Scientists on Reddit

Jerry Coyne

Evolutionary biologist, author of Why Evolution Is True

u/Jerry_Coyne ↗AMA only

How we know it's theirs

The 2015 r/science AMA, posted from this account

We retrieved 1 post and 40 comments from u/Jerry_Coyne, all from 2015, most often in r/science.

Best moment

A redditor wrote in r/science

On “Science AMA Series: I'm Jerry Coyne, evolutionary biologist and author of FAITH VERSUS FACT and WHY EVOLUTION IS TRUE. AMA!”

Hi Dr. Coyne, What is one of the most amazing thing you know as a evolutionary biologist that normal people might not?

u/Jerry_Coyne replied

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When I look at a squirrel, for instance, I see it through the eyes of natural selection, and to me that makes the experience immensely richer. Think of all that morphology and behavior that has evolved: the teeth, the fur, the tendency to run around the other side of the tree when they see you, their remarkable agility. And all the fantastic metabolism and biochemistry going on inside! All that results from replicating molecules sorting themselves out, with the better-replicating ones being the ones that survive.

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More moments

A redditor wrote in r/science

On “Science AMA Series: I'm Jerry Coyne, evolutionary biologist and author of FAITH VERSUS FACT and WHY EVOLUTION IS TRUE. AMA!”

I have a more technical question; At some point, one of our ancestors had two chromosomes fused, and the chimpanzees didn't. But didn't that render this ancestor genetically incompatible with the rest of his/her species? Or was the fused-chromosome ape, still able to reproduce…

u/Jerry_Coyne replied

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In fact, for chromosome fissions and fusions (the latter are more common, so I'll use that as an example), there's often no selective disadvantage to the new chromosome. When it's formed, it pairs up fine with its two-chromosome ancestor in the individual that experienced the fusion. If pairing is normal (as it often is, with each of the separated chromosomes lining up alongside the homologous arm of the fused chromosome), then meiosis--the formation of sperm and eggs--will proceed normally, and there will be no sterility. Given the vagaries of reproduction, the fused chromosome can come to be "fixed" (everyone has it) in a population, as it did in our ancestors.

The evidence that there's often no reproductive disadvantage to many fusions (or fissions) comes from both direct observation as well as the fact that some populations, such as mice in northern Italy, show individuals with all kinds of fused or "fissed" chromosomes, and when you bring them into the lab their fertility is normal.

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