Summary of Women's Bodies, Women's Lives
Summary of Zihlman, Adrienne. Women's Bodies, Women's Lives: An Evolutionary Perspective. In . The Evolving Female. Princeton University Press, 1997.
Summary by Nichole Cipoletti, Amanda Smolich and Aimee Niwa
For many years the evolution of man has been pondered -- such as, hunting, survival techniques, and provision of resources. After researching this and the "locomotion"(13) system, a term indicating individuals ability to walk long distances and to carry objects, Zihlman thought of not only man using the "locomotion" system to hunt for food, but woman were thought of as well. In the 1970s, Zihlman began to focus her energy on women's roles in evolution. Zihlman and colleagues' major emphasis was to understand female contributions in evolution and putting women into the evolutionary picture as active participants in mate choice and in the wider social world. In order to relate women to evolution, studying the woman's body and the functions of this body is necessary.
A life history perspective brings two necessary notions, time and process together, by taking into account growth and development as individuals move through life, this as well as long-term adaptations for both survival and reproduction. "The life history theory allows the exploration of females in terms of what each sex has to do to survive and reproduce"(14). However, many factors of women's lives are often ignored focusing only on one aspect, child-care or labor. Zihlman has one notion for the evolutionary success of women, their successful mobility during late pregnancy and lactation otherwise known as "behavioral flexibility"(14). The structural basis lies within the body, in muscles, bones, the nervous system, and the behavioral expression occurs in the context of the social group and physical environment. Thus, locomotion, illustrates reproduction and individual experiences within an environment.
The Locomotor System
For females, the mammalian locomotor system enables "foraging and traveling"(15) even during the weighted, later stages of pregnancy and during lactation. This mobility is possible because of a well developed "muscular system, flexible mobile joints, motor skills, and a high metabolism"(15). A mobility that man didn't have to endure, thus a woman's strength, when reviewing evolution, is highly cherished, for without it their would be no children nor supplies for living, which woman would forage for during her weighted pregnancy.
Survival of Human Offspring
Mammals have a distinct bond with their offspring, which for example no other reptile entails. The offspring's assurance of survival depends solely on adult assistance, especially the female/mother's assistance. The lactating female is facilitated by the infant's keen sense of smell and hearing and "the ability to emit vocalizations,"(16) which are perceived as high frequency sounds. Therefore, the survival of young mammals depends on maintaining contact with the mother, through smells and vocal pleas. The bonds developed during this period become the foundation for social bonds with other individuals later in life. The limbic system allows this interaction to occur, birds and reptiles do not have this. Damage to this area of the brain interferes with maternal care, for it disrupts emotions.
The mammalian system of reproduction involves physiological responses in bone, fat, and hormones. Through new structures, mammary glands and fat deposits, female anatomy and physiology is shaped. There is no direct fossil evidence of mammary glands, or fat stores in the earliest mammalian fossils, however milk is produced to feed the young.
Primates vs. Humans (Women)
Parallel to infant primates which can hold onto its mother from birth by means of clinging to it's mother's hair with nails and strong hands and feet, it is also of importance for a human baby to be close to it's mother. From the female's point of view, "her primate locomotor system equips her for carrying young on her body through all reproductive stages"(16). This mobility underlies female behavior flexibility and plays a key role in the ability to adjust her behavior to meet the demands of reproduction. This mobility is important to the infant, for the infant moves from it's mother from birth, therefore after birth the infant must have a means to feel that security until secure with itself.
Meeting the Demands of Reproduction
The major portions of adult female's lives are spent in pregnancy and taking care of their children. When the woman is not pregnant, she experiences a cycle of ovulation and menstruation. Women continue in their sexual activities until they get pregnant and sometimes into the beginning stages of pregnancy. Females and their infants adjust in various physiological and behavioral ways to meet the demands of survival and caring for offspring. Physiological capabilities of female primates are similar to other mammals. The weight they gain when pregnant is partly for the purpose of lactation. During lactation, calcium is taken from the mother's bones and put into the breast milk for the infant, which assists the bone and tooth formation of the infant. When the infant is done breastfeeding, the mother's bone calcium is replenished.
Mother-Infant Interaction and Social Living
The duration and nature of mother-infant interactions depends on their species pattern. For example, in baboons, mothers carry their infants all day, through travel and foraging, for about eight months. The relationship between growth and weaning may also vary among and within species. For instance, monkeys grow faster, so they wean earlier while baboons wean late because their growth is slow
Social living provides many benefits to a mother. It offers protection for lactating females and their infants. It gives mothers more time to do other things if they have a group member or "babysitter" to watch over the infant. For primates, social living would give the mother more time for resting and grooming. This style of living promotes survival of the mother and investment in the social future of her infant.
Women's Bodies: Mobility, Work, and Reproduction
From cross-cultural studies of women, it is becoming increasingly clear that women's physical capabilities are amazing. Until food production came 10,000 years ago, women traditionally traveled long distances to collect and carry food, and nursed and carried their infants at the same time. They adjusted to the demands of ovulation, gestation, lactation, work, and childcare. Their bodies have evolved in response to what was needed to survive and reproduce.
The human species is unusual among mammals and primates in that they have an abundant amount of body fat, and women have significantly more fat than men and children. Women's bodies are made up of, on average, 25% fat whereas men have only 14%. Why do women have so much body fat? From an evolutionary perspective, women need this body fat to meet the demands of lactation and work effort. The fat serves as a cushion against nutritional value, and contributes to successful reproduction at all levels: ovulation, conception, and completion of pregnancy, lactation, and the survival of infants.
The amount of body weight devoted to fat alters the proportions of other body tissues. In women, 36% of body weight is muscle and in men, it is 43%. Muscle groups that have been modified in women include muscles of the hip, thigh, and leg, which provided braking and balance functions. Women are capable of endurance in long-distance walking and running and their thigh muscle strength is similar to that of men's.
Humans share with other apes a large clavicle, a broad and flat chest, and well-developed shoulder and arm musculature. Women are less muscular in their upper trunk and upper limbs. Even so, women are capable of heavy work and they do such work throughout their lives.
Women's Lives: Mobility, Work, and Reproduction
For most of history, humans had a nomadic way of life. It is under these conditions that human lives and bodies evolved. A study done on the hunter-gatherer !Kung in Botswana provides a perspective on how nomadic life affects women. The findings challenge the traditional image of the stay-at-home, weak, immobile woman. The contributions of women from this study include: finding water, collecting, hunting, transporting food, traveling long distances, carrying heavy loads, and taking care of others, all the while carrying and nursing their infants.
In foraging and horticultural societies, women perform the same range of tasks as men. In a rural area of Nepal, all agricultural labor is valued equally, and everyone works. In many other cultures, women work hard, travel long distances, and hunt. In each culture, the combination of work and childcare practices may affect the survival of children and then may influence a women's reproductive effort. "It is evident that when all dimensions of women's lives are looked at in a variety of cultures, women around the world do it all'. Women are physically capable of performing a full range of tasks including hard labor; child care is simply added to the other tasks that women already perform"(16).
Zihlman, Adrienne. The Evolving Female. Women's Bodies, Women's Lives: An Evolutionary Perspective. Princeton University Press, 1997.
A.Focuson women rather than men
B. Examining the relationship between anatomy and behavior
C. Sorting Variation in fossil anatomy
D. Portraying women's activities in evolutionary reconstructions
II. The Role of Locomotion
A. Female mobility while supporting a fetus or newborn.
a. Infant-maternal contact through lactation and suckling with maternal care.
b. Audio-vocal communication.
III. Meeting the Demands of Reproduction
A. Anatomy and Physiology
B. Individual Activity
C. Mother-Infant Interaction
IV. Women's Bodies: Mobility, Work, and Reproduction
A. The amazing body of a woman.
B. Body fat in women.
C. Proportion of body fat in comparison to muscle.
D. Human pattern of fat distribution.
V. Women's Lives: Mobility, Work, and Reproduction
A. Nomadic life affects women.
B. Types of activities women perform.
C. Fossil Record.
D. Social Communication and Dependent Infants.
Critical Review Points
Interesting or Informative Points Made by the Author
-One basis for the evolutionary success and behavioral flexibility of women and other female primates is their continued mobility during late pregnancy and lactation.
-Women's added body weight from pregnancy is available for later lactation.
- Women's bodies respond to activities throughout their lives and while maintaining their own mobility and survival.
Arguments Made by the Author that We Disagreed With and/or Required Further Explanation
-Why she proposed, earlier in life, survival features evolved to promote male activities such as hunting.
-What is the complete argument about the function of human body fat.
Questions that Require Further Explanation
-Things are found out later about women, but will women always follow men?
-How exactly does the mother-infant bond really get made?
- Why women have to endure so many bodily changes in comparison to men?