(Basic Books: 2009)
“I believe the transformative moment that gave rise to the genus Homo...stemmed
from the control of fire, and the advent of cooked meals. Cooking
increased the value of our food. It changed our bodies, our brains, our
use of time, and our social lives. It also made us consumers of
external energy and thereby created an organism with a new relationship
to nature, dependent on fuel.... The fossil record shows that before
our ancestors came to look like us, they were humanlike in walking
upright, but...they were the size of chimpanzees, they climbed well,
they had ape-sized bellies, and they had protruding, apelike
muzzles...[and brains] barely larger than chimpanzees.... The
transition is first signalled at 2.6 million years ago,
by...cobblestones deliberately clashed to produce a tool....[and]
knife-making suggests planning, patience, cooperation, and organized
behavior. Old bones continue the story. By around 2.3 million years
ago, the first tentative record emerges of a new species.... Habilines
appear to have been about the same small size as
australopithecines...yet they are thought to be the knife-makers, and
they had brains twice as big as those of living nonhuman apes....
Between 1.9 and 1.8 million years ago, the second critical step was
taken: some habilines evolved into Homo erectus...[who]
even appear to have grown and matured slowly, in the manner of modern
humans...[and] had small jaws and small teeth, that were poorly adapted
for eating the tough raw meat of game animals. These weaker mouths
cannot be explained by Homo erectus’s
becoming better at hunting. Something else must have been going
on.... Cooking food does many things. It makes our food safer,
creates rich and delicious tastes, and reduces spoilage. Heating can
allow us to open, cut, or mash tough foods. But none of these
advantages is as important as a little-appreciated aspect: cooking
increases the amount of energy our bodies obtain from our food. The
extra energy gave the first cooks biological advantages.... Their genes
spread, [and] their bodies responded by biologically adapting to cooked
food, shaped by natural selection to take maximum advantage of the new
diet. There were changes in anatomy, physiology, ecology, life history,
psychology, and society.... We humans are the cooking apes, the
creatures of the flame.”
While most treatments of human evolution still hew fairly closely to
the old hypotheses, across the field a variety of genuinely fresh
approaches are making much more sense of the full range of available evidence...from the mimetic
culture of Merlin Donald, to Christopher Boehm’s counter-hierarchy, and
Jonathan Kingdon’s revolutionary mix of anatomical and biogeographical
insight. The latest in this chain of work is also perhaps the best
supported - and the easiest to outline - being Richard Wrangham’s Catching Fire (2009)...the first exhaustive treatment of the evidence for cooking as
the key which enabled the basic transition from ape to human. For while
Kingdon - and a few others - have indeed made this basic claim before,
nobody had examined the full implications of such a claim...thereby
showing that it is, in fact, remarkably well-supported by a wide
variety of evidence.
And the starting point is a remarkably simple one: even in modern
sedentary societies, eating high-quality domesticated foodstuffs (w/no
dangerous seasonal variability) - frequently ground to a pulp by
mechanical food processors (rather than laboriously chewed) - human
beings attempting to survive on purely raw foods are 1/- always hungry,
2/- thin to dangerously underweight (about 50% of women cease to
menstruate), 3/- reliant upon oils/fats for calories to a much
greater extent than would be possible for virtually all
hunter-gatherers. And, before anyone raises the counter-case of
traditional (raw) Eskimo/Inuit diets, this - like their myriad
words for snow - is yet another “learned” myth about these isolated
peoples. Like every society studied by anthropology, raw food among the Inuit is mainly a snack consumed out of camp...
Unfortunately, simplistic assumptions by early nutritionists - as well
as such myths - have tended to obscure the nutritional value of cooking
until recently. However, high-quality science is now demonstrating that
processing food can have a major impact...
“The mechanisms
increasing energy gain in cooked food, compared to raw food, are [now]
reasonably well understood. Most important, cooking gelatinizes starch,
denatures protein, and softens everything..... Raw starch [for example]
is poorly digested, often only half as well as cooked starch....
[Similarly,] denatured proteins are [up to 40%] more digestible because
their open structure exposes them to the action of digestive
enzymes.... [However,] heat is only one of several factors that promote
denaturation. Three others are acidity, sodium chloride, and drying,
all of which humans use in different ways.... Although gelatinization
and denaturation are largely chemical effects, cooking also has
physical effects on the energy food provides...[reducing] the costs of
digesting, absorbing, and assimilating [foodstuffs].... Admittedly,
cooking can have some negative effects. It leads to energy losses
through dripping during the cooking process and by producing
indigestible protein compounds, and it often leads to a reduction of
vitamins. But, compared to the energetic gains, those processes...[are]
relatively unimportant, compared to the impact of more calories....
[For] the result was a new evolutionary opportunity.”
“Evolutionary tradeoffs
are common. Compared to chimpanzees, we climb badly but we walk well.
Our awkwardness is due partly to our having long legs and flat feet,
but those same legs and feet enable us to walk more efficiently than
other apes. In a similar way, our limited effectiveness in digesting
raw food is due to our having relatively small digestive
systems...[that] enable us to process cooked food with exceptional
proficiency.... The evolutionary benefits stem from the fact that
digestion is a costly process that can account for a high proportion of
an individual’s energy budget - often as much as locomotion.... The
main differences all involve humans having relatively small features.
We have small mouths, weak jaws, small teeth, small stomachs, small
colons, and small guts overall...[with] the surface area of the stomach
less than one-third the size expected for a typical mammal of our
body-weight.... [Interestingly,] in carnivores, meat spends a long time
in the stomach, allowing intense muscular contractions of the stomach
wall to reduce raw meat to small particles that can be digested
quickly...through the small intestine. By contrast, humans resemble
other primates in keeping food in our stomachs for a short time...then
passing it slowly through the small intestine. Lacking the carnivore
system...we humans are inefficient at processing chunks of raw
meat....[Furthermore,] evolutionary adaptation to cooking might
likewise explain why humans seem less prepared to tolerate toxins than
do other apes.”
So...why, precisely, this tradeoff?
Well...primates are predominantly social animals - and there’s a
well-attested intelligence arms race in such species, driven by the
overwhelming need to monitor shifting group alliances & outwit the
opposition. However, brain tissue is very expensive to run - when
indolent, every human’s fifth meal is eaten solely to power the brain -
and animals can only have the brain they can reliably afford...as brain
tissue energy consumption is relatively stable across the wake-sleep
divide. Therefore, the key lies in the general quality of diet...
As to the archaeology, the earliest well-documented site for fire use
(currently) is dated at 790,000 years ago, in Israel, albeit there are
many hints that earlier dates/locations are quite tenable.
Unfortunately, the best evidence comes from geologically young caves in
soft rock - particularly limestone - which have a half-life of around a
quarter of a million years...meaning the best is basically unavailable
by the time we come to the critical period of erectus evolution. However, as Wrangham explains:
“In response to a major
change in diet, species tend to exhibit rapid and obvious changes in
their anatomy. Animals are superbly adapted to their diets, and over
evolutionary time the tight fit between food and anatomy is driven by
food rather than by the animal’s characteristics. Fleas do not suck
blood because they happen to have a proboscis well designed for
piercing mammalian skin; they have the proboscis because they are
adapted to sucking blood.... Therefore, we can identify when cooking
began by searching the fossil record...[and] the change must mark when
cooking became...a predictable daily occurance...and [it] also marks
the time when fire was controlled so effectively that it was never lost
again.”
Close attention to details here allows Wrangham not only to link the
(slight) rise in brainpower of the Australopithecines to newly-regular
tuber consumption, and meat to habilines - both now-standard in the
literature - but also to note a shortfall between unprocessed raw meat
consumption re the purported tradeoff into brain tissue. The
parallels are very interesting here, as are the implications:
“Chimpanzees...show
that meat eating is difficult with ape jaws.... Perhaps because of this
hard work and inefficiency, chimpanzees sometimes decline the
opportunity to eat meat, despite their usual enormous enthusiasm for
it.... When eating muscle, chimpanzees are forced to chew it slowly,
taking as much as an hour to chew one-third of a kilogram....
[However,] habilines had access to more advanced techniques. Their
bones are found close to stone hammers, fist-size spheres whose shapes
provide vivid testimony of their repeated use. Habilines probably used
the hammers partly to smash prey bones to extract the marrow. They also
doubtless used the hammers to crack open nuts, as West African
chimpanzees do. as well as to make other tools...[and] could equally
have been used for tenderizing meat.... Even relatively crude hammering
would have reduced the costs of digestion...[and] I suspect this was
one of the most important cultural innovations in human origins.”
“Reliance on cooked
food has...allowed our species to thoroughly restructure the working
day. Instead of chewing for (literally) half of their time, as the
great apes tend to do,women in subsistence societies tend to spend the
active part of their days collecting and preparing food. Men, liberated
from the simple biological demands of a long day’s commitment to
chewing raw food, engage in productive or unproductive labor as they
wish. In fact, I believe cooking has made possible one of the most
distinctive features of human society: the modern form of the sexual
division of labor.”
“Among
hunter-gatherers....women and men spend their time days seeking
different kinds of foods, and the foods they obtain are eaten by both
sexes.... Although the specific food types varied from place to place,
women always tended to provide the staples, whether roots, seeds, or
shellfish. These foods normally needed processing, which could involve
a lot of time and laborious work.... Men by contrast tended to search
for foods that were especially appreciated, but could not be found
easily, or predictably.... Human families are unique compared to other
species, because each household is a little economy.... The classic
explanation in physical anthropology [revolves around] meat...and an
unstated assumption was that the food was raw. But if food was raw, the
sexual division of labour is unworkable...[as,] conservatively it would
[include] just over five hours of chewing in a twelve hour day....
[Moreover,] apes also have to pause between meals.... Therefore, a five
hour chewing requirement becomes an eight- or nine-hour commitment to
feeding. Eat, rest, eat, rest.”
Which hardly allows any time for hunting.... Although Wrangham doesn’t
explore this factor, I think it reinforces the emerging consensus that
habilines almost certainly were improved scavengers, rather than
reliant upon hunting to any great degree - and that they also probably
had some social arrangements unique to their group which made this
workable. On the other hand, Wrangham’s made it clear by this point
that raw food sharing - according to later models - is simply not on
the cards, since physiology/time use are weighed so strongly against
it. However, cooking may have solved that problem...but, it also
introduced a series of fresh ones to replace it - the “solution” to
which was predominantly patriarchy, sexual division of labour, and
pair-bonding. And, as Wrangham himself observes: “It’s not a pretty
picture.”
“An evening meal cooked
by a woman serves her and her children’s needs. It also helps her
husband by giving him a predictable source of food, allowing him to
spend his day doing whatever activity he chooses. But while the
arrangement is comfortable for both sexes, it is particularly
convenient for the male. Why should a female cook for him? ...[And]
overall, cooking is the most female-biased activity of any.... Even the
apparent exceptions conform...to the general rule...[as there is] an
important distinction between two types of cooking: cooking done for
the family, done by women, and cooking for the community, done by
men.... The rule that domestic cooking is women’s work is astonishingly
convincing.”
“Nonhuman primates
mostly pick and eat their food at once. But hunter-gatherers bring food
to a camp for processing and cooking, and in the camp, labor can be be
offered and exchanged.... [Crucially,] relying on cooking creates foods
that can be owned, given, or [easily] stolen.... Cooking takes time, so
lone cooks cannot easily guard their wares from determined thieves,
such as hungry males without their own food. Pair-bonds solve the
problem.... According to this idea, cooking created a simple marriage
system...a primitive protection racket in which husbands used their
bonds with other men in the community to protect their wives from being
robbed, and women returned the favor by preparing their husbands’
meals. The many beneficial aspects of the household, such as
provisioning by males, increases in labor efficiency, and creation of a
social network for child-rearing, were additions consequent to solving
the more basic problem: females needed male protection, specifically
because of cooking.”
And the evidence supporting this perspective will be surprising to
many...much of it universal across studies of mobile hunter-gatherers.
Women’s food is private/domestic...and acceptable forms of begging for
it are extremely circumscribed, whereas men’s food is parcelled out across the
collective, typically via elaborate formulae. However, once the
men’s food share enters the domestic/female economy, it joins the
women’s food in being subject to strong cultural norms, which severely
restrict access. Not only must married women cook for their husbands -
although they may have help - but (other than her kin) wives do not feed
other men, except with the explicit sanction of the husband. This - in
direct contrast to many such cultures’ more freewheeling attitudes
towards sex, tends to suggest that Wrangham is right...the foundation
of monogamy is in the regulation/reduction of competition over food/not
sex, as is traditionally assumed. Let’s look at some of the details:
“Under this system, an
unmarried woman who offers food to a man is effectively flirting, if
not offering betrothal...[and] cofeeding is often the only marriage
ceremony.... [Conversely,] among many hunter-gatherers, sexual
intercourse is not tightly restricted to marriage. Wives are free to
have sexual relations with several men at the same time, and may do so
even when their husbands protest.... When an Australian aboriginal wife
deserts her husband, wrote Phyllis Kaberry, he can easily replace her
role as a sexual partner, but he suffers because he has lost someone
tending his hearth. The loss is important because a bachelor is a sorry
creature in subsistence societies, particularly if he has no kin....Men
need their personal cooks because the guarantee of an evening meal
frees them to spend the day doing what they want, and allows them to
entertain other men. They can find opportunities for sexual
interactions more easily than they can find a food provider.”
“Anthropologists often
see marriage as an exchange in which women get resources and men get a
guarantee of paternity. In that view, sex is the basis of our mating
system; economic considerations are an add-on. But...in animal species,
the mating system is adapted to the feeding system, rather than the
other way around.... Furthermore, food relationships [among
hunter-gatherers] appear more tightly regulated than sexual
relationships...[and] when a woman feeds a man, she is immediately
recognized as being married to him. Western society is not alone in
thinking that the way to a man’s heart is through his stomach.”
“It is impossible to
know how rapidly cooking would have ended individual self-sufficiency
after it was first practised, but in theory the protective pair-bond
system could have evolved quickly.... But, at least we can say that
three of the key behavioral elements found in the hunter-gatherer
system - male food guards, female food suppliers, and respect for
other’s possessions - are found in other animals, suggesting that a
primitive version of the modern food-protection regime could have
evolved rapidly among early cooks.”
Moreover, fire use/cooking has flow-on effects in other
directions...some of which clearly affected our physical and mental
evolution. Let Wrangham explain:
“If Homo erectus used fire...they could sleep in the same way as people do nowadays in
the savanna. In the bush, people lie close to the fire, and for most or
all of the night, someone is awake. When a sleeper awakens, he or she
might poke at the fire and chat a while, allowing another to fall
asleep. In a twelve-hour [equatorial] night, with no light other than
what the fire provides, there is no need to have a continuous
eight-hour sleep. An informal system of guarding easily emerges...[and]
to judge from records of attacks by jaguars, modern hunter-gatherers
are safer in camp at night than they are on the hunt by day.... [In
addition,] their new practice of cooking roots and meat meant that food
obtained from trees was less important.... [So,] when they no longer
needed to climb trees to find food or sleep safely, natural selection
rapidly favored the anatomical changes that facilitated long-distance
communication, and led to living completely on the ground.”
“[Furthermore,] once
our ancestors controlled fire, they could [also] keep warm even when
they were inactive. The benefit would have been high: [largely
hairless] humans would have been better able to travel long distances
during hot periods, when most animals are inactive. They could then run
for long distances in pursuit of prey, or to reach carcasses
quickly.... [Moreover,] even our ancestors’ emotions are likely to have
been influenced by a cooked diet. Clustering around a fire to eat
and sleep would have required...considerable tolerance...[although] a
version of this had probably already started before cooking, when
groups of habilines clustered about a meat carcass.... If the intense
attractions of a cooking fire selected for individuals who were more
tolerant of one another, an accompanying result should have been a rise
in their ability to stay calm as they looked at each other, so they
could better assess, understand, and trust one another.... Such changes
in social temperament would have contributed to a growing ability to
communicate, including the evolution of language....[And so] the newly
delicious cooked diet led to their evolving smaller guts, bigger
brains, bigger bodies and reduced body hair; more running; more
hunting; longer lives; calmer temperaments; and a new emphasis on
bonding between females and males. The softness of their cooked plant
foods selected for smaller teeth, the protection fire provided at night
enabled them to sleep on the ground and lose their climbing ability,
and females likely began cooking for males, whose time was increasingly
free to search for more meat and honey. While other habilines
elsewhere in Africa continued for several hundred thousand years to eat
their food raw, one lucky group became Homo erectus - and humanity began.”
Richard Wrangham’s Catching Fire (2009) is one of the most deceptively clear books I’ve ever read.
“Deceptively” because - whether you like it or not - it re-centres the
extremely complex matter of human evolution around an extremely
compelling and interlocked set of evidence which, quite basically,
admits of no other real explanation. This is groundbreaking stuff...
But perhaps the most crucial influence Catching Fire will have lies in its very real potential to enable the synthesis of
hitherto disparate - yet important - aspects of human evolution.
Clearly, for example, Wrangham’s “hearth politics” provides the crucial
context in which Christopher Boehm’s “counter-hierarchies” not only
can, but necessarily arise...with the additional input of sexual
selective processes - albeit considerably more economic/pragmatic than,
say, Geoffrey Miller has envisaged. Similarly, the developmental
interaction arguments of Ellen Dissanayake & Sarah Blaffer Hrdy can
be expected to come fully into their own once the (partial) taming of
the male hierarchy is underway...then leading through to properly
mimetic culture/proto-language, and so on... All up, I’m beginning to
suspect we now have all the truly critical theoretical ingredients we
need to understand to transition to genus Homo...even if that final move to species sapien is still only partially accounted for.
Clearly written & argued, evidentially overwhelming, and
entertaining to boot...this one will be enormously influential. And,
hopefully soon. I can hardly wait to read mature syntheses to come.
“We once thought of our
species as infinitely adaptable, particularly in our diet. Different
peoples survive on diets that range from 100 percent plants to 100
percent animals.... Taken to extremes, our species seems to be free to
create our own evolutionary ecology. [But] the cooking commitment says
otherwise. The human ancestral environment was full of uniform
problems: how to get fuel, how to regulate feeding competition, how to
organize society around fires. The big problem of diet was once how to
get enough cooked food, just as it is still for millions of people
living around the world. But, for those of us lucky enough to live with
plenty. the challenge has changed. We must find ways to make our
ancient dependence on cooked food healthier.”
(Wrangham, pp.206-7)
