The evolution of the human brain explains how we got so fat

It’s strange that we haven’t come up with a better way of neatly explaining the origin of life to skeptics other than The Big Bang. For one thing, the term was coined somewhat in jest by one of the theory’s staunchest detractors. During a 1949 BBC radio broadcast, astronomer Fred Hoyle (who was all about the continuous expansion theory) was the first to utter the moniker, in an attempt to illustrate how implausible the whole thing was, yet to this day, academicians and civilians alike privilege the title over all others. What’s more, as many have already pointed out, the name actually does a disservice to the content of the theory, with “Big” implying size even though space wasn’t a thing when it occurred-technically speaking, and there wasn’t actually a “Bang.”

The popularity of the pet name neither breaks my leg nor picks my pocket, but it does seem to roll off the tongues of dense-talking-snake-enthusiasts with irritating ease. I mostly feel bad for the people that dedicate their lives to relevant breakthroughs; breakthroughs that sometimes offer only a single clue to the most pressing “Who Done It?” case of all time.

It’s an exciting thing to watch from the sidelines, thousands of cosmologist, physicists and podcast hosts eagerly lining up to add one more pixel to a canvas that is dispiritingly closer to being vacant than it is to being completed. I recall physicist and director of the NASA Institute for Universal Biology, Nigel Goldenfeld, who applied physics and emergent states of matter to an equation that is usually only discussed in biological terms. 

Follow Ladders on Flipboard!

Follow Ladders’ magazines on Flipboard covering Happiness, Productivity, Job Satisfaction, Neuroscience, and more!

Every once in awhile pioneering research on the subject is less about populating the frame and more about acquiring the tools to make a new one, as is the case with a new report published this year in the journal Genome Biology and Evolution.

Second only to how did we get here? Is how did we get so fat? Our scrappy simian cousins may only be a chromosome away from us but we’re worlds apart as far as body fat is concerned. It’s not uncommon for a healthy adult human body to be composed of anywhere between 14% to 31% body fat compared to the 9% body fat found on an average chimpanzee. At some point, after humans split with other primates in the evolutionary tapestry, the method in which the former packaged DNA in their fat cells altered drastically. The end result, according to Devi Swain-Lenz, a postdoctoral associate in biology at Duke University and the lead researcher behind the new study, hindered our ability to turn white fat into brown fat. 

Brown fat vs. White fat

White adipose tissue (often referred to as white fat) is segmented by two different variations, visceral fat or subcutaneous fat. Visceral fat refers to the white fat stored within the abdominal cavity and located near several vital organs, including the liver, intestines, and stomach while subcutaneous fat is the stuff located just beneath the skin, the stuff that gathers around our waists and gifts us beer bellies, thunder thighs and so forth. White fat like brown fat serves its purpose but an excess of it is a pretty reliable predictor for several serious illnesses. Too much subcutaneous fat will companion traditionally undesirable features, but an increased build-up of visceral fat is the one you have to worry about, as this is the one associated with increased risk for conditions like diabetes, cancer, heart disease, and even depression.

Conversely, brown and similarly beige fat, the former of which is primarily found in the upper neck and upper back, helps us burn calories, generate heat and regulate our body temperature. Lean people tend to have a much larger reserve of brown fat than overweight people do, though evolution has collectively curbed our ability to fund the conversion.

A collection of fat samples abstracted from chimps, humans and rhesus macaques monkeys was compared by Swain-Lenz and Duke biologist Greg Wray with the help of a technique called ATAC-seq. The researchers noted around 780 DNA regions that had become bunched in humans but were still accessible to the other primate species observed in the study. Upon further inspection, it was revealed that the genomes that better enabled us to convert calorie storing white fat to beige or brown fat were effectively tucked away. 

“We’ve lost some of the ability to shunt fat cells toward beige or brown fat, and we’re stuck down the white fat pathway. It’s still possible to activate the body’s limited brown fat by doing things like exposing people to cold temperatures, but we need to work for it.”Swain-Lenz told India Today.

The human brain has just about tripled in size since we branched off from the other primates six to eight million years ago. To support this urgent rate of growth, our bodies began to produce more white fat than brown fat, as the human brain requires an exorbitant amount of energy (more than any other tissue in fact.) This fascinating retcon behind why we’ve become considerably less sinewy than chimps might additionally provide some useful insights into the ever-present obesity crisis, though Swain-Lenz cautions us against holding our breath for a super solution to our obesity problem. 

“Maybe we could figure out a group of genes that we need to turn on or off, but we’re still very far from that,” Swain-Lenz continued. “I don’t think that it’s as simple as flipping a switch. If it were, we would have figured this out a long time ago,”