The Curse of a Big Head-sweat, childbirth pain and clothing

Glenn Morton (
Mon, 30 Dec 1996 09:07:00

The Curse of a Big Head

Copyright 1996 G.R. Morton. This can be freely copied and
distributed if unaltered and no monetary charge is made.

Genesis 3:16-21 (NIV) "To the woman he said, 'I will
greatly increase your pains in childbearing; with pain you
will give birth to children. Your desire will be for your
husband, and he will rule over you.' To Adam he said,
'Because you listened to your wife and ate from the tree
about which I commanded you, 'You must not eat of it,'
"Cursed is the ground because of you; through painful toil
you will eat of it all the days of your life. It will
produce thorns and thistles for you, and you will
eat the plants of the field. By the sweat of your brow you
will eat your food until you return to the ground, since
from it you were taken; for dust you are and to dust you
will return.' Adam named his wife Eve, because she would
become the mother of all the living. The LORD God made
garments of skin for Adam and his wife and clothed them."

While I know that large numbers of Christians do not take
this account as a piece of history, there is a very
interesting set of circumstances in anthropology which ties
many of the features of this story together. These features
are the pain of childbirth, sweat, and the need for
clothing. All of these have a singular cause--a big head. In
what follows I will quote the original authors because the
experts can say it better than I.

The brain is a huge consumer of energy. Human adults
use about 20 percent of their metabolic energy running the
brain. (Johanson and Shreeve, p. 263) Left alone the brain
would quickly over heat and die. Even modest increases can
be fatal; raising the brain temperature to 106 degrees
Fahrenheit causes brain damage. This fact means that the
brain must be cooled and the temperature stabilized.
Physically, there are several ways to accomplish this--heat
conduction, convection or a fluid coolant system. Convection
only works in fluids and the brain is not fluid and heat
conduction through the skull is too slow. The only real
solution is a coolant system like an automobile uses. The
cooling system must be efficient. Dean Falk, one of the
world's leading authorities on hominid brains, advanced a
theory in which the hominid brain could not grow any bigger
than the cooling system attached to it. The theory
originated from a comment by her mechanic. She writes Falk,
1992, p. 156):

"It was an 'aha' experience, if ever I've had one, and
the weirdest combination of events led to it. First, the
engine in my 1970 Mercedes needed major surgery. I took it
to Walter Anwander (a whiz) in Lafayette, Indiana, who
completely rebuilt the engine. One day, while enumerating
the wonders beneath the hood (about which I definitely
needed schooling), Walter pointed to the radiator and told
me 'the engine can only be as big as that can cool.' I
didn't think much about it at the time."

The brain, like that engine, can only be as big as the
cooling system it has. If the brain overheats, the brain is
ruined just like overheating a car engine will ruin it. In
the brain the blood acts as the coolant. The brain has
several emissary veins which go from the interior of the
skull to the skin of the face. These veins are part of the
"radiator" system. When a person is cold, blood flows from
the cranium outward in these veins. But when a person
exercises and becomes overheated, the blood flow reverses
and blood flows into the cranium. The reason for this
reversal is that the skin of the face (the brow included)
acts as a radiator, cooling the blood which then enters the
brain to cool that organ. Some of the veins are preserved
in the skulls of extinct hominids (and man) in the form of
emissary foramina (a foramina is a hole in the skull see
Falk 1992 p. 153). Thus a record of the size and number of
emissary foramina are preserved in ancient skulls for
anthropologists to examine. Falk (1992, p. 159) notes:

"It was beautiful. For the past two million years, the
increase in frequencies of emissary foramina kept exact pace
with the sharp increase in brain size in Homo. Clearly, the
brain and the veins had evolved rapidly and together. I saw
that Cabanac's letter was right and that I had unwittingly
charted the evolution of a radiator for the brain in my
earlier work on emissary foramina. As Anwander had said
about my car, the engine can only be as big as the radiator
can cool. Apparently, the same is true for heat-sensitive

But emissary veins are only part of the cooling
mechanism in mankind. Sweat is the reason that the facial
skin cools and the cooling of the skin cools the blood
destined for the brain. What do we know about sweat?

The human sweating system is unique among mammals.
Bernard Campbell (1974, p. 280-282) describes the function
of sweat glands:

"The sweat glands fall into two groups: the apocrine
and eccrine glands. The apocrine glands secrete the odorous
component of sweat and are primarily scent glands that
respond to stress or sexual stimulation. Before the
development of artificial scents and deodorants, they no
doubt played an important role in human society. In modern
man these glands occur only in certain areas of the body, in
particular in the armpits, the navel, the anal and genital
areas, the nipples, and the ears. Surprisingly enough,
glands in the armpits of man are more numerous per unit area
than in any other animal. There is no doubt that the
function of scent in sexual encounter is of the greatest
importance even in the higher primates and man.
"The eccrine glands, which are the source of sweat
itself, have two functions in primates. Their original
function was probably to moisten friction surfaces, such as
the volar pads of hand and foot to improve the grip, prevent
flaking of the horny layer of the skin, and assist tactile
sensitivity. Glands serving that function are also found on
the hairless surface of the prehensile tail of New World
monkeys and on the knuckles of gorilla and chimpanzee hands,
which they use in quadrupedal walking. Glands in these
positions are under the control of the brain and adrenal
bodies, and in modern man an experience of stress may
produce sweaty palms.
"The second and more recently evolved function of the
eccrine glands is the lowering of body temperature through
the evaporation of sweat on the surface of the body. The
hairy skin of monkeys and apes carries eccrine glands, but
they are neither so active nor so numerous as in man.
Modern man is equipped with between two and five million
active sweat glands, and they play a vital part in cooling
the body. The heat loss that results from the evaporation
of water from a surface is enormously greater than that
which could be expected to occur as a result of simple
radiation. The fact that sweat contains salt necessitates a
constant supply of the mineral if man is to survive in a
tropical climate.
"It has been observed that like almost all mammals,
primates sweat very little. Even hunting carnivores, such
as dogs, lose heat by other means, such as panting.
Sweating has evolved as a most important means of heat loss
in man, a fact that is surely correlated with the loss of
his body hair. The apparent importance in human evolution
of achieving an effective means of heat loss indicates
without doubt that early man was subject to intense muscular
activity, with the production of much metabolic heat; he
could not afford even the smallest variation in body
temperature. With such a highly evolved brain, the
maintenance of a really constant internal environment was a
need of prime importance in human evolution."

With this need to dissipate heat in order to maintain a
constant brain temperature, hair becomes a problem. Hair
traps the sweat and hinders evaporation. Zihlman and Cohn
(1986, p. 308) relate:

"How might early hominids have dissipated the heat load
generated internally, as well as externally from the sun?
One way is through the skin. The skin of modern humans
contrasts with that of other, nonhuman primates in four
features: 1) humans have a great density (over two million)
of functioning eccrine sweat glands over the entire body
surface; 2) loss of the apocrine sweat glands has been
associated with hair loss, and has occurred except in the
ano-genital and axillary regions; 3) hair follicles are
diffuse and hair shafts are noticeably reduced in size; 4)
skin pigment ranges from dark to light.
"How might these features be interpreted in a
functional and evolutionary way? There is the remarkable
thermo-regulatory function of eccrine sweat glands.
Sweating can deliver two litres of water to the skin surface
in two hours and carry off almost 600 calories of heat.
Hair tends to trap moisture, so that sweat evaporation is
more effective with reduced hair. Interestingly, the number
of hair follicles in humans is similar to that in
chimpanzees and gorillas, but the much reduced size of hair
shafts in humans gives a hairless appearance."

Why do we have hair on our head? Zihlman and Cohn (1988, p.
404) inform us:

"Hair retention on the head is probably important in
protecting the scalp from the sun's ultraviolet rays and may
assist in stabilizing the temperature of the brain. Human
populations are variable in the amount of body hair present,
but in all of them the skin surface is hairless enough to
permit efficient heat loss from sweating."

Radiatively, hair on the top of the head absorbs the
solar heat and re-radiates most of it. An absorbing layer
can reduce by half the amount of energy reaching the top of
the skull.

When is it likely that mankind needed this cooling
mechanism for heat removal? Probably fairly early. For
modern men even moderate exertion on the savanna increases
the heat production by 100% over the resting levels. Since
Homo erectus was as large as we are (Ruff, 1993, p. 56),
similar exertions on the plains would yield similar heating.
Even the smallest Homo erectus has a brain which is over
twice as large as that of the chimpanzee which can get by
without sweating. Homo erectus would need to sweat. Since
he needed to sweat, then he needed to be relatively hairless
as we are.

If he were relatively hairless, then the Homo erectus who
lived in Georgia (former USSR Larick and Ciochon, 1996, p.
548-550) would have been ill-equipped to handle the winter
temperatures below zero Fahrenheit which occur from time to
time in that area. He would have needed clothing. Because
of these considerations, Anthropologists like Brian Fagan
were forced to conclude (Fagan, 1990 p. 76):

"For Homo erectus to be able to adapt to the more temperate
climate of Europe and Asia, it was necessary not only to
tame fire but to have both effective shelter and clothing to
protect against heat loss. Homo erectus probably survived
the winters by maintaining permanent fires, and by storing
dried meat and other foods for use in the lean months."

This is a very human set of behaviors and Homo erectus was
found in European Georgia 1.6 million years ago.

Now to tie up the final item, pain in childbirth. Among
mammals there are two patterns of brain growth. The first
pattern is called altriciality. In this pattern the animal
is born helpless and extremely immature. The brains of
altricial animals are usually half the size of the adult's,
and double in size by adulthood. Because of this it takes
lots of parental effort to raise the young. Animals
following this pattern usually have litters and perform this
care for multiple offspring at once. Cats, with their blind
and helpless kittens are altricial. The other pattern is
precocial. In this pattern the offspring are usually born
single and from birth are able to get around quite well.
Their brains are nearly adult size at birth. The are alert
and all their organs are functioning. An example of this
pattern is the horse, the wildebeest etc., where the young
will run with the herds within minutes.

Now, according to Walker and Shipman (1996, pp220-222),
altricial species almost never have bigger brains than
precocial species. The reason is that for all mammals save
one, the brain grows rapidly during gestation but then grows
less rapidly after birth. There is a kink in the graph of
brain size vs. time which occurs at birth. Altricial
species whose immature state at birth and subsequent slow
down in the rate of growth forever remain behind the more
maturely born precocial species.

What humans seem to have accomplished is the trick of
keeping the brain growing ar the embryonic rate for one year
after birth. Effectively, if humans are a fundamentally
precocial species, our gestation is (or should be) 21
months. However, no mother could possibly pass a year old
baby's head through the birth canal. Thus, human babies are
born "early" to avoid the death of the mother. Walker and
Shipman (1996, p. 222) write:

"Humans are simply born too early in their development,
at the time when their heads will still fit through their
mothers' birth canals. As babies' brains grow, during this
extrauterine year of fetal life, so do their bodies. About
the time of the infant's first birthday, the period of fetal
brain growth terminates, coinciding with the beginnings of
speech and the mastery of erect posture and bipedal

This pattern of growth has huge implications. Every
other primate doubles their brain weight from birth to
adulthood. But due to the early birth of humans, we triple
our brain's birth rate. Our last 12 month of fetal growth
rate of the brain occurs outside the sensorially deprived
womb. The vast quantities of sensory input during the first
year of life affects the rate and nature of the neural
connections. Because of this year of helplessness, parents
must provide close physical and emotional support for the
infant. Unlike chimp babies who can cling to their mother's
fur, human infants cannot even hang on to mother in spite of
having the hand reflex. The mother has no fur because she
sweats and she sweats because of a big brain which is why
she gives birth to her child early. This early birth then
requires the mother to care for the infant and increases the
bond between mother and child which partially makes us

So, what is the birth pattern in Homo erectus? It is
human. Shipman and Walker (1989,p. 388-389) point out that
the adult Homo erectus cranial capacity was 950 cc. If they
followed the ape-like pattern of doubling their brain size
after birth, they would need to be born with a brain size of
around 400 cc. Following the discovery of a nearly complete
Homo erectus skeleton, the approximate size the erectus
birth canal is known. A head with a 400 cc brain is 10 cm
too big to fit through the birth canal. Estimates place the
maximum fetal brain size able to fit through the erectus
birth canal at just 231 cc (Walker and Shipman, 1996, p.
226-227). Homo erectus had a human pattern of birth and
must have endured similar pain in childbirth.

To close, it would appear that there is a single underlying
cause of God's curse for the man and woman and it is an
increase in brain size. This increase also caused the loss
of hair requiring clothing when mankind eventually inhabited
northern climes. Homo erectus is found in European Georgia
1.6 million years ago. Without fire or clothing, he would
have been unlikely to survive the more severe winters in
that area.

The fact that Homo erectus was saddled with the problems
given to Adam and Eve after the fall has theological
implications for the status of Homo erectus, the time
during which Adam lived as well as who is eligible for
salvation. I have long contended that humanity in the
theological sense is much older than most Christians are
willing to admit. If sweat and increased pain in childbirth
and clothing are not signifying of humanity and the Fall,
what then does theologically separate us from mere animals?

It is also intriguing to me that the ancient Hebrew writer
would choose as a curse for man and woman, two different
maledictions which can be caused by a single phenomenon--an
increase in brain size. This single cause also would require
the loss of hair and the subsequent need for clothing.
There is no way that the Hebrew writer could have had the
knowledge to purposefully construct this tale. Is this a
fortuitous conjunction of statements or is it divine


Campbell,Bernard, 1974. Human Evolution, (Chicago: Aldine

Fagan,Brian M. 1990. The Journey From Eden, (London: Thames
and Hudson)

Falk, Dean, 1992 Braindance,(New York: Henry Holt and Co.)

Johanson, Donald and James Shreeve, 1989, Lucy's Child,
(New York: William Morrow).

Larick, Roy and Russell L. Ciochon, 1996, "The African
Emergence and Early Asian Dispersals of the Genus
Homo."American Scientists, 84(Nov/Dec, 1996).

Ruff, Christopher B., 1993, "Climatic Adaptation and Hominid
Evolution: The Thermoregulatory Imperative," Evolutionary
Anthropology, 2:2, p. 53-60,

Shipman, P. and A. Walker, 1989. "The Costs of Becoming a
Predator," Journal of Human Evolution, 18, 373-392.

Walker, Alan and Pat Shipman, 1996, The Wisdom of the Bones,
(New York: Alfred Knopf).

Zihlman, Adrienne L. and B. A. Cohn, 1986, "Responses of
Hominid Skin to the Savanna," South African Journal of
Science, 82:2, p. 307-308.

Zihlman, Adrienne L. and B. A. Cohn, 1988, "The Adaptive
Response of Human Skin to the Savanna" Human Evolution,


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