 Keratins are a major component of hairs.Humans still have nine functional type I hair keratin genes, but the loss of that particular gene may have caused the thinning of human body hair.Based on the assumption of a constant molecular clock, the study predicts the gene loss occurred relatively recently in human evolution—less than 240 000 years ago, but both the Vindija Neandertal and the high-coverage Denisovan sequence contain the same premature stop codons as modern humans and hence dating should be greater than 750 000 years ago.