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.
A new paper in Proceedings of the Royal Society dovetails with some posts I’ve put up on the peopling of Japan of late. The paper is Bayesian phylogenetic analysis supports an agricultural origin of Japonic languages:
Languages, like genes, evolve by a process of descent with modification. This striking similarity between biological and linguistic evolution allows us to apply phylogenetic methods to explore how languages, as well as the people who speak them, are related to one another through evolutionary history. Language phylogenies constructed with lexical data have so far revealed population expansions of Austronesian, Indo-European and Bantu speakers. However, how robustly a phylogenetic approach can chart the history of language evolution and what language phylogenies reveal about human prehistory must be investigated more thoroughly on a global scale. Here we report a phylogeny of 59 Japonic languages and dialects. We used this phylogeny to estimate time depth of its root and compared it with the time suggested by an agricultural expansion scenario for Japanese origin. In agreement with the scenario, our results indicate that Japonic languages descended from a common ancestor approximately 2182 years ago. Together with archaeological and biological evidence, our results suggest that the first farmers of Japan had a profound impact on the origins of both people and languages. On a broader level, our results are consistent with a theory that agricultural expansion is the principal factor for shaping global linguistic diversity.
I don’t know the technical details of linguistics to comment, but the alignment between the linguistic model and archeology is pretty impressive to me. There’s a 95% confidence interval which can push the time back to 4,000 years, so there’s some fudge factor too. The basic technique is borrowed from phylogenetics. This is pretty clear when you notice that one of the algorithms seems to be the same one used in the rice genomics paper. Nick Wade covers the paper in The New York Times, so no need for me to give a blow-by-blow in a domain where I don’t have much insight anyway.
The economist Samuel Bowles recently had a paper out in PNAS which caught my attention, Cultivation of cereals by the first farmers was not more productive than foraging. This naturally begs the question: why did farming conquer foraging as a lifestyle? First, let’s look at the abstract:
Did foragers become farmers because cultivation of crops was simply a better way to make a living? If so, what is arguably the greatest ever revolution in human livelihoods is readily explained. To answer the question, I estimate the caloric returns per hour of labor devoted to foraging wild species and cultivating the cereals exploited by the first farmers, using data on foragers and land-abundant hand-tool farmers in the ethnographic and historical record, as well as archaeological evidence. A convincing answer must account not only for the work of foraging and cultivation but also for storage, processing, and other indirect labor, and for the costs associated with the delayed nature of agricultural production and the greater exposure to risk of those whose livelihoods depended on a few cultivars rather than a larger number of wild species. Notwithstanding the considerable uncertainty to which these estimates inevitably are subject, the evidence is inconsistent with the hypothesis that the productivity of the first farmers exceeded that of early Holocene foragers. Social and demographic aspects of farming, rather than its productivity, may have been essential to its emergence and spread. Prominent among these aspects may have been the contribution of farming to population growth and to military prowess, both promoting the spread of farming as a livelihood.
My own working assumption is that the “first farmers” existed in a state of land surplus, and so like the medieval peasants in the wake of the Black Death found themselves released from Malthusian constraints, at least until their natural increase swallowed up their affluence. Bowles gives several reasons to be skeptical of this conjecture. The list in table 2 shows the positive and negative biases in the model when one back-projects later stages of farming to the initial period. Metal tools, well developed distribution channels, and more productive varieties, were features of mature agricultural societies. On the time-insensitive scale the necessity of planning ahead and waiting patiently for the crop to be ripe count against the gains of the farming way of life as well. The main variable which would weight in favor of farming is the land surplus alone, though Bowels argues that the ethnographic data as to the benefits of a surfeit of this input factor of production is mixed. I am skeptical of this point, though I can’t say I’ve dug deeply into the literature.
There are other factors, such as the fact that farmers were immobile, and so subject to attack. A shift toward a few crops also reduced the diversity of the diet, and therefore entailed a trade off between a diet rich in micronutrients, fiber, protein, and fat, to one overloaded on carbohydrates. Finally, a reliance on a few crops also means heightened “tail risk.” Think of the Irish potato blight. Hunter-gatherer populations would usually have a more diverse portfolio, and so be buffered more from environmental shocks.
After linking to Marnie Dunsmore’s blog on the Neolithic expansion, and reading Peter Bellwood’s First Farmers, I’ve been thinking a bit on how we might integrate some models of the rise and spread of agriculture with the new genomic findings. Bellwood’s thesis basically seems to be that the contemporary world pattern of expansive macro-language families (e.g., Indo-European, Sino-Tibetan, Afro-Asiatic, etc.) are shadows of the rapid demographic expansions in prehistory of farmers. In particular, hoe-farmers rapidly pushing into virgin lands. First Farmers was published in 2005, and so it had access mostly to mtDNA and Y chromosomal studies. Today we have a richer data set, from hundreds of thousands of markers per person, to mtDNA and Y chromosomal results from ancient DNA. I would argue that the new findings tend to reinforce the plausibility of Bellwood’s thesis somewhat.
The primary datum I want to enter into the record in this post, which was news to me, is this: the island of Cyprus seems to have been first settled (at least in anything but trivial numbers) by Neolithic populations from mainland Southwest Asia.* In fact, the first farmers in Cyprus perfectly replicated the physical culture of the nearby mainland in toto. This implies that the genetic heritage of modern Cypriots is probably attributable in the whole to expansions of farmers from Southwest Asia. With this in mind let’s look at Dienekes’ Dodecad results at K = 10 for Eurasian populations (I’ve reedited a bit):
A new paper in The New Journal of Physics shows that a relatively simple mathematical model can explain the rate of expansion of agriculture across Europe, Anisotropic dispersion, space competition and the slowdown of the Neolithic transition:
The front speed of the Neolithic (farmer) spread in Europe decreased as it reached Northern latitudes, where the Mesolithic (hunter-gatherer) population density was higher. Here, we describe a reaction–diffusion model with (i) an anisotropic dispersion kernel depending on the Mesolithic population density gradient and (ii) a modified population growth equation. Both effects are related to the space available for the Neolithic population. The model is able to explain the slowdown of the Neolithic front as observed from archaeological data
The paper is open access, so if you want more of this:
Just click through above. Rather, I am curious more about their nice visualization of the archaeological data:
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):