Sex, genomes, history: molecular, evolutionary and cultural effects on human genetic diversity.

A single drop of blood from a man or a male great ape now contains enough DNA to trace how social rules, like who marries whom, have shaped human genetic diversity over thousands of years. This project addresses a fundamental gap: we know surprisingly little about how cultural behaviours—such as patrilocality (women moving to their husband’s village) or polygyny—leave measurable marks on the Y chromosome and X chromosome, compared with the rest of the genome. By sequencing roughly 4 million DNA bases from each of eight great apes and twenty humans, then analysing larger population samples from Europe and the British Isles, the researchers will directly compare male-inherited (Y), female-inherited (X), and autosomal DNA. This allows them to separate the effects of natural selection from the effects of marriage rules, migration, and major demographic events like the Neolithic spread of farming. The work is fundamental science. It will not produce a diagnostic test or a drug. But understanding how social organisation sculpts genetic variation is essential for interpreting human evolutionary history and for correctly modelling population genetics in medical studies. Similar curiosity-driven work on sex chromosomes has already revealed how gene conversion between X and Y can cause male infertility—a reminder that mapping these ancient processes can, over time, illuminate modern reproductive health.