The John Hawks weblog, which I think is one of the best science blogs around, and which I check daily, often has interesting stuff in it. Dr. Hawks is a biological anthropologist working at the University of Wisconsin, and he has a range of biological anthropology-related interests, including, of course, the very important subject of human evolution. He is also very interested in the subject of gene "introgression", and he spends a good deal of time writing about it. Genetic introgression , for those who have never heard of this term, is basically the crossing-over of genetic material from one closely-related species to another. Some species of organisms are well-known for interbreeding and producing perfectly fertile offspring. These species are very closely related; perhaps some of them are not "species" at all, but "subspecies", that is geographical variants of a very widespread, and adaptable larger species. Where I live, there are two species or subspecies of gulls(though field guides always list them as two species!): "Western" gulls(Larus occidentalis) and "glaucous winged" gulls(Larus glaucescens). They interbreed, and for all practical purposes, the gulls in the Puget Sound area are considered a hybrid group, no matter what they "look like". The thing both species(or subspecies, or whatever they are), have in common is -- pink feet! Another complication, though it doesn't happen around here, is that "glaucous winged" gulls will also perfectly happily mate with "herring" gulls(Larus argentatus) in Western Alaska, at least. "Herring" gulls also have pink feet. And all these gulls are, shall we say, opportunistic generalists in their habits, and are very widespread across any number of habitats. Which means that the "species" are known to exchange genes far and wide. There are "glaucous winged" gulls in the Queen Charlotte Islands that have "western" gull genes, though the northern limit of "western" gull range is-- you guessed it -- Puget Sound. And the southern limit of "glaucous winged" gull territory is Puget Sound and coastal Washington State.
I go into such detail about these apparent species "mixtures" because while this idea is fairly new and controversial, at least in some circles, it appears that these sorts of "mixings'" are more common in nature, at least under certain circumstances, than a lot of people like to suppose. And it's well-known among canid specialists(that is, people who study wolves, coyotes, jackals, etc), that all members of the genus Canis(wolves, coyotes, jackals, "red" wolves, etc). are "interfertile", that is, they can interbreed and produce fertile offspring. And it's also well-known that some 75% of all "wolves" around the Great Lakes area, have mitochondrial DNA sequences associated with coyotes. It appears that all the famous Isle Royale wolves, whose ups and downs have been closely monitored for some fifty years now, have "coyote genes", apparently inherited from some female coyote who mated with a male wolf in Ontario. Some of the descendants of this pairing are the wolves who now inhabit Isle Royale. It is also thought that these pairings are or were "one way", that is, female coyotes x male wolves. In a lot of cases, this may well be the case. But now the John Hawks weblog has comments about a paper, and links to another paper about wolf/coyote hybridization that appear to show that many of the "coyotes" in the northeastern quadrant of the US have "wolf" genes. I'm not surprised at this, not at all. Like the aforementioned gulls,both wolves and coyotes are opportunistic generalists. Both live in a variety of environments, and there are a number of places where their environments overlap. Coyotes are smaller in size and lighter in weight, and tend, as a rule to go after smaller prey than wolves, but otherwise, their habits are much the same: they howl, form packs, hunt together as a pack on occasion(though they do more "lone" hunting, for obvious reasons, than wolves), have the same gestation periods at the same times of year, depending on climate and latitude, dig dens and tend their young in pretty much the same way, etc., etc. Coyotes, to the surprise of many who don't know much about the general habits of the genus Canis, not only form packs, but, at least until wolves were reintroduced to Yellowstone, hunted larger prey like elk and deer there(not quite as efficiently, though; that was one reason why wolves were reintroduced). The "coywolves" of the northeastern US and southeastern Canada hunt deer, and are apparently good at it. At the present time, though, these canids are generally classified as coyotes. They intermediate in size between coyotes and wolves, have somewhat darker and furrier coats than coyotes in the western US. This is probably a partly climatic adaptation; winters in the northeastern US and southeastern Canada can get pretty cold. And yes, they chow down on the local deer. Nor are they "solitary", as the Hawks blog post implies other coyotes are. But then, as I said, wherever they are not disturbed, coyotes actually form packs, just like wolves, and defend their territories, just like wolves. They certainly do within the Seattle City limits; people have actually observed "several" coyotes acting together, and what they are observing is most likely a pack, just like wolves.
In any case, John Hawks is very interested in this, because he is very interested in genetic introgression. One might ask exactly what a biological anthropologist is doing,getting all excited about wolves, coyotes, and other wild canids, but there's method behind his apparent madness: things like this may well have happened in the course of human evolution. While I am not as excited about "introgression" of genes, per se, either in other organisms or in prehistoric humans of any kind, it may well be one mechanism which has made "us" what we are as a species, today. And I have a feeling that there were human "hybrid zones" from time to time during the course of prehistory, and yeah, Neandertals were part of this. Like wolves that nearly got wiped out by people shooting them, Neandertals had small, scattered populations that were vulnerable in various ways, and it's quite possible that some of them, from time to time, just got absorbed in early "modern" populations. No enough to obviously "show", but enough to have possibly made an impact on early "modern" populations. There isn't much evidence of this at the present, except possibly indirectly, but I suspect that with more sophisticated genetic techniques, such traces might later be found. Because, like wolves and coyotes, Neandertals and "moderns" had very, very similar coping strategies as I suggested in the previous post So, I really think it stands to reason that "we" have acted, in the past, not too differently from the way wolves and coyotes are acting in the northeastern Us and southern Canada, at least as far as genetic exchanges are concerned So thanks, Dr. Hawks, for providing me an excuse for another long, complex blog post!
Anne G
6 comments:
I live in Connecticut and I believe there are coydogs here (male coyote breeding with bitches), and like coywolves, they are fertile. Interestingly, a dog breeding with a female coyote is rarer and the offspring are classified as dogotes.
From what I've read, the neanderthal genome is very similar to that of modern man, so even if we're able to recover a complete neanderthal genome from remains, it isn't certain that we'll be able to find any distinguishing markers.
There's a whole new area of research called epigenetics, where scientists suggest that where the DNA is like the hardware of a computer, the epiDNA is the set of instructions that tells the hardware how to function. I just saw a program about this on one of the cable channels where some identical twins were studied where one of the twins had a very different outcome than the other twin. The scientists now think the reason is because something mutated in one of the twin's epiDNA. One example was where one girl had developed normally where the other had severe autism.
Fascinating stuff.
"it appears that these sorts of 'mixings' are more common in nature, at least under certain circumstances, than a lot of people like to suppose".
And I'm absolutely flabbergasted that everyone doesn't yet automatically assume that to be so. I remember you commenting at a site where I pointed out the phenomenon was very common with Anas ducks, and probably more widespread than just for that genus. But I see that these days all references to the hydidising ability of ducks claim it to be unusual, virtually confined to them. Anything to avoid facing up to the reality that species cannot be rigidly defined and that we are not totally separate from all that has gone before.
"And I have a feeling that there were human 'hybrid zones' from time to time during the course of prehistory, and yeah, Neandertals were part of this".
I agree totally. Yet if anyone has the audacity to mention this on any anthropology sites one gets a very heated response I'm thinking especially of Maju's site, leherensuge, where I've been suffering that problem. Perhaps you'd like to join in. It's in his blog about the Acheulian in Europe being older than previously thought.
Joan:
Like I said, all members of the genus Canis(and this includes domestic dogs, as well as wolves, coyotes, jackals, etc), can interbreed and produce fertile offspring. There have been experimental crossings of jackals x coyotes, that produce fertile offspring, for that matter. It wouldn't happen in the wild, since jackals live in Africa and Asia, and coyotes in the New World, but all members of this genus are closely related, and apparently relatively recently evolutionarily separated. Also many workers consider dogs a subspecies of wolf(Canis lupus familiaris, if you want to get techincal). Another point you brought up: I don't know all that much about genes and genetics, but I do know that (a) we are only just beginning to learn about the way a lot of DNA actually works, and (b) that environments -- which can include prenatal environments -- often have an effect on the way any particular gene is expressed and (c) a lot of genes may "work together" to produce a given characteristic in an organism. This makes the whole business of genetics very complicated and often subtle, in ways we yet know little about. But that's for a blog post, I guess, since some of these things are alluded to in my Great Medieval Science Fiction Masterpiece With Neandertals.
terryt:
This kind of hybridizing is common among Anas ducks, and I've seen examples of it, locally. And, as I said, it's common among Larus gulls, at least in the norhtern hemisphere. Many people are surprised, however, that it appears to be fairly common among certain mammals, and the genus Canis is one of them. My own belief, which I've expressed elsewhere, is that this was probably a fezature of the genus Homo, to, practically from the beginning. Again, this is something that is more or less implied in my book(s), but it's also one reason I consider them science fiction. I happen to be familiar, in a way, with Maju, though I'm not familiar with his website or blog or whatever it is. I'll be glad to check this out; he also contributes with some frequency to a blog called A Very Remote Period Inideed, which often has interesting "prehistoric" information. Oddly enough, there are "anthropological" people who are quite willing to consider the idea that Neandertals may have been part of the "mix" of at least some "modern" humans, even if that contribution was rather small, mainly due to the apparently small size of the Neandertal population. Be that as it may, I will check that Lehrensuge or leherensuge site out and see what I think.
Forgive my ignorance on this subject, but wasn't it once thought that neanderthals predated modern humans, but now there is some fossil evidence that shows both to have been around at the same time?
Joan:
YOur question is not "ignorant" at all. Neandertals, as a distinct type, seem to have existed in Eurasia from about 230,000 years ago to about 25,000 years ago or so. "Modern" humans arose in AFrica about 200,000 years ago. Both groups coincided or coexisted in Europe for about 20,000 years until Neandertals died out. And the ancestor of both groups existed in Africa maybe 600,000 years or maybe 300,000 years ago, when one group of them wandered north and presumably Neandertals were their descendants. So yes, this is a long way of saying that N's both preceded, in a way, and later coexisted with "modern" humans.
Anne G
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