Too cool, part 49: Genetics and Human Evolution

Professor Ceiling Cat Emeritus (sometimes known as Dr. Jerry Coyne) over at Why Evolution Is True brought this one up, and normally I’d just send you over there for this, but it relates directly to a few posts that I’ve done in the past, so I went ahead an embedded it here.

Dr. Matthew Cobb is a Professor of Zoology at the University of Manchester, and through the Cardiff University School of Medicine, recently gave an online lecture regarding our human ancestry – what we presently know, what we don’t, and how quickly that changes. This was directly related to a post of mine from earlier this year, but far more detailed and comprehensive (of course,) and so it deserves a look if you have even the faintest interest in our ancestry, most especially the fairly recent (in paleontological terms,) African emigration aspect of it. It’s long, but very detailed and informative, so don’t let the length daunt you.

Genetics and Human Evolution

The ability to extract and sequence even just portions of DNA from found remains advanced our understanding of our ancestors hugely, and corrected a lot of misconceptions; remains can give us a time frame for when a given individual was present at some location, but genetics can give us a time frame for where they’d been before that, and who they were related to. The unfortunate thing is, DNA breaks down over time, more so within certain conditions, so the older the remains, the less we can obtain from them in this way. This may be only a matter of time, however; recall that portions of DNA have been extracted from Tyrannosaur bones, dating better than 60 million years older than any hominids, so chance, new finds, and improved techniques may open this up a lot further, perhaps within only a few years.

One thing that was not answered, however, was a question that I’d posed in my linked post above, to wit: given their ability to interbreed, wouldn’t Homo neanderthalensis and Homo sapiens actually be the same species, perhaps subspecies therein? And of course, the Denisovans, should they receive a species distinction themselves in the near future, would also be a subset, since we can easily find more than just traces of both Neanderthals and Denisovans in existing populations of humans today. Which, it needs to be said, is damned fascinating – should any study open up in my area to study such genetic traces, you can be sure I’ll be available to donate a genetic sample.

This video was responsible for introducing to me the Wallace Line, an imaginary line between Indonesian islands where the peculiar diversity of (mostly animal) species on either side, despite only a narrow separation, provoked Alfred Russel Wallace into creating a demarcation between the islands that prevented interbreeding; this was as continental drift was just a casual and highly-debated theory. Through his observation of the difference in species, Wallace stumbled onto evidence of both plate tectonics and the appearance of land bridges during the last ice age; the line named after him represents a strait, formed by the movement of the continental plates, that was not opened by the receding oceans during the ice age. Thus, species that populated the Indonesian and Australian land masses while they were joined, millions of years ago, got separated by the continental movement, then among a selection of the islands, rejoined during the ice age; among the islands that did not rejoin, the species continued to diverge as they evolved and now present distinctly different species.

[I have to note that the island of Flores in Indonesia, the home of Homo floresiensis, lies very close to the Wallace line, but since the hominids were capable of using boats and rafts by the time of that ice age, the land bridges were not necessarily a factor in hominid distribution.]

Anyway, if you haven’t already, grab a cup of whatever and sit down to watch the video – it’s fascinating, and well worth the time.