Best and Kamilar's study on eccrine sweat glands in primates published in The Journal of Human Evolution.

Friday, February 23, 2018

University of Massachusetts anthropologists Andrew Best and Dr. Jason Kamilar's study, The evolution of eccrine sweat glands in human and nonhuman primates, has been published in the Journal of Human Evolution. Given that humans’ ability to sweat is unique in the animal kingdom, Best and Kamilar embarked on a research project to better understand the phenomenon.

Current ideas posit that we gained the ability to sweat more than two million years ago when our ancestors started to live in more dry and open habitats and walked or ran long distances. This is difficult to test, as sweat glands do not fossilize, leading Best and Kamilar to use a comparative approach. They compared living primate species to examine the relationship between temperature and rainfall and sweat gland characteristics.

“It’s interesting that some monkeys and apes use sweating to cool off because they have quite a lot of body hair, which blunts evaporation, making sweating less effective” said Best.  “We wondered if detailed characteristics of the sweat glands could tell us more about how sweating evolved in these primates, and in turn, infer how it may have evolved in the human lineage.”

Doctoral student Best and assistant professor Kamilar examined many primate species, including humans, compiling data on sweat glands published in the 1960’s and 1970’s. They found that primate species living in hot, dry climates tend to have sweat glands associated with more glycogen, which could be used to supply more energy for producing sweat. In addition, these primates also had more blood vessels feeding their sweat glands, which could also permit greater sweat production.  Their results suggest that these traits were produced as a result of natural selection.  

Kamilar explained: “Although humans are the ultimate ‘sweaters’, it seems that other primates similarly respond to warm and dry climates, evolving traits that increase sweating ability”.  This also suggests an earlier start to the beginnings of human sweating. “The current view is that our tremendous sweating capacity evolved near the beginning of our genus, when we lost much of our body hair and were very physically active”, said Best. “Our results suggest that initial increases in sweating capacity could have come much earlier, setting the stage for greater reliance on sweating later.”

The next phase of this research project will focus on variation in sweating and sweat glands in modern humans, testing hypotheses about the role of climate in activating sweat glands early in life. This work will be performed in collaboration with Harvard’s Dr. Dan Lieberman and the University of Pennsylvania’s Dr. Yana Kamberov.

Read the Full Article