Pure Pedantry

Science has a fascinating review about the history of cooking and its relation to human evolution. Richard Wrangham, a Harvard primatologist, has been pushing the idea that the expansion in Homo erectus‘ skull size was the result of additional energy released by cooking meat:

What spurred this dramatic growth in the H. erectus skull? Meat, according to a longstanding body of evidence. The first stone tools appear at Gona in Ethiopia about 2.7 million years ago, along with evidence that hominids were using them to butcher scavenged carcasses and extract marrow from bones. But big changes don’t appear in human anatomy until more than 1 million years later, when a 1.6-million-year-old skull of H. erectus shows it was twice the size of an australopithecine’s skull, says paleoanthropologist Alan Walker of Pennsylvania State University in State College. At about that time, archaeological sites show that H. erectus was moving carcasses to campsites for further butchering and sharing; its teeth, jaws, and guts all got smaller. The traditional explanation is that H. erectus was a better hunter and scavenger and ate more raw meat than its small-brained ancestors.

But a diet of wildebeest tartare and antelope sashimi alone isn’t enough to account for these dramatic changes, says Wrangham. He notes that H. erectus had small teeth–smaller than those of its ancestors–unlike other carnivores that adapted to eating raw meat by increasing tooth size. He argues that whereas earlier ancestors ate raw meat, H. erectus must have been roasting it, with root vegetables on the side or as a fallback when hunters didn’t bring home the bacon. “Cooking produces soft, energy-rich foods,” he says.

To find support for his ideas, Wrangham went to the lab to quantify the nutritional impact of cooking. He found almost nothing in food science literature and began to collaborate with physiologist Stephen Secor of the University of Alabama, Tuscaloosa, who studies digestive physiology and metabolism in amphibians and reptiles. Secor’s team fed 24 Burmese pythons one of four diets consisting of the same number of calories of beef: cooked ground beef, cooked intact beef, raw ground beef, or raw intact beef. Then they estimated the energy the snakes consumed before, during, and after they digested the meat, by measuring the declining oxygen content in their metabolic chambers. Pythons fed cooked beef spent 12.7% less energy digesting it and 23.4% less energy if the meat was both cooked and ground. “By eating cooked meat, less energy is expended on digestion; therefore, more energy can be used for other activities and growth,” says Secor.

Secor also helped Wrangham and graduate student Rachel Carmody design a pilot study in which they found that mice raised on cooked meat gained 29% more weight than mice fed raw meat over 5 weeks. The mice eating cooked food were also 4% longer on average, according to preliminary results. Mice that ate raw chow weighed less even though they consumed more calories than those fed cooked food. “The energetic consequences of eating cooked meat are very high,” says Wrangham. (Emphasis mine.)

Wrangham’s argument is controversial, however. There is a problem of timing with respect to when human ancestors developed fire. Most evidence suggests that they did not have fire nearly as early as Wrangham is suggesting:

Wrangham’s synthesis of nutritional, archaeological, and primatological data adds up to a provocative hypothesis that hot cuisine fueled the brain. “It’s such a nice explanation,” says paleoanthropologist Leslie Aiello, president of the Wenner-Gren Foundation in New York City. She says the smaller teeth in H. erectus indicate to her that it wasn’t chewing much tough raw food: “Something must be going on. If only there were evidence for fire.”

And that’s the stumbling block to Wrangham’s theories: Cooking requires fire. Irrefutable evidence of habitual cooking requires stone hearths or even clay cooking vessels. Solid evidence for hearths, with stones or bones encircling patches of dark ground or ash, has been found no earlier than 250,000 years ago in several sites in southern Europe. Charred bones, stones, ash, and charcoal 300,000 to 500,000 years ago at sites in Hungary, Germany, and France have also been assigned to hearths. And burned flints, seeds, and wood found in a hearthlike pattern have been cited as signs of controlled fire 790,000 years ago in Israel (Science, 30 April 2004, p. 725).

But even the earliest of those dates are long after the dramatic anatomical changes seen in H. erectus, says Wrangham. He notes that evidence for fire is often ambiguous and argues that humans were roasting meat and tubers around the campfire as early as 1.9 million years ago.

Indeed, there are a dozen claims for campfires almost that ancient. At the same meeting, paleoanthropologist Jack Harris of Rutgers University in New Brunswick, New Jersey, presented evidence of burned stone tools 1.5 million years ago at Olduvai Gorge in Tanzania and at Koobi Fora in Kenya, along with burned clay. H. erectus has been found at both sites. Claims by other researchers include animal bones burned at high temperatures 1.5 million years ago at Swartkrans, South Africa, and clay burnt at high temperatures 1.4 million years ago in the Baringo basin of Kenya.

But where there is smoke there isn’t necessarily cooking fire: None of these teams can rule out beyond a doubt that the charring comes from natural fires, although Harris argues that cooking fires burn hot at 600° to 800°C and leave a trail different from that of bush fires, which often burn as low as 100°C. (Emphasis mine.)

Fascinating.

Oh, and by the way. I had always suspected that raw foodists were full of it. Now I know why.

Comments

  1. #1 Roy
    June 25, 2007

    Hearths would not appear until people began camping in the same place for at least a while. Hunter-scavengers on the move would make their fires nearby, wherever there was fuel. There would be no reason to reuse a campfire.

    For a model of this, consider the Australian outback. For thousands of years, aborigines have made campfires, but how much evidence of the campfires remains, even though millions were made? Only when people reuse a place do they develop fire pits, where things would accumulate over time, and thus would be the first evidence of a hearth.

    Were you never a Boy Scout? After a campfire is burnt out, one good rain and it’s all but obliterated. You’d have a hard time finding the site you used last summer. Within a few years, all evidence is gone.

  2. #2 Frank
    June 25, 2007

    Roy’s comments are invalid because of the many cases of aluvial burial of campsites and thus hearths by flooding. The changing of course of streams and flooding are extremely common the worl over for good preservation of archaeological sites. Charcoal from buried hearths is often dated because of the C14 radiocarbon but of course this method does not extend back to the very early times needed for Homo Erectus sites. It would work well for the Australian sites cited by Roy.

  3. #3 Frank
    June 25, 2007

    For a specific example the reputed oldest reliably dated site in the New World, Monte Verde in Chile, is an alluvial buried site with great preservation of perishable materials.

  4. #4 Scott Lloyd
    June 26, 2007

    Maybe the mice eating cooked meat were larger because cooking food destroys enzymes in the food and thus the rats were eating a less healthy diet? I don’t really think heating up food is a very smart / healthy thing to do. Why in the world would cooking have increased our brain size? It would probably have made it so people could eat meat without it coming from a fresh kill, though.

  5. #5 Atomic Scrotum
    June 26, 2007

    Woohoo! Go meat! Suck it, vegans!

  6. #6 Bob
    June 26, 2007

    Frank, did you bother to fully consider Roy’s comment? It doesn’t sound like it. A group on the move and lighting fires where wood was available might make a great many small, one time, fires which wouldn’t leave a great deal of charcoal or remains behind to be found. Small ash piles like those would also be easily washed away by your streams and flooding. Larger, more frequently or heavily used, spots would be much more likely to generate firepits with substancial material that could survive the elements.

    Why isn’t there evidence of many, many, tens of thousands of Aboriginal firepits? Because only the heavily used ones, or the rare other, survive. Along a similiar line of reasoning, maybe the “many” cases you quote are in fact the few heavily used or rare small fire survivors. Prove they are not. If they are, then no conclusions can be drawn from the found sites.

  7. #7 sciencefox
    June 26, 2007

    Humans brain size may or may not have increased as stated in the article by eating heated meats in the past, but I am sure that nowadays with all the additives, antibiotics, hormones, chemicals, etc. in meats intelligent homo sapiens are avoiding it altogether. Not any definitive links yet, however, critical thinking about Mad Cow Disease points to a crisis in the near future that no campfire will cure.

  8. #8 Matthew Strebe
    June 26, 2007

    Scott, did you read the article? Cooking the food is a form of pre-digestion. Yes, it breaks down complex carbohydrates, enzymes, and proteins into simpler forms, so that the body doesn’t need to do as much work to break it down, resulting in a net energy gain. For modern humans, it would make little difference because we’re drowning in food. But for proto-humas who were constantly on the brink of starvation, it was a major and dramatic factor in increasing the amount of energy they had for luxuries like thinking.

    I’m sorry this doesn’t fit with your religion, but science rarely does.

  9. #9 Tim
    June 26, 2007

    Is it possible that early man of this period moved from hunting/ fresh meat to carrion eating? Half rotten meat would be far more easily digested as it is already partially broken down. Modern man tenderizes his beef this way. Perhaps a massive die out of a species during this time period?

  10. #10 Text Generator
    June 26, 2007

    Matthew, on the contrary, eating cooked food makes digestion harder, because raw food contains enzymes which aid in its own digestion. Also eating cooked food will raise the toxicity in your body due to the lack of these same enzymes. Additionally, raw food is more nutritious than that which has been cooked.

  11. #11 Oldfart
    June 26, 2007

    Give me a blood warm juicy medium-rare steak to a raw one any time. Yum. Yum. Yum.
    I prefer that to the boiled or raw or steamed living children of vegetables.
    Vegans are EVIL!

  12. #12 Phillip J. Eby
    June 26, 2007

    Methinks that somebody overestimates how much chewing is required for eating raw meat. My personal experience is that raw meat requires *less* chewing, not more. It’s harder to chew raw, for sure, but there’s also no *need* to chew it; you tear off pieces with your front teeth and swallow the pieces, and it digests *easier* than cooked meat.

    And yes, I speak from personal experience; once you get used to eating raw meat, you lose the taste for having it cooked. The only part of cooking that still works for me is that it softens hard fats and makes them tastier. I suspect, however, that in a fresh kill the fats would be warm and soft already; that is not currently something I have any experience with, however. :)

    IMO, the survival value of cooking with respect to meat is merely that you can cook meat that you wouldn’t want to eat raw. Supermarkets routinely sell meat with theoretical expiration dates of how long it’s good for, but I rarely eat meat raw that’s got less than 3 days till its theoretical expiration date. At best, I cut off the brown bits and sear the rest.

    So, speaking from practical experience, if fire helped us get more food energy, it likely has more to do with things like fire-hardened spears and arrows, driving off predators, and extending the useful life of a kill, than it does to somehow getting more energy out of the meat itself. Personally, cooked meat makes me get tired and bloated, but raw meat usually energizes me.

  13. #13 Ken
    June 26, 2007

    I think the idea of enzymes aiding digestion is ludicrous. Our stomachs have specific acid stable enzymes (that are made within our own bodies) to breakdown foreign proteins and enzymes (and yes, I know that enzymes are a subset of proteins). And since when have you seen a steak digest itself? Raw or otherwise, meat doesn’t have anything that makes itself easier to breakdown/digest.

  14. #14 Kavien
    June 26, 2007

    Isn’t it just as likely that cooking meat makes it more stable (less likely to spoil). The ability to eat for a longer period of time means that primitive man was able to get more nutrients from his food instead of having to live on his own fat stores (think bears hibernating in winter).

    Think about it. Caribou beef jerky kept in a pack to last through the long winter months means less people they would have to eat when times got lean.

  15. #15 Oldfart
    June 26, 2007

    I’m not sure those who eat raw meat and who are commenting here have actually tried raw WILD meat other than that bait they call sushi.
    Wild meat is different from our domesticated and corn-fattened meats. So I am told. Chewing on meat from an old Caribou is NOT going to be an easy task. Or even a young Caribou for that matter. Go chew on some of them for awhile and report back.

  16. #16 idiot
    June 27, 2007

    this theory is one big paradox. we had the brain power to cook meat and create fire, yet it was this process which increased our brain power? talk about paradox. same applies to hunting.

    what happened to good old evolution? freaks with big brains succeeded and normal ancestors with small brains didn’t so the big brained monkeys passed on their genes.

    it’s a silly debate in my opinion.

  17. #17 Anonymous Coward
    June 27, 2007

    One of the things about eating raw meat, is that you don’t actually chew it. it is too tough. The way to eat fresh raw meat (of any kind) is to tear it into as small a piece as you can, and swallow it whole. that’s how the lions do it, and that’s how my cat does it.

  18. #18 Mike
    July 2, 2007

    Ken,
    The muscle cells which make up meat contain a variety of proteases such as calpain, which breakdown the sarcomeric structure after the animal is killed. That is why expensive beef is “aged” for 3 weeks or more.

    The energy gains for cooked meat are relatively small in contrast to the energy gains between meat versus the tubers and plants that early man would otherwise be eating. If cooking had any impact, it would most likely be on reduction of illness from eating bad meat, particularly carion.

  19. #19 Frank
    July 8, 2007

    Bob,my point is that rare sites do occur in the archaeological record, particularly in areas subject to flooding or burial by other natural causes (i.e. volcanic ash). You can rarely say “never occurs” when it comes to the archaeological record. All of the early man finds are rare occurrences because neither the human remains or the artifacts were intentionally buried. Accidents do happen, thats my point. If they didn’t we wouldn’t have much of a fossil record.`

  20. #20 Magnus
    March 19, 2008

    Matthew, I just wanted to comment on one detail you wrote: “But for proto-humas who were constantly on the brink of starvation …”

    Why would proto-humans be constantly on the brink of starvation? What about other animals in their natural environment? The eagle, the antilope, the shark, the wolf, the gorilla. Are they constantly on the brink of starvation?

  21. #21 JMB
    October 16, 2008

    Before you judge “rawfoodist full of it” maybee you should check : Rudh Heidrich an triatlon athlete 73 years old.

    Blood pressure : 90 /60
    Bone density : 430
    Total Cholesterol below 115, you bet !!

    No supplements, no Meds !! Just raw food (vegan) . You could read her book eventualy :-)
    Why to argue about Nutrition when we see the results of the diet that you are pushing on the general population?

    http://www.wellnessnow.us/nutrition/the-ultimate-test

  22. #22 megan
    October 21, 2009

    Evolution suggests that humans started off as ocean dwellers, therefore we ate a lot of poultry. Poultry does not need fire in order to be “cooked” or to be “consumed with less energy”. Anything with citrus is able to cook white meat, but of course not to the extent of how fire can cook it. I wonder if the fruits(citrus contained fruit) getting mixed with meat could have been an accidental cause in the evolutionary changes in human physiology. I can see how fish meat can be digested with less energy, and therefore possibly causing physiologcal changes. However, I am having a hard time imagining how red meat would be the cause to changes in physiology if no techniques of cooking were available, so I can understand where the skeptics’ viewpoints are coming from. What else would make red meat easier to digest? What about letting meat sit out and dry?–Doesn’t that make digestion of meat easier?

  23. #23 Aaron
    March 1, 2010

    Not only does raw food contain more nutrients, but eating raw avoids the toxins that are created when cooking with high temperatures. This is a large leap to connect cooking foods with brain size increasing in my opinion.

    Some people do great on a vegan raw food plan, but the other 75% or so of the population will not. There’s never one plan that works for all, but many studies suggest raw has more nutrition.

  24. #24 Wayne
    July 27, 2010

    I have witnessed dramatic physical and mental benefits with a natural raw food diet. When you were a baby, if you were breastfed, you started with a raw diet. Sometime later, you were probably introduced to a cooked food and spit it out quickly but after a while became used to and eventually addicted. Cooked food is addictive and can be difficult to get off of. Keep at it and keep working towards more and more raw. The benefits are enormous. Also be sure to include lots of Greens, a variety of lettuces and leaves from various plants. Victoria Boutenko can tell you why.

  25. #25 Three Ninjas
    February 15, 2011

    “Evolution suggests that humans started off as ocean dwellers, therefore we ate a lot of poultry.”

    Wait…what?!?!???

  26. #26 Robert
    June 6, 2011

    The article mentioned “Olduvai Gorge”. I would like to point out that the correct name is “Oldupai Gorge”. It was never Olduvai. It was a mistranslation or misheard. How do I know this? I’ve been there, twice. There is a big sign there, and the rangers make a point of telling tourists that the name is Oldupai.