Our ancient hominin relatives who wandered around Africa were a lot hairier than most of us modern humans. However a few rare examples of people who grow excessive amounts of hair are still found today. Pictured are males, and a female (bottom right with magnified inset), of a particularly hirsute Mexican family. It is thought that such people are exhibiting genetic atavism – whereby genes that were once responsible for an ancestral trait, such as a full coat of body hair, and that have altered their expression over the course of human evolution, have somehow reverted to their ancestral pattern. In the case of this Mexican family, researchers have found a chromosomal rearrangement that affects a gene called FGF13. The FGF13 protein is expressed in hair follicles and is thought to regulate their growth and activity, possibly explaining why this gene’s misregulation has caused an ancestral-like overgrowth of hair.
Written by Ruth Williams
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