Evolution and humans: only we sweat (Evolution)

by David Turell @, Monday, April 23, 2018, 04:34 (2190 days ago) @ David Turell

We don't have much body ha=air and we have sweat glands, as another difference from animals:


"Millions of years ago, digestion consumed most of the calories we ate. Our brain takes 20 times more energy than any other organ in the body. So for our brain to develop, we needed a higher density food, and meat fit the bill.

"One theory of human evolution states that our ancestors began eating meat about 2 million years ago, which rapidly expanded the development of their brains. Since meat packed a lot of calories and fat, a diet including it over time allowed the brain to grow larger. But how did we get that meat?

"One way was eating carcasses. The human tapeworm evolved from the kind that infects dogs and hyenas research tells us, meaning at some point, we must’ve fed on the same carcasses as them, and came into contact with their saliva. But this wasn’t the only way.

"They must’ve taken part in hunting too. Yet, hominins didn’t begin using stones and sticks for hunting until about 200,000 years ago. So between 2.3 million and 200,000 years ago, how did they hunt? According to journalist and writer Christopher McDougall, author of the book Born to Run, we ran game animals to death in order to feast upon them.

"The ability to run long distances and sweat—so as not to overheat, allowed our ancestors to wear out quarry. Sweating was the key factor. Consider a gazelle running over long distances and being chased by our progenitors. The fact that they can sweat and the gazelle can’t means they can last far longer in the heat of the African Savannah.

"Game animals like the gazelle over time become overheated and have to stop to catch their breath, allowing early hunters to make short work of them, a strategy we call today persistence hunting. Some remote tribes still take part in it and there’s evidence that it was a strategy utilized all over the world in the distant past.

"Human sweat is actually a very efficient cooling system, arguably the most effective in the animal kingdom. After about five miles or so, a gazelle needs to stop, rest, and breathe, or risk damaging itself, even dying. Such an animal can only fully extend its diaphragm when not running, while walking upright freed our ancestors from such an issue.

"Research shows that several traits simultaneously evolved around the same time, about 1.89 million years ago. These were walking upright, hairless skin, sweating, and the ability to run great distances. One reason for all of these rapid changes might have been climate change. The Earth warmed over this same period, shifting the habitat from forest to open grassland, and allowing our ancestors to walk upright and even run in open space. It may have also forced them to hunt animals for food."

Comment: I don't buy that climate drove evolution but it must have played a role. But it is fascinating that only we sweat, while the others pant. Another amazing difference that isn't explained but any obvious need for that alteration in physiology driven by natural selection. More evidence for God directing our speciation.

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