To “Why, exactly, should we believe that humans are descended from simpler forms of life?”, Mark Frank responds,
This is really very simple. Either:
1. We descended from a simpler form of life.
2. We descended from an equally complicated form of life which has left no trace.
3. We didn’t descend from any form of life but somehow sprang into existence (as adults I guess as human babies can’t survive by themselves).
Be honest – which seems the most plausible?
Actually, it is even simpler than Mark Frank makes out. Nothing is at issue if I just decline to offer an opinion.
His 1. would seem plausible except for the people shouting that we are 98 percent chimpanzee. And they’re the strongest supporters of common descent. They want it rammed down everyone’s throat from kindergarten to the retirement home.
Yet not only is their claim implausible on its face (anyone can tell the difference between a human and a chimpanzee), it is unsatisfactory. It leaves unaccounted for everything of which we would like an account.
His 2. is hardly implausible. It would be a familiar situation to any adopted child who can’t trace birth parents. As an account, is it unsatisfactory principally because it amounts to saying that there is no information available? That might be true, but I don’t know that it is.
His 3. is really not much different from 2., in that no further information about origins is likely to be available.
So the actual choice, assuming Frank’s list is exhaustive, is between an account offered by people whose judgement can be seriously questioned and accounts that point to the futility of seeking further information.
It’s a good thing Thomas Huxley coined the term agnostic (“it is wrong for a man to say he is certain of the objective truth of any proposition unless he can produce evidence which logically justifies that certainty”). That just about characterizes what I consider the wisest position just now on common descent.
See also: What can we responsibly believe about human evolution?
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