270 million years ago, a shark pooped near the coast of Brazil. That poop was fossilized and preserved into a coprolite, which is the scientific term for fossilized poop. Scientists found that shark poop, and have been carefully studying it. We don't know exactly what they were looking for, but we do know what they found -- and it's gross.
The coelacanth is a fish that belongs to a family of fishes that were very common in the Devonian period of the Paleozoic Era, about 400 million years ago. So what? Well, the coelacanth is actually thriving along the African coast whereas all its relatives went extinct or evolved beyond recognition in the intervening hundreds of millions of years, making the coelacanth what some people call a "living fossil."
What's more, it appears that there are two distinct populations of the creatures, one living in the the Cormoros, a set of islands near Madagascar and the other living all up and down the African coast. At first, it was thought that the two populations must have split off from each other fairly recently, due to prevailing currents or some other factor. Researchers recently took a look at the mitochondrial genome of 23 of the fish and made an unexpected discovery: The two groups split, at the very least, hundreds of thousands of years ago.