Cooked Food
This passage is adapted from an article by Mary Evans that originally appeared in The Economist (© 2009 by Mary Evans).
- You are what you eat, or so the
- saying goes. But Richard
- Wrangham, of Harvard
- University, believes that this
- is true in a more profound
- sense. It is not just you who
- are what you eat, but the
- entire human species. And
- with Homo sapiens, what
- makes the species unique in
- Dr. Wrangham’s opinion is
- that its food is so often cooked.
- Cooking is a human universal.
- No one other than a few
- faddists tries to survive on
- raw food alone. And the
- consumption of a cooked
- meal in the evening is normal
- in every known society.
- Moreover, without cooking,
- the human brain could not
- keep running. Dr. Wrangham
- thus believes that cooking and
- humanity are coeval.
- In fact, as he outlined to the
- American Association for the
- Advancement of Science, in
- Chicago, he thinks that cooking
- and other forms of preparing
- food are humanity’s “killer
- app”: the evolutionary change
- that underpins all of the other
- changes that have made people
- such unusual animals.
- Humans became human with
- the emergence of a species called
- Homo erectus. This had a
- skeleton much like modern man’s
- —a big, brain-filled skull and a
- narrow pelvis and rib cage, which
- imply a small abdomen and thus
- a small gut. Hitherto, the
- explanation for this shift from the
- smaller skulls and wider pelvises
- of man’s apelike ancestors has
- been a shift from a vegetable-
- based diet to a meat-based one.
- Meat has more calories than
- plant matter, the theory went.
- A smaller gut could therefore
- support a larger brain.
- Dr. Wrangham disagrees. When
- you do the sums, raw meat is
- still insufficient to bridge the
- gap. He points out that even
- modern “raw foodists,” members
- of a back-to-nature social
- movement, struggle to maintain
- their weight—and they have
- access to animals and plants
- that have been bred for the
- table. Pre-agricultural man
- confined to raw food would
- have starved.
- Start cooking, however, and
- things change radically. Cooking
- breaks starch molecules into
- more digestible fragments. It
- “denatures” protein molecules,
- so that their amino-acid chains
- unfold and digestive enzymes
- can attack them more easily.
- And heat physically softens
- food. That makes it easier to
- digest, so even though the
- stuff is no more calorific, the
- body uses fewer calories dealing
- with it.
- In support of his thesis, Dr.
- Wrangham, who is an
- anthropologist, has ransacked
- other fields and come up with
- an impressive array of material.
- Cooking increases the share of
- food digested in the stomach
- and small intestine, where it
- can be absorbed, from 50% to
- 95% according to work done
- on people fitted for medical
- reasons with collection bags at
- the ends of their small intestines.
- Another telling experiment,
- conducted on rats, did not rely
- on cooking. Rather the
- experimenters ground up food
- pellets and then recompacted
- them to make them softer. Rats
- fed on the softer pellets weighed
- 30% more after 26 weeks than
- those fed the same weight of
- standard pellets. The difference
- was because of the lower cost
- of digestion. Indeed, Dr.
- Wrangham suspects the main
- cause of the modern epidemic
- of obesity is not overeating
- but the rise of processed foods.
- These are softer, because that
- is what people prefer. Indeed,
- the nerves from the taste buds
- meet in a part of the brain called
- the amygdala with nerves that
- convey information on the
- softness of food. It is only after
- these two qualities have been
- compared that the brain
- assesses how pleasant a
- mouthful actually is.
- The archaeological evidence for
- ancient cookery is equivocal.
- Digs show that both modern
- humans and Neanderthals
- controlled fire in a way that
- almost certainly means they
- could cook, and did so at least
- 200,000 years ago. Since the
- last common ancestor of the
- two species lived more than
- 400,000 years ago, fire-control
- is probably at least as old as
- that, for they lived in different
- parts of the world, and so could
- not have copied each other.
- Older alleged sites of human
- fires are more susceptible to
- other interpretations, but they
- do exist. And traces of fire are
- easily wiped out, so the lack of
- direct evidence for them is no
- surprise. Instead, Dr.
- Wrangham is relying on a
- compelling chain of logic. And
- in doing so he may have cast
- light not only on what made
- humanity, but on one of the
- threats it faces today.