Gorilla DNA reveals hidden genes behind male fertility

In gorillas, almost exclusively the dominant male mates. Other males in the group produce almost no offspring. This makes sperm competition unnecessary, since there is effectively only one rival who counts. This is known as sperm competition, and its absence turns out to have far-reaching genetic consequences for a species.

Researchers compared the genome of gorillas with that of 261 other mammal species. They examined which genes were under weaker selective pressure in gorillas, a process called relaxed purifying selection. Genes under purifying selection are normally kept efficiently free from harmful mutations. When that selective pressure disappears, damaging variants accumulate.

578 genes with compromised integrity

The researchers identified 578 genes in gorillas where selection was significantly relaxed. These genes are strongly expressed in male germ cells and involved in meiosis, the cell division that produces sperm. In the absence of sperm competition, harmful amino acid mutations accumulated in these genes.

Using the fruit fly Drosophila, the team showed that 41 of these genes are genuinely required for normal fertility, despite their function in that process being previously unknown. This makes them candidates for further investigation in male infertility.

Link to human infertility

Notably, the human counterparts of these gorilla genes more often carry loss-of-function variants in men with severe fertility problems. This is an association, not causal proof. But it does point toward future diagnostic research. From an ageing and reproductive health perspective, the study illustrates how evolutionary pressure shapes reproductive biology across generations, and how that information can open new avenues for medicine.

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