The human diet today is very different than the diets of other primates, implying major changes following the split of the human and chimpanzee/bonobo lineages about 6 million years ago. For example, at various timepoints our ancestors began consistently eating meat, cooking food with fire, and consuming products from domesticated plants and animals. Such dietary shifts are important to study because they were likely associated with important cultural and biological changes like tool use and increased brain size. However, the timing of some of these dietary shifts is extremely difficult to study with only archeological and fossil data, leading to uncertainty. In this article, we discuss how studies of human tapeworm parasites can help. Tapeworms could only have been acquired once meat was being consistently consumed and then may have later adapted to heat stress from human cooking.

Objectives: The ability to use visual signals to identify individuals is an important feature of primate social groups, including humans. Sheehan and Nachman (2014) showed that loci linked to facial morphology had elevated levels of diversity and interpreted this as evidence that the human face is under frequency-dependent selection to enhance individual recognition (Nature Communications 5). In our study, we tested whether this pattern is found in non-human ape species, to help understand whether individual recognition might also play a role in species other than humans. Materials and methods: We examined levels of genetic diversity in an available population genomic dataset of humans, chimpanzees, bonobos, gorillas, and orangutans for three sets of loci, (1) loci linked to facial morphology, (2) loci linked to height, and (3) neutrally evolving regions. We tested whether loci linked to facial morphology were more variable than loci linked to height or neutrally evolving loci in each of these species. Results: We found significantly elevated diversity in loci linked to facial morphology in chimpanzees, gorillas, and Sumatran and Bornean orangutans. Discussion: Our findings closely parallel those of Sheehan and Nachman and are consistent with the idea that selection for facial diversity and individual recognition has not only shaped the evolution of the human face, but it has similarly shaped the evolution of most of our closest primate relatives. We also discuss alternative hypotheses for this pattern.

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