What *is* molecular anthropology?

[lagarvelho]

Just out of sheer curiosity, how would anybody go about defining "molecular anthropology"? The answer might seem obvious, but after reading a book called "What it Means to be 98% Chimpanzee", I'm not so sure.  Maybe somebody could help out here?
Anne G

[Alec Christensen]

I would define molecular anthropology as the study of anthropological research questions by biomolecular means. I suspect that most people who use the term basically mean "genetic anthropology," but using a finer level of resolution than traditional studies of genetic polymorphisms. Not that I've ever loved the term "genetic anthropology" either.

For purposes of Palanth, that is, when we are restricting ourselves to questions of human evolution broadly defined, molecular anthropology would mean the study of human evolutionary processes by means of 1) molecular genetic variation in living human and ape populations, and 2) what limited genetic information can be extracted from ancient remains.

Anybody got a better definition? And, on that subject, has anyone read the following article, just prepublished in PNAS:

Y genetic data support the Neolithic demic diffusion model

Lounès Chikhi *, Richard A. Nichols , Guido Barbujani , and Mark A. Beaumont ¶
*Department of Biology, University College London, Darwin Building, London WC1E 6BT, United Kingdom; School of Biological Sciences, Queen Mary, University of London, London E1 4NS, United Kingdom; Dipartimento di Biologia, Università di Ferrara, via L. Borsari 46, I-44100 Ferrara, Italy; and ¶School of Animal and Microbial Sciences, University of Reading, Whiteknights, P.O. Box 228, Reading RG6 6AJ, United Kingdom

Edited by Henry C. Harpending, University of Utah, Salt Lake City, UT, and approved June 11, 2002 (received for review March 18, 2002)

There still is no general agreement on the origins of the European gene pool, even though Europe has been more thoroughly investigated than any other continent. In particular, there is continuing controversy about the relative contributions of European Palaeolithic hunter-gatherers and of migrant Near Eastern Neolithic farmers, who brought agriculture to Europe. Here, we apply a statistical framework that we have developed to obtain direct estimates of the contribution of these two groups at the time they met. We analyze a large dataset of 22 binary markers from the non-recombining region of the Y chromosome (NRY), by using a genealogical likelihood-based approach. The results reveal a significantly larger genetic contribution from Neolithic farmers than did previous indirect approaches based on the distribution of haplotypes selected by using post hoc criteria. We detect a significant decrease in admixture across the entire range between the Near East and Western Europe. We also argue that local hunter-gatherers contributed less than 30% in the original settlements. This finding leads us to reject a predominantly cultural transmission of agriculture. Instead, we argue that the demic diffusion model introduced by Ammerman and Cavalli-Sforza [Ammerman, A. J. & Cavalli-Sforza, L. L. (1984) The Neolithic Transition and the Genetics of Populations in Europe (Princeton Univ. Press, Princeton)] captures the major features of this dramatic episode in European prehistory.

The abstract is available at http://www.pnas.org/cgi/content/abstract/162158799v1, but I won't have access to the full text until a) I go into the office or b) two issues subsequent to the one that this appears in are published.

I personally am becoming increasingly fond of the demic diffusion model, although I am still unsure of whether or not Indo-European languages spread along with agriculture.

Cheers,

Alec Christensen

[Greg]

I am reminded of a remark made by a very smart person, possibly Glynn Isaac (and somewhat tongue in cheek) that “Scientific Archaeology” is the use of machines to study things that we can’t see.

I agree that molecular anthropology is essentially, and broadly defined as the study of anthropological questions via analysis of DNA and DNA products (proteins etc.).  And, I’d love to see further discussion of the demic diffusion model.

[lagarvelho]

Greg and Alex:

Whether or not "less than 30 per cent of Europeans are descended from the original hunter-gatherers", and farming was spread along with people from the Middle East(I'm just going to mostly lurk and learn on this one), demic diffusion is actually a fairly common means for a population to spread.  That is, if I understand the term correctly.  E.g., little bits and pieces of populations break off from a larger one and spread out to "open" territories, set up camp, so to speak, and proceed --- and then as the population grows in that region, more little bits and pieces of populations break off and spread somewhere else.  And it's old, in evolutionary terms, since a fair number of animals have probably spread in much the same way.
Anne G

[Dale Hoogeveen]

In regard to the initial spread of agricultural practise in Europe.

It seems to me that 30% local male participation in an immigrant population is an extremely important marker of local participation.
Considering the very small scale of the populations involved (likely on the order of extended families or less), IMO a single model should produce a more homogenous resulting population.

Factoring in the extreme nature of human behavioural flexibility and the significant amount of retained local male genetics, I think that we must add at least one other model of some type and probably more than one to the mix.  30% retention of local male genetics suggests significant local exposure to and participation in imported agricultural practise and therefore likely significant local spread, without the necessity of transporting imported genetics.  Female transportion of agricultural practise would also be transparent to Y chromosome heredity.  Just to point out two possibilities.  Patrilocal mate exchange could produce a greater dominance of type in male ancestry, favoring, of course, the surviving life style for a third, and producing an automatic skewing of the ratios.  (Mate exchange networks would further complicate that factor.)  

It seems to me that the model must get hybridized and cannot be a single mode, and perhaps does not actually have a dominant form, although there certainly does seem to be a relatively common result, but that does not automatically indicate a single pathway or even a dominant one to get there.

Peace

Dutch

[John Goodrum]

Anne writes:

>Just out of sheer curiosity, how would anybody go about defining "molecular anthropology"?
>The answer might seem obvious, but after reading a book called "What it Means to be 98%
>Chimpanzee", I'm not so sure.  Maybe somebody could help out here?

I read Marks' book earlier this year but not much of it stuck with me, except that it was pretty
heavy on the politics.  Henry Harpending has a humorous review of it at:
http://harpend.dsl.xmission.com/Documents/    (marks.ajpa.review.pdf)

I've been reading the Klein and Takahata book, "Where Do We Come From? - The Molecular
Evidence for Human Descent" this past week - I have no self-discipline so I started with the
last three chapters which cover human evolution - and it's been hard to put down.  At least
to an interested layman like myself, it seems to be a really excellent presentation of what
we've learned from genetics so far, well worth the $50.

John

[lagarvelho]

John:

<<I read Marks' book earlier this year but not much of it stuck with me, except that it was pretty
heavy on the politics.  Henry Harpending has a humorous review of it at:
http://harpend.dsl.xmission.com/Documents/    (marks.ajpa.review.pdf)>>

Yes, I suppose you could say it's kind of "heavy on the politics", depending on how you define "politics". My "take" on this is that it's "heavy on the politics" because Marks is concerned(and I think rightly so)that some of the interpretations of some of these genetic findings can be and are being misused by certain people.  This should be cause for concern.  He *does* write in an extremely humorous way,  however, and I think it's part of a beginning of a much-needed correction to the idea that "nature trumps nurture", which is an idea that has gotten increasingly popular in the past few years.  Ideas like these often have political consequences, which, I hasten to add, are outside the normal boundaries of a group like this, so I won't go any farther than that at this time.  

[Jacques Cinq-Mars]

I hasten to add, are outside the normal boundaries of a group like this, so I won't go any farther than that at this time.  
Anne G

Yes, you are certainly right about this. In my experience, P-discussions have a tendency, most of the time, to wreck havoc, very rapidly, in otherwise very sensible threads. So, unless they are somehow kept palaeoanthropologically relevant, instead of being, as they frequently are, just reflections of issues that are essentially of concern to American society in general -- after all we are trying to keep the Forum as internationally palatable as possible --they should be avoided.

And the best way to do this, is to not even bring up the P-word.

Jacques Cinq-Mars

[lagarvelho]

Jacques:

<<Yes, you are certainly right about this. In my experience, P-discussions have a tendency, most of the time, to wreck havoc, very rapidly, in otherwise very sensible threads. So, unless they are somehow kept palaeoanthropologically relevant, instead of being, as they frequently are, just reflections of issues that are essentially of concern to American society in general -- after all we are trying to keep the Forum as internationally palatable as possible --they should be avoided.>>

Don't worry.  I won't.  Can't guarantee that some idiot won't wander onto here and try something, though(and being a forthright and opinionated person, I have a hard time not taking such bait, but I will do my best).  But no such word will be uttered by *me*.
Anne G

[Jois]

I am reminded of a remark made by a very smart person, possibly Glynn Isaac (and somewhat tongue in cheek) that &#8220;Scientific Archaeology&#8221; is the use of machines to study things that we can&#8217;t see.

I agree that molecular anthropology is essentially, and broadly defined as the study of anthropological questions via analysis of DNA and DNA products (proteins etc.).  And, I&#8217;d love to see further discussion of the demic diffusion model.

How is a program for molecular anthropologists set up? Would the students have (essentially) a double major?  Need a M.S.degree?
Maybe not gain an extensive background in linguistics, social anthropology? Seems like something's gotta give.

Jois

[Greg]

Regarding setting up a program:

At the graduate level, I don't think it is ever realistic to have a student get more than an exposure to the "four" (our however many) fields.  There was a time when it was possible for one person to read all the high points of literature in all the fields and still find time to do their own research, but those days are gone.  

Our program (at UMN) is now very individualized.  A student who studies any specialty (molecular anthropology, taphonomy, lithics, etc.) gets breadth training in accordance with what they may be missing from earlier work (BA, MA, etc.) and intensive training in whatever areas are necessary.  This means that certain things are hard to do ... such as a baseline experience of all students going through the same exact class or all students having read almost exactly the same set of classics, etc.

We do not sacrifice exposure to a wide range of topics, and the students are very much getting trained as anthropologists.  The point of an individualized program is to train studetns as anthropologist and area/method specialists at the same time.  No non-individualized program could ever be optimized to do this.