Articles on cooked food & how humans developed
I thought these articles were pretty interesting, about how humans developed bigger brains because of cooking foods. Take a look, it’s a good read.
http://www.huffingtonpost.com/2012/1...n_2033975.html
Cooked Food Allowed Evolution Of Primates' Big Brains, Scientists Say
by Ann Gibbons on 22 October 2012
Eating a raw food diet is a recipe for disaster if you're trying to boost your species' brainpower. That's because humans would have to spend more than 9 hours a day eating to get enough energy from unprocessed raw food alone to support our large brains, according to a new study that calculates the energetic costs of growing a bigger brain or body in primates. But our ancestors managed to get enough energy to grow brains that have three times as many neurons as those in apes such as gorillas, chimpanzees, and orangutans. How did they do it? They got cooking, according to a study published online today in the Proceedings of the National Academy of Sciences.
"If you eat only raw food, there are not enough hours in the day to get enough calories to build such a large brain," says Suzana Herculano-Houzel, a neuroscientist at the Federal University of Rio de Janeiro in Brazil who is co-author of the report. "We can afford more neurons, thanks to cooking."
Humans have more brain neurons than any other primate—about 86 billion, on average, compared with about 33 billion neurons in gorillas and 28 billion in chimpanzees. While these extra neurons endow us with many benefits, they come at a price—our brains consume 20% of our body's energy when resting, compared with 9% in other primates. So a long-standing riddle has been where did our ancestors get that extra energy to expand their minds as they evolved from animals with brains and bodies the size of chimpanzees?
One answer came in the late 1990s when Harvard University primatologist Richard Wrangham proposed that the brain began to expand rapidly 1.6 million to 1.8 million years ago in our ancestor, Homo erectus, because this early human learned how to roast meat and tuberous root vegetables over a fire. Cooking, Wrangham argued, effectively predigested the food, making it easier and more efficient for our guts to absorb calories more rapidly. Since then, he and his colleagues have shown in lab studies of rodents and pythons that these animals grow up bigger and faster when they eat cooked meat instead of raw meat—and that it takes less energy to digest cooked meat than raw meat.
In a new test of this cooking hypothesis, Herculano-Houzel and her graduate student, Karina Fonseca-Azevedo, now a neuroscientist at the National Institute of Translational Neuroscience in Săo Paulo, Brazil, decided to see if a diet of raw food inherently put limits on how large a primate's brain or body could grow. First, they counted the number of neurons in the brains of 13 species of primates (and more than 30 species of mammals). The researchers found two things: One, that brain size is directly linked to the number of neurons in a brain; and two, that that the number of neurons is directly correlated to the amount of energy (or calories) needed to feed a brain.
After adjusting for body mass, they calculated how many hours per day it would take for various primates to eat enough calories of raw food to fuel their brains. They found that it would take 8.8 hours for gorillas; 7.8 hours for orangutans; 7.3 hours for chimps; and 9.3 hours for our species, H. sapiens.
These numbers show that there is an upper limit on how much energy primates can get from an unprocessed raw diet, Herculano-Houzel says. An ape's diet in the wild differs from a modern "raw food diet," in which humans get sufficient calories from processing raw food in blenders and adding protein and other nutrients. In the wild, other apes can't evolve bigger brains unless they reduce their body sizes because they can't get past the limit of how many calories they can consume in 7 hours to 8 hours of feeding per day. But humans, she says, got around that limit by cooking. "The reason we have more neurons than any other animal alive is that cooking allowed this qualitative change—this step increase in brain size," she says. "By cooking, we managed to circumvent the limitation of how much we can eat in a day."
This study shows "that an ape could not achieve a brain as big as in recent humans while maintaining a typical ape diet," Wrangham says.
Paleoanthropologist Robert Martin of The Field Museum in Chicago, Illinois, agrees that the new paper does "provide the first evidence that metabolic limitations" from a raw food diet impose a limit on how big a primate's brain—or body—can grow. "This could account for small brain sizes of great apes despite their large body sizes." But "the jury is still out" on whether cooking was responsible for the first dramatic burst of brain growth in our lineage, in H. erectus, Martin says, or whether our ancestors began cooking over a fire later, when the brain went through a second major growth spurt about 600,000 years ago. Hearths show up in the archaeological record 800,000 years ago and the regular use of fire for cooking doesn't become widespread until more recently.
But to Herculano-Houzel's mind, our brains would still be the size of an ape's if H. erectus hadn't played with fire: "Gorillas are stuck with this limitation of how much they can eat in a day; orangutans are stuck there; H. erectus would be stuck there if they had not invented cooking," she says. "The more I think about it, the more I bow to my kitchen. It's the reason we are here."
ScienceNOW, the daily online news service of the journal Science
++++++++++++++++++++++++
http://news.nationalgeographic.com/n...ealth-science/
What Makes Us Human? Cooking, Study Says
Surge in brain size 1.8 million years ago linked to cooking
Nicholas Mott
Published October 26, 2012
Did you eat a hot meal today? It's a smart thing to do, as our ancestors learned.
According to a new study, a surge in human brain size that occurred roughly 1.8 million years ago can be directly linked to the innovation of cooking.
Homo erectus, considered the first modern human species, learned to cook and doubled its brain size over the course of 600,000 years. Similar size primates—gorillas, chimpanzees, and other great apes, all of which subsisted on a diet of raw foods—did not.
"Much more than harnessing fire, what truly allowed us to become human was using fire for cooking," said study co-author Suzana Herculano-Houzel, a neuroscientist at the Institute of Biomedical Sciences at the Federal University of Rio de Janeiro in Brazil.
(Related: "Cooking Gave Humans Edge Over Apes?")
A Diet Unfit for King Kong
Herculano-Houzel and colleague Karina Fonseca-Azevedo measured the body and brain masses of primates and compared them with their caloric intake and hours spent eating. Unsurprisingly, the results showed a direct correlation between calories and body mass. In other words, the bigger you are, the more you have to eat.
But since there are only so many hours in the day, a primate can only become so big. A gorilla, for instance, is the largest primate. Yet it can only eat for ten hours a day, due to limited food supply, the time it takes to find that food, and the lengthy process of chewing through tough fibrous plants.
This results in a maximum weight of around 440 pounds (200 kilograms). On this diet, said Herculano-Houzel, "King Kong could not exist."
Even if he did, his brain would be comparatively small. That's because brain matter "costs" more calories than other body mass, according to the "expensive tissue hypothesis." (See brain pictures.)
And as the team write in their paper, gorillas could never eat enough nutrients to support their enormous size and the expensive tissue of the brain. "Apes can't afford both brain and body," said Herculano-Houzel.
Humans can't either. But when we came to a fork in the evolutionary road—brawn this way, brains that way—we took the cerebral route. This development came to be known as encephalization: We ended up with brains that are much bigger than our body size would indicate.
Cooking was the key, said Herculano-Houzel, whose study appeared this week in the journal Proceedings of the National Academy of Sciences. Heating our food unlocked nutrition: 100 percent of a cooked meal is metabolized by the body, whereas raw foods yield just 30 or 40 percent of their nutrients.
Applying fire to food also softens tough fibers, releases flavors, and speeds up the process of chewing and digesting. The extra nutrition, and the improved eating experience, allowed our prehistoric ancestors to spend less time searching for food—and less time chewing through tough plants for meager caloric reward.
(See "Eating Crocodile Helped Boost Early Human Brains?")
Cooking, therefore, gave us both the nutrition we needed to develop large brains and the time we needed to use them for things more interesting than chewing.
It was at this point, said Herculano-Houzel, that having a large brain stopped being an evolutionary liability—a feature that required a lot of effort to support with nutrients—and became an asset: something that could help us gain those nutrients more easily. We could now spend time thinking of better ways to hunt, to live, to develop culture, art, and early technologies—all the things that made us who we are now.
Evolving or Devolving?
Some today think this was a culinary misstep. They advocate eating prehistoric meals as a way of fighting modern ailments.
Proponents of raw-food diets, for example, don't prepare their meals at all. Like the gorilla, they simply munch away on raw fruits and vegetables.
Why? Some of them believe that heating food over 40 degrees Fahrenheit (4 degrees Celsius) destroys natural enzymes present in plants—molecular structures that help us digest proteins missing in processed foods. Others consider a retrogressive diet more environmentally sound, citing the various problems caused by modern industrial food production and distribution. And some folks simply eat raw foods as a quick way to shed a few pounds.
But "if you're healthy, this is a terrible idea," said Herculano-Houzel. "Sure, you'll lose weight very fast—you'll be eating all day and still feel starved."
That's because the low nutritional yield from raw foods requires massive consumption. In other words, if you want to sustain an active lifestyle, eating raw foods takes time and energy of its own.
Besides, said Herculano-Houzel, cooked food simply tastes better. "Even apes, when offered a choice of raw food or spaghetti and meatballs, will take the meatballs every time."
(See "Human Ancestors Ate Bark—Food in Teeth Hints at Chimplike Origins.")
But too much highly caloric, immediately gratifying foods can be dangerous, too. Diseases like obesity, hypertension, diabetes, and heart disease are all connected to overindulging our taste for refined sugars and processed foods. Humans would do well not to choose the meatballs every time.
Cooking Like a Caveman
"We have not adapted to this modern lifestyle with processed foods and sugars everywhere," said John Durant, author of the blog Hunter-Gatherer.com. "This is why we're seeing lots of major health concerns."
Durant is at the forefront of a different retrogressive movement: the Paleo-diet. Like the raw-foodists, his dietary philosophy entails taking a step back in the evolutionary food chain and eating, literally, like a caveman.
That culinary lifestyle—lots of meat, fresh organic fruits and vegetables, nuts and berries, nothing processed—is at odds with modern meals, which tend to offer thousands of calories, are readily available, and can be eaten quickly.
"In terms of evolutionary biology," said Durant, "we spent far longer as hunter-gatherers than anything else. So what does our metabolism recognize and process well? We're best adapted to eat like our natural ancestors."
Paleo is a relatively new diet, and Durant's claims about dietary evolution have yet to be scientifically verified or denied. Many doctors warn that cutting dairy and grains could lead to a dangerous lack of important nutrients. Cavemen might have been fit, but they did not have a lengthy lifespan.
Yet even Durant, who frequently runs barefoot in Central Park, thinks raw-food-only diets are a bit extreme. "It's not really about nutrition," he said, "just anti-cooking."
Our Next Meal
Eating like our ancestors may prevent modern diseases of overconsumption, but cooking is, after all, what drove our evolution this far.
So what is the next step? And is there still room for us to evolve? (Read about four ways we may, or may not, evolve.)
Herculano-Houzel thinks so. Human brain size "may not be capped out yet," she said. "Over the last couple of centuries our body size has increased due mainly to changes in our diet, to increased access to better nutrition."
She added that we could continue to evolve bigger and bigger brains—with the right diet. What exactly that is, however, is still a matter of taste.
+++++++++++++++++++++++++++++++++++
