanations in terms of logical relations and laws. Salmon, on the other hand, is a realist1.

As a side note, Bas van Fraassen, another important figure in the philosophy of explanation (who, for various reasons, I will mention only in passing in my book) describes his position as ‘constructive empiricism’. While the anti-realist is an ‘atheist’ in terms of unobservable entities and makes the strong claim that they are not real, a constructive empiricist is ‘agnostic’: s/he neither knows nor cares whether they exist, and their reality is not a required feature of the approaches to explanation proposed by van Fraassen and those who follow him.

Salmon essentially uses two arguments in support of the reality of the unobservable. The first relates to extending the range of our senses. He talks about what he can see in a book with tiny print with and without his glasses, and notes that it would seem very odd to claim that the full stops on the page are not real when he has his glasses off but are real when he has his glasses on and can observe them. He then extends this, noting that the optics of a microscope are based on the exact same principles as the optics used in making his glasses, so it makes sense to consider the things that can be observed through a microscope to be real.

The argument then extends to telescopes and things like the moons of the planets in our solar system, which are not visible to the naked eye. The objection has been made by others that we could, in principle, travel to the moons of the planets and verify their existence with our senses but that we can’t (‘Fantastic Voyage’ aside) travel to the microscopic realm to check our observations in the same way.

In response to this, Salmon talks about a process by which a grid is designed at macroscale then shrunk and manufactured at microscopic scale and used for things like counting bacteria in a sample under a microscope. It seems quite silly to claim that, at the scale when we can no longer observe it directly with our unaided senses, such a grid loses its reality.

The final argument is based on the work of Jean Perrin, who started out observing Brownian motion (the way in which very small particles suspended in a fluid (gas or liquid) exhibit random movement, which is explained as being caused by collisions with the particles in the fluid, e.g. water molecules or nitrogen molecules in air). Brownian motion allows the direct observation (though usually aided by a microscope, because particles small enough to be bumped off course by a single molecule are pretty small) of the effects of molecules, although the molecules themselves cannot be seen. Perrin used Brownian motion to find the value of Avogadro’s Number, 6.02 x 1023, a very important number in chemistry that relates the molecular and macro scales.

The really interesting thing, though, is that Perrin then went on to find 13 different and independent ways to determine the value of Avogadro’s number, such as electroplating silver out of a solution and measuring the current used for a given mass of silver, radioactive decays and so on. The fact that a range of independent experiments, across a range of different branches of chemistry and physics, all yielded the same number (within experimental error) is at least pretty strong inferential empirical evidence for the reality of atoms, molecules and electrons.

When we get to photons and other entities at the level where quantum phenomena are dominant, it gets more complex still… things sometimes behave like particles and sometimes like waves. Are they ‘real’? They help us to create good – if complex (literally) – explanations.

I have to admit that, while in general I’m probably inclined toward realism, if I had to swear to it, hand on heart, constructive empiricism would be an attractive approach for me. Or is that just a copout?

There’s a good, if somewhat technical, introduction to some of the issues in explanation here: https://www.iep.utm.edu/explanat/ For me, it makes too much of the implications of this realist/anti-realist distinction, when I find other aspects of explanation more interesting and important, but nonetheless it does a nice job of sketching the last 70 years in the philosophy of this issue, since Hempel and Oppenheim’s seminal paper in 1948.

More Salmon shortly.

  1. Like many other terms in science and philosophy, ‘realist’ has a technical and an everyday meaning. In everyday parlance, a ‘realist’ is someone who takes the world as it is, as opposed to an ‘idealist’ who seeks to work as though the world follows – or ought to follow – some ideal order. It’s important to distinguish that sense of the term ‘realist’ from the technical meaning discussed in this post.