Paleolakes and socioecological implications of last glacial "greening" of the South African interior.

Determining the timing and drivers of Pleistocene hydrological change in the interior of South Africa is critical for testing hypotheses regarding the presence, dynamics, and resilience of human populations. Combining geological data and physically based distributed hydrological modeling, we demonstrate the presence of large paleolakes in South Africa's central interior during the last glacial period, and infer a regional-scale invigoration of hydrological networks, particularly during marine isotope stages 3 and 2, most notably 55 to 39 ka and 34 to 31 ka. The resulting hydrological reconstructions further permit investigation of regional floral and fauna responses using a modern analog approach. These suggest that the climate change required to sustain these water bodies would have replaced xeric shrubland with more productive, eutrophic grassland or higher grass-cover vegetation, capable of supporting a substantial increase in ungulate diversity and biomass. The existence of such resource-rich landscapes for protracted phases within the last glacial period likely exerted a recurrent draw on human societies, evidenced by extensive pan-side artifact assemblages. Thus, rather than representing a perennially uninhabited hinterland, the central interior's underrepresentation in late Pleistocene archeological narratives likely reflects taphonomic biases stemming from a dearth of rockshelters and regional geomorphic controls. These findings suggest that South Africa's central interior experienced greater climatic, ecological, and cultural dynamism than previously appreciated and potential to host human populations whose archaeological signatures deserve systematic investigation.

Ostrich eggshell bead strontium isotopes reveal persistent macroscale social networking across late Quaternary southern Africa.

Hunter-gatherer exchange networks dampen subsistence and reproductive risks by building relationships of mutual support outside local groups that are underwritten by symbolic gift exchange. Hxaro, the system of delayed reciprocity between Ju/'hoãn individuals in southern Africa's Kalahari Desert, is the best-known such example and the basis for most analogies and models of hunter-gatherer exchange in prehistory. However, its antiquity, drivers, and development remain unclear, as they do for long-distance exchanges among African foragers more broadly. Here we show through strontium isotope analyses of ostrich eggshell beads from highland Lesotho, and associated strontium isoscape development, that such practices stretch back into the late Middle Stone Age. We argue that these exchange items originated beyond the macroband from groups occupying the more water-stressed subcontinental interior. Tracking the emergence and persistence of macroscale, transbiome social networks helps illuminate the evolution of social strategies needed to thrive in stochastic environments, strategies that in our case study show persistence over more than 33,000 y.

Static and moving frontiers: the genetic landscape of Southern African Bantu-speaking populations.

A consensus on Bantu-speaking populations being genetically similar has emerged in the last few years, but the demographic scenarios associated with their dispersal are still a matter of debate. The frontier model proposed by archeologists postulates different degrees of interaction among incoming agropastoralist and resident foraging groups in the presence of "static" and "moving" frontiers. By combining mitochondrial DNA and Y chromosome data collected from several southern African populations, we show that Bantu-speaking populations from regions characterized by a moving frontier developing after a long-term static frontier have larger hunter-gatherer contributions than groups from areas where a static frontier was not followed by further spatial expansion. Differences in the female and male components suggest that the process of assimilation of the long-term resident groups into agropastoralist societies was gender biased. Our results show that the diffusion of Bantu languages and culture in Southern Africa was a process more complex than previously described and suggest that the admixture dynamics between farmers and foragers played an important role in shaping the current patterns of genetic diversity.

Coalescence and fragmentation in the late Pleistocene archaeology of southernmost Africa.

The later Pleistocene archaeological record of southernmost Africa encompasses several Middle Stone Age industries and the transition to the Later Stone Age. Through this period various signs of complex human behaviour appear episodically, including elaborate lithic technologies, osseous technologies, ornaments, motifs and abstract designs. Here we explore the regional archaeological record using different components of lithic technological systems to track the transmission of cultural information and the extent of population interaction within and between different climatic regions. The data suggest a complex set of coalescent and fragmented relationships between populations in different climate regions through the late Pleistocene, with maximum interaction (coalescence) during MIS 4 and MIS 2, and fragmentation during MIS 5 and MIS 3. Coalescent phases correlate with increases in the frequency of ornaments and other forms of symbolic expression, leading us to suggest that population interaction was a significant driver in their appearance.

Rovibrational energy transfer in Ne-Li2(A1Sigmau+,v=0): Comparison of experimental data and results from classical and quantum calculations.

Absolute rate constants for rotational and rovibrational energy transfer in the system Ne-Li2(A1Sigmau+) were measured by a dispersed fluorescence technique following excitation of the (v = 0,j = 18) initial level of Li2(A1Sigmau+). The rate coefficients for Deltav = 0 processes decline monotonically with increasing |Deltaj|. The Deltav = 1 rate coefficients are also peaked near Deltaj = 0 but show a broad shoulder extending to approximately Deltaj = 30. Classical trajectory calculations and accurate quantum mechanical close-coupled calculations were used to compute theoretical rate constants from an ab initio potential surface. The agreement between the classical and quantum calculations is very good. The calculations slightly overestimate the measured rate constants for Deltav = 0, Deltaj or= 20, implying that the anisotropy of the ab initio surface is too small at short range and too large at long range. For Deltav = 1 collisions, the calculations agree well with experiment for Deltaj 0 collisions, disagreeing with experiment by a factor of 2 for Deltaj approximately 20 but agreeing better at higher and lower Deltaj. Analysis of classical trajectories indicates that the vibrationally inelastic collisions fall into two groups corresponding to equatorial and near-end impacts; the former generally produce small Deltaj while the latter produce large Deltaj. Studies of a simple model potential show that this dual mechanism may be a general phenomenon not limited to the particular potential surface employed here. Criteria controlling the relative importance of the two vibrational excitation routes are enumerated.

Defining the 'generalist specialist' niche for Pleistocene Homo sapiens.

Definitions of our species as unique within the hominin clade have tended to focus on differences in capacities for symbolism, language, social networking, technological competence and cognitive development. More recently, however, attention has been turned towards humans' unique ecological plasticity. Here, we critically review the growing archaeological and palaeoenvironmental datasets relating to the Middle-Late Pleistocene (300-12 thousand years ago) dispersal of our species within and beyond Africa. We argue, based on comparison with the available information for other members of the genus Homo, that our species developed a new ecological niche, that of the 'generalist specialist'. Not only did it occupy and utilize a diversity of environments, but it also specialized in its adaptation to some of these environmental extremes. Understanding this ecological niche provides a framework for discussing what it means to be human and how our species became the last surviving hominin on the planet.