When it comes to the architecture of the human genome, it’s only a matter of time before harmful genes — genes that could compromise future generations — arise in a population. These mutations accumulate in the gene pool, primarily affected by a population’s size and practices like marrying within a small community. New research published in the Proceedings of the National Academy of Sciences (PNAS) journal provides rare direct evidence showing that increased homozygosity — meaning two identical alleles in a genome — leads to negative effects on fertility in a human population.

An international team of researchers, including UC Davis Associate Professor of Anthropology Nicolas Zwyns, has uncovered the earliest known representation of a sexed personal ornament in human history. The study, published in Scientific Reports, describes and analyzes a phallus-shaped black pendant discovered in northern Mongolia and dating back to 42,000 years ago. In addition to pushing back the timeline for sexed symbolic representation in the archaeological record, the pendant was discovered in a location where Homo sapiens mingled with other ancient human species, including the extinct Denisovans. The research adds more fuel to the debate about whether figurative depictions in art was a trait exclusive to Homo sapiens in ancient human history.