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New research suggests that humans evolved to run on less water than our immediate primate family


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When you think about what separates humans from chimpanzees and other monkeys, you can think of our big brains or the fact that we get around on two legs rather than four. But we have another characteristic: water efficiency.

It is the home of a new study that, for the first time, measures exactly how much water humans lose and replace each day compared to our immediate living animal families.

Our bodies constantly lose water: when we sweat, go to the toilet, even when we breathe. This water needs to be refilled to keep blood volume and other body fluids within normal intervals.

And yet, research was published March 5 in the journal Current biology shows that the human body uses 30% to 50% less water a day than our closest cousins. In other words, among primates, humans evolved to be the low-current model.

An ancient shift in our body̵

7;s ability to conserve water may have enabled our hunter-gatherer fathers to venture farther away from streams and ponds in search of food, said lead author Herman Pontzer, associate professor of evolutionary anthropology at Duke University.

“Even being able to walk a little further without water would have been a great advantage when early humans began living in arid, savannah landscapes,” Pontzer said.

The study compared the water turnover of 309 people with a variety of lifestyles, from farmers and hunter-gatherers to office workers with 72 monkeys living in zoos and shrines.

To maintain fluid balance within a healthy area, the body of a human or any other animal is a bit like a bathtub: “Water that comes in must be equal to water that comes out,” Pontzer said.

Loss e.g. Water by sweating, and the body’s thirst signals kick in and ask us to drink. Chug more water than your body needs and the kidneys get rid of the extra fluid.

For each individual in the study, the researchers calculated water intake via food and drink on the one hand and water lost via sweat, urine and the gastrointestinal tract on the other hand.

When they added all the inputs and outputs, they found that the average person treats about three gallons or 12 cups of water each day. A chimpanzee or gorilla living in a zoo undergoes twice as much.

Pontzer says the researchers were surprised by the results because humans among primates have an amazing ability to sweat. Per square inch of skin “humans have ten times as many sweat glands as chimpanzees have,” Pontzer said. It allows a person to sweat more than half a gallon during an hour-long workout – the equivalent of two Big Gulps from a 7-Eleven.

In addition, the great apes – chimpanzees, bonobos, gorillas and orangutans – live lazy lives. “Most monkeys spend 10 to 12 hours a day resting or feeding, and then they sleep for 10 hours. They really only move a few hours a day,” Pontzer said.

But the researchers checked for differences in climate, body size and factors such as activity level and calories burned per day. So they concluded that the water savings for humans were real and not just a function of where individuals lived or how physically active they were.

The results suggest that something changed during human development that reduced the amount of water our body uses every day to stay healthy.

So as of now, we could probably still only survive a few days without drinking, Pontzer said. “You probably won’t break the organic cord, but at least you’ll get one longer if you can go further without water.”

The next step, Pontzer says, is to find out how this physiological change happened.

One hypothesis suggested by the data is that our body’s thirst response was adjusted so that we generally want less water per day. Calorie compared to our monkey families. Even as babies, long before our first solid food, the ratio of water to calories for human breast milk is 25% less than the milk of other great monkeys.

Another possibility lies before our face: Fossil evidence suggests that humans about 1.6 million years ago, with the onset of Homo erectus, began to develop a more prominent nose. Our cousins ​​gorillas and chimpanzees have much flatter noses.

Our nasal passages help save water by cooling and condensing the water vapor from exhaled air and converting it back into fluid on the inside of our nose where it can be reabsorbed.

Having a nose that protrudes more may have helped early people retain more moisture with each breath.

“There is still a mystery to be solved, but it is clear that people are saving water,” Pontzer said. “Finding out exactly how we do it is where we’re going, and it’s going to be really fun.”

Elephants have found the highest volume of water loss ever recorded in a land animal

More information:
“Evolution of Water Conservation in Humans,” Herman Pontzer, Mary H. Brown, Brian M. Wood, David A. Raichlen, Audax. ZP Mabulla, Jacob A. Harris, Holly Dunsworth, Brian Hare, Kara Walker, Amy Luke, Lara R. Dugas, Dale Schoeller, Jacob Plange-Rhule, Pascal Bovet, Terrence E. Forrester, Melissa Emery Thompson, Robert W. Shumaker, Jessica M. Rothman, Erin Vogel, Fransiska Sulistyo, Shauhin Alavi, Didik Prasetyo, Samuel S. Urlacher and Stephen R. Ross. Current biologyMarch 5, 2021. DOI: 10.1016 / j.cub.2021.02.045

Provided by Duke University School of Nursing

Citation: New study suggests humans evolved to run on less water than our immediate primate family (2021, March 5) Retrieved March 5, 2021 from https://phys.org/news/2021-03-humans-evolved- closest-primate-relatives .html

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