The oral microbiome plays key roles in human biology, health, and disease, but little is known about the global diversity, variation, or evolution of this microbial community. To better understand the evolution and changing ecology of the human oral microbiome, we analyzed 124 dental biofilm metagenomes from humans, including Neanderthals and Late Pleistocene to present-day modern humans, chimpanzees, and gorillas, as well as New World howler monkeys for comparison. We find that a core microbiome of primarily biofilm structural taxa has been maintained throughout African hominid evolution, and these microbial groups are also shared with howler monkeys, suggesting that they have been important oral members since before the catarrhine–platyrrhine split ca. 40 Mya. However, community structure and individual microbial phylogenies do not closely reflect host relationships, and the dental biofilms of Homo and chimpanzees are distinguished by major taxonomic and functional differences. Reconstructing oral metagenomes from up to 100 thousand years ago, we show that the microbial profiles of both Neanderthals and modern humans are highly similar, sharing functional adaptations in nutrient metabolism. These include an apparent Homo-specific acquisition of salivary amylase-binding capability by oral streptococci, suggesting microbial coadaptation with host diet. We additionally find evidence of shared genetic diversity in the oral bacteria of Neanderthal and Upper Paleolithic modern humans that is not observed in later modern human populations. Differences in the oral microbiomes of African hominids provide insights into human evolution, the ancestral state of the human microbiome, and a temporal framework for understanding microbial health and disease.

The variation of orbit shape has been investigated, especially its role in population classification. However, previous studies that treated orbit shape as a linear metric or non-metric trait have not produced conclusive quantitative data to show whether orbit shape is an accurate reflection of population affinity. Thus, in this study in order to examine regional variation in the orbit shape of contemporary Asian, African, and European populations we use geometric morphometrics with a novel standardization technique. A standardized orbital plane was obtained and each specimen was photographed. The results from this study show that regional variation in orbit shape exists. The Asian orbital contour was generally tall, rounded, and its inferior contour was symmetrical. The European tended to be square and more inclined, with the African being shorter. Moreover, the orbit shape of some specimens from these three regions overlapped. The similarities between the Asian and European samples were much smaller than those between Africans and Asians, or Africans and Europeans. Additionally, intergroup variability was larger on the bones of the maxilla and zygoma which form the inferior contour of the orbit, compared with the frontal bone forming the superior contour. The most variable areas of the orbit concentrate on the internal aspect of the upper margin, on the contours near the frontomalare orbitale and zygomaxillare. The application of geometric morphometrics with the newly developed standardization protocol to examine orbit shape between individuals from different geographic areas, has demonstrated its use to measure quantitatively human orbit shape, variation, and population affinity.

No abstract

No abstract