Sometime late last week, a story started circulating around various science news feeds, that went something like this: "Neandertals had sex with humans". The source of these headlines(and news stories with lots of speculation) was Svante Pääbo, a paleogenetics specialist at the Max Planck Institute in Leipzig, Germany He has done a lot of work on woolly mammoth genomes(he was one of the first to extract and sequence the woolly mammoth genome), and, more germane to this discussion, Neandertals. It seems that Pääbo is kind of hinting around that he's going to publish some bombshell about Neandertal(and "modern" human) mating habits in the paleolithic era.
In the meanwhile, however, several news outlets have glommed onto this story, with various, shall we say, viewpoints. One of the (slightly) more "sober" of these -- at least it does quote Pääbo and some others at some length -- come from the Times Online, and is, I think, fairly sensible, in view of the fact that the actual scientific paper hasn't come out yet. No doubt Svante Pääbo will speak to the press at length, when he is finished sequencing the Neandertal genome. To be fair, his team has sequenced Neandertal mitochondrial DNA, and has come up with a bunch of differences in sequence, though the vast majority of "our" and "their" genome is identical! And, to Pääbo's credit, what he says, in the above mentioned video, and in print, is, perhaps deliberately, inconclusive.
However, this hasn't stopped some people from "getting wild". Chris Stringer, a paleoanthropologist who has long studied Neandertals, seems to think that "if" they "had sex", they must have been like horses and donkeys, that classic example from Biology 101 showing that species are defined as separate(more or less), when they cannot mate and produce fertile offspring. Or at least that's what the above-mentioned Times Online article seems to imply. It should be noted here that I have a lot of respect for Dr. Stringer. He has worked on Neandertals for a long time, and has garnered a good deal of respect in many quarters for this work, which is careful, but which, in my opinion, may be influenced by whatever biases he has acquired over a lifetime of work. And when it comes to Neandertals, there are plenty of biases at work, and always have been, practically from the minute of the first "official" discovery back in 1856. Just to remind everybody, this was three years before Charles Darwin announced his theory of evolution. People then had no idea what human evolution might have been like, and Neandertals were fortunate or unfortunate, to be the first "nonmodern" human type ever discovered. About all I can say to Dr. Stringer is, I would love to show him around various bodies of water in the Seattle area, give him a bird identification field guide, and then ask him what kind of gull he sees walking around the shores of Green Lake or Lake Washington, or the Ballard Locks, or. . . . What he might not realize is, the gull population around here is a "hybrid" one: they are a mixture of "Western" gulls(Larus occidentalis) and "Glaucous winged" gulls(Larus glaucescens). The Puget Sound area is the southern end of the "glaucous winged" gull range, and "Western" gulls have been flying, and settling, north for some time. They meet here. And mate. And produce apparently fertile offspring. The gulls obviously don't care about such minor details as what species they are supposed to belong to. Their only criterion for being a suitable mate is (a) is the potential mate of the opposite sex and (b) do they have pink feet? Both "glaucous winged" and "Western" gulls have pink feet. To complicate things even further, in western Alaska, "glaucous winged" gulls mate with "herring" gulls(Larus argentatus), and yes, they, too, produce fertile offspring. And they both have pink feet. I can imagine the gull gene pool . It kind of boggles the mind. The reason this is possible is, that these gull populations were separated in various places during the last glacial advance, and because of the separations, these gull populations all diverged, genetically speaking -- somewhat. But not enough, apparently, to create anything like a reproductive barrier. Among "generalistic" species, and gulls are pretty darn generalistic, if you've ever seen one in action(they'll eat just about anything), this is not as uncommon an occurrence as one might think. And so, the gulls around here are called "Puget Sound hybrids", because they may look like "glaucous winged" or "Western" gulls, but they have cheerfully been exchanging genes for an apparently not inconsiderable time. After all, there are no glaciers to impede their attempts to mate, at least not at the moment. Besides, evolution is a decidedly messy and complicated business. That includes the human variety.
But if Dr. Stringer still wasn't convinced that such things are possible, I would love to see the expression on his face when, on my theoretical journey, we stopped off at Isle Royale, Michigan. As many people are aware, Isle Royale National Park is world-famous, and its wolves have been studied intensively and extensively for some 50 years now. Except there's one thing about them: These wolves aren't entirely wolf. They have mitochondrial DNA sequences characteristic of coyote populations. And there certainly are coyote populations nearby, though not on Isle Royale itself. But then, the "wolves" of Isle Royale trotted themselves across Lake Superior and onto Isle Royale during an especially cold winter, when that part of Lake Superior froze over,it is thought, in about 1948. And they've been there ever since. They came from nearby Ontario, Canada, where there are also numerous coyotes. . . .and at the time, people thought nothing of trying to shoot every wolf they could shoot. The wolves were probably safer on Isle Royale at the time; there certainly weren't very many of them, and coyotes seem to be somewhat more adept at not getting themselves shot. But that's another story. I should add that, to someone just looking at them, the wolves of Isle Royale look like wolves; they're big, furry, mostly gray, and they regularly hunt moose, when the hunting is good. They don't exactly look like coyotes, other than the general resemblance all members of the genus Canis(dogs, wolves, coyotes, jackals, "red wolves") have to one another. But they still have these "coyote genes".
And if Dr. Strnger still wasn't convinced, I'd take him somewhere in New England, to pay a visit to the "coyotes" there. The New England coyotes now appear to have some "wolf" genes -- they are somewhat larger, darker, and furrier than their western counterparts. This is partly due to the fact that it generally gets colder in the winter in, say Massachusetts, than it does in the Puget Sound region; coyotes around here don't need to grow a lot of fur in the wintertime, though they do grow some.
The thing here is, at least from what I've gleaned in my readings(and I* keep on reading this stuff as it comes out), the members of the genus Homo, which include both Neandertals and "moderns", had, long before there were any Neandertals, evolved to be "generalistic". That is, they were, and are, capable of, and not too fussy about, eating just about anything, and adjusting t6o whatever environment they found, and find themselves in. True, the origin of both "ancient" and "modern" humans is somewhere in Africa, but people wander, and adapt. And, 300, 200, 04 50,000 years ago, there were small populations scattered all over the Old World. Their numbers generally weren't very big, and in many cases, their populations tended to be local and somewhat scattered. But they were there, and they would follow game, in cold climates and in warm ones. They would sometimes meet each other(as Neandertals and "moderns" may have in Israel and elsewhere in the Middle East, but this has always been true for that region). And, I suspect, some of these little groups may have exchanged genes.
It's another question entirely, whether these small populations of whatever kind, were able to pass their "paleolithic" genes to later populations that began to take up farming, and because they had more "reliable" sources of food, were probably more numerous. As it was, Neandertal populations appear to have been quite small and scattered; more so than "modern" ones, who kept coming from Africa anyway. And later Paleolithic "modern" humans(whether or not they had any "Neandertal" genes), were smaller than later "Neolithic"(farming) ones; their genes may well have simply gotten swamped out of existence, just as (in my opinion)Neandertal genes likely were.
Which brings me back to Svante Pääbo and his possible "bombshell". He is probably right that Neandertals and "modern" humans "mixed it up" on occasion when their populations met, in any number of ways and for any number of reasons. And I'm guessing, since both Neandertals and "moderns" had evolved to be "generalistic", that, like the gulls, and coyotes x wolves, were perfectly capable of producing fertile offspring. Whether they had much opportunity to do this is no doubt another story. And, absent a time machine, there is no way of telling if this was the case. But I think the capability was there, if for no other reason than both groups seem to have had broadly similar strategies for accomplishing tasks like hunting or making tools or setting up dwelling places.
This is difficult, nowadays, for a lot of people to believe, because most of them have been told, over and over and over again(if they pay any attention to these things) that Neandertals were fundamentally "different" in some basic way. Well, as far as I, and a number of other people can tell, they just weren't -- at least not in a behavioral sense. Just like wolves and coyotes, or the "hybrid gulls" of Puget Sound. And that belief, based on what evidence I've read in learned papers, gentle reader, is partly why I ended up writing a Great Medieval Science Fiction Masterpiece With Neandertals.