Don’t Sweat It: An Anthropological Look at the Science of Perspiration
You know those humid days, the real thick and steamy ones? You know why they're so uncomfortable? Because your sweat isn’t evaporating. The function of sweating developed over the course of human evolution, a span of millions of years. When sweat evaporates, it absorbs body heat. When it’s humid, the air is already saturated with water vapor so sweat evaporates at a lower rate. No evaporation, no cool down.
As you may have noticed, though, (especially in the summer months) some people sweat significantly more than others. Andrew Best, a doctoral student in the UMass Amherst Department of Anthropology, is trying to figure out why that is.
"Our ancestors were able to walk and run long discances, which is only possible if you can cool."
It’s fitting for Best. A quick glance at his website and Twitter feed provides an outline of who he is: a long-distance runner, mountain biker, cyclocross racer, and research enthusiast. Best is an endurance athlete, to put it mildly, which explains his fascination with what Angela Lamb, a dermatologist at the Icahn School of Medicine at Mount Sinai, described as “the urine of the skin.”
The Science of Sweat
Best’s research is focused on sweat gland density. He aims to see if the density is related to where people grew up, and if it affects the body’s ability to cool itself. Sweat as a mechanism for cooling was as monumental a human development as the ability to walk on two legs. When early humans migrated out of Africa and dispersed around the world, sweat glands likely evolved to adapt to changing environments. This allowed our distant ancestors to travel great distances through varying climates – a feat only made possible by the ability to sweat.
“This is sort of an underappreciated piece of the puzzle of human evolution,” said Best, a veteran of the Boston Marathon, Providence Marathon, and Mt. Washington Road Race, among other demanding competitions.
Simple Questions, Big Project
To find out if sweat gland density is related to the environment, Best recruited volunteers from differing childhood climate backgrounds and geographies. He’s measuring sweat gland density in six locations on the body using a method called pilocarpine iontophoresis, which stimulates the glands to produce sweat. A layer of silicone material is applied in which sweat droplets leave an impression, which allows Best to account for density.
To determine the relationship between sweat gland density and the body’s ability to regulate heat, Best had 20 endurance athletes to ride a stationary bike for an hour inside a metabolic chamber. This allows him to measure the amount of heat produced by the body, and how much heat is removed by sweating. He also records sweat gland density using the pilocarpine iontophoresis method. The facility is one of just 26 in the world that enables accurate measurement of metabolic rate and heat dissipation.
“It’s a pretty big project for what are fairly simple questions,” said Best.
For his work, the Leakey Foundation’s Board of Trustees awarded Best with one of 35 research grants. Best works in the lab of Jason Kamilar, associate professor of anthropology, and a colleague of his, Andrew Zamora, who also conducts research in Kamilar’s lab, also won a grant from the Leakey Foundation. In addition, Best won a grant from the Wenner-Gren Foundation.