Edibles and Evolution
Primal Kitchens
The most dramatic moment in human evolution took place about
1.9 million years ago, with the emergence of homo erectus.
"Something radical happened," says professor of anthropology Richard
Wrangham. "The change happened almost too quickly for the fossil
record to record its intermediate stages."
The australopithecine creatures who inhabited the
African woodlands before that time looked and acted more like chimpanzees
than humans. They were short and short-legged; females weighed only
about 60 pounds, males about twice as much. They had large faces,
mouths, teeth, and guts, and arms and shoulders that were well adapted--like
those of chimps--to hanging for hours in trees, where they could
both forage for food and sleep. Then a markedly different creature
suddenly emerged from one of the australopithecine populations,
and within 100,000 years had spread from Africa to Europe and probably
Asia. Homo erectus looked so much like modern humans, Wrangham
says, that "if you dressed one in clothes, put a hat on her, and
walked her down a Manhattan street, she wouldn't draw too many stares."
In a Current
Anthropology article published last December, Wrangham and
coauthors James Holland Jones, assistant senior tutor in Mather
House, Greg Laden of the University of Minnesota, Ford professor
of the social sciences David Pilbeam, and research assistant Nancylou
Conklin-Brittain advance a new theory to account for the sudden
change. They suggest that the discovery of fire and its corollary,
cooking, occurred much earlier in prehistory than generally believed--and
furthermore, that the innovation of cooking fundamentally reshaped
the body. "All humans cook, and cooking has such big effects on
what you can digest that it would necessarily have major impact
on any species that adopts it," Wrangham explains. "Things like
the shape and size of teeth, for example, are closely adapted to
what you eat. But until now, no one has suggested any time [frame
for] when cooking evolved that coincides with big changes in the
morphology of the body."
The cooking hypothesis is bold because scholars routinely link
the origin of cooking to archaeological indications of fire--and
there is scant evidence for human control of fire earlier than 300,000
to 400,000 years ago. "But," says Wrangham, "fire doesn't leave
much behind in the archaeological record." Furthermore, recent thermal
and paleomagnetic data obtained from reddened patches of rock in
Kenya suggest the existence of hearths as old as 1.6 million years.
"We know that the environment was getting drier [1.9 million years
ago]," Wrangham says, "so lightning, for example, would start natural
fires. One can imagine a root being cooked by chance, then found
and eaten by an australopithecine who liked it."
"Most foraging peoples live under nutritional stress," Pilbeam
notes, and cooking expands the range of edible food and improves
its overall quality. Wrangham explains, "Cooking breaks down indigestible
molecules and makes them digestible. Starch in uncooked roots, for
example, is often in a crystalline form. Until it's heated, our
digestive systems can't use it." That means our ancestors could
obtain as much nutrition from one roasted tuber as they could from
several raw ones, and therefore needed to eat less. Consequently,
over time, they might have developed smaller, flatter guts and the
inward-tilting ribs seen in homo erectus. Cooking also softens
food, diminishing the need for big teeth that can shear and pulverize.
Indeed, with the emergence of homo erectus, "You see a greater
reduction in the size of teeth than at any other point in our ancestry,"
Wrangham says. Smaller teeth also mean smaller faces, as well as
much smaller mouths. And controlled fire would also help defend
against night predators, a necessity for creatures who were now
sleeping not in trees, but on the ground.
Where foraging apes usually pop food immediately into their mouths,
the advent of cooking--a time-consuming activity--meant that hominids
had to wait while the foods that they had collected were readied
for eating. (The first "homes" were probably pantries at hearthsides.)
But with waiting comes the possibility of theft. "The female suddenly
becomes vulnerable to a new problem--she can easily lose her food
to the much larger, dominant Australopithecus males who might
steal it, profiting from her hours of foraging effort," Wrangham
says. Pilbeam adds, "She would have an incentive to attach herself
to a male defender who could guard the food supply. This could be
the point at which human monogamy first occurred."
Under these conditions, females would compete with each other
for the best male protectors, in terms of both their strength and
agility and their ability to summon allies. The researchers speculate
that to attract such males to their hearths, these early women became
"sexier," evolving an extended period of sexual desirability, including
the concealed ovulatory pattern of human females, and copulating
throughout the menstrual cycle. "The theft hypothesis portrays the
human family as originating in a swirl of sexual and domestic politics
around a kitchen hearth," writes Wrangham, who later adds a classical
allusion: "Prometheus is said to have created humans by quickening
clay figures with fire. If the foraging and mating systems of humans
were indeed shaped powerfully by cooking, the ancient Greek myth
may have been close to the truth."
~Craig Lambert
