In the early 2000s FOXP2 was dubbed the “language gene”. It was a sexy story. Humans exhibited accelerated adaptive evolution on this locus in relation to our relatives. Additionally, vocally oriented lineages such as birds and whales were also subject to the same process.
But over the past five years or so I’ve heard a lot of skepticism of the early claims as more genomic datasets have come online. Cell has a new paper which pretty much smashes the door down and breaks the skepticism out into the open, No Evidence for Recent Selection at FOXP2 among Diverse Human Populations:
FOXP2, initially identified for its role in human speech, contains two nonsynonymous substitutions derived in the human lineage. Evidence for a recent selective sweep in Homo sapiens, however, is at odds with the presence of these substitutions in archaic hominins. Here, we comprehensively reanalyze FOXP2 in hundreds of globally distributed genomes to test for recent selection. We do not find evidence of recent positive or balancing selection at FOXP2. Instead, the original signal appears to have been due to sample composition. Our tests do identify an intronic region that is enriched for highly conserved sites that are polymorphic among humans, compatible with a loss of function in humans. This region is lowly expressed in relevant tissue types that were tested via RNA-seq in human prefrontal cortex and RT-PCR in immortalized human brain cells. Our results represent a substantial revision to the adaptive history of FOXP2, a gene regarded as vital to human evolution.
