Understanding the timing and character of Homo sapiens expansion out of Africa is critical for inferring the colonisation and admixture processes that underpin global population history. It has been argued that dispersal out of Africa had an early phase, particularly ~130-90 thousand years ago (ka), that only reached the East Mediterranean Levant, and a later phase, ~60-50 ka, that extended across the diverse environments of Eurasia to Sahul. However, recent findings from East Asia and Sahul challenge this model. Here we show that H. sapiens was in the Arabian Peninsula before 85 ka. We describe the Al Wusta-1 (AW-1) intermediate phalanx from the site of Al Wusta in the Nefud Desert, Saudi Arabia. AW-1 is the oldest directly dated fossil of our species outside Africa and the Levant. The palaeoenvironmental context of Al Wusta demonstrates that H. sapiens using Middle Palaeolithic stone tools dispersed into Arabia during a phase of increased precipitation driven by orbital forcing, in association with a primarily African fauna. A Bayesian model incorporating independent chronometric age estimates indicates a chronology for Al Wusta of ~95-86 ka, which we correlate with a humid episode in the later part of Marine Isotope Stage 5 known from various regional records. Al Wusta shows that early dispersals were more spatially and temporally extensive than previously thought. Early H. sapiens dispersals out of Africa were not limited to winter rainfall-fed Levantine Mediterranean woodlands immediately adjacent to Africa, but extended deep into the semi-arid grasslands of Arabia, facilitated by periods of enhanced monsoonal rainfall.

Africa hosts the greatest human genetic diversity globally, but legacies of ancient population interactions and dispersals across the continent remain understudied. Here, we report genome-wide data from 20 ancient sub-Saharan African individuals, including the first reported ancient DNA from the DRC, Uganda, and Botswana. These data demonstrate the contraction of diverse, once contiguous hunter-gatherer populations, and suggest the resistance to interaction with incoming pastoralists of delayed-return foragers in aquatic environments. We refine models for the spread of food producers into eastern and southern Africa, demonstrating more complex trajectories of admixture than previously suggested. In Botswana, we show that Bantu ancestry post-dates admixture between pastoralists and foragers, suggesting an earlier spread of pastoralism than farming to southern Africa. Our findings demonstrate how processes of migration and admixture have markedly reshaped the genetic map of sub-Saharan Africa in the past few millennia and highlight the utility of combined archaeological and archaeogenetic approaches.

The amount of phenotypic variation between conspecifics is largely a result of the opposing forces of constraint and plasticity. Because selection is the product of competition between individuals of the same species, understanding the interactions between these forces is vital to understanding evolution. We investigated levels of intraspecific variation in the catarrhine skeleton using a morphometric analysis of 245 crania and 189 appendicular postcranial skeletons. We identified regions of interest from the literature and made comparisons of intraspecific variation between the appendicular postcranium and cranium, the forelimb and hind limb, the diaphyses and epiphyses of long bones, and the diaphyses of the proximal and distal segments of the limbs. We confirmed that variation is significantly higher in the appendicular postcranium than in the cranium, in the forelimb compared to the hind limb, and in the diaphyses compared to the epiphyses. Further, we found that this pattern was repeated in 12 species spanning the infraorder, suggesting a characteristic of catarrhines in general. The relatively low level of variation in the cranium suggests that constraint is more widespread in this region compared to the appendicular postcranium, which is more plastic, especially in the diaphyses of the forelimb. In contrast to previous studies, we found the diaphyses of the distal segment to be more variable than the diaphyses of the proximal segment. The results from this study, which show regional differences in intraspecific variation, will aid the interpretation of evolutionary and plastic influences on morphological variation and inform decisions about which skeletal regions are suitable for answering specific evolutionary questions.