Human evolution: we use less water than apes, monkeys (Introduction)

by David Turell , Friday, March 05, 2021, 18:36 (1146 days ago) @ David Turell

We have a different water control result, using less:

https://phys.org/news/2021-03-humans-evolved-closest-primate-relatives.html

"Our bodies are constantly losing water: when we sweat, go to the bathroom, even when we breathe. That water needs to be replenished to keep blood volume and other body fluids within normal ranges.

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

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"'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 said.

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"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 GI tract, on the other hand.

"When they added up all the inputs and outputs, they found that the average person processes some three liters, or 12 cups, of water each day. A chimpanzee or gorilla living in a zoo goes through twice that much.

"Pontzer says the researchers were surprised by the results because, among primates, humans have an amazing ability to sweat. Per square inch of skin, "humans have 10 times as many sweat glands as chimpanzees do," Pontzer said. That makes it possible for a person to sweat more than half a gallon during an hour-long workout—equivalent to two Big Gulps from a 7-Eleven.

"Add to that the fact that the great apes—chimpanzees, bonobos, gorillas and orangutans—live lazy lives. "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 hours a day," Pontzer said.

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

"The findings suggest that something changed over the course of human evolution that reduced the amount of water our body uses each day to stay healthy.

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"The next step, Pontzer says, is to pinpoint how this physiological change happened.

"One hypothesis, suggested by the data, is that our body's thirst response was re-tuned so that, overall, we crave less water per calorie compared with our ape relatives. Even as babies, long before our first solid food, the water-to-calories ratio of human breast milk is 25% less than the milks of other great apes.

"Another possibility lies in front of our face: Fossil evidence suggests that, about 1.6 million years ago, with the inception of Homo erectus, humans started developing a more prominent nose. Our cousins gorillas and chimpanzees have much flatter noses.

"Our nasal passages help conserve water by cooling and condensing the water vapor from exhaled air, turning it back into liquid on the inside of our nose where it can be reabsorbed.

"Having a nose that sticks out more may have helped early humans retain more moisture with each breath."

Comment: Another way humans are very different from ancestor primates.