“Directed mutations” means that the cell alters its own genome for its own protection, rather than simply being the recipient of random interventions.
APOBEC enzymes are thought to defend human cells against viruses by mutating them so they don’t work any more. Pinto et al. wondered if there might be evidence of APOBEC enzymes acting on human and ape genomes as well. Think of it as a sort of “collateral damage” in the war against viruses. In their survey, they found eight thousand unique clusters of mutations that look like APOBEC mutations in the human genome, as well as the genomes of Neandertal and Denisovans. They found almost a half million that were unique to the entire genus Homo. The fact that these mutations are unique to these different forms of human indicates that this enzyme has indeed altered human genome sequences since creation. And that’s just one version of an enzyme family that has multiple variants in the human genome. More.
See also: Biochemist Todd Wood on homo Naledi burials
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