New Discoveries About Human History

Logic Bomb writes "The New York Times has an extensive article (free reg req, of course) about how scientists are finally able to take advantage of genetic data to really trace human history. Tracing mutations in genes is allowing anthropologists to map humanity's migrations going back 50,000 years...far longer than the 3,500 or so that we've been keeping historical records for. It's quite an interesting read."

Comments

Paper from Science

[Mad Hughagi]

Here's the actual paper found in the Nov. 10th issue of Science that prompted the media run-offs.

Re:Paper from Science

[tesserae]

I don't know about Colin Renfew's book (Archaeology and Language; the Puzzle of Indo-European Origin [Jonathan Cape, London, 1987] is Citation #3, from the Science paper) and its acceptance by linguists, but Renfew's a well-accepted researcher in the field. A few years back, he received the Fyssen Foundation's International Prize, which is awarded annually to a scientist who has conducted distinguished research in ethology, human paleontology, anthropology, psychology, epistemology, logic, or the neurosciences. It's a prestigious award, and the list of recipients reads like a Who's Who in those fields.

Maybe it's a problem to the linguists that Renfew's an anthropologist?

(FWIW, I very nearly switched my major from physics to anthropology... if I'd had the inclination, I could have taken a couple more classes and had a double major. It still interests me, and I also subscribe to both Science and Nature so I can follow developments in the field. I definitely don't share your opinion of Renfew.)

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Re:Paper from Science

[Black Parrot]

FWIW, the paper by Colin Renfew that the authors cite (reference #3) is almost universally rejected, nay, despised, among people with the faintest clue about the prehistory and interrelationship of the various languages in the Indo-European family.

Re:Paper from Science

[Black Parrot]

> Maybe it's a problem to the linguists that Renfew's an anthropologist?

Interesting question.

First, let me point out that I'm not an authority on this. (I am at best an advanced amateur on the linguistic side.) My comment merely stems from observation of what actual authorities say, apparently very nearly unanimously.

Second, though I know much more about linguistics than I do about archaeology/anthropology, I am also a "fan" of those fields, and would be extremely reluctant to make any kind of blanket assumption that linguistic evidence trumps their evidence, or vice versa.

Third, I was vaguely aware that Renfrew was renowned in his field, and so perhaps I should have said more about that than I did. Also, I remember reading about Renfrew's IE hypothesis in Scientific American shortly after he first published it, and at the time I found it both sensible and appealing. It's just that now that I know more about it, I find it impossible to reconcile with the linguistic evidence. (Or, more accurately, I find that others better informed than myself find the reconciliation impossible.)

For people interested in that particular debate, I would recommend Mallory's In Search of the Indo-Europeans. Mallory is an archaeologist. The book is one step removed from a popularizing account, in the same sense that Scientific American is a step removed from a popularizing account of science; if you are moderately intelligent, moderately well-read, moderately patient, and fairly interested in the subject matter, you should be able to master the book.

Mallory apparently wrote the book partly, or perhaps even primarily, as a response to the controversy stirred up by Renfrew. However, the book is not written as a polemic. IIRC he mentions Renfrew explicitly only a handful of times (though he consistently disagrees with him in those mentions).

One very likeable thing about Mallory is that he does not feel compelled to produce a Grand Unified Theory That Explains Everything. He simply surveys the evidence and does the best he can with it. Metaphorically speaking, he proves some interesting lemmata, but finds himself unable to combine them into a theorem. More on Mallory near the end of this post.

[The following is for the benefit of any lurkers; I don't want you to think I'm trying to lecture you on topics that you probably understand better than I do.]

There is an interesting tension between linguistics and archaeology. I do not think of it as animosity, because I honestly think workers in both disciplines would really like to be able to use each other's work as orthogonal evidence to support a good theory. (Notice the current article's citation of both archaeologists {Renfrew,Gimbutas} and lingiusts {Ruhlen}.)

Unfortunately, this collaboration does not always work in practice.

There is a very appealing, albeit very naive, temptation to assume that a population of humans can be associated with a culture (what archaeologists study) and a language (what linguists study) in a 1:1:1 fashion. However, this is not necessarily the case.

The disconnect between population and language can be illustrated easily by looking at who speaks English in the modern world. Any notion of "the English speakers" as a meaningful genetic designation goes right out the window, since you can find native speakers of English who have biological ancestors hailing from every corner of the world. (To put it bluntly, look at the correlation between skin color and speaking English. But any other designation of a population on the basis of speaking English is not going to be very informative either, beyond the fact that they all do speak English.)

The disconnect between population and culture was well illustrated by an archaeology professor I once had. About a generation ago there was a rapid replacement, throughout most of the industrial world, of beverage containers made from tin-plated iron, by beverage containers made from aluminum. Unfortunately for any naive theories, this cultural horizon was not associated with any sort of population replacement, invasion, intrusion, or even fresh contact with another culture. It was simply an in situ development. The difference is hard, perhaps impossible, to detect rigorously simply on the basis of archaeological analysis.

So regarding the naive 1:1:1 relationship, you cannot say with certainty that either half holds absolutely, let alone the whole thing. Any attempt to map archaeology onto language, or vice versa, is going to have to rely on a chain of inferences only as strong as its weakest link.

Now back to Mallory. He reports on a very nice archaeological analysis by Gimbutas (also cited in the Science article, and well regarded by historical linguists) that makes a plausible chain of inferences between the Kurgan culture of the steppes and the speakers of an early IE dialect, probably ancestral to the Indic, Iranian, Baltic, and Slavic sub-families of IE (represented respectively by modern Hindi, Farsi, Lithuanian, and Russian, plus many other languages both living and dead).

Some would like to derive the entire IE language/population/culture from that Kurgan culture, but Mallory balks at that. (And IMO with good reason.)

The problem arises when you step back and look at western Europe. There, you can make an equally plausible chain of inferences to derive the speakers of the language(s) ancestral to the Celtic family (Irish, Welsh, etc.) from the Hallstadt culture, and arguably even back to the Urnfield culture.

So far, so good. The problem arises because nobody, whether linguist or archaeologist, seems willing to derive the Hallstadt/Urnfield culture from the Kurgan, or vice versa. So to preserve a unified early IE culture, which would seem to be a well-justified desire in principle, you would have to derive both the western European and the steppe culture from a single earlier culture. I'm not aware of anyone who would even posit a suggestion, except perhaps Renfrew. (And I say "perhaps" because I'm not sure even he would derive the Kurgan culture from an Anatolian antecedent. No one else that I know of seems interested in doing so, and at any rate Renfrew's posited common ancestor would be so far back in time that it stretches belief that the languages of western Europe would have remained so transparently related to the languages of western Asia well into the historical period.)

Despite many efforts to pin down "the IE homeland" over the last couple of centuries, the problem seems to be beyond solution with the knowlege we currently possess. At any rate that's my take on it.

I don't pretend that the above in any way disproves Renfrew, because frankly, I don't even remember the details of his model. I do stand by my assertion that, so far as I have observed, historical linguists almost universally reject his model. However, as suggested by tesserae, it is not hard to imagine that archaeoligists would subscribe to Renfrew and universally reject conflicting claims from linguists (though Mallory does not seem to fit that pattern).

caveat lector: the the sake of brevity, I have included some gross simplifications in the "facts" above. If not already so far off topic, interesting and sometimes critical comments could be made about Gimbutas and Ruhlen as well. Also, as the saying goes, "Your spelling may vary."

Re:Paper from Science

[tesserae]

Excellent post! It's great to see posts based on understanding of the subject, rather than just speculation from afar (problems always look easier when they're in someone else's specialty, don't they?).

I agree that there's not necessarily animosity between linguists and anthropologists, any more than there's necessarily animosity between geneticists and anthropologists. It's just that the methodology and details of subject matter vary enough between the disciplines that each can't easily map their own descriptive language onto the other discipline, or the other's onto theirs. Despite this, they keep trying... often without realizing what the true issues are.

It's sad that the questions you've raised (along with many like them) may never be answered, because the "minority" languages which might provide insight into the problem are fast disappearing: the increasing homogeneity of humanity leads to loss of all the differences (not just linguistic, but also genetic and cultural) which could reveal the solutions. What's not been recorded at this point, might truly be lost forever.

In the end, we might be left with little but the genetic analyses, which can illuminate only a part of our history.

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Damn registration...

[spankfish]

I don't suppose there is a mirror of this around?

Both those sites need rego. That truly sucks.

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Re:Damn registration...

[daftgirl]

Here's the partners.nytimes link to the story.

Clarity

[karma_policeman]

Dr. Douglas Wallace of Emory University sez:
"The Y chromosome has a great future. But it is a very new technology."

Maybe he should rephrase that. ;)

What happened 50 000 years ago

[iktos]

The article guesses that language might have been something which changed around then.

There's another thing which makes us very different from all our predecessors: They apparently never travelled over water unless they could see land.

Another point in the article I'd like to comment is the part about the earliest populations remaining in Basque and Scandinavia. Well, Scandinavia was ice covered until a few thousand years ago, so if you're seeing more signs of immigrants from 45 000 years ago there than in other parts compared to those who arrived 10 000 years ago I wonder if you're not just seeing a random effect, since for practical purposes there wasn't any population there 10 000 years ago.

Re:What happened 50 000 years ago

[B'Trey]

There's another thing which makes us very different from all our predecessors: They apparently never travelled over water unless they could see land.

While this is generally true, there is ample evidence that it was at least occasionally untrue. The Viking's settlement on North America is just one example.

Re:What happened 50 000 years ago

[TA]

"Well, Scandinavia was ice covered until a few thousand years ago, so if you're seeing more signs of immigrants from 45 000 years ago there than in other parts compared to those who arrived 10 000 years ago I wonder if you're not just seeing a random effect, since for practical purposes there wasn't any population there 10 000 years ago."
It definitely was a population in Scandinavia 10 000 years ago, in the north of Norway there are lots of archeological remains from at 10 000 years ago. People were living near the sea. Sea levels were quite much lower back then, but the coastline wasn't entirely covered by ice 10 000 years ago. Those people are as far as we can see the ancestors of many of the people living in the area today.
TA

Re:What happened 50 000 years ago

[Jayman2]

Well they were believed not to sail where they could not see land, but similarities in technologies between the australian aboriginals and other tribes in mainland Asia have suggested that they may have migrated very early. Even though they could have been "Island-hopping" to some extent this still required long stretches of sailing with no sight of land.

Re:What happened 50 000 years ago

[spankfish]

Correct me if I am wrong, but apparently, 50k years ago, sea levels were much lower than they are now. Therefore, much of the Indonesian archipelago is reckoned to have been connected by land. The ancestors of the Australian Aboriginals could have walked there most, if not all, of the way from what's now Malaysia.

Perhaps other races at the time did not have the technology to survive crossing vast distances of ocean. People have always been curious, haven't they? Maybe they went off into the ocean and just died before they got anywhere, a lot of the time.

Speaking of ancient races, there must have been a hell of a lot of sea exploration going on before western "civilization" got big, I mean look at all those islands in the Pacific that were not only populated, but FOUND in the first place. Bloody amazing if you ask me. Like Easter Island. In the middle of nowhere. Covered in massive stone heads. Incredible.

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Re:What happened 50 000 years ago

[iktos]

The Vikings weren't our predecessors in a biological sense. I mean those at 50 000+ years ago.

Re:What happened 50 000 years ago

[iktos]

Perhaps other races at the time did not have the technology to survive crossing vast distances of ocean. People have always been curious, haven't they?

Of course you need technology and experience to find an island in middle of the ocean, but you don't need much just set out to see what's over the horizon and come back.

We're curious, yes; But perhaps those humans (or perhaps pre-humans) who didn't explore the whole world weren't, and maybe that's the crucial difference.

No human species differentiation

[StrawberryFrog]

> Do we have species differentiation going on within the homo sapiens clan?

Given the way that the 20th century has mixed together previously isolated branches of the human race, definitely no. We are becoming more homogenous, not less.

Side note re inbreeding.

[Black Parrot]

Notice that you have 2 biological parents, 4 biological grandparents, 8 biological great-grandparents, and so forth, for 2^N ancestors at the Nth preceding generation. This number grows exponentially.

Meanwhile, population has been growing geometrically (exponentially?) as well, but in the opposite direction in time.

So at some point, the number of your posited (great*)grandparents must exceed the human population of the earth at that time.

For example, take 30 generations ago, a nominal 25 years per generation, and assume no non-human input, then you can calculate that you needed about a billion (28*great)-grandparents a mere 750 years ago, when the world's human population was surely much less than one billion. Another ten generations back and you would have needed a trillion (38*great-grandparents), still a mere 1,000 years ago.

That's right, folks. We're all inbred like the veriest Ozark Hillbillies.

Humor aside, I wonder whether any biologists here can tell us something quantitative about the rate of the, erm, call it "biofeedback", in a modern human's genes, and how that rate compares to other species, such as chimps.

Re:Side note re inbreeding.

[spankfish]

This is an interesting point, but you seem to be forgetting that for the vast majority of human existence, parents have generally had more than one child. Usually at least two or three. Refactor that into the calculation, it ought to bring the numbers down significatly. Say for the 30 generation example, assuming only that each pair of parents produced 3 offspring. 3 children with two distinct parents. Let's call that 1 child with 2/3 of a distinct parent. Going back over time with the same rate compouding, you get the picture.

Although, yes, it's probably reasonable to assume that we are all related in some way. Although I wonder about couples who cannot have children - perhaps in some cases their DNA is just different enough to have a chance of not being able to create a human embryo.

Do we have species differentiation going on within the homo sapiens clan? We must, surely, or at least the very beginnings of it. It's ludicrous to think that we couldn't be evolving, after all, we're still shagging and mutating, and what else do you need for evolution to occur?

Also, you can't really leave the non-human element out of this. There is evidence around that homo sapiens and homo neanderthalis mated on numerous occasions.

Imagine the soap opera potential in that. (chuckle)

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Re:Side note re inbreeding -- Human Evolution.

[BMagneton]

1 child with 2/3 of a distinct parent.

You've got to be a bit careful when using these measures. The 'distinct parent' number seems more like it would be useful for thinking about how much population broadening goes on, and how much general inbreeding there is. But I can't see how it changes the likelihood that you have a particular set of (n x great)-grandparents in common. More reasurring generally for the inbreddedness, but no less creepy for thinking about specific examples.

Do we have species differentiation going on within the homo sapiens clan? We must, surely, or at least the very beginnings of it. It's ludicrous to think that we couldn't be evolving, after all, we're still shagging and mutating, and what else do you need for evolution to occur?

You need at least two more things that are assumed by most, but are actually pretty significant: evolutionary pressure (you don't breed) and a population to propogate the mutations. There's also a timescale issue, which says that groups need to be distinct and pressures felt over long enough of a timescale. For most serious mutations, this means at least a couple dozen generations worth. (Although this last comes with a caveat or two. See below)

I would argue that only very limited forms of evolution are going on in the human race right now. Mostly this seems to be due to technology.

For evolutionary pressure, we have removed the pressure due to all but the most serious afflictions. There's a bevy of disorders, such as hemophilia, that would have killed enough of the effected population (And yes, I know about dominant and non-dominance: the statistics over generations will still select away from the traits anyway, even if it doesn't show up in every individual) to provide an evolutionary pressure. We have completely relieved many of these pressures.

For the seperate population issue, we have technology again. There is so much interaction between seperate populations via modern transportation, that over the timescales of generations, I sincerely doubt that speciation could occur with humans on our present earth.

Now, the timescale issues become different for certain systems which themselves evolve at an accelerated rate. It also becomes different for selection pressures that occur almost entirely in one generation, and not statistically over many individuals. I would argue that the prime example of this is disease. The immune system has mechanisms built in to evolve over the course of an individual's lifetime, and differences of a single protein, expressed due to a single or a triplet of nucleotides, can make a huge difference.

Look at the African continent. The enormity of the HIV problem over there is staggering. But the selection process for children infected is fast enough to cut them off before they can have children, and the consequences are dire for every single individual. There must be a fantastic amount of evolution going on within that population.

Now, I'm not trying to make light of the problem, or suggest that it be treated as an experiment. It's a real problem, causing real human suffering, and we should try to alleviate it as soon as we can. But those are the instincts and imperatives of modern society, to alleviate suffering, which in most cases means taking off evolutionary pressure.

So yeah, the human race is evolving. But for the world as it currently exists, it's a different and more limited sort of evolution than the simple cases we are taught as classical evolutionary theory.

Also, you can't really leave the non-human element out of this. There is evidence around that homo sapiens and homo neanderthalis mated on numerous occasions.

Well, maybe. I've seen a couple debates go by on that one, and I don't consider myself well informed enough to make that call. Still, it doesn't change the calculus of ancestor number if there were a little extra diversity back there.

Imagine the soap opera potential in that. (chuckle)

Ever read Clan of the Cave Bear?

Not that great a book in my opinion, but it does get some mileage on exactly that premise.

BMagneton