From Jenny Morber at National Geographic, a look at five examples of “regressive evolution,” including:
Now, in a shock to biologists, a close look at a 300-million-year-old hagfish fossil reveals that the [now blind] animals once had working eyes—and evolution took them away.
The discovery challenges the way scientists think about the origins of the eye. Living hagfish are remarkably unchanged from their ancient counterparts, and so scientists long thought that modern, sightless hagfish eyes represented a kind of intermediate step between the primitive light-sensing spots in many invertebrates and the camera-like eyes of vertebrates, including humans. More.
Not so, apparently. Stranger still is the fact that selective breeding of different populations of blind cave fish enabled sight to be restored in some offspring because the losses involved different genes. And, as Morber reports, researchers have tweaked chicken embryos to the point of giving them the beginnings of teeth.
Morber closes, “No matter why birds lost their teeth, several lines of research suggest that it did not take much genetic change to make the switch.” No, but in this case, reversing it required purposeful action resulting from knowledge and intelligence.
The loss process is also called ”devolution” and is easier to spot in parasites, where it is much more rampant.
See also: Devolution: Getting back to the simple life
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