Human evolution; we are fattest primate (Introduction)

by David Turell , Thursday, June 27, 2019, 22:21 (1975 days ago) @ David Turell

Another reason we are not chimps:

https://www.sciencedaily.com/releases/2019/06/190626160337.htm

" Despite having nearly identical DNA sequences, chimps and early humans underwent critical shifts in how DNA is packaged inside their fat cells, Swain-Lenz and her Duke colleagues have found. As a result, the researchers say, this decreased the human body's ability to turn "bad" calorie-storing fat into the "good" calorie-burning kind.

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"Compared to our closest animal relatives, even people with six-pack abs and rippling arms have considerable fat reserves, researchers say. While other primates have less than 9% body fat, a healthy range for humans is anywhere from 14% to 31%.

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"Normally most of the DNA within a cell is condensed into coils and loops and tightly wound around proteins, such that only certain DNA regions are loosely packed enough to be accessible to the cellular machinery that turns genes on and off.

"The researchers identified roughly 780 DNA regions that were accessible in chimps and macaques, but had become more bunched up in humans. Examining these regions in detail, the team also noticed a recurring snippet of DNA that helps convert fat from one cell type to another.

"Not all fat is created equal, Swain-Lenz explained. Most fat is made up of calorie-storing white fat. It's what makes up the marbling in a steak and builds up around our waistlines. Specialized fat cells called beige and brown fat, on the other hand, can burn calories rather than store them to generate heat and keep us warm.

"One of the reasons we're so fat, the research suggests, is because the regions of the genome that help turn white fat to brown were essentially locked up -- tucked away and closed for business -- in humans but not in chimps.

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"Humans, like chimps, need fat to cushion vital organs, insulate us from the cold, and buffer us from starvation. But early humans may have needed to plump up for another reason, the researchers say -- as an additional source of energy to fuel our growing, hungry brains.

"In the six to eight million years since humans and chimps went their separate ways, human brains have roughly tripled in size. Chimpanzee brains haven't budged.

"The human brain uses more energy, pound for pound, than any other tissue. Steering fat cells toward calorie-storing white fat rather than calorie-burning brown fat, the thinking goes, would have given our ancestors a survival advantage."

Comment: Our DNA may look like a chimp's but we are very different i kind, as this study shows.