Richard Wrangham has tasted chimp food, and he doesn’t like it. “The typical fruit is very unpleasant,” the Harvard University biological anthropologist says of the hard, strangely shaped fruits endemic to the chimp diet, some of which look like cherries, others like cocktail sausages. “Fibrous, quite bitter. Not a tremendous amount of sugar. Some make your stomach heave.” After a few tastings in western Uganda, where he works part of the year on his 20-year-old project studying wild chimpanzees, Wrangham came to the conclusion that no human could survive long on such a diet. Besides the unpalatable taste, our weak jaws, tiny teeth and small guts would never be able to chomp and process enough calories from the fruits to support our large bodies.
Then, one cool fall evening in 1997, while gazing into his fireplace in Cambridge, Mass., and contemplating a completely different question—“What stimulated human evolution?”—he remembered the chimp food. “I realized what a ridiculously large difference cooking would make,” Wrangham says. Cooking could have made the fibrous fruits, along with the tubers and tough, raw meat that chimps also eat, much more easily digestible, he thought—they could be consumed quickly and digested with less energy. This innovation could have enabled our chimplike ancestors’ gut size to shrink over evolutionary time; the energy that would have gone to support a larger gut might have instead sparked the evolution of our bigger-brained, larger-bodied, humanlike forebears.
In the 10 years since coming on his theory, Wrangham has stacked up considerable evidence to support it, yet many archaeologists, paleontologists and anthropologists argue that he is just plain wrong. Wrangham is a chimp researcher, the skeptics point out, not a specialist in human evolution. He is out of his league. Furthermore, archaeological data does not support the use of controlled fire during the period Wrangham’s theory requires it to.
Wrangham, who first encountered chimps as a student of Jane Goodall’s in 1970, began his career looking at the way ecological pressures, especially food distribution, affect chimp society. He famously conducted research into chimp violence, leading to his 1996 book Demonic Males. But ever since staring into that fire 10 years ago, he has been plagued with thoughts of how humans evolved. “I tend to think about human evolution through the lens of chimps,” he remarks. “What would it take to convert a chimpanzeelike ancestor into a human?” Fire to cook food, he reasoned, which led to bigger bodies and brains.
And that is exactly what he found in Homo erectus, our ancestor that first appeared 1.6 million to 1.9 million years ago. H. erectus’s brain was 50 percent larger than that of its predecessor, H. habilis, and it experienced the biggest drop in tooth size in human evolution. “There’s no other time that satisfies expectations that we would have for changes in the body that would be accompanied by cooking,” Wrangham says.
The problem with his idea: proof is slim that any human could control fire that far back. Other researchers believe cooking did not occur until perhaps only 500,000 years ago. Consistent signs of cooking came even later, when Neandertals were coping with an ice age. “They developed earth oven cookery,” says C. Loring Brace, an anthropologist at the University of Michigan at Ann Arbor. “And that only goes back a couple hundred thousand years.” He and others postulate that the introduction of energy-rich, softer animal products, not cooking, was what led to H. erectus’s bigger brain and smaller teeth.
So Wrangham did more research. He examined groups of modern hunter-gatherers all over the world and found that no human group currently eats all their food raw. Humans seem to be well adapted to eating cooked food: modern humans need a lot of high-quality calories (brain tissue requires 22 times the energy of skeletal muscle); tough, fibrous fruits and tubers cannot provide enough. Wrangham and his colleagues calculated that H. erectus (which was in H. sapiens’s size range) would have to eat roughly 12 pounds of raw plant food a day, or six pounds of raw plants plus raw meat, to get enough calories to survive. Studies on modern women show that those on a raw vegetarian diet often miss their menstrual periods because of lack of energy. Adding high-energy raw meat does not help much, either—Wrangham found data showing that even at chimps’ chewing rate, which can deliver them 400 food calories per hour, H. erectus would have needed to chew raw meat for 5.7 to 6.2 hours a day to fulfill its daily energy needs. When it was not gathering food, it would literally be chewing that food for the rest of the day.
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Add CommentBesides the possibility that our ancestors didn't have sufficient control of fire, the other major reason that Wrangham's hypothesis may be wrong is that we don't need to assume that our ancestors ate the same thing as modern day chimpanzees.
Reply | Report Abuse | Link to thisIndeed, it is quite likely that they did not. The food that can give us all the protein and nutrition that is needed for big brains is fish and shell fish. It is quite likely that our ancestors evolved on beaches along lakes and streams (the locations of many of the fossilized remains in Africa today). This is consistent with the Amphibious-generalist hypothesis of human evolution put forward by Andrew Lewis .
http://www.geocities.com/Athens/Acropolis/4314/intromhh.html
All our other aquatic adaptations can also be explained by this theory.
If you visit Africa today you see that only the big animals (and humans) occupy the riparian ecosystems - lions, hippos and crocidiles. All the other animals, including the chimps, don't dare spend much time on the ground along the streams. Yet, these are by far the best ecosystems on the continent - replete with abundant food supplies and water - highly sought after but inaccessible except to the smartest and strongest. This is the key difference between us and chimpanzees - our ancestors took over the beaches sometime in the past and everything we've done since has evolved from this intitial change in habitat.
Colin Buss
I was thinking the same thing about as the above poster about fish. We still eat raw fish today in the form of sushi. Is it really that nutritionally different when it is cooked (fish I mean)? Furthermore, what about nuts? Those are extremely high in protein and fat, and we know our ancestors ate a lot of nuts. Add to that tubers and roots. Doesn't seem cooked food is so mandatory to explain all this required energy and smaller teeth. I always thought cooked food developed as a means to address sanitation more than anything... it was interesting to learn that it is in fact more efficiently digested. PS loved the subtle jab at vegans in there!
Reply | Report Abuse | Link to thisSorry, shouldn't say "sanitation". Anyway, I thought cooked food came about because the heat killed potentially dangerous parasites.
Reply | Report Abuse | Link to thisI think this is a brilliant idea, and it just makes too much sense, possibly because I'm a non-expert who's not bogged down by preconceived notions. Humans cook almost everything, even pet food! Cooked food tastes better - doesn't that at the very least imply an evolved preference?
Reply | Report Abuse | Link to thisRaw fish? Shellfish? Absurd.
For this to be a viable theory, you've got to believe that basically ALL humans ate fish during the ENTIRE million or so years that the bigger brain/smaller gut/weaker teeth evolution thing happened.
That's ridiculous - catching fish efficiently is probably just as complex a process (duh, you need a fishing rod or nets) as controlling fire - and observing fire in action (think forest fires started by lightning) would have been a lot easier and more common than figuring out tools. Remember, this all occurred before even language was invented, or farm animals, or farming, or virtually anything else, by a species only slightly more evolved than today's chimps. Also, keep in mind that no primates use any tool even remotely as complex as a fishing rod or net, or think to catch fish. Does any land creature rely on fish as a major dietary staple?
Or think, if raw fish was so common in our distant past, and indeed fueled our evolution, why is it so rare today (really, of all major cultures, only the Japanese do it)? Why do most people cook fish, if we ALL evolved through eating raw fish?
Lastly, look at the evolutionary angle - if raw fish was so intimately tied to our evolution for even 500,000 years, we would have adapted our bodies and minds more to the ocean. We can't even see underwater! Our hold our breaths for more than a minute of activity! Except for Micheal Phelps, our bodies are obviously designed more for running than swimming. How the can anyone argue that we are adapted to catching and eating raw fish?
I think this is a brilliant idea, and it just makes too much sense, possibly because I'm a non-expert who's not bogged down by preconceived notions. Humans cook almost everything, even pet food! Cooked food tastes better - doesn't that at the very least imply an evolved preference?
Reply | Report Abuse | Link to thisRaw fish? Shellfish? Absurd.
For this to be a viable theory, you've got to believe that basically ALL humans ate fish during the ENTIRE million or so years that the bigger brain/smaller gut/weaker teeth evolution thing happened.
That's ridiculous - catching fish efficiently is probably just as complex a process (duh, you need a fishing rod or nets) as controlling fire - and observing fire in action (think forest fires started by lightning) would have been a lot easier and more common than figuring out tools. Remember, this all occurred before even language was invented, or farm animals, or farming, or virtually anything else, by a species only slightly more evolved than today's chimps. Also, keep in mind that no primates use any tool even remotely as complex as a fishing rod or net, or think to catch fish. Does any land creature rely on fish as a major dietary staple?
Or think, if raw fish was so common in our distant past, and indeed fueled our evolution, why is it so rare today (really, of all major cultures, only the Japanese do it)? Why do most people cook fish, if we ALL evolved through eating raw fish?
Lastly, look at the evolutionary angle - if raw fish was so intimately tied to our evolution for even 500,000 years, we would have adapted our bodies and minds more to the ocean. We can't even see underwater! Our hold our breaths for more than a minute of activity! Except for Micheal Phelps, our bodies are obviously designed more for running than swimming. How the can anyone argue that we are adapted to catching and eating raw fish?
@BKBigFish - Once a small population learns a new way of doing things (eating fish) that confers an evolutionary advantage, then they become the group that is more robust. Therefore, if a group of protohominids had eaten fish, that would theoretically make them stronger and over time they would take the lion's share of resources when in competition with those groups who did not eat fish. So, no, this was not a behavior that spontaneously appeared among disparate proto-human populations, but could have been learned over time after discovery by multiple populations.
Reply | Report Abuse | Link to thisLand animals that eat fish? I can start the list with otters, bears, raccoons...
While eating raw fish is not common in modern cultures, it is by no means rare. In environments where fresh fish is readily available, there are more than a few popular dishes. Ceviche is popular throughout Latin America, poisson cru is well-know in French Polynesia and its sister dish, poke can be found in Hawaii. In fact, when fresh fish was not readily available, there was regular trading of fish between inland and coastal populations in pre-Colombian South America.
One last thing to note is that iodine deficiency is huge problem worldwide for populations that do not have access to seafood. How could we evolve to be reliant on a nutrient that is only available in substantial amounts in sea-derived food products?
Let's start feeding chimpanzees cooked meat and see what happens in a few thousand years.
Reply | Report Abuse | Link to this"Let's start feeding chimpanzees cooked meat and see what happens in a few thousand years."
Reply | Report Abuse | Link to thisI was thinking the same thing.
In many part of the world, people get almost all of there nutritional requirements from eating a mixed diet of nuts, fruits and roots. Nutritional requirement of expanding brain could have been met by our ancestors well through foods available in nature. Probably it was not food but development of tool-making and other cultural changes required for survival of slender bodied ancestor in wild, that kickstarted development of brain.
Reply | Report Abuse | Link to thisI searched this topic because in reading the book "Pottinger's Cats" I'd learned that cats cannot subsist on a diet of which a major component is cooked or pasteurized. The reason that they can't is that they require the enzymes in the raw food (enzymes are denatured at temperatures as low as 118F.) Obviously we can do fairly well on primarily cooked diets, which means that our pancreas has evolved so that it can generate enough digestive enzymes to require few from (raw) food.
Reply | Report Abuse | Link to thisI don't know how long such evolution requires but it does damage the 'raw fish' theory.
Another evolution is the presence of sugar & other simple carbohydrate digesting enzymes in our saliva, which wouldn't evolve on a diet primarily consisting of raw fish. Such amylase enzymes are also injected further downstream in our digestive tract. To me this says that sugars & starches have been a major component of our diets for a very long time, perhaps the dominant component.
It would be interesting to know if we share this type of saliva with our primate kin - if we do that suggests it comes from a common ancestor, i.e. a very, very long time ago. More than a couple of million years back. That would push the raw fish idea out of contention.
Don't read into what I've said as anti-raw food. At present we've gone too far in killing enzymes. While enzymes in foods are great for us, they are the enemy of the food processing industry - they make things spoil. And our great fear of microbes in our food also fuels the killing because enzymes are in the line of fire. Heck, they are pasteurizing or irradiating everything that isn't pre-cooked. Our pancreas, as marvelous as it is, needs some help from our foods - virtually every known disease involves a lack of an enzyme or enzyme co-factor (vitamins are co-factors). So don't throw sticks at the vegans or vegetarians because they typically worry about keeping some food enzymes intact, while most of us give them zero thought.
For you cat lovers, feeding your housebound cat cooked food won't kill it - the problems typically show up in the offspring, worse in the second generation but not a problem in third generation because, as Pottenger found, there won't be a third generation.