The Humble Platypus

Does the platypus provide evidence for the theory of evolution?

“Now, more than 200 years later, a team of scientists has determined the platypus's entire genetic code. And right down to its DNA, it turns out, the animal continues to strain credulity, bearing genetic modules that are in turn mammalian, reptilian and avian.

There are genes for egg laying -- evidence of its reptilian roots. Genes for making milk, which the platypus does in mammalian style despite not having nipples. Genes for making snake venom, which the animal stores in its legs.”

I suppose it is a great feat of science to determine an animal’s entire genetic code, but I note that in this case at least, this feat does not tell us a whole lot more about the platypus than we already could know by simply looking at it: it has features that we normally associate with mammals, reptiles, and birds.

The idea that this accomplishment provides evidence for the theory of evolution, however, is simply not true. It is not only bad science, it is bad philosophy. To see this, consider the reasoning that you would have to use to reach this conclusion.

1. A platypus shares a trait with reptiles, insofar as it lays eggs.
2. Animals that share traits with other lower forms of animals are probably descended from them.
3. Therefore, a platypus is probably descended from reptiles.

This reasoning contains what is called in philosophy the fallacy of begging the question—that is, assuming the conclusion in the reasoning that you use to reach the conclusion.

It does this by assuming that common traits are probably an indication of evolution, which is the very thing that we are trying to prove. You cannot simply assume this and reason to the fact of evolution, you need to prove it.

In fact, from the point of view of reason, the sharing of common traits could just as easily be used as a proof that the platypus and mammals are both created by God:

1. A platypus shares a trait with reptiles, insofar as it lays eggs.
2. Animals that share traits with other kinds of animals probably share a common creator.
3. Therefore, the same Being—God—probably created both the platypus and mammals.

This reasoning also begs the question, but no more so than the reasoning that leads to the conclusion of evolution. From the point of view of reason, there is no reason to accept either conclusion and doing so would just be a matter of preference.

A further observation: even disregarding this fallacy, this kind of reasoning can only lead to probabilities and not the kind of certainties that one normally associates with science.