Tag: Agriculture

Population replacement in Neolithic Spain?

By Razib Khan | June 28, 2012 1:16 pm

There’s a new ancient DNA paper out which examines the maternal lineage and the autosomal background of two individuals extracted from a Spanish site dated to 7,000 years before the present. That is, during the European Mesolithic. In other words, these are the last wave of Iberian hunter-gatherers before agriculture. I have placed the PCA, with some informative labels, to illustrate the peculiarity of these samples. Here’s the abstract:

The genetic background of the European Mesolithic and the extent of population replacement during the Neolithic…is poorly understood, both due to the scarcity of human remains from that period…The mitochondria of both individuals are assigned to U5b2c1, a haplotype common among the small number of other previously studied Mesolithic individuals from Northern and Central Europe. This suggests a remarkable genetic uniformity and little phylogeographic structure over a large geographic area of the pre-Neolithic populations. Using Approximate Bayesian Computation, a model of genetic continuity from Mesolithic to Neolithic populations is poorly supported. Furthermore, analyses of 1.34% and 0.53% of their nuclear genomes, containing about 50,000 and 20,000 ancestry informative SNPs, respectively, show that these two Mesolithic individuals are not related to current populations from either the Iberian Peninsula or Southern Europe.

Here’s another PCA showing one individual on a more fine-grained representation of European populations:

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CATEGORIZED UNDER: Agriculture, Anthroplogy

Cain, Where is Abel thy brother?

By Razib Khan | May 30, 2012 4:06 am

Community differentiation and kinship among Europe’s first farmers (via Dienekes):

Community differentiation is a fundamental topic of the social sciences, and its prehistoric origins in Europe are typically assumed to lie among the complex, densely populated societies that developed millennia after their Neolithic predecessors. Here we present the earliest, statistically significant evidence for such differentiation among the first farmers of Neolithic Europe. By using strontium isotopic data from more than 300 early Neolithic human skeletons, we find significantly less variance in geographic signatures among males than we find among females, and less variance among burials with ground stone adzes than burials without such adzes. From this, in context with other available evidence, we infer differential land use in early Neolithic central Europe within a patrilocal kinship system.

I have already stated on this weblog that we will probably begin to discern a rather strong pattern soon of an interleaved genetic pattern across Eurasia and Africa where we can infer that populations in an expansionary demographic phase absorbed a host of other groups (more, or less). The exact details are to be worked out, but I’m moderately confident in this sort of pattern.

But these results align with another of my expectations, which I have rather stronger confidence in: that in parts of Eurasia the emergence of agriculture was correlated with the rise of powerful patrilineal kinship groups, which served as the cores of pre-historic polities. I no longer believe that demographic expansion due to cultural innovation can be separated from the likely political and social consequences of these changes. No, rather what we saw with the rise of agriculture was another powerful social innovation, collective units of large numbers of males who operated as one in the quest for land, women, and material self-enrichment. I do not mean to imply here that violence began with the Neolithic. Rather, I simply believe that the numbers enabled by agriculture allowed for specialization and scalability to fundamentally change the game. This was a high stakes “winner-take-all” bet.

As these males spread across the landscape, enabled by their culture (agriculture) and propagating their culture (language), in many cases their genetic-demographic signal may have been diluted across the wave of advance. But their cultural cohesion remained, and I believe that the patterns of Y chromsomal patterns evident across the modern world are an echo of their elimination of rivals. A tree of many Abels was pruned, as a few Cains proliferated like weeds.

CATEGORIZED UNDER: Uncategorized
MORE ABOUT: Agriculture

Facing the ocean

By Razib Khan | April 28, 2012 11:35 pm

Halford Mackinder’s conceptualization of the world


With the recent publication of the paper on the archaeogenetics of Neolithic Sweden I feel like we’re nearing a precipice. That precipice overlooks lands of great richness, filled with hope. It’s nothing to fear. It is in short a total re-ordering of our conception of the recent human past, at minimum. The “pots not people” paradigm arose in archaeology over the past few generations due to both scholarly and ideological factors. The scholarly ones being that intellectuals of the 19th and early 20th century made assumptions of extremely tight correspondence between material and cultural characteristics, and demographic dynamics, which seem to have been false. Therefore, the rise of an Anglo-Saxon England and the marginalization of Celtic Britain to the western fringes was not just a cultural reality, but also a fundamentally racial one, as Germans replaced Celts in totality. The ideological problem is that this particular framework was take as a given by the Nazis during World War II, lending a bad odor to the

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MORE ABOUT: Agriculture

The last days of Grendel

By Razib Khan | April 26, 2012 10:27 pm

A new paper in Science has just been published which in its broad outlines has been described in conference presentations. When examining the autosomal genetic variation of three individuals of the hunter-gatherer Pitted Ware Culture (PWC), and one of the agriculturalist Funnel Beaker Culture (TRB), the authors found that the two groups were sharply differentiated. The number of SNPs was on the order of 10,000 or so if I read the methods correctly. This is rather thin for studying contemporary within European population differences (~100,000 or more seems to be safe), in particular using hypothesis based clustering algorithms (it seems more manageable for PCA). But the findings are strong enough that I think we shouldn’t discount them. The most fascinating aspect of the results is that while the PWC seem to exhibit affinities with Northern and Northeastern Europeans, the TRB individual seems more similar to extant Southern Europeans!

Others have already commented extensively on the results. Keeping in mind the small sample sizes, limitation of comparisons, and the relatively thin marker set, I think the primary result we can take away from these findings is that old models of pure cultural and demographic diffusion are false. By this, I mean that prior debates which culminated in the early aughts on the “Paleolithic vs. Neolithic” contribution to the ancestry of modern Europeans were fundamentally premised on a demographic diffusion dynamic, whereby genes and ideas exhibited a continuous flow across a flat and featureless landscape. On the contrary, the basic outlines we are seeing here is that the human past exhibited spatial and temporal discontinuity. And why should this surprise us? There is no dialect continuum between Spanish and Chinese across Eurasia. Rather, broad language families are sharply differentiated from each other at zones of contact. Though there are theoretical reasons why the variation in genes should be more clinal, the reality remains that cultural parameters are going to shape the outlines of genetic variation, and those parameters are discontinuous.

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CATEGORIZED UNDER: Agriculture, Anthroplogy
MORE ABOUT: Agriculture, Europe

The agricultural "express train"

By Razib Khan | March 25, 2012 11:25 pm

One model for the spread of the agricultural way of life into Europe is of inexorable “demic diffusion” via a “wave of advance” of farming populations met by a land surplus. Conceptually and analytically it’s an elegant model. It’s also fundamentally methodologically individualistic, and so in keeping with the spirit of the age. There’s no need to appeal to higher order social structure or organization, farmers who have a specific cultural toolkit drive the dynamic through endogenous growth in pre-state cultures through the production of large families. This growth washes over the frontier of the advance, and the original locus of the demographic pulse synthesizes across a transect with the indigenous substrate. In the early aughts historical geneticists Bryan Sykes and L. L. Cavalli-Sforza sparred over whether demic diffusion was useful or not as a conceptual framework. Sykes reported chromosomal results which implied that 75 percent of the ancestry of Europeans derives from Pleistocene hunter-gatherers. Cavalli-Sforza’s riposte was that the original model did not specify a particular Paleolithic-Neolithic ratio, but rather characterized a dynamic which emphasized the necessity of migration as a mediator for cultural changes (the two perspectives are outlined in Seven Daughters of Eve and A Genetic and Cultural Odyssey).

 

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CATEGORIZED UNDER: Anthroplogy
MORE ABOUT: Agriculture

Human behavior over the ages

By Razib Khan | January 7, 2012 2:49 pm

Over at Scientific American Eric Michael Johnson has a very long post up, The Case of the Missing Polygamists. It is a re-post of something he already published at Psychology Today a few years ago. Though provisionally a review of Sex at Dawn, Johnson covers a lot of ground, and also has extensive quotations from Sarah Blaffer Hrdy.

I’m reflecting upon the post for a second time because it is very rich in ideas, and lays out may different general concepts and specific propositions. The bottom line from what I can gather is that Johnson agrees with those thinkers who believe that agriculture and the Neolithic revolution to a great extent reshaped social relations, and give us a skewed perception of “normal” human societies. I’m not going to rehash all of the points in the piece, but will focus on just a few which I think I can extend upon fruitfully.

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The words of the father

By Razib Khan | September 18, 2011 10:01 pm

Over at A Replicated Typo they are talking about a short paper in Science, Mother Tongue and Y Chromosomes. In it Peter Forster and Colin Renfrew observe that “A correlation is emerging that suggests language change in an already-populated region may require a minimum proportion of immigrant males, as reflected in Y-chromosome DNA types.” But there’s a catch: they don’t calculate a correlation in the paper. Rather, they’re making a descriptive verbal observation. This observation seems plausible on the face of it. In addition to the examples offered, one can add the Latin American case, where mestizo populations tend to have European Y chromosomal profiles and indigenous mtDNA.

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CATEGORIZED UNDER: Anthroplogy, Genetics, Human Genetics

A world full of children

By Razib Khan | July 31, 2011 12:07 am

The figure to the left is from a new paper in Science, When the World’s Population Took Off: The Springboard of the Neolithic Demographic Transition. It reports the findings from 133 cemeteries in the northern hemisphere in regards to the proportion of 5-19 year old individuals. When calibrated to period when agriculture was introduced into a specific region there seems to be a clear alignment in terms of a demographic transition toward a “youth bulge.” Why? A standard model of land surplus explains part of it surely. When farmers settle “virgin land” there is often a rapid “catch up” phase toward the Malthusian limit, the carrying capacity. Another possibility though is that sedentary populations did not need to space their offspring nearly as much as mobile hunter-gatherers. Whatever the details, the facts remain that the data do point to a shift in the age pyramid during this period. The author wonders as to the possible cultural implications of this. There is an a priori assumption that a young vs. old age profile in a society constrains its choices and channels its energies (e.g., think the “baby boom” generation in the USA). A final interesting point is that the authors note that today we are seeing the last gasp of this transition toward large numbers of children, as fertility drops toward replacement all across the world. That too may have some cultural consequences.

Here’s a podcast with the author. Link via Dienekes.

CATEGORIZED UNDER: Culture, Environment

"What if you're wrong" – haplogroup J

By Razib Khan | June 28, 2011 2:52 pm

Back when this sort of thing was cutting edge mtDNA haplogroup J was a pretty big deal. This was the haplogroup often associated with the demic diffusion of Middle Eastern farmers into Europe. This was the “Jasmine” clade in Seven Daughters of Eve. A new paper in PLoS ONE makes an audacious claim: that J is not a lineage which underwent recent demographic expansion, but rather one which has been subject to a specific set of evolutionary dynamics which have skewed the interpretations due to a false “molecular clock” assumption. By this assumption, I mean that mtDNA, which is passed down in an unbroken chain from mother to daughter, is by and large neutral to forces like natural selection and subject to a constant mutational rate which can serve as a calibration clock to the last common ancestor between two different lineages. Additionally, mtDNA has a high mutational rate, so it accumulates lots of variation to sample, and, it is copious, so easy to extract. What’s not to like?

First, the paper, Mutation Rate Switch inside Eurasian Mitochondrial Haplogroups: Impact of Selection and Consequences for Dating Settlement in Europe:

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Grain, disease, and innovation

By Razib Khan | June 18, 2011 2:04 am

I just finished reading a review of the literature since 1984 on the bioarchaeology of the transition to agriculture. Stature and robusticity during the agricultural transition: Evidence from the bioarchaeological record:

The population explosion that followed the Neolithic revolution was initially explained by improved health experiences for agriculturalists. However, empirical studies of societies shifting subsistence from foraging to primary food production have found evidence for deteriorating health from an increase in infectious and dental disease and a rise in nutritional deficiencies. In Paleopathology at the Origins of Agriculture (Cohen and Armelagos, 1984), this trend towards declining health was observed for 19 of 21 societies undergoing the agricultural transformation. The counterintuitive increase in nutritional diseases resulted from seasonal hunger, reliance on single crops deficient in essential nutrients, crop blights, social inequalities, and trade. In this study, we examined the evidence of stature reduction in studies since 1984 to evaluate if the trend towards decreased health after agricultural transitions remains. The trend towards a decrease in adult height and a general reduction of overall health during times of subsistence change remains valid, with the majority of studies finding stature to decline as the reliance on agriculture increased. The impact of agriculture, accompanied by increasing population density and a rise in infectious disease, was observed to decrease stature in populations from across the entire globe and regardless of the temporal period during which agriculture was adopted, including Europe, Africa, the Middle East, Asia, South America, and North America.

The abstract makes the conclusion more cut & dried than it is. It’s the result of aggregating their literature review and arriving at a net conclusion. Yes, on the balance agriculture did result in the deterioration of health. The old truism that farmers are a small and ill lot in comparison to hunter-gatherers seem to be correct in the generality. But the literature review also makes it clear that when it comes to something like stature there are often periodic reversals of the trend toward decrease in size. There may be spottiness of the record, and sampling error, but I began to wonder if we might not be seeing evidence of evolution & innovation in action!

Consider the checkered history of the potato in Ireland. In the 18th century the Irish shifted toward the potato faster than most other European peoples, and so entered into a phase of massive population expansion. On a per unit basis the potato was nutritional gold. Unfortunately we all know that the blight of the 19th century triggered a series of social and demographic catastrophes.

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CATEGORIZED UNDER: Agriculture, Anthroplogy, Culture

Why rice is so nice

By Razib Khan | June 7, 2011 5:49 am

The Pith: What makes rice nice in one varietal may not make it nice in another. Genetically that is….

Rice is edible and has high yields thanks to evolution. Specifically, the artificial selection processes which lead to domestication. The “genetically modified organisms” of yore! The details of this process have long been of interest to agricultural scientists because of possible implications for the production of the major crop which feeds the world. And just as much of Charles Darwin’s original insights derived from his detailed knowledge of breeding of domesticates in Victorian England, so evolutionary biologists can learn something about the general process through the repeated instantiations which occurred during domestication during the Neolithic era.

A new paper in PLoS ONE puts the spotlight on the domestication of rice, and specifically the connection between particular traits which are the hallmark of domestication and regions of the genome on chromosome 3. These are obviously two different domains, the study and analysis of the variety of traits across rice strains, and the patterns in the genome of an organism. But they are nicely spanned by classical genetic techniques such as linkage mapping which can adduce regions of the genome of possible interesting in controlling variations in the phenotype.

ResearchBlogging.orgIn this paper the authors used the guidelines of the older techniques to fix upon regions which might warrant further investigation, and then applied the new genomic techniques. Today we can now gain a more detailed sequence level picture of the genetic substrate which was only perceived at a remove in the past through abstractions such as the ‘genetic map.’ Levels and Patterns of Nucleotide Variation in Domestication QTL Regions on Rice Chromosome 3 Suggest Lineage-Specific Selection:

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Mediterranean men on the move

By Razib Khan | May 31, 2011 3:06 pm

ResearchBlogging.orgSeriously, sometimes history matches fiction a lot more than we’d have expected, or wished. In the early 2000s the Oxford geneticist Bryan Sykes observed a pattern of discordance between the spatial distribution of male mediated ancestry on the nonrecombinant Y chromosome (NRY) and female mediated ancestry in the mitochondrial DNA (mtDNA). To explains this he offered a somewhat sensationalist narrative to the press about possible repeated instances of male genocide against lineage groups who lost in conflicts.

Here is a portion of the book of Numbers in the Bible:

15 – And Moses said unto them, Have ye saved all the women alive?

16 – Behold, these caused the children of Israel, through the counsel of Balaam, to commit trespass against the LORD in the matter of Peor, and there was a plague among the congregation of the LORD.

17 – Now therefore kill every male among the little ones, and kill every woman that hath known man by lying with him.

18 – But all the women children, that have not known a man by lying with him, keep alive for yourselves.

Then there is the rape of the Sabine women. The ethnogenesis of the mestizo and mulatto populations of the New World in large part was the union between non-European women and European men. These are hard brutal myths and hard brutal facts. But do they reflect an essential aspect of the dynamics which have shaped our species’ past?

I’m not willing quite yet to add a confident weight upon this possibility, but this seems to be part at least part of the picture. You see a major disjunction on male and female lineages among South Asians for example. A new paper in PNAS adds weight to this possibility, albeit only incrementally. Ancient DNA reveals male diffusion through the Neolithic Mediterranean route:

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CATEGORIZED UNDER: Anthroplogy, Genetics, Genomics

Europeans as Middle Eastern farmers

By Razib Khan | April 19, 2011 2:48 pm

ResearchBlogging.orgThe Pith: Over the past 10,000 years a small coterie of farming populations expanded rapidly and replaced hunter-gatherer groups which were once dominant across the landscape. So, the vast majority of the ancestry of modern Europeans can be traced back to farming cultures of the eastern Mediterranean which swept over the west of Eurasia between 10 and 5 thousand years before the before.

Dienekes Pontikos points me to a new paper in PNAS which uses a coalescent model of 400+ mitochondrial DNA lineages to infer the pattern of expansions of populations over the past ~40,000 years. Remember that mtDNA is passed just through the maternal lineage. That means it is not subject to the confounding dynamic of recombination, allowing for easier modeling as a phylogenetic tree. Unlike the autosomal genome there’s no reticulation. Additionally, mtDNA tends to be highly mutable, and many regions have been presumed to be selectively neutral. So they are the perfect molecular clock. There straightforward drawback is that the history of one’s foremothers may not be a good representative of the history of one’s total lineage. Additionally the haploid nature of mtDNA means that genetic drift is far more powerful in buffeting gene frequencies and introduced stochastic fluctuations, which eventually obscure past mutational signals through myriad mutations. Finally, there are serious concerns as to the neutrality of mtDNA…though the authors claim to address that in the methods. I should also add that it also happens to be the case that there is less controversy and more surety as to the calibration of mutational rates of mtDNA than the Y chromosomal lineages of males. Their good for determining temporal patterns of demographic change, and not just tree structures.

Here’s the abstract, Rapid, global demographic expansions after the origins of agriculture:

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CATEGORIZED UNDER: Genetics, Genomics, Geography

The day of the farmer

By Razib Khan | March 29, 2011 11:01 pm

About five months ago I read Peter Bellwood’s First Farmers: The Origins of Agricultural Societies. Bellwood’s thesis is simple: that the first adopters of farming entered into a period of rapid demographic expansion and by and large replaced non-farming groups. The populations which dominate the world today in this model are then the descendants of the very small set of cultures which ~10,000 years ago triggered the Neolithic Revolution. When Bellwood presented his thesis in the mid-2000s many would have dismissed it out of hand. Today I believe we have to take this model seriously.

There are two primary reasons from my perspective why I am now thinking about Bellwood’s thesis a great deal. First, the archaeogenetic inferences based on distributions of modern allele frequencies which suggested that the Neolithic Revolution in Europe was a matter of cultural diffusion seem far shakier. With such genetic models no longer taken for granted the recent historical, semi-historical, and ethnographic evidence, on farming transitions must be given much more weight. The case of the Bantu expansion in Africa seems to be semi-historical. The Bantu farmers themselves were not literate but their wave of advance was in historical time. Tellingly, the Bantu speaking populations of Southern Africa are genetically more similar to the Fang of Cameroon then they are to the Khoisan to their west! More well documented has been the attempts by Europeans to settle various lands overseas in their colonial adventures. They have been able to marginalize populations which did not habitually practice intensive agriculture relatively easily (note that the locus of Afrikaner settlement was initially around the Cape, where Bantu influence was minimal and Khoikhoi pastoralists were dominant). In contrast, in regions like Mesoamerica where obligate intensive agricultural civilization had deep roots there was no biological replacement, but hybridization.

An argument can be made that the initial farmers did not have so many advantages over their hunter-gatherer neighbors. So the power and force of the mass agricultural way of life which bore down upon the indigenes of Australia was qualitatively different because the Europeans who arrived were the outer wave of an ancient and ruthlessly efficient civilization of farmers, honed to brutal perfection through the cauldron of inter-group competition over thousands of years. I think the best counter argument against this is the evidence of rapid sweeps of cultural forms in European in prehistory, as well as rapidity of the success of the Bantu agricultural toolkit.

The new genome blogger Diogenes expresses the thesis of agricultural replacement to near maximal levels in the model which he is attempting to test with ADMIXTURE runs. Here are his propositions (formatting reedited for clarity):

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CATEGORIZED UNDER: Anthroplogy, Genetics, Genomics

The shadow of the Emishi

By Razib Khan | March 24, 2011 3:57 pm

Randy McDonald just pointed me to a 2008 paper in AJHG, Japanese Population Structure, Based on SNP Genotypes from 7003 Individuals Compared to Other Ethnic Groups: Effects on Population-Based Association Studies. It speaks to an issue I brought up earlier in my post, Sons of the farmers, the story of Japan, which describes the ethnogenesis of the Japanese modern people from the Yayoi culture. The Yayoi presumably brought rice from the Asian mainland, probably from what is today southern Korea. But the Japanese islands were not uninhabited before this period. Japan was home to the Jomon culture, which has a rather storied history in the annals of archaeology. The Jomon seem to have been a predominantly hunter-gatherer population which was also sedentary, and engaged in the production of objects such as pottery which are normally associated with more advanced farming societies. I have a difficult time crediting the ~13,000 year period of continuous development which is attributed to the Jomon, but, it does seem likely that the period between 2,000 and 2,500 years before the present did mark a sharp cultural discontinuity in the Japanese islands, as Jomon gave way to Yayoi.

A related issue to this indisputable cultural shift is the question of whether it was accompanied by a demographic transition. This particular debate is fraught with politics, but we have enough genetic information that we can hazard a tentative guess. It does look like the Jomon-Yayoi cultural shift was accompanied by a significant demographic transition. In particular, the Ainu of the north and the inhabitants of the Ryukyu islands in the south seem distinctive from the majority of Japanese who inhabit the core islands. The hypothesis that these peoples are more related to the Jomon, or directly descended from them. One must distinguish these two groups though; the Ainu remained culturally distinctive from the Japanese, in lifestyle and language before their de facto absorption into the Japanese of late. In contrast, the people of the Ryukyus today seem to be clearly related to the southern Japanese in both language and lifestyle. If the Ryukyu islanders preserve more of the Jomon ancestral heritage, it may simply be due to the dilution of the signal of the original Yayoi pioneers as they moved south.

But there is another piece of the puzzle which has always been a point of curiosity for me: what happened to the non-Japanese populations of northern Honshu? Termed Emishi, these people retained a distinctive identity in northern Honshu until ~1,000 years ago. Fragmentary references in the historical texts make it clear that these people did not speak Japanese natively, and were physically different in appearance, being a “hairy” and “bearded” people. This is how the Ainu were also described, and because of the Emishi’s geographical proximity to Hokkaido it is presumed there may have been a cultural continuity. It turns out that the 2008 paper hints at the genetic imprint of the Emishi.

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CATEGORIZED UNDER: Genetics, History

Swedes not so homogeneous?

By Razib Khan | February 10, 2011 1:37 pm


Credit: David Shankbone

The more and more I see fine-scale genomic analyses of population structure across the world the more and more I believe that the “stylized” models which were in vogue in the early 2000s which explained how the world was re-populated after the last Ice Age (and before) were wrong in deep ways. I’m talking about the grand narratives outlined in works such as Bryan Sykes’ The Seven Daughters of Eve, the subtitle of which was “The Science That Reveals Our Genetic Ancestry.” If I had less faith in science to always ultimately right its course I’d probably become a post-modernist type who asserts that all these stories are fictions. Sykes’ model in particular seems to be very likely incorrect because of the utilization of ancient DNA to elucidate population movements past in Europe. From what we can gather it looks like coarse attempts to infer past distributions from current distributions (of specific lineages and their diversity) resulted in a great deal of false clarity. We’re not talking differences on the margins, but fundamental confusions. For example, Basques were always assumed to be a viable “reference” population for descendants of European hunter-gatherers. This was one of the linchpins of older historical genetics models. It turns out that this fixed assumption may have been a false one.

Not only were our past assumptions in simple models wrong, but the real explanations may also be rather complex. It turns out that ancient DNA of the “first farmers” and their “hunter-gatherer” neighbors in Central Europe reveals a lot of discontinuity between both these groups and modern Europeans. Why? It may be that in fact there were multiple migrations, and the palimpsest is going to be a tough cookie to excavate. But there’s no need to be disheartened, the old paradigms came crashing down thanks to data.

ResearchBlogging.orgWith that in mind I’ve been particularly interested in the European fringe, the far west and north. If any hunter-gatherer descendants survive in large numbers, it will be here. This is why I’m curious as to the genetics of the Sami as well as the archaeology which tracks the spread of agriculture in Northern Europe. A new paper in PLoS ONE focuses on Sweden, Swedish Population Substructure Revealed by Genome-Wide Single Nucleotide Polymorphism Data:

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CATEGORIZED UNDER: Genetics, Genomics, Geography, History

One diabetes gene to explain it all?

By Razib Khan | December 7, 2010 12:01 pm

372px-PresidentTaftTelephoneCrop
President William Howard Taft

It is the best of times, it is the worse of times. On the one hand the medical consequences of human genomics have been underwhelming. This is important because this is the ultimate reason that much of the basic research is funded. And yet we’ve learned so much. The genetic architecture of skin color has been elucidated, and we’ve seen a clarification of patterns of natural selection in the human genome. The finding last spring of Neandertal admixture in modern human populations is perhaps the most awesome pure science finding of late, coming close to resolving a decades old debate in anthropology. This doesn’t cure cancer, but it does connect the dots about the human past, and that’s not trivial. We are species haunted by our memories, so we might as well get them right!

But all hope is not lost. Research continues. And one area which general surveys of genomic variation have usually shown to be targets of natural selection, and, also have clear and immediate biomedical relevance, is that of metabolism. How we eat, and how we process and integrate the food we eat, is of obvious fitness relevance in the evolutionary and medical senses. It turns out that there is even variation in our saliva which is probably due to natural selection. The combination of diversity in human cuisine and susceptibility to the diseases of modern life indicate possibilities as to the relationship between past selection pressures and contemporary patterns of genetic variation. Of course one has to tread softly in this area, there are the inevitable confounds of environment, as well the unfortunate probability of any given locus being of small effect size in its influence on any given trait.

ResearchBlogging.orgA new paper in Genome Research reports a SNP which seems to have been subject to natural selection in Eurasians within the last 10,000 years. This variant is located within an exon on a gene, GIP, which produces peptides critical in the regulation of various metabolic pathways, in particular insulin response. A possible biomedical relevance to risk susceptibility is then explored subsequent to the evolutionary genomic preliminaries. Adaptive selection of an incretin gene in Eurasian populations:

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Men at work: hoes, ploughs, and steel

By Razib Khan | December 2, 2010 6:51 pm

800px-Maler_der_Grabkammer_des_Sennudem_001
Ancient Egyptian farmer ploughing a field


Recently several weblogs have pointed to a new working paper on the role of plough-based agriculture vs. hoe-based agriculture in shaping cultural expectations about male and female labor force participation specifically, and the differentiation of gender roles more generally. My first reaction was: “doesn’t everyone know this already?” I am a cursory reader of the anthropological literature and the assumption that a shift from relatively extensive hoe-based agriculture (e.g., slash & burn, gardening, etc.) to a more intensive plough-based mode of production seems to suffuse the literature. Before touching on the major points in the paper itself I did a quick literature search, on the order of five minutes, and found something from 1928 which already assumed the major parameters which are now being mooted today, The Division of Work According to Sex in African Hoe Culture. I read the whole paper, and it remains surprisingly relevant (though some of the terminology and frameworks are a bit dated naturally). Here’s a selection:

Eduard Han, to whom the ethnological study of economics owes a considerable number of important discoveries which have been published repeatedly and in varying forms, seems to have paid scarcely enough attention to the good work of the scholars who preceded him in the fight for the recognition of the outstanding position of women in the lower forms of soil cultivation. Steinmetz and quite recently Koppers,’ have pointed out that Buckland already attributed to the female sex the invention of the most ancient method of soil cultivation, or hoe culture…Here we find, in particular,a clearer statement of the arguments of Grosse, Bachofen, and others about the connexion of matriarchal society and lower forms of soil cultivation. Matriarchy and hoe culture are assigned to definite chronologically determined stages of civilization (older forms of the so-called ‘two class culture’, and later ones of ‘bow culture’). Koppers, of the Austrian branch associates matriarchy and hoe culture with these two civilizations….

It is not our business here to study in detail the researcheson the zones of culture,which may be regardedas successfulup to a certain point, though we shall have to refer to them incidentally. It suffices to state that a connexion between woman and hoe culture, nay more, between that social system where the woman rules, matriarchal society, and primitive soil cultivation is universally acknowledged to exist.

Ignore some of the terms and concepts which might seem loaded or outmoded today. Rather, observe that in 1928 a distinction between hoe-based and plough-based agriculture was widely accepted in terms of the cultural consequences. Why? Just take a look at an old-fashioned plough vs. hoe (at least old-fashioned compared to the sort of mechanized devices you can find in catalogs today):

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CATEGORIZED UNDER: Anthroplogy, Economics

Pandora's Seed: The Unforeseen Cost of Civilization

By Razib Khan | November 5, 2010 3:03 am

1400062152The cockroach as we know it has been around for ~140 million years. That’s a rather long run. The evolutionary design of the cockroach seems to be well suited to avoiding obsolescence; it’s withstood the test of time. I suspect that the particular example of the roach is often used to illustrate the blindness of evolution because of its lack of aesthetic alignment with the the values of modern humanity. Unlike the elegant wasp or the industrious bee the cockroach seems to have few redeeming characteristics on first blush. The Hutus referred to the Tutsis as cockroaches before and during the Rwanda genocide of 1994. And yet the roach succeeds, it breeds, and it flourishes.

Some of the same class of issues pertain to our own species. What we feel to be edifying, to be aesthetically pleasing, may not comport with the final judgement of history, of evolution. The narrative of man ascending which has become so popular since the Enlightenment turns out to present us with some problems when one realizes that our species seems to have regressed on particularly transparent metrics such as height and cranial capacity since the last Ice Age. But the prevailing wisdom of the ancients that we descend from an Edenic Golden Age also does not seem to necessarily comport with the record at hand either. Just as the past is cloudier than we once perceived it to be, so the future often looks muddled from the perspective of the present. How did man come to be? What should we be? And why should we be? These are a combination of positive and normative questions, and Spencer Wells tackles them in his newest book, Pandora’s Seed: The Unforeseen Cost of Civilization.

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CATEGORIZED UNDER: Culture, Health, History, Human Evolution

Völkerwanderung back with a vengeance

By Razib Khan | October 17, 2010 3:50 am

800px-European_Middle_Neolithic

The German magazine Der Spiegel has a rather thick new article out reviewing the latest research which is starting to reintroduce the concept of mass folk wanderings into archaeology. The title is How Middle Eastern Milk Drinkers Conquered Europe. In the story you get a good sense of the recent revision of the null model once dominant within archeology that the motive forces of history manifested through the flow of pots and not people. This viewpoint came to ascendancy after World War II, and succeeded an older method of interpretation which presumed a tight correlation between race and culture. It repudiated the idea that the flow and change of pottery styles and extant patterns of linguistic dialects may have been markers for the waxing and waning of peoples.

Obviously a pots-not-people model had some major exceptions even during its heyday. The demographic explosion of European peoples after 1492, and especially the Anglo peoples after 1700, occurred within the light of history. Even if it hadn’t it would be ludicrous on the face of it to assert that the modern American population were derived from the indigenous populations, and that they had simply adopted the language, religion and folkways of the British conquerors of North America. But outside the presumed aberration of the European imperialist and colonial venture of the modern era the details on the ground were obscure enough that a model could be imposed from without.

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CATEGORIZED UNDER: Anthroplogy
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