One thing you notice as soon as you participate in evolution discussions is that you don’t understand anything about evolution. This is true whatever your background. You notice in most of the criticisms of a biochemist like Behe or an origins-of-life PhD like Meyer that they somehow neglected to learn the rudiments of evolution. My own background was zoology and medicine, but it has never prevented the “You don’t understand the first thing…” accusations. Some people might argue that those with weak arguments prefer to say, “You wouldn’t understand…” than argue their case, but the alternative is to go back and try to reach that basic, essential comprehension.
So let’s start with the scientific definition of the theory, which is… well, it’s hard to be sure, because there seem to be so many. The broadest is “descent with modification”, but that’s hardly a definition as it would encompass Lamarckism, and other pre-Darwinian ideas like Lyell’s version of special creation.
“Common Descent”? Deny it and you’ll be called a creationist, but it was only a working assumption by Darwin, and now we know the evidence to be muddied by very extensive horizontal gene transfer, the evolutionists who propose multiple origins for life are hard to refute. Certainly HGT prevents it being the definition of the theory.
Darwin himself postulated natural selection leading to increasing perfection through infinitesimal minor variations of the species, but everybody accepts that that’s inadequate both because perfection doesn’t happen and because variations are discrete genetic events, which was why the standard paradigm now is Neo-Darwinian. So what’s the definition of that?
One frequent description is “random mutation and natural selection”. But in the pure, mathematical, expression of Neodarwinian theory found in population genetics, mutation is significantly downplayed, and evolution is defined as “changing gene frequencies.” Indeed I was criticised on BioLogos for failing to understand that most evolution occurs without mutations at all, macroevolution being only microevolution at a larger scale. Mutations serve only to top up the gene pool. Natural selection does everything that matters.
Yet here are more problems. For a start some of the most oft-quoted work on evolution recently is Lenski’s long experiment on E. coli, whose whole design limits the genetic variation to show how truly random mutation (not merely with regard to fitness) really does produce the goods of evolution, once acted on by natural selection.
The common ground here, then, is natural selection – that’s perhaps the key to understanding. But even in Darwin’s time, opponents pointed out that there was no evidence that races within species showed any measurable difference in fitness, if indeed one could ever define “fitness”. Some biologists seem to take it as axiomatic that natural selection has limited, or even zero, ability to increase fitness once one gets beyond the one-gene simplification of population genetics. The reasons are not hard to see. Humans have 20,000 protein-coding genes, each represented by different alleles that vary randomly. Numerically most reproductive failure is caused by accidental factors – a whole brood eaten by a predator, a harsh winter randomly diminishing food and so on. It is argued, more than plausibly, that in the real world, selective pressure acting on the whole genome cannot possibly select individual superior genes.
Indeed, start talking about adaptive survival, and the name of Kimura quickly comes up. Most variation comes from near-neutral mutations which are never subject to selection (those unimportant mutations have become central again!), and the main role of the environment is purifying selection, which is only a fancy way of saying that if mutations are bad enough, they kill you. Adaptive selection is still said to have a role, but how much, in practice, when it is swamped by the effects of thousands of neutral changes? If it doesn’t happen at all, how would you know? Others have even argued that natural selection is more a force for stasis than change.
The neutral theory seems to have gained ground over adaptive evolution, but abandons entirely Darwin’s idea of increasing fitness, and indeed of any mechanism to explain the “appearance of design” at the heart of Darwin’s argument. Indeed Eugene Koonin’s assessment of the state of play puts eukaryote evolution down primarily to neutral mutation swamping purifying selection to produce
a casualty ward of horrors the awesome organisational and functional complexity we see around us.
But that “illusion” of superb design is not Darwin’s perception only, because nature actually consists of nothing but examples of unfathomable functionality, whether at the level of molecular machines, unbelievably complex insect life-cycles or just the fascinating interactions of any large ecological system. When did you last hear David Attenborough say that narwhals manage surprisingly well in the ice considering how poorly adapted neutral mutation has rendered them? Who is welcoming global warming on the basis that lots of maladapted organisms may well find life easier once purifing selection can catch up with the backlog?
We haven’t yet even moved beyond the realm of microevolution. Kimura’s theory is really just a refinement (or demolition) of population genetics. Lenski’s work only scales up to speciation level if you dismiss the work showing that beneficial mutations rapidly become too rare to account for what Darwin took as his title, but failed to explain: the origin of the species (and genera, orders, classes and phyla).
Palaeontologists have, I think, finally persuaded a majority that the Darwinian model of gradualism really is a non-starter for speciation, but as saltation is still definitely not part of evolution (for reasons someone may be able to explain) we can say that the appearance of design occurs in the appearance of the blink of an eye through all that neutral mutation, shift in gene frequency and natural-selection-acting-on-20K-genes speeding up to rates never observed in the laboratory.
I won’t even talk about the fancy new mechanisms proposed by the Shapiros and Margulis of this world, because the mainstream either considers them heterodox or of peripheral importance. They’re still considered “evolution” by their proponents, though, maybe because they don’t actually completely contradict the conventional wisdom. But also, perhaps, because nobody’s ever defined what the theory of evolution actually is.
Are we any closer now to a definition of “basic evolution” to give us a starting point? If you say “random” you’ll be told it’s not random, but guiding natural selection. If you say “selection” you’ll have neutral mutation thrown at you. If you say “mutation” you’ll be told to go back to the Hardy-Weinberg Equation. If you say “stasis” you’ll be told about the genetic clock. Talk about the genetic clock, and Dawkins will tell you that “constant speedism” is a caricature of Darwinism.
British Museum palaeontologist Colin Patterson woke up one morning to the sickening realisation that after working on evolution for twenty years there wasn’t one thing he could say he knew about it. That’s unusual – most scientists are utterly sure they do know, but that you don’t. They may not be able to give you a satisfactory definition, or agree amongst themselves about what the theory consists of, and what it doesn’t. But they wake up knowing that it’s true for all that. This suggests to me that evolution is not so much a theory, as a brand. It can accommodate gradualism, punctualism, adaptationism, neutral-theory, trees-of-life, webs-of-life, random mutation and natural genetic engineering. It could happily make room for Lamarck if epigenetics became incontrovertible.
But it will still bear the trademark, “Darwin’s Theory of Evolution”, just so long as it sticks to one closely defined axiom: “God must not get a foot in the door.”