Hydrological changes in the African tropics since the Last Glacial Maximum

Over the past 25 years, Boyd and Richerson have become well-known across a wide range of disciplines for their path-breaking work on evolution and culture. This work collects twenty of the influential but relatively inaccessible published articels that form the backbone of this research. It could not be more timely given the growing influence of evolutionary psychology. The papers - which were published in a diverse set of journals and which are not easily available - a conceptually linked and form a cohesive, unified evolutionary account of human culture. Their interdisciplinary research is based on two notions. First, that culture is crucial for understanding human behavior: unlike other organism, socially transmitted beliefs, attitudes and values heavily influence our behavior. Secondly, culture is part of biology: the capacity to acquire and transmit culture is a derived component of human psychology, and the contents of culture are deeply intertwined with our biology. Taking off from these two assumptions, Boyd and Richerson's novel idea is that culture is a pool of information, stored in the brains of a population, that gets transmitted from one brain to another by social learning processes. Among their conclusions: culture can account for both our astounding ecological success as well as the maladaptations that characterize much of human behavior. Interest in Boyd and Richerson's work spans anthropology, psychology, economics, philosophy, and political science, and has influenced work on animal behavior, economics and game theory, memes, and even archaeology.

/pdf/the-origin-and-evolution-of-cultures-14vx5m6p7t.pdf

The Origin and Evolution of Cultures

Late Quaternary dynamics of southern Africa's winter rainfall zone

The flora of the south-western tip of southern Africa, the Cape flora, with some 9000 species in an area of 90,000 km2 is much more speciose than can be expected from its area or latitude, and is comparable to that expected from the most diverse equatorial areas. The endemism of almost 70%, on the other hand, is comparable to that found on islands. This high endemism is accounted for by the ecological and geographical isolation of the Cape Floristic Region, but explanations for the high species richness are not so easily found. The high species richness is accentuated when its taxonomic distribution is investigated: almost half of the total species richness of the area is accounted for by 33 'Cape floral clades'. These are clades which may have initially diversified in the region, and of which at least half the species are still found in the Cape Floristic Region. Such a high contribution by a very small number of clades is typical of island floras, not of mainland floras. The start of the radiation of these clades has been dated by molecular clock techniques to between 18 million years ago (Mya) (Pelargonium) and 8 Mya (Phylica), but only six radiations have been dated to date. The fossil evidence for the dating of the radiation is shown to be largely speculative. The Cenozoic environmental history of southern Africa is reviewed in search of possible triggers for the radiations, climatic changes emerge as the most likely candidate. Due to a very poor fossil record, the climatic history has to be inferred from larger scale patterns, these suggest large-scale fluctuations between summer wet (Palaeocene, Early Miocene) and summer dry climates (Oligocene, Middle Miocene to present). The massive speciation in the Cape flora might be accounted for by the diverse limitations to gene flow (dissected landscapes, pollinator specialisation, long flowering times allowing much phenological specialisation), as well as a richly complex environment providing a diversity of selective forces (geographically variable climate, much altitude variation, different soil types, rocky terrain providing many micro-niches, and regular fires providing both intermediate disturbances, as well as different ways of surviving the fires). However, much of this is based on correlation, and there is a great need for (a) experimental testing of the proposed speciation mechanisms, (b) more molecular clock estimates of the age and pattern of the radiations, and (c) more fossil evidence bearing on the past climates.

The radiation of the Cape flora, southern Africa

Several independent trajectories of subsistence intensijcation, often leading to agriculture, began during the Holocene. No plant-rich intensijcations are known from the Pleistocene, even from the late Pleistocene when human populations were otherwise quite sophisticated. Recent data from ice and ocean-core climate proxies show that last glacial climates were extremely hostile to agriculture-dry, low in atmospheric CO,, and extremely variable on quite short time scales. We hypothesize that agriculture was impossible under last-glacial conditions. The quite abruptfinal amelioration of the climate was followed immediately by the beginnings of plant-intensive resource-use strategies in some areas, although the turn to plants was much later elsewhere. Almost all trajectories of subsistence intensijcation in the Holocene are progressive, and eventually agriculture became the dominant strategy in all but marginal environments. We hypothesize that, in the Holocene, agriculture was, in the long run, compulsory. We use a mathematical analysis to argue that the rate-limiting process for intensijcation trajectories must generally be the rate of innovation of subsistence technology or subsistence-related social organization. At the observed rates of innovation, population growth will always be rapid enough to sustain a high level of population pressure. Several processes appear to retard rates of cultural evolution below the maxima we observe in the most favorable cases.

/pdf/was-agriculture-impossible-during-the-pleistocene-but-wl723cmtgc.pdf

Was agriculture impossible during the pleistocene but mandatory during the holocene? a climate change hypothesis

Correlation between Vegetation in Southwestern Africa and Oceanic Upwelling in the Past 21,000 Years

A high resolution marine pollen record from site GeoB1023, west of the northern Namib desert provides data on vegetation and climate change for the last 21 ka at an average resolution of 185 y. Pollen and spores are mainly delivered to the site by the Cunene river and by surface and mid-tropospheric wind systems. The main pollen source areas are located between 13°S and 21°S, which includes the northern Namib desert and semi-desert, the Angola-northern Namibian highland, and the north-western Kalahari. The pollen spectra reflect environmental changes in the region. The last glacial maximum (LGM) was characterised by colder and more arid conditions than at present, when a vegetation with temperate elements such as Asteroideae, Ericaceae, and Restionaceae grew north of 21°S. At 17.5 ka cal. B.P., an amelioration both in temperature and humidity terminated the LGM but, in the northern Kalahari, mean annual rainfall in the interval 17.5-14.4 ka cal. B.P. was probably 100–150 mm lower than at present (400–500 mm/y). The Late-glacial to early Holocene transition includes two arid periods, i.e. 14.4–12.5 and 10.9–9.3 ka cal. B.P. The last part of the former period may be correlated with the Younger Dryas. The warmest and most humid period in the Holocene occurred between 6.3 and 4.8 ka cal. B.P. During the last 2000 years, human impact, as reflected by indications of deforestation, enhanced burning and overgrazing, progressively intensified.

Vegetation and climate changes during the last 21 000 years in S.W. Africa based on a marine pollen record

Southwest African climate independent of Atlantic sea surface temperatures during the Younger Dryas

Southeast trade wind variations during the last 135 kyr: evidence from pollen spectra in eastern South Atlantic sediments

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Correlation between Vegetation in Southwestern Africa and Oceanic Upwelling in the Past 21,000 Years

Vegetation and climate changes during the last 21 000 years in S.W. Africa based on a marine pollen record

Southwest African climate independent of Atlantic sea surface temperatures during the Younger Dryas

Southeast trade wind variations during the last 135 kyr: evidence from pollen spectra in eastern South Atlantic sediments