Evolution is a fact, right?
(How to discuss evolution with knowlegable people - like your biology teacher)
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Creationists often make the mistake of thinking that there is little substantial evidence for the theory of evolution. We ought to remember that the theory would not be so widely held if the evidence were not substantial and persuasive. But is that evidence conclusive, so that to deny evolution puts you in the same league as a member of the Flat Earth Society?
Most biologists, people who really know what they are talking about, would say a hearty ‘Yes!’ How can you argue with that?
One approach is exemplified by Jonathan Sarfati’s article “15 Ways to Refute Materialistic Bigotry” (www.answersingenesis.org), on the Answers in Genesis website. This was written in response to an item in Scientific American called “15 Answers to Creationist Nonsense” (www.sciam.com). Both articles are entertaining and informative, though the titles betray the bad-tempered tone of the discussion! This kind of antagonism is not usually fruitful, and we need to find a better way of conducting debate. The apostle Peter advised us to discuss with ‘gentleness and respect’ (1 Peter 3:15-16) good advice if you are looking for a calmer discussion. So here is a different approach; just ask a few hard questions and keep on asking them until you get good answers.
(Brief digression - I have all sorts of problems with the Answers in Genesis aproach to the Bible and to evolution, I will get an article written on this sometime soon)
Question one - What is the quality of the evidence for one species evolving into another? (The word ‘quality’ is important here – insist on getting good stuff!) A knowledgeable person will touch on fossils, comparative morphology, genetics, observed examples of natural selection and geographical distribution of species. None of these are conclusive in themselves, but taken together they form a powerful case – to most biologists it is clear that living forms have changed over time and that this must have given rise to new species.
Now, it is possible to object that a lot of the evidence is indirect and some relies on deductions and reconstructions of what might have happened. Yet it is important not to overplay this. It is not good enough to say, “No one has seen a species evolve so it is unscientific to say it happened”. No one has ever seen electromagnetic radiation, but an intimate knowledge of how it works gives us things like mobile ‘phones and personal computers. The evidence for species evolving from other species is not bad, actually; and quibbling about this is a bad ditch to die in. But there is a second question coming up.
Question two – What is the quality of the evidence for the evolution of new groups of organisms? For example, how can it be shown that birds evolved from reptiles? If it is hard to demonstrate that one species has evolved from another, very similar, organism it is much harder to demonstrate how a completely new group of organisms has arisen. Scientists are keen to protest that it has happened, and try to model how it happened. But they fail to demonstrate how it has happened. In John Rennie’s article, ’15 Answers to Creationist Nonsense’ his answer to this question is very instructive:
‘In the model called allopatry, developed by Ernst Mayr of Harvard University, if a population of organisms were separated from the rest of it’s species by geographical boundaries, it might be subjected to different selective pressures. Changes would accumulate in the isolated population. If those changes became so significant that the splinter group could not or routinely would not breed with the original stock, then the splinter group would be reproductively isolated and on it’s way to becoming a new species.’
John Rennie op. cit.
I am sorry that this passage is not a killer quote… but that is the point… this is the best he can do, and he is the editor in chief of Scientific American. Bear in mind too that Rennie is not discussing reptiles into birds here, just one species into another closely related species. So what is the quality of the evidence for the evolution of new groups of organisms? To be sure, the actual evidence is skimpy and it’s value has been overstated.
Question three - What is the quality of the evidence for the origin of life from non-living material? John Rennie, once more, is very helpful on this:
‘Creationists sometimes try to invalidate all of evolution by pointing to science’s current inability to explain the origin of life. But even if life on earth turned out to have a nonevolutionary origin (for instance, if aliens introduced the first cells billions of years ago), evolution since then would be robustly confirmed by countless microevolutionary and macroevolutionary studies.’
John Rennie op. cit.
Darwin wrote The Origin of Species in 1859. After almost 150 years science is still unable, according to Rennie, to explain the origin of life. This is a substantial weakness if your entire world-view depends on the evolution of life from non-organic material, isn’t it? What is the quality of the evidence for the origin of life from non-living material? It is pretty lousy, actually.
What is the quality of the evidence for the origin of the inorganic universe from nothing? Until the middle of the last century Physicists thought that the universe had no beginning, it had always existed and would always exist (the Steady State theory). In this view, the origin of the universe was not relevant because it had no beginning.
This view has almost disappeared in the light of the powerful evidence indicating that the universe began with an immense explosion (the Big Bang theory). For a long time, some physicists held out against the idea of a universe with a beginning because they saw it could lead directly to a kind of belief in God. They fought long and hard but finally had to concede that the universe had originated with the big bang. It had a beginning.
Who pushed the button, I wonder?
Conclusion
When we fight about the details of speciation and the evidence for evolution we can get bogged down in a bad tempered exchange about little things – instead try to concentrate on the big stuff – what evolution cannot adequately explain. Evolution is a good theory about the origin of species, less capable of explaining the origin of widely different groups of organisms, but a lousy explanation of the origin of life.
Your friends who argue that it is a fact are over-stating the case. When they disagree with this, don’t argue; just ask them for good quality evidence!