Humans evolved to need less water than primate relatives, study finds
(KTVX) -- When you think about how far mankind has come mentally, technologically and physically, we see great strides, especially when compared with our primate relatives. But there is another feature that sets us apart from our chimpanzee and ape ancestors: water efficiency.
A study conducted by Duke University's School of Nursing measures precisely how much water humans lose and replace each day compared with our closest living animal relatives and found that humans have evolved to be run on less water.
Our bodies are constantly losing water -- when we sweat, go to the bathroom, even when we breathe. And to keep our blood volume and other body fluids within their normal ranges, water constantly needs to be replenished but apparently not as much as for our animal cousins.
Research illustrates that the human body tends to use 30% to 50% less water per day than primates, according to another study, published March 5 in the journal Current Biology.
"While humans drink daily to maintain water balance, rainforest-living great apes typically obtain adequate water from their food and can go days or weeks without drinking," the report said.
An ancient shift in the human body's ability to conserve water may have enabled our hunter-gatherer ancestors to venture farther from streams and watering holes in search of food, said lead author Herman Pontzer, associate professor of evolutionary anthropology at Duke University.
"Even just being able to go a little bit longer without water would have been a big advantage as early humans started making a living in dry, savannah landscapes," Pontzer added.
According to Pontzer, the research compared the water turnover of 309 people with a range of lifestyles, from farmers and hunter-gatherers to office workers, with that of 72 apes living in zoos and sanctuaries.
He added that life is all about balance: "Water coming in has to equal water coming out."
Pontzer explained that when a person begins to sweat, the body's thirst signals kick in informing them to take in the water it exerted.
When conducting the study, Pontzer said each researcher calculated water intake via food and drink on one hand and water lost via sweat, urine and the GI tract on the other.
Researchers discovered that the average person tends to process about 12 cups of water each day. According to officials, a chimpanzee or gorilla living in a zoo typically goes through twice that much.
Pontzer said he and the other researchers were surprised because "among primates, humans have an amazing ability to sweat."
"Humans have 10 times as many sweat glands as chimpanzees do," Pontzer said.
According to officials, that makes it possible for a person to sweat more than half a gallon during an hour-long workout — equivalent to two 7-Eleven Big Gulps.
The findings are even more notable considering that chimpanzees, bonobos, gorillas and orangutans tend to live rather sedentary. "Most apes spend 10 to 12 hours a day resting or feeding, and then they sleep for 10 hours. They really only move a couple of hours a day," Pontzer said.
Overall, the study suggests that changes in climate, diet, and behavior over the course of human evolution apparently reduced the amount of water our bodies use each day to stay healthy.