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- Researchers discover a new feature of human evolution.
- Humans have evolved to use less water per day than other primates.
- The nose is one of the factors that allows humans to be water efficient.
Scientists have discovered a new characteristic that distinguishes humans from other primates like chimpanzees. Research shows that the human body uses 30% to 50% less water per day than our closest animal relatives.
Certainly our brain power and the ability to walk upright are essential to make us special, but the efficiency with which the human body uses water is another major difference. This characteristic probably emerged as an evolutionary adaptation in ancient hunter-gatherers, who had to venture further and further away from water sources in search of food, thinks lead author Herman Pontzer. associate professor of evolutionary anthropology at Duke University.
“Just being able to go a little longer without water would have been a great advantage as early humans started making a living in arid savanna landscapes,” Pontzer said.
As our bodies are constantly shedding water through processes like urinating or sweating, it is necessary for water levels to be restored. “To sustain life, humans and other land animals must maintain a tight balance between gaining and losing water each day,” as the authors of the article write.
For the study, the researchers looked at this cycle of water consumption and loss in 309 people from a variety of backgrounds. These included farmers, hunter-gatherers, and office workers, who were compared to 72 monkeys spread across zoos and sanctuaries.
A model of water renewal for humans and chimpanzees who have pools of fat-free mass and similar body water.
Credit: Current Biology
Scientists calculated the water intake of each person participating in the study, whether it was from food or drink. They also tracked the amount of water lost through urine, sweat, or the gastrointestinal tract. With all the numbers added up, it became clear that the body of an average person passes around 3 liters of water every day. That makes about 12 cups. A chimpanzee or a gorilla suffers twice as much.
The results were surprising as humans tend to sweat more than other primates. In a square inch of skin, “humans have 10 times more sweat glands than chimpanzees,” Pontzer explained. We can sweat about half a gallon in 30 minutes of training. We also lead much more active lives than the monkeys at the zoo, with most monkeys only moving a few hours a day, scientists say. So how come we use so much less water?
The researchers believe that the very real difference in water treatment that they have observed in humans compared to other primates is related to evolutionary mechanisms. Our bodies have had to adapt to need less water to stay healthy.
Scientists are now focused on determining exactly how this change happened. The data suggests that our sense of thirst diverged from that of other monkey parents. We just don’t want that much water. In particular, the water / calorie ratio is 25% lower in human breast milk than in monkey milk.
It is also possible that our noses have a lot to do with it. The fossils highlight the fact that humans began to have a more protruding nose than its evolutionary cousins around 1.6 million years ago, with the dawn of Homo erectus. In contrast, gorillas and chimpanzees have flatter noses.
What is good about our nose? As we tend to exhale water vapor, the nasal passages cool it and condense it, turning it into liquid. This liquid collects inside the nose and reappropriates in the body. Essentially, having a protruding nose probably helped ancient humans retain more moisture when they breathe.
Read the study published in Current Biology.
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