Why Do Humans Have Thumbs and Not Fins?Biology Paleontology Science Videos STEM Education 

Why Do Humans Have Thumbs and Not Fins?


Did you know we can trace the evolution of our hands, and thumbs, back to a 375 million-year-old fish called Tiktaalik? Watch this video with paleontologist and geneticist Dr. Neil Shubin to learn what a fish and a little blue hedgehog can teach us about the evolution of thumbs. This is a video from Dr. Joe Hanson’s It’s Okay To Be Smart series.



Tiktaalik is a 375 years-old fish with fins. When we look under its fin rays and take off the scales, what we find are versions of our upper arm, elbow, forearm, and wrist. And then we can trace that all the way up from fish to land-living animals. By studying those ancient bones, researchers discovered that the arms that carried that fish out of the water aren’t that different from ours.

Genes are being turned on and off in different parts of your developing hand in different ways. When a signal is produced in that little patch of tissue that migrates across the developing finger bud, the cells respond to it and develop different fingers.

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