The brain of an adult human uses 25% of the total energy expended by the entire organism, much higher than our closest primate relatives, whose brains use about 8% of their energy. The high energy cost of building, using, and maintaining our brains has long presented a riddle to evolutionary theorists. Where did this extra energy come from?
One idea is that as our ancestors switched to a meat-heavy diet, our large guts—which were capable of digesting large amounts of vegetative material—shrunk. Since meat generally contains a greater density of protein and calories than vegetables, this digestive shift allowed our ancestors to target a more efficient form of energy, while helping them develop the brainpower to hunt it. Evidence from many corners of the animal kingdom suggests that the meat eaters are smarter.
But many scientists believe that the speed with which the human brain evolved suggests that a gradual shift to a meat based diet was too gradual to fully explain this development.
“Cooking produces soft, energy-rich foods,” says Richard Wrangham, a primatologist at Harvard. This, he explains, increases the efficiency with which the food’s energy is extracted. Fewer calories are spent in digestive efforts, which leaves a higher margin of caloric recovery.
Conducting research on Burmese pythons, Wrangham and a colleague, Stephen Secor, determined that the pythons spent 12.7% less energy digesting meat that was cooked. “By eating cooked meat, less energy is spent on digestion; therefore, more energy can be used for other activities and growth,” suggests Secor.
Although the python experiment focused on meat digestion, cooking increases access to calories in both hunted meat and gathered plants. Just as the heat from cooking gelatinizes the matrix of collagen in animal flesh, it also opens up tightly woven carbohydrate molecules in plants to make them easier to absorb.
Subsequent experiments on mice showed that raw food eaters weighed less than mice that ate cooked food—even though the raw food diet had more total calories. “This suggests that our ancestors would have been able to get rapid benefits out of cooking,” says Wrangham.
But wait. Maximal caloric absorption may have been useful back in the day, but now we have an epidemic of obesity in developed countries. Following Wrangham’s line of reasoning, food processing, like cooking, makes more calories available. Perhaps today’s overprocessed food, along with cooking, less exercise, etc., is contributing to obesity. You think?
Even if it’s true that cooked meat may have helped us evolve to where we are, I think it’s worth considering that the next dietary breakthrough might come from the opposite culinary corner: raw vegetables!
I’m probably about to lose some readers, who sentences ago were licking their chops at the thought of greasy, bloody, delicious meat. But I’ve been noticing a growing community of “raw-foodists,” who seem quite happy and healthy, with neither meat nor heat in their food. And there is an unmistakable brightness of eyes that I have come to associate with the raw-foodists.
For example, consider the group I encountered at the Durango farmers’ market the other week. Their market stand, which represents the nonprofit Turtle Lake Refuge (turtlelakerefuge.org), is vibrant and fun. Flanked by a bicycle-powered smoothie maker on one side and a bike-powered juicer on the other, the table is laid out with some very interesting and tasty items: acorn chocolate, nut cheese cabbage rolls, and purslane kimchi. The food ranged from really good to downright spectacular, especially the cabbage rolls and acorn chocolate.
Technically, raw food has not been heated above 118 degrees. “Enzymes start to break down at 120,” explains Katrina Blair, a founding member of Turtle Lake. She says that the abundance of living enzymes in raw food can provide energy sources and nutrients unavailable in food that has been cooked.
“We’re into getting life out of food closer to when it’s still alive,” she says.
“Every other creature eats 100% raw,” says Katrina, a statement that’s confirmed by scientists who say that cooking separates us from the other animals. But while those looking back in time consider cooking a good thing, some of those looking forward aren’t so sure – and they are the ones with light pouring out of their eyes.
And the raw-foodists are hardly obese. In general they are lean and wiry, which supports the findings of the scientists who found animals that eat cooked food are larger in size.
Maybe in times of scarcity it is good to maximize calories. But in times of abundance and obesity, there is a growing body of scientific data finding support in every animal, large and small, that has been studied in this way, which suggests animals that eat less live longer. There are a lot of possible explanations floating around, but few refute the basic premise that, assuming you are meeting your basic nutritional requirements, you live longer by living leaner.
So while the evolution of our brain may have been dependent on cooked meat, maybe the next step will be about cultivating a different kind of sensor, one that factors in compassion, a sense of place, long life, and light spilling from your eyes.
Ask Ari: Hung up on tender deer
Q: Dear Flash,
My research has revealed that back straps are NOT as tender as we think relative to some other cuts. Experiments on my wife and kids compared deer backstrap steak to certain hindquarter cuts – all from the same animal, cooked the same way, and eaten during the same meal. The results have been 100% in favor of the hindquarter meat when it comes to tenderness. I know this differs from your experiments, but I’m sticking with my results!
My brother-in-law says if the animal is hung in a way that puts the muscles in a stretch, the meat is more tender. When I hang our animals, I do so from the Achilles and for two to three days. How do you do yours? Perhaps, we should try hanging from the neck and put heavy weights on the back legs and see what happens. Anyway, since hunting season is soon, we have some work to do.
[For space I had to edit out a recipe included in Don’s letter, for Brasato al Midollo - a dish that he says is supposedly “so carnal, so pleasure-inducing, so deliciously orgasmic that for centuries, virgins under the age of 20 were forbidden to eat it.”]
A: Dear Don,
I hang my animals by the neck, in part for the reason you mentioned. Also, the longer period of time you hang an animal, “they” say, the more tender it will be. Attaching weights to the legs might help…
I’m still working on a cow elk from last year that’s so tender all over you can practically eat it with a spoon – which is good, considering my new raw-food kick. Just kidding.
Does anyone else out there have insight into this tender matter?
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