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
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