According to a study of the Western African Pygmies in Cameroon, published in PLoS Genetics, genes that may be responsible for the relatively small size of pygmies have been identified by a team of geneticists from the University of Pennsylvania. On average, pygmy men stand just 4'11" tall.
In addition, based on genetic signatures of natural selection, the study reveals that hormonal pathways and immune system regulation may have been the evolutionary drivers of pygmies' short stature.
The researchers conducted a genome-wide association study in order to identify genes that affect the height of pygmies, and discovered several promising candidates in the region of chromosome 3.
They found that genes DOCK3 and CISH stood out the most - both have previously been associated to size variation.
CISH has also been involved in becoming susceptible to infectious diseases. This finding could be significant, given that pygmies who live in a tropical climate have to deal with the heavy burdens of parasites and other agents that cause disease.
In addition, the team found genetic variations in the pygmies that seem to be subject to natural selection. In several cases, they discovered that the variations were linked to biological pathways that control reproductive hormone activation, such as growth hormone regulation and immune system function.
Sarah Tishkoff, senior author on the study, and a Penn Integrates Knowledge Professor, explained:
"Genes in those pathways are important in reproduction and metabolism and that was intriguing in light of the hypothesis that the reason Pygmies are short is so that they can reach reproductive maturity early.
Early reproduction could be a significant advantage in Pygmies, whose life spans average between 15 and 24 years."
Furthermore, the teams' multi-faceted approach may also be used to research other complex genetic traits, from disease susceptibility to physical characteristics.
Written By Grace Rattue