The secret about human evolution found in spit

Genetic detectives discover surprising findings about our evolution by studying saliva

What does a protein in our spit called MUC7 that all of us have - but most of us have never heard of - have to do with human history? A surprising amount, as a recent paper by Xu et al. has discovered. Despite being a rather obscure protein to most of us, MUC7 is actually quite important - it helps get rid of bacteria and other junk in our oral tracts.

One of the most interesting features of the gene that encodes MUC7 is that it contains a series of repeated DNA sequences (called the "PTS repeat region" for the amino acids these sequences encode: proline, threonine, and serine). Repeated structural elements are a fairly common feature of the genome, and these regions tend to be where many interesting evolutionary events occur.