Moles are very strange vertebrates

Extra fingers don’t come out of nowhere, even when they have adaptive value.

These days in the news, we have an interesting example of the way inherited sets of genes and body plans limit the options for adaptation: the mystery of the mole’s second thumb. Short version: some moles (genus Talpa) have a second « thumb » on their forelimbs, which is one more digit than other modern vertebrates – an oddity in need of explanation.

But biologist Christian Mitgutsch, from Zurich, and colleagues, have shown that, just like what happened in the famous case of the panda’s thumb, these mole species have evolved their supplementary digit out of a wrist bone, and the result is a large six-finger « hand » very efficient for digging, indeed.

It’s also one of many examples of something this recent post by P. Z. Myers on aliens touches on: the idea that a good look at how evolution works here on Earth should give pause to science-fiction writers, film-makers and designers… Before they imagine life on alien planets too much like ours, let them see how different adaptive solutions already crop up among the multitude of living forms on our home planet!

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