Svante Pääbo and colleagues were the first to sequence the Neanderthal genome from fossils and compare the sequences to modern humans. According to the data shown here, did the two species interbreed when they overlapped in Europe? Explain.

Video transcript

Welcome back. Here's the next question. When Svante PAAbo and his colleagues sequenced the entire empty genome of Neanderthal, they found low genetic diversity in spite of having samples collected from a wide geographic area. On average, the empty DNA of neanderthals is one third as diverse as humans. What does this imply? Well it's important as we look at the question we're trying to answer. What does this imply the sport imply is important because it means it's not going to be a definite right answer. It's sort of asking what's the what's a reasonable inference? A reasonable conclusion we can draw from this. So with that in mind let's evaluate our answers, remembering that M. T. D. N. A. Is mitochondrial DNA is inherited only from the mother and therefore shows a slower rate of change or mutation. Since it's only being inherited from a single parent, you're not having a combination of DNA from two parents where you can have recombination and other things that lead to a more rapid rate of mutation. So M. T. D. N. A. Along with Y. D. N. A inherited only from the father is often used in ancestry studies because of that slow, predictable rate of change. So let's evaluate our answer choices. Choice A says neanderthals have a larger population than modern day humans. Um Well this would not be a conclusion. You would draw from the finding of low genetic diversity because a larger population would generally lead to greater genetic diversity. You've got lots of different individuals and they can mate with each other and combine their genes in many many different ways. So that would not be a conclusion, we would draw from this information, Choice B says neanderthals had a small population size. Well, this is definitely something we could imply from this. Low genetic diversity often implies a small population because the smaller population, the higher chance of inbreeding and that will increase the similarity among members of the population as inbreeding increases, leading to low genetic diversity. So, because we have this imply here, I'm not going to select it and move on yet just in case there's something that makes more sense further on, but I'm going to mark it as this is a pretty good candidate for our answer. Choice C. Says humans evolved from neanderthals. Well, that may or may not be the case, but our data that we're observing here does not lead to that conclusion. There's nothing about low genetic diversity very much lower than modern humans. That would lead you to conclude humans evolved from neanderthals. And finally, Choice D. Says neanderthals and humans are distantly related. Again, the information that there was a low genetic diversity in Neanderthal population doesn't lead you to any sort of conclusion about the relatedness of humans and neanderthals. So not our answer. So we've now eliminated the other answers. So we can go back to Choice B that we've marked and say that neanderthals had a small population size is a reasonable inference from the observation of low genetic diversity. See you in the next video.