A Harvard primatologist thinks that the invention of barbecue occurred 1.9 million years ago, fueling the expansion of the early hominid brain.
Monday, June 18, 2007
Around 1.9 million years ago, something extraordinary happened to the chimp-like hominids called Homo erectus. Their brains began to enlarge, becoming double the size of those of chimpanzees. Several theories are beginning to coalesce about why this happened. One is that early people began to eat more and better meat around this time, which allowed more calories to be consumed faster. This led to a shrinking of gastrointestinal organs and an increase in brain size that essentially traded guts for gray matter.
Our big brains need this extra energy. Modern humans eat about the same number of calories as other primates that approximate their weight, but we suck up an average of 25 percent of our body's energy expenditure, compared with the 8 percent sucked up by apes. Human babies use 60 percent of their energy to feed their heads.
Anthropologists have assumed that H. erectus ate their burgers and steaks raw, since most early fire pits discovered so far date back about 500,000 years, with the oldest, in Israel, dating back 790,000 years. Charred stones and tools associated with human sites have been discovered that date back as much as 1.5 million years, but these might have been naturally occurring fires.
Now Harvard University's Richard Wrangham has provided some evidence that the very distant ancestors of America's top chefs indeed may have learned to cook their antelope and rabbit. Cooking makes both plants and meat softer and easier to chew, providing more calories with less effort. What's more, human teeth got smaller and duller at around this time, which is the opposite of what would have happened if people had had to rip and chew lots of raw meat.
Wrangham worked with Stephen Secor, an animal physiologist from the University of Alabama at Tuscaloosa, who ran experiments to test the energy required by pythons to consume cooked versus raw meat; Secor also ran experiments on mice to gauge the impact of cooked versus raw meat. The snakes used almost 25 percent less energy chowing down cooked meat; the mice gained more weight and grew slightly longer. The fast turnaround in the mice indicates that cooked meat might have had a quick and dramatic evolutionary impact on early people.
Reducing the time and energy required to chew and digest raw meat means more energy available for other uses--such as feeding a voracious brain that's getting bigger and bigger. Wrangham also thinks that the modern rise in the consumption of cooked meat may contribute to the obesity epidemic; the same goes for processed food, which is even easier to eat and digest. Wrangham presented his findings at a recent paleoanthropology meeting in Cambridge, in the United Kingdom.
Paleoanthropologists are excited by Wrangham's findings and provocative ideas, but the absence of definitive proof of campfires appearing at the same time that human brains doubled in size is a problem. Many still believe that humanity's first cooked meal came much later--about 800,000 to 500,000 years ago, when the human noggin began growing again, expanding by about 30 percent into the modern-size brain.
One question that I'd like to ask evolutionary biologists and paleoanthropologists is why the huge expansion of our brains led to such seemingly unique traits in humans like advanced language skills and acute self-awareness. Would these same traits develop in other mammals if they were fed a diet of broiled beef over several generations? I wonder how many generations of mice it would take to replicate what happened to us--that is, I'd like to see if mouse brains double or triple in size, and also what our furry little friends would do with all that extra neural material.
Citation:
Science 15 June 2007:Vol. 316. no. 5831, pp. 1558 - 1560 DOI: 10.1126/science.316.5831.1558
Comments
dmm on 06/20/2007 at 1:54 PM
128
But then, farm animals have been purposely bred to be big and docile, the better to eat or perform menial labor, so maybe the selective breeding for these traits is overcoming any effect of diet. (Do we really want a talking cow?) One counterexample remains, however: dogs. Dogs have been domesticated for a very long time, are often bred to be smart, and have much more access to cooked food than wolves, coyotes, etc. Yet dogs are not smarter than wild canines, and they don't have noticeably larger brains.
gabrielg01 on 06/20/2007 at 4:33 PM
270
dmm on 07/03/2007 at 4:12 AM
128
The pertinent question, though, is: are sheep smarter or dumber than their undomesticated counterpart? I don't know about sheep. However, I've tried to hunt wild turkeys and I can definitely say they are smart.
Can anyone comment on how smart/dumb domesticated turkeys are?
gabrielg01 on 06/20/2007 at 4:32 PM
270
1) Chimps and bonobos can be taught how to make fire, and how to use it. This does not require some kind of sophisticated training program. The bonobos will learn by simply watching what we are doing. They learn every step of camp fire making: gathering of branches, building a pyramid-like shape with the small twigs at the core, placing the dry paper at the core, and then carefully lighting it with a cigarette lighter. Possibly they could also learn tougher, more primitive fire making methods.
So the point is that apes got to this point of intelligence without using fire. And they may cross the "fire divide" without help.
2) There were some human cultures that existed without fire, even in a cold climate: indigenous Tasmanians. How about that?... Granted, Tasmanians did not develop too much culturally speaking. Nevertheless, they were fully humans, who existed without fire for thousands of years. They had the same hungry big brains as we do. This proves that you don't need fire to be human.
3) Many animals seem to show an IQ that endows them with capabilities in excess of what they actually need to survive. Humans as hunter-gatherers have the ability to develop extremely sophisticated and abstract mental constructs: mathematics, philosophy etc. This seems like overkill if we think that humans were meant survive in the African savanna. Why do we need the capability to develop and understand calculus, if we just had to survive by picking fruits, kill small animals, and migrate from point A to point B while avoiding predators?
Interestingly, many other animals also have mental skills that seem far in excess of what they actually need to survive.
So to make a long story short, this evolutionary "fire story" is not as simple as people try to make it look. Researchers are often victims of wishful thinking.
iam730 on 06/21/2007 at 2:47 PM
3
Perhaps they thought this simpler view would make good soundbite material for the network news' science round-ups?