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The significance of Shuidonggou Locality 12 to studies of hunter-gatherer adaptive strategies in North China during the Late Pleistocene Quaternary International. The early appearance of Shuidonggou core-and-blade technology in north China: Implications for the spread of Anatomically Modern Humans in northeast Asia?

Quaternary International. Effects of the bow on social organization in Western North America. Evolutionary Anthropology. Why foragers choose acorns before salmon: Storage, mobility, and risk in aboriginal California Journal of Anthropological Archaeology. Microblade technology and the rise of serial specialists in north-central China Journal of Anthropological Archaeology. Introduction: The domestication of plants and animals: Ten unanswered questions Biodiversity in Agriculture: Domestication, Evolution, and Sustainability.

Early steps in agricultural domestication Biodiversity in Agriculture: Domestication, Evolution, and Sustainability. Unexamined bodies of evidence Science. Archaeological records of Dadiwan in the past 60 ka and the origin of millet agriculture Chinese Science Bulletin. The origins of food production in north China: A different kind of agricultural revolution Evolutionary Anthropology.

Constraints on the development of agriculture. Current Anthropology. Cultural innovations and demographic change Human Biology. Agricultural origins and the isotopic identity of domestication in northern China. Macroevolutionary theory and archaeology: Is there a big picture? Handbook of Evolution. The transition to agriculture in northwestern China Developments in Quaternary Science.

Holocene hunter-gatherers Archaeology At the Millennium: a Sourcebook. A simple model of technological intensification Journal of Archaeological Science. Agriculture, archaeology, and human behavioral ecology Behavioral Ecology and the Transition to Agriculture. Techniques for assessing standardization in artifact assemblages: Can we scale material variability? The first changes in seed crop plants generally include larger seeds, the loss of natural seed dispersal mechanisms, and the loss of seed dormancy.

These changes do not necessarily require any conscious selection by cultivators. Once humans began to intensively exploit wild seed plants, especially once they prepared seedbeds and deliberately planted seeds, these changes will tend to be automatic. Larger seeds yield more competitive seedlings in the artificial seedbed. Those seeds that do not drop off the stalk are more likely to be harvested, favoring genotypes with non-shattering seed heads.

With humans controlling the time of planting and storing seed in cool, dry locations, seed dormancy, rather than producing adaptively facultative germination, merely increases the chance that a seed will fail to germinate in time to be harvested. As Flannery observed, it is not clear which species is the domesticated and which the domesticator in agriculture! Some plants responded to human harvest in such a way that they induced humans to plant more of that species in competition with others, raise larger numbers of children to plant still more fields, and eventually to carry the plant across continents.

Of course, every human population includes close observers and inveterate experimenters. No doubt deliberate ingenuity and sustained artificial selection also played roles in the evolution of domesticates, as they do in the development and conservation of landraces today Brush The overall pattern of subsistence intensification is clearly consistent with the hypothesis that agriculture was impossible in the Pleistocene but mandatory in the Holocene, but the real test is whether or not we can give a satisfactory account of the variation in the rate and sequence of intensification.

Work on this project is in its infancy, and only some rather preliminary and speculative answers are possible. In general, external processes of macroevolution will tend to operate at longer time scales and internal processes at shorter time scales. Evolution has to be flexible and rapid enough to roughly track environmental variation, and environmental variation is greater at longer than shorter time scales. Those species that fail to track longer-term variation will go extinct, and will not contribute to the evolutionary processes we see in action.

At the same time, no evolutionary process responds instantaneously. There is always stickiness at short enough time scales. If the world were simple, the time scales of internal and external processes would be entirely separate. To a first approximation, the lack of agriculture before the Holocene is due to the external effect of the Pleistocene climate; after that the rate of progress toward ever more intensive subsistence is largely regulated by internal processes.

However, external causes did not entirely disappear in the Holocene. To completely isolate the effects of internal processes we have to control for residual external effects. Climate change may play a small role. The Holocene climate is only invariant relative to the wild oscillations of the last glacial Lamb, For example, seasonality difference between summer and winter insolation was at a maximum at the beginning of the Holocene and has fallen since.

Agriculture at marginal altitudes in places like the Andes seems to respond to Holocene climatic fluctuation Kent While the effect of Holocene climate fluctuations on regional sequences must always be kept in mind, the dominance of the nearly always monotonic tendency to increased subsistence efficiency per unit land seems likely to be driven by other processes.

Geography may play a big role. Diamond argues that Eurasia has had the fastest rates of cultural evolution in the Holocene because of its size and to a lesser extent its orientation. Plausibly, the number of innovations that occur in a population is, to a first approximation, a function of total population size and the flow of ideas between sub-populations.

Societies acquire most innovations by diffusion from other societies, and isolated societies will be handicapped in their rate of innovation by a slower rate of diffusion. Eurasia is the largest continent and is especially large in its east-west dimension. Innovations occurring at one end of the continent will eventually diffuse to the other, spreading along lines of latitude with relatively similar environments.

Small land-masses like Australia and New Guinea are substantially isolated from the larger world and have a much smaller base of innovators. The Americas, though quite respectable in size, are oriented with their major axis north-south. Consequently innovations have to mainly spread across lines of latitude from the homeland environment to quite different ones. Wheat varieties originating in the Near East could spread to Spain and to Western China without substantial modification.

The maize moving north from Mexico would have to be selected to respond appropriately to longer day length and a shorter growing season. Maize spreading to South America would have to move through a belt of hot, wet, tropics with little day length variation before reaching the cool, semiarid, subtropical highlands of South America so similar to its original homeland. In the case of domestication, the distinction between external and internal regulation of process rates is ambiguous without further definition.

The genetic changes in the proto-domesticate, as it responds to cultural practices, are external to the cultural evolutionary system in one sense. In another, the coevolutionary system as a whole is, perhaps, more naturally seen as having intertwined the evolution of human culture and plant and animal genomes as to make such a distinction artificial. Human genomes may also be involved in the coevolutionary system. Agriculture requires pre-adapted plants and animals.

In each center of domestication, people domesticated only a handful of the wild plants that they formerly collected, and of this handful even fewer are widely adopted outside those centers. The same is true for domesticated livestock. Wheat, rice, and maize make disproportionate contributions to total world crop production. Cattle, sheep, goats, hogs, and chickens make an outsized contribution to total world livestock production.

Zohary and Hopf have listed some of the desirable features in plant domesticates. Aside from obvious things like large seed size, most Near Eastern domesticates had high rates of self-fertilization. This means that farmers can select desirable varieties and propagate them with little danger of gene flow from other varieties or from weedy relatives.

Maize, by contrast, outcrosses at high rates. Perhaps the later and slower evolution of maize compared to Near Eastern domesticates is due to the difficulty of generating responses to selection in the face of gene flow from unselected populations. Smith discusses the many constraints on potential animal domesticates. For example, many large ungulates like deer depend upon rapid flight to avoid predators. They are thus very skittish and adapt poorly to human handling.

Larger herd ungulates that are less susceptible to large predators, like cattle, have shorter flight distances and more stolid temperaments. Even in the most favorable cases, the evolution of new domesticates is not an instantaneous process. In at least some times and some places, the rate of evolution of domesticates was likely the rate-limiting step in the agricultural intensification process.

Diamond , drawing on the work of Blumler , notes that the Near Eastern region has a flora that is unusually rich in large-seeded grasses Table 2. California has so many climatic, topographic, and ecological parallels with the precocious Fertile Crescent that its very tardy development of plant-intensive subsistence systems is a considerable puzzle.

The presence of a large suite of agriculturally preadapted plants in the Near East but not in California provides a plausible hypothesis to explain the difference in agriculture but not plant intensification itself. The macroevolutionary patterns in which we are most interested are the processes strictly internal to cultural evolution that might limit the rate of intensification.

We Boyd and Richerson ; Bettinger view cultural evolution as a Darwinian process of descent with modification. Evidence about the macroevolutionary tempo and mode of cultural evolution bear directly on our picture of the micro scale processes that form the body of the theory. For many characters human decisions have relatively weak effects in the short run although they can be powerful when integrated over many people and appreciable spans of time.

If the rational-choice element in our models is sufficiently strong, then the rate of cultural evolution itself will never be rate limiting and cultural evolution will lack the Darwinian element. The tempo of subsistence intensification will then be entirely governed by external or coevolutionary processes. Selective processes can also cause quite rapid evolution compared to the time scales of external processes.

Selection acts to drive populations up slopes of fitness toward peaks in an adaptive topography. If fitness topographies are smooth, the populations climb more or less directly and quickly to global optima. On the other hand, if fitness topographies are rough, much more complex trajectories will ensue. Populations will tend to get stuck on local peaks in the foothills of a fitness topography.

Chance events may eventually carry small populations across fitness valleys. For example, minor climate change may shift the topography allowing one population to escape a local peak and run up to a higher one. A population of populations a metapopulation in the jargon will, by various historically contingent routes, gradually filter to higher and higher fitness peaks.

Historically minded scholars have always believed that such complexities were important e. Vayda , but only recently have models of biological, cultural, and economic change become sophisticated enough to investigate them formally. Typically the structural changes in such models are straightforward extensions of classical models that behave ahistorically.

We think that such models should lead to closer and more productive interactions between theorists and historians Boyd and Richerson Several internal processes may lead to rough fitness topographies and thus act to limit the rate of cultural evolution of intensification. New technological complexes evolve with difficulty. One problem that will tend to slow the rate of cultural and organic evolution is the sheer complexity of adaptive design problems. As engineers have discovered when studying the design of complex functional systems, discovering optimal designs is quite difficult.

Blind search algorithms often get stuck on local optima. Piecemeal improvements at the margin are not guaranteed to find globally optimal adaptations by myopic search. Yet, myopic searches are what Darwinian processes do. The large step change in environment at the Pleistocene-Holocene transition set off the trend of subsistence intensification of which modern industrial innovations are the latest examples.

The diversity of trajectories taken by the various regional human sub-populations since 11, B. We believe that the discussion above is not only a basic review of the main cultural macroevolutionary hypotheses currently entertained by scholars but also a crude picture of how cultural macroevolution has actually happened.

Social scientists are in the habit of treating these processes as mutually exclusive hypotheses. They seem to us to be competing but certainly not mutually exclusive. At the level of qualitative empiricism, tossing any one out entirely leaves puzzles that are hard to account for and produces an obvious caricature of the actual record of change.

If this conclusion is correct, the task for historically minded social scientists is to refine estimates of the rates of change that are possible due to the various evolutionary processes and to estimate of how those rates change as a function of natural and socio-cultural circumstances. Sustaining agriculture under conditions of much higher high frequency environmental variation than farmers currently cope with would be a very considerable technical challenge.

At the very best, lower CO 2 concentrations and lower world average precipitation suggest that world average agricultural output would fall considerably. In one sense, though, the Holocene is not just another interglacial. Recall that Petit et al. Current anthropogenic global warming via greenhouse gasses threatens to elevate world temperatures to levels that in past interglacials apparently triggered a large feedback effect producing a relatively rapid decline toward glacial conditions.

The Arctic ocean ice pack is currently thinning very rapidly Kerr No one can yet estimate the risks we are taking of a rapid return to colder, drier, more variable environment with less CO 2 , nor evaluate exactly the threat such conditions imply for the continuation of agricultural production.

Nevertheless, the intrinsic instability of the Pleistocene climate system, and the degree to which agriculture is dependent upon the unusually long Holocene stable period, should give one pause Broecker Allen, J. Brandt, A. Brauer, H. Hubberten, B. Huntley, J. Keller, M. Kraml, A. Mackensen, J. Mingram, J. Negendank, N. Nowaczyk, H.

Oberhansli, W. Watts, S. Wulf and B. Nature Ammerman, A. Man An, Z. World Archaeology 23 2 Bar-Yosef, O, and R. Gebauer, pp. Bellwood, P. Harris, pp. Smithsonian Institution Press, Washington, D. Bettinger, R. Plenum, New York. Billman and G. Feinman, pp. Feinman and T. Plenum, New York, in press. American Antiquity Blumler, M. Thesis, University of California, Berkeley.

UMI, Ann Arbor. Boyd, R. University of Chicago Press, Chicago. In History and Evolution , edited by M. Nitecki, pp. Bradley, R. Academic Press, San Diego. Braidwood, R. Scientific American 3 Braidwood, R,J. Studies in Ancient Oriental Civilization University of Chicago Oriental Institute, Chicago. Braidwood, L. Braidwood, B. Howe, C. Reed, and P. Watson editors.

Bretting P. Economic Botany 44 Supplement. Broecker, W. Science Brush, S. Crop Science Carroll, R. Cambridge University Press, Cambridge. Cavalli-Sforza, L. Menozzi, and A. Princeton University Press, Princeton. Childe, V. Watts, London. Clark, P. Alley, and D. Cohen, M. Yale University Press, New Haven. Academic Press, Orlando. In The Origins of Agriculture , edited by C. Cowan and P. Watson, pp.

Crosby, A. Crowley, T. Oxford University Press, New York. Darwin, C. American Home Library, New York. Day, R. Barnett, J. Geweke, and K. Schell, pp. Diamond, J. Norton, New York. Ditlevsen, P. Svensmark, and S. Durham, W. Stanford University Press, Stanford. Easterlin, R. Journal of Economic Behavior and Organization Ehret, C. University of Virginia Press, Charlottesville. Eldredge, N.

In Models in Paleobiology , edited by T. Schopf, pp. San Francisco: Freeman. Elston, R. Xu, D. Madsen, K. Zhong, R. Bettinger, J. Li, P. Brantingham, H. Wang and J. Antiquity Endler, J. Fairbank, J. Flannery, K. Annual Review of Anthropology Frank, R. Free Press, New York.

Frogley, M. Gifford-Gonzales, D. In press. African Archaeological Review. Goring-Morris, N. Harris, D. University College London Press, London. In Origins of Agriculture , edited by C. Reed, pp. Mouton, The Hague. Hayden, B. Price and B. Henry, D. University of Pennsylvania Press, Philadelphia.

Imamura, K. Johnson, T. Scholz, M. Talbot, K. Ketts, R. Ricketts, G. Ngobi, K. Buening, I. Ssemmanda and J. Lamb, H. Lee, R. Coleman and R. Schofield, pp. Basil Blackwell, Oxford. Levinton, J. Lindert, P. Journal of Interdisciplinary History Katz, S. Hediger, and L. Kent J. Browman, pp Westview, Boulder.

Kerr, R. Klein, R. Kirch, P. Lindsay, L. Jennings , edited by C. Condie and D. Fowler, pp. Anthropological Papers No. University of Utah, Salt Lake City. MacNeish, R. Tringham, pp. University of Oklahoma Press: Norman.

Matson, R. Archaeology Southwest McNeill, W. Anchor, Garden City NY. Martin, P. Klein editors. University of Arizona Press, Tucson. Mayewski, P. Twickler, M. Morrison, R. Alley, P. Bloomfield and K. Murray, J. Springer-Verlag, Berlin. North, D. Partridge, T. Bond, C. Hartnady, P. Vrba, G. Denton, T. Partridge, L. Burckle, pp. Petit, J. Jouzel, D. Raynaud, N. Barkov, J. Barnola, J.

Basile, M. Bender, J. Cappellaz, M. Davis, G. Delaygue, M. Delmotte, V. Kotlyakov, M. Legrand, V. Lipenkov, C. Lorius, L. Saltzman, and M. Price, T. Richerson, P. Eibl-Eibesfeldt and F. Salter, pp. Berghahn, New York. Human Nature In Evolution of Cognition , edited by C. Heyes and L. Rindos, D. Academic Press, London. Rogers, E. Sage, R. Global Change Biology Simpson, G. Columbia University Press, New York. Smith, B. Scientific American Library, New York.

Steward, J. University of Illinois Press, Urbana. Steig, E. Brook, J. White, C. Sucher, M. Bender, S. Lehman, D. Morse, E. Waddington, and G. Stuiver, M. Reimer, E. Bard, J. Beck, G. Burr, K. Hughen, B. Kromer, G. McCormack, J.

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However, the variability that occurred on the time scales of the major glacial advances and retreats is also correlated with great variance at much shorter time scales. For the last , years, very high-resolution data are available from ice cores taken from the deep ice sheets of Greenland and Antarctica. Resolution of events lasting little more than a decade is possible in ice 90, years old, improving to monthly after 3, years ago.

During the last glacial, the ice core data show that the climate was highly variable on time scales of centuries to millennia GRIP ; Clark et al. The 18 O curve is a proxy for temperature; less negative values are warmer.

The figure also shows histograms illustrating the obvious. The last glacial period was arid and extremely variable compared to the Holocene. Sharp excursions lasting a millennium or so occur in estimated temperatures, atmospheric dust, and greenhouse gases. The intense variability of the last glacial carries right down to the limits of the nearly 10 year resolution of the ice core data. Figure 2 shows Ditlevsen et al.

Not only was the last glacial much more variable on time scales of a century or more yr low pass filter but also on much shorter time scales yr high pass filter. Even though diffusion within the ice core progressively erases high frequency variation in the core, the shift from full glacial conditions about 18, years ago to the Holocene interglacial is accompanied by a dramatic reduction in high frequency variation.

The Holocene the last relatively warm, ice free 11, years has been a period of very stable climate, at least by the standards of the last glacial. Once a more intensive subsistence system is possible, it will, over the long run, replace the less intensive subsistence system that preceded it. The reason is simple: all else equal, any group that can use a tract of land more efficiently will be able to evict residents that use it less efficiently.

More intensive uses support higher population densities, or wealthier societies per capita, or both. An agricultural frontier will tend to expand at the expense of hunters and gatherers as rising population densities on the farming side of the frontier motivate pioneers to invest in acquiring land from less efficient users.

Whether the competition for land is economic, military, or for social prestige, the hunter-gatherer will be offered an attractive purchase price, dismal choices between flight, submission, or military defense at long odds against a more numerous foe, or an attractive idea about how to become richer through farming.

Subsistence improvement generates both literal and metaphorical arms races. The archaeology supports this argument Bettinger in press. Societies in all regions of the world undergo a very similar pattern of subsistence intensification in the Holocene, albeit at very different rates.

Since ever more intensive subsistence systems have continued to evolve right up to the present, we do not have to worry about any very significant relaxation in the selection pressure for more efficient subsistence during the Holocene. A set of sustainable equilibrium adaptations to the Holocene may exist, but we have not yet discovered them.

Thus, the experiment is rather clean. The Pleistocene-Holocene transition was a massive environmental change that was followed by more or less unchanged environmental conditions for the last 11, years. In response, human cultural evolution has generated a macroevolutionary trend towards more efficient production per unit land area. Given that competitive arms races drive the evolution of food production, the problem is to discover what the rate-limiting steps are in the cultural evolutionary processes leading to more intensive subsistence.

The mode of acquisition of agriculture rarely indigenous development, more commonly diffusion , rate of progress, and exact sequence of forms of subsistence will depend upon local ecological and social conditions, regional setting, historical happenstance, and the like. Thus, each example of independent evolution of agriculture and each case of spread by conquest or diffusion is a case that can be examined for clues as to the relative importance of different evolutionary processes.

The prospects for getting data adequate to test hypotheses are good. Archaeologists, in their attempts to explain particular transitions to plant rich and eventually agricultural subsistence in particular locations typically offer scenarios that are implicitly, at least, competitive ratchet models. Pristine origins of agriculture require plants that are susceptible to improvement via domestication. There have to be ways of incorporating proto-domesticates into the subsistence systems of hunter-gatherers.

Seasonality may be important in establishing a premium on large scale planting for storage for the low productivity season. If the local ecological conditions for intensification are favorable, it occurs irreversibly. Workers such as MacNeish , Flannery , and Harris , inspired by a particular sequence of intensification leading to agriculture, attempt to draw generalizations that should apply to other sequences.

As information has improved about the particular sequences, a complex pattern of similarities and differences between cases has appeared. Similarly, the spread of agriculture from its original centers to more distant regions is susceptible to archaeological, linguistic and biological investigations Cavalli-Sforza, et al. Studies of hunter-gatherer sequences of intensification that stop far short of agriculture similarly often give us ecological and socially detailed accounts of the intensification processes including some with a quite clear account of the way the competitive ratchet probably worked before agriculture proper e.

Bettinger and Baumhoff Aside from other forms of the climate change hypotheses described above, archaeologists have proposed two prominent internal hypotheses, population growth and cultural evolution, to explain the timing of the origin event. They were formulated before the nature of the Pleistocene-Holocene transition was understood, but are still the hypotheses most widely entertained by archaeologists MacNeish Neither hypothesis provides a close fit with the empirical evidence.

He imagines that subsistence intensification is driven by increases in population density, and that a long, slow buildup of population gradually drove people to intensify subsistence systems to relieve shortages caused by population growth, eventually triggering a move to domesticates.

Looked at one way, this idea is just the population growth part of the competitive ratchet. However, this argument fails to explain why pre-agricultural hunter-gatherer intensification and the transition to agriculture began in numerous locations after 11, years ago Hayden Assuming that humans were essentially modern by the Upper Paleolithic, they would have had 30, years to build up a population necessary to generate pressures for intensification.

Even much smaller rates would be sufficient to generate population pressure in far less than 30, years. The natural time scale of demographic processes is far too short to explain the long period of low population density in the Pleistocene followed by a rather sudden, widespread interest in intensification of subsistence in a narrow, rather recent, time horizon.

It is also too rapid to explain the rather gradual increase in the sophistication of agriculture and other production systems over the last ten millennia. Since the population explanation for agriculture and other adaptive changes connected with intensification remains very popular among archaeologists, it is worth taking the time here to examine it formally.

The logistic equation is one simple, widely used model of the population growth. The rate of change of population density, N , is given by:. When this ratio is equal to zero the population grows at its maximum rate; there is no population pressure. When the ratio is one, Malthusian checks prevent any population growth at all. Serendipitous inventions e. For example, only the rare single invention is likely to so much as double carrying capacity.

If such an invention spreads within a population that is near its previous carrying capacity, it will still face half the maximum population pressure. One might think that this result is an artifact of the very simple model of population growth. However, it easy to add much realism to the model without any change of the basic result. Here we consider three such extensions: more realistic population dynamics, a model with dispersal in space, and a model in which people respond to population pressure by intensifying subsistence.

It seems intuitive that this would increase the length of time necessary to reach a given level of population pressure. However, this intuition is wrong. Reduced population pressure at low densities leads to more rapid initial population growth, and since population growth is exponential this more than compensates for the fact that higher densities have to be reached to achieve the same level of population pressure.

Suppose that the initial population of anatomically modern humans was only about 10 4 and that the carrying capacity for hunter-gatherers is very optimistically 1 person per square kilometer. The difference between increasing population pressure by a factor of and by a factor of 10, is only about years!

Here N x is the population density at a point x in a one dimensional environment. Equation 5 says that the rate of change of population density in a particular place is equal to the population growth there plus the net effect of random, density-independent dispersal into and out of the region. The parameter d measures the rate of dispersal, and is equal to the standard deviation of the distribution of individual dispersal distances.

In an environment that is large compared to d, a small population rapidly grows to near carrying capacity at its initial location, and then, as shown in Figure 4 Redrawn from Ammerman and Cavalli-Sforza , begins to spread in a wave-like fashion across the environment at a constant rate. Thus at any given point in space, populations move from the absence of population pressure to high population pressure as the wave passes over that point.

With these quite conservative values, it takes less than years for the wave front to pass from low population pressure to high population pressure. More realistic models that allow for density dependent migration also yield a constant, wave-like advance of population Murray , and although the rates vary, we believe that the same qualitative conclusion will hold. Intensification: The models so far assume that the carrying capacity of the environment is fixed save where it is increased by fortuitous inventions.

However, we know that people respond to scarcity caused by population pressure by intensifying production, for example by shifting from less intensive to more intensive foraging. Since intensification increases carrying capacity, intuition suggests that it might therefore delay the onset of population pressure. However, as the following model shows, this intuition, too, is faulty.

Intensification allows greater population increases over the long run, but it does not change the timescales on which population pressure occurs. Thus per capita income declines as population size increases, but for a given population size, greater intensification raises per capita income. As in the previous models, we assume that as population pressure, now measured as falling per capita income, increases, population growth decreases.

In particular, assume:. If per capita incomes are above this value, population increases; if per capita income falls below y s , population shrinks. If I is fixed, this equation is another generalization of the logistic equation. To allow for intensification we assume that people intensify whenever their per capita income falls below a threshold value y i.

When per capita income is less than the threshold value y i , people intensify increasing the carrying capacity and therefore decreasing population pressure. The rate at which intensification changes is governed by the parameter a. If such a population begins in an empty habitat, it experiences two distinct phases of expansion. Figure 5. Initially, per capita income is near the maximum, and population grows at the maximum rate.

As population density increases, per capita income drops below y i , and the population begins to intensify, eventually reaching a steady state value. The steady state per capita income is above the minimum for subsistence but below the threshold at which people experience population pressure and intensify their production.

Thus, there is an initial phase in which the population grows rapidly until population growth is slowed by population pressure followed by a steady state in which population pressure is constant, and just enough intensification occurs to compensate for population growth.

For plausible parameter values, the second phase of population growth steady state is reached in less than a thousand years. Interestingly, increasing the intrinsic rate of intensification, a , or the intensification threshold, y i , reduces the waiting time until population pressure is important. This picture of the interaction of demography and intensification leads to predictions quite different from those of scholars like Cohen For example, we do not expect to see any systematic evidence of increased population pressure prior to major innovations something that apparently did not occur in the case of agricultural origins, Hayden Some human populations might have curtailed birth rates in order to preserve higher incomes at any given level of I.

The rest of the above analysis then applies with K measured in suitably emic terms. Cultural differences in the value of y s or K Coale, will make evidence of stress more likely in populations where the effective carrying capacity is close to the subsistence carrying capacity compared to populations that reduce population growth rates some ways from absolute subsistence limits set by preventative checks.

Similarly, populations that begin to intensify at a relatively high value of y i , will be less likely to suffer in environmental crunches. In other words, population pressure will tend to stay constant to the extent that rates of population growth and intensification are successful in adjusting subsistence to current conditions.

Normally population growth and decline are quite rapid processes relative to rates of innovation and will keep average population size quite close to K. Short-term departures from K caused by short-term environmental shocks and windfalls should be the commonest reasons to see especially stressed or unstressed populations.

This proposal is also quite consistent with the competitive ratchet. The issue is when the settling in process began. If our argument is correct, settling in could only begin in the latest Pleistocene and at the beginning of the Holocene. However, if we interpret his argument to be that the settling in process began with the evolution of behaviorally modern humans, the time scale is wrong again.

The first test of the general hypothesis outlined here is whether the great mass of human societies have indeed been on an out-of-equilibrium trajectory toward more intensive subsistence techniques for the last 15, years especially for the last 11, years.

Most evolutionary scenarios imply quite different patterns. For example, if the Pleistocene-Holocene transition played a small role in creating environmental conditions favoring agriculture, then subsistence innovations should not be correlated with its appearance. Table 1 gives a rough time line for the origin agriculture in seven fairly well understood centers of domestication, two more controversial centers, two areas that acquired agriculture by diffusion, and two areas that were without agriculture until European conquest.

The list of independent centers is complete as far as current evidence goes, and while new centers are not unexpected it is hard to believe that the present list will be doubled by further investigation. The areas that acquired agriculture by diffusion are very numerous, so the three areas in Table 1 are but a small sample.

The number of non-arctic areas without agriculture at European contact is small and the two listed, Western North America and Australia, are the largest and best known. Archaeologists are convinced that the seven centers of domestication are indeed independent on several grounds. First, the domesticates taken up in each center are distinctive and no evidence of domesticates from other centers turns up early in the sequence. For example, the Eastern North American center took into cultivation sunflower, a goosefoot, marsh elder, a squash, and other local plants.

Long after these plants were taken into cultivation, maize was traded into the region and was grown in small quantities beginning around 2, B. However, it remained a minor domesticate until around 1, B. The Eastern squash is closely related to the Mexican squash, but genetic and morphological evidence indicates that two subspecies were independently taken into cultivation.

Second, archaeology suggests that none of the centers had agricultural neighbors at the time that their initial domestications were undertaken. The two problematic centers, New Guinea and Lowland South America, present difficult archaeological problems Smith Sites are hard to find and organic remains are rarely preserved. The New Guinea evidence consists of apparently human constructed ditches that might have been used in controlling water for taro cultivation.

The absence of documented living sites associated with these features makes their interpretation quite difficult. The Lowland South American evidence consists of starch grains embedded in pottery fragments and phytoliths, microscopic silicious structural constituents of plant cell walls. The large size of some early starch grains and phytoliths convinces some archaeologists that root crops were brought under cultivation in the Amazon Basin at very early dates. Given the recency with which the Eastern North American and North and South China centers were firmly established, the discovery of a few more centers is likely.

Note that the date of the initiation of agriculture varies quite widely. Henry , and then reverted to mobile hunting and gathering during the sharp, short Younger Dryas 12,, B. Post-Natufian cultures began to domesticate the same species virtually the moment warm and stable conditions returned after the Younger Dryas, around 11, B. In North, and possibly South, China, however, agriculture probably followed within a thousand years even though the earliest clearly agricultural complexes are considerably later Crawford ; An Agriculture may prove to be as early in North China as in the Near East, since the earliest dated sites, which extend back to B.

Excavations in North China north of the earliest dated agricultural sites document a technological change around 11, B. In all known cases, the independent centers of domestication show a sequence beginning with a shift from a hunter-gatherer subsistence system based disproportionately upon the capture of large game to a strategy based upon small game and especially plant seeds or other labor-intensive plant resources Hayden The reasons for this shift are the subject of much work among archaeologists Bettinger in press.

These shifts invariably occur in the latest Pleistocene or later. Driven by the competitive ratchet, hunter-gathers who subsidize the hunting population with a large measure of plant-derived calories will tend to deplete the most desirable big game to levels that cannot sustain hunting specialists.

Once better climates made the shift possible, the first escalation began in what would become the agricultural subsistence race. The cases where intensification of plant gathering did not lead to agriculture are in some ways as interesting as the cases in which it did.

The Jomon of Japan represents one extreme Imamura Widespread use of simple pottery, a sure marker of well developed agricultural subsistence in Western Asia, was very early in the Jomon, contemporary with the latest Pleistocene Natufian in the Near East. By 11, yrs B. However, the Jomon domesticated no plants, although they cultivated a few minor crops like bottle gourds. Agriculture came to Japan with imported rice from the mainland only about 2, B.

Interestingly, acorns were a major item of Jomon subsistence. The people of California were another group of sedentary hunter-gatherers that depended heavily on acorns. However, in California the transition to high plant dependence began much later than in the Jomon Wohlgemuth Millingstones for grinding small seeds became important after 4, B.

After 2, B. In the latest period, after B. Other peoples with a late onset of intensification include the Australians. The totality of cases tell us that any stage of the intensification sequence can be stretched or compressed by several thousand years even though reversals are rare Harris ; Price and Gebauer Farming gave way to hunting and gathering in the southern and eastern Great Basin of North America after a brief extension of farming into the region around 1, B. Lindsay A similar reversal occurred in southern Sweden between 2, and 1, B.

Once well-established agricultural systems exist, they expand at the expense of hunting and gathering neighbors Bellwood The spread into Europe is best documented. Agriculture reached the Atlantic seaboard about 6, B. The regularity of the spread, and the degree to which it was largely a cultural diffusion process as opposed to a population dispersion as well, are matters of debate.

Cavalli-Sforza et al. They imagine that pioneering agricultural populations moved into territories occupied by hunter-gatherers, intermarried with the pre-existing population. The then mixed population in turn sent agricultural pioneers still deeper into Europe. They also suppose that the rate of spread was fairly steady, though clearly frontiers between hunter-gathers and agriculturalists stabilized in some places Denmark, Spain for relatively prolonged periods.

Zvelebil stresses the durability of frontiers between farmers and hunter-gatherers and the likelihood that in many places the diffusion of both genes and ideas about cultivation was a prolonged process of exchange across a comparatively stable ethnic and economic frontier. Further archaeological and paleo-genetic investigations will no doubt gradually resolve these debates.

Clearly, the spread process is at least somewhat heterogeneous. Other examples of the diffusion of agriculture are relatively well documented. For example, maize domestication is dated to about B. New Mexico; Smith ; Matson In this case, the frontier of maize agriculture stabilized for a long time, only reaching the Eastern U.

Maize failed entirely to diffuse westward into the Mediterranean parts of California even though peoples growing it in the more arid parts of its range in the Southwest used irrigation techniques that would have worked well there. As with the origin process, the rate of spread of agriculture exhibits an interesting degree of variation. A number of plant and animal biologists have taken an interest in the process of the evolution of domesticates Zohary and Hopf , Rindos , Bretting , Smith, The first changes in seed crop plants generally include larger seeds, the loss of natural seed dispersal mechanisms, and the loss of seed dormancy.

These changes do not necessarily require any conscious selection by cultivators. Once humans began to intensively exploit wild seed plants, especially once they prepared seedbeds and deliberately planted seeds, these changes will tend to be automatic. Larger seeds yield more competitive seedlings in the artificial seedbed. Those seeds that do not drop off the stalk are more likely to be harvested, favoring genotypes with non-shattering seed heads.

With humans controlling the time of planting and storing seed in cool, dry locations, seed dormancy, rather than producing adaptively facultative germination, merely increases the chance that a seed will fail to germinate in time to be harvested. As Flannery observed, it is not clear which species is the domesticated and which the domesticator in agriculture!

Some plants responded to human harvest in such a way that they induced humans to plant more of that species in competition with others, raise larger numbers of children to plant still more fields, and eventually to carry the plant across continents.

Of course, every human population includes close observers and inveterate experimenters. No doubt deliberate ingenuity and sustained artificial selection also played roles in the evolution of domesticates, as they do in the development and conservation of landraces today Brush The overall pattern of subsistence intensification is clearly consistent with the hypothesis that agriculture was impossible in the Pleistocene but mandatory in the Holocene, but the real test is whether or not we can give a satisfactory account of the variation in the rate and sequence of intensification.

Work on this project is in its infancy, and only some rather preliminary and speculative answers are possible. In general, external processes of macroevolution will tend to operate at longer time scales and internal processes at shorter time scales. Evolution has to be flexible and rapid enough to roughly track environmental variation, and environmental variation is greater at longer than shorter time scales.

Those species that fail to track longer-term variation will go extinct, and will not contribute to the evolutionary processes we see in action. At the same time, no evolutionary process responds instantaneously. There is always stickiness at short enough time scales. If the world were simple, the time scales of internal and external processes would be entirely separate.

To a first approximation, the lack of agriculture before the Holocene is due to the external effect of the Pleistocene climate; after that the rate of progress toward ever more intensive subsistence is largely regulated by internal processes. However, external causes did not entirely disappear in the Holocene. To completely isolate the effects of internal processes we have to control for residual external effects. Climate change may play a small role. The Holocene climate is only invariant relative to the wild oscillations of the last glacial Lamb, For example, seasonality difference between summer and winter insolation was at a maximum at the beginning of the Holocene and has fallen since.

Agriculture at marginal altitudes in places like the Andes seems to respond to Holocene climatic fluctuation Kent While the effect of Holocene climate fluctuations on regional sequences must always be kept in mind, the dominance of the nearly always monotonic tendency to increased subsistence efficiency per unit land seems likely to be driven by other processes.

Geography may play a big role. Diamond argues that Eurasia has had the fastest rates of cultural evolution in the Holocene because of its size and to a lesser extent its orientation. Plausibly, the number of innovations that occur in a population is, to a first approximation, a function of total population size and the flow of ideas between sub-populations.

Societies acquire most innovations by diffusion from other societies, and isolated societies will be handicapped in their rate of innovation by a slower rate of diffusion. Eurasia is the largest continent and is especially large in its east-west dimension. Innovations occurring at one end of the continent will eventually diffuse to the other, spreading along lines of latitude with relatively similar environments.

Small land-masses like Australia and New Guinea are substantially isolated from the larger world and have a much smaller base of innovators. The Americas, though quite respectable in size, are oriented with their major axis north-south.

Consequently innovations have to mainly spread across lines of latitude from the homeland environment to quite different ones. Wheat varieties originating in the Near East could spread to Spain and to Western China without substantial modification.

The maize moving north from Mexico would have to be selected to respond appropriately to longer day length and a shorter growing season. Maize spreading to South America would have to move through a belt of hot, wet, tropics with little day length variation before reaching the cool, semiarid, subtropical highlands of South America so similar to its original homeland.

In the case of domestication, the distinction between external and internal regulation of process rates is ambiguous without further definition. The genetic changes in the proto-domesticate, as it responds to cultural practices, are external to the cultural evolutionary system in one sense. In another, the coevolutionary system as a whole is, perhaps, more naturally seen as having intertwined the evolution of human culture and plant and animal genomes as to make such a distinction artificial.

Human genomes may also be involved in the coevolutionary system. Agriculture requires pre-adapted plants and animals. In each center of domestication, people domesticated only a handful of the wild plants that they formerly collected, and of this handful even fewer are widely adopted outside those centers. The same is true for domesticated livestock. Wheat, rice, and maize make disproportionate contributions to total world crop production. Cattle, sheep, goats, hogs, and chickens make an outsized contribution to total world livestock production.

Zohary and Hopf have listed some of the desirable features in plant domesticates. Aside from obvious things like large seed size, most Near Eastern domesticates had high rates of self-fertilization. This means that farmers can select desirable varieties and propagate them with little danger of gene flow from other varieties or from weedy relatives.

Maize, by contrast, outcrosses at high rates. Perhaps the later and slower evolution of maize compared to Near Eastern domesticates is due to the difficulty of generating responses to selection in the face of gene flow from unselected populations.

Smith discusses the many constraints on potential animal domesticates. For example, many large ungulates like deer depend upon rapid flight to avoid predators. They are thus very skittish and adapt poorly to human handling. Larger herd ungulates that are less susceptible to large predators, like cattle, have shorter flight distances and more stolid temperaments. Even in the most favorable cases, the evolution of new domesticates is not an instantaneous process.

In at least some times and some places, the rate of evolution of domesticates was likely the rate-limiting step in the agricultural intensification process. Diamond , drawing on the work of Blumler , notes that the Near Eastern region has a flora that is unusually rich in large-seeded grasses Table 2. California has so many climatic, topographic, and ecological parallels with the precocious Fertile Crescent that its very tardy development of plant-intensive subsistence systems is a considerable puzzle.

The presence of a large suite of agriculturally preadapted plants in the Near East but not in California provides a plausible hypothesis to explain the difference in agriculture but not plant intensification itself. The macroevolutionary patterns in which we are most interested are the processes strictly internal to cultural evolution that might limit the rate of intensification.

We Boyd and Richerson ; Bettinger view cultural evolution as a Darwinian process of descent with modification. Evidence about the macroevolutionary tempo and mode of cultural evolution bear directly on our picture of the micro scale processes that form the body of the theory. For many characters human decisions have relatively weak effects in the short run although they can be powerful when integrated over many people and appreciable spans of time.

If the rational-choice element in our models is sufficiently strong, then the rate of cultural evolution itself will never be rate limiting and cultural evolution will lack the Darwinian element. The tempo of subsistence intensification will then be entirely governed by external or coevolutionary processes. Selective processes can also cause quite rapid evolution compared to the time scales of external processes.

Selection acts to drive populations up slopes of fitness toward peaks in an adaptive topography. If fitness topographies are smooth, the populations climb more or less directly and quickly to global optima. On the other hand, if fitness topographies are rough, much more complex trajectories will ensue. Populations will tend to get stuck on local peaks in the foothills of a fitness topography.

Chance events may eventually carry small populations across fitness valleys. For example, minor climate change may shift the topography allowing one population to escape a local peak and run up to a higher one. A population of populations a metapopulation in the jargon will, by various historically contingent routes, gradually filter to higher and higher fitness peaks. Historically minded scholars have always believed that such complexities were important e.

Vayda , but only recently have models of biological, cultural, and economic change become sophisticated enough to investigate them formally. Typically the structural changes in such models are straightforward extensions of classical models that behave ahistorically. We think that such models should lead to closer and more productive interactions between theorists and historians Boyd and Richerson Several internal processes may lead to rough fitness topographies and thus act to limit the rate of cultural evolution of intensification.

New technological complexes evolve with difficulty. One problem that will tend to slow the rate of cultural and organic evolution is the sheer complexity of adaptive design problems. As engineers have discovered when studying the design of complex functional systems, discovering optimal designs is quite difficult.

Blind search algorithms often get stuck on local optima. Piecemeal improvements at the margin are not guaranteed to find globally optimal adaptations by myopic search. Yet, myopic searches are what Darwinian processes do.

The large step change in environment at the Pleistocene-Holocene transition set off the trend of subsistence intensification of which modern industrial innovations are the latest examples. The diversity of trajectories taken by the various regional human sub-populations since 11, B.

We believe that the discussion above is not only a basic review of the main cultural macroevolutionary hypotheses currently entertained by scholars but also a crude picture of how cultural macroevolution has actually happened. Social scientists are in the habit of treating these processes as mutually exclusive hypotheses. They seem to us to be competing but certainly not mutually exclusive. At the level of qualitative empiricism, tossing any one out entirely leaves puzzles that are hard to account for and produces an obvious caricature of the actual record of change.

If this conclusion is correct, the task for historically minded social scientists is to refine estimates of the rates of change that are possible due to the various evolutionary processes and to estimate of how those rates change as a function of natural and socio-cultural circumstances. Sustaining agriculture under conditions of much higher high frequency environmental variation than farmers currently cope with would be a very considerable technical challenge.

At the very best, lower CO 2 concentrations and lower world average precipitation suggest that world average agricultural output would fall considerably. In one sense, though, the Holocene is not just another interglacial. Recall that Petit et al. Current anthropogenic global warming via greenhouse gasses threatens to elevate world temperatures to levels that in past interglacials apparently triggered a large feedback effect producing a relatively rapid decline toward glacial conditions.

The Arctic ocean ice pack is currently thinning very rapidly Kerr No one can yet estimate the risks we are taking of a rapid return to colder, drier, more variable environment with less CO 2 , nor evaluate exactly the threat such conditions imply for the continuation of agricultural production. Nevertheless, the intrinsic instability of the Pleistocene climate system, and the degree to which agriculture is dependent upon the unusually long Holocene stable period, should give one pause Broecker Allen, J.

Brandt, A. Brauer, H. Hubberten, B. Huntley, J. Keller, M. Kraml, A. Mackensen, J. Mingram, J. Negendank, N. Nowaczyk, H. Oberhansli, W. Watts, S. Wulf and B. Nature Ammerman, A. Man An, Z. World Archaeology 23 2 Bar-Yosef, O, and R.

Gebauer, pp. Bellwood, P. Harris, pp. Smithsonian Institution Press, Washington, D. Bettinger, R. Plenum, New York. Billman and G. Feinman, pp. Feinman and T. Plenum, New York, in press. American Antiquity Blumler, M. Thesis, University of California, Berkeley. UMI, Ann Arbor. Boyd, R. University of Chicago Press, Chicago. In History and Evolution , edited by M. Nitecki, pp. Bradley, R. Academic Press, San Diego. Braidwood, R. Scientific American 3 Braidwood, R,J. Studies in Ancient Oriental Civilization University of Chicago Oriental Institute, Chicago.

Braidwood, L. Braidwood, B. Howe, C. Reed, and P. Watson editors. Bretting P. Economic Botany 44 Supplement. Broecker, W. Science Brush, S. Crop Science Bettinger and P. Bettinger , P. Richerson , Robert Boyd Published Evolutionary scholars advance two major sorts of hypotheses to explain big events, such as the origin of agriculture.

One hypothesis assumes that natural selection is so powerful that organisms are always close to an evolutionary equilibrium with current environment. Thus, any major changes will be a result of external processes having to do with the environment. Save to Library. Create Alert. Launch Research Feed. Share This Paper. Citation Type. Has PDF. Publication Type. More Filters. The beginning of herding and animal management: the early development of caprine herding on the Konya plain, central Anatolia.

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