Evolution And History

Humans Stand on Their Own Two Feet 165

Biocultural Connection

Evolution and Human Birth

Because biology and culture have always

shaped human experience, it can be a

challenge to separate the influences of

each of these factors on human prac-

tices. For example, in the 1950s, pa-

leoanthropologists developed the theory

that human childbirth is particularly dif-

ficult compared to birth in other mam-

mals. This theory was based in part on

the observation of a “tight fit” between

the human mother’s birth canal and the

baby’s head, though sev-

eral other primates also

possess similarly tight fits

between the newborn’s

head or shoulders and the

birth canal. Nevertheless,

changes in the birth canal

associated with bipedal-

ism coupled with the

evolution of large brains

were held responsible for

difficult birth in humans.

At the same historical

moment, American child-

birth practices were

changing. In one genera-

tion from the 1920s to the

1950s, birth shifted from

the home to the hospital.

In the process childbirth

transformed from some-

thing a woman normally

accomplished at home,

perhaps with the help of a

midwife or relatives, into

the high-tech delivery of a

neonate (the medical term

for a newborn) with the

assistance of medically

trained personnel. Women

in the 1950s were gener-

ally fully anesthetized dur-

ing the birth process.

Paleoanthropological

theories mirrored the cul-

tural norms, providing a

scientific explanation for

the change in American

childbirth practices.

As a scientific theory,

the idea of difficult

human birth stands on shaky ground.

No fossil neonates have ever been re-

covered, and only a handful of complete

pelves (the bones forming the birth

canal) exist. Instead, scientists must ex-

amine the birth process in living humans

and nonhuman primates to reconstruct

the evolution of the human birth pattern.

Cultural beliefs and practices,

however, shape every aspect of birth.

Cultural factors determine where a birth

occurs, the actions of the individuals

present, and beliefs about the nature of

the experience. When paleoanthropolo-

gists of the 1950s and 1960s asserted

that human childbirth is more difficult

than birth in other mammals, they may

have been drawing upon their own cul-

tural beliefs that childbirth is dangerous

and belongs in a hospital.

A quick look at global neonatal

mortality statistics indicates that in

countries such as the

Netherlands and Sweden,

healthy well-nourished

women give birth suc-

cessfully outside of

hospitals, as they did

throughout human evo-

lutionary history. In other

countries, deaths related

to childbirth reflect mal-

nutrition, infectious dis-

ease, and the low social

status of women, rather

than an inherently faulty

biology.

BIOCULTURAL

QUESTION

Though well-nourished

healthy women success-

fully birth their babies

outside of hospital set-

tings, Caesarean section

(C-section) rates have

been rising in indus-

trialized societies. In

the United States one

in three births is by C-

section. The C-section

rates in many Latin

American countries are

greater than 50 percent

of all births. What cul-

tural factors have led

to this practice? Would

your personal approach

to birth change with

the knowledge that hu-

mans have successfully

adapted to childbirth?

Man Ray (1890–1976) © ARS, NY. Statuette of Ixcuina, Mexican Goddess of Maternity. 1890–1941. Gelatin silver print, 9-1/16 x 6-7/8”. Gift of James Thrall Soby (204.1991). Digital Image © The Museum of Modern Art/Licensed by SCALA/Art Resource, NY/Artists Rights Society (ARS)

Tlazolteotl, the earth mother goddess of the Aztecs, is depicted

here giving birth in a squatting position, which is favored by women

throughout the world. For hospital births, women generally have to

work against gravity to bring a child in the world, as they tend to be

placed on their backs with their legs in stirrups for the benefit of at-

tending physicians.

Dean Falk, Wheeler developed this hypothesis through
comparative anatomy, experimental studies, and the
observation that humans are the only apes to inhabit the
savannah environment today.

Many other animals, however, inhabit the savannah,

and each of them possesses some mechanism for coping

with heat stress. Some animals, like many of the carni-

vores, are active only when the sun is low in the sky, early