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Biology 202
2006 Second Web Paper
On Serendip
Across the industrialized world, the average age for childbirth is increasing. Birth rates, in many industrialized countries, have fallen so low that governments are facing an economic crisis waiting to happen as aging populations are unable to be supported by a dwindling number of working adults. And soon the baby boomers will retire, tipping the balance, and becoming the largest generation in history to retire. Society was not constructed for these challenges. Part of the problem is that women are having fewer children at younger ages. We assume because of evolutionary theories and religious doctrines that childbirth would be desired rather than shunned. This mystery has more to do with society and culture than the structure of the brain.
To examine this dichotomy of societal versus biological influences on the desire to procreate, one must examine the brain. Reproduction is governed by a complex balance of hormones. Aside from the effect of pheromones on reproductive cycles and tendencies, five hormones play central roles: gonadotropin releasing hormone (GnRH) secreted by the hypothalamus, follicle-stimulating hormone (FSH) and lutenizing hormone (LH) secreted by the pituitary gland, and estrogen and progesterone secreted by the ovaries.(1) These hormones vary in presence during the course of a woman's menstrual cycle. (2) Logically, affecting one of these hormones should affect the reproductive capabilities and urges of a woman.
In normal conditions, these hormones are regulates in a feedback loops to maintain optimum conditions for reproduction. The hypothalamus plays a key role in this process and communicated through a blood portal to the anterior pituitary gland and stimulates the creation of gonadotropins, luteinizing hormone and follicle stimulating hormones.(3)
At the University of California, Berkeley, researchers have found that a previously ignored hormone called gonadotropin-inhibitory hormone (GnIH) halts reproduction by inhibiting GnRH.(4) Whereas GnRS stimulates the pituitary gland to activate the reproductive system, GnIH simply inhibits this function. While this finding has only been established in rats, it is likely that it is also present in humans since the human genome also contains a gene for GnIH. Thus, if one wanted to increase a person's natural propensity towards having children without a balancing mechanism, one needs to eliminate the GnIH protein.
The GnIH protein is already controlled by estradiol, which reduces the production of GnIH when necessary. George Bentley, involved in the UC Berkeley study, states in regards to the results that "this is an example of the reproductive system being fine tuned." Fine tuning the system is an essential element of regulating how reproduction functions. The fine tuning may also be one of the many factors which create the sensation of a "biological reproductive clock" urging women to have children while they are still fertile.
People, women more than men, are drawn to protect children. The close facial features of a young face inspire protective and nurturing instincts in people. Evolutionarily, we have a tendency to protect our next of kin, but in general we tend to also protect children. It is logical considering evolutionary issues. If one is not in a position to protect one's one genetic material, one automatically defers outwards to a more general species protective instinct. Humans have long displayed their favoritism of children to many other age groups. Children are given specific rights and privileges – something which today would is taboo for gender differences. In addition, the United Nations' High Commission for Human Rights implemented the Declaration of the Rights of the Child, specifying that "special safeguards" are necessary for children because "mankind owes to the child the best that it has to give." If we have an instinctive biological desire to reproduce, this is logical behavior because of limited resources and dangers involved in reproduction.Selection of who to protect stems from psychological mechanisms related to choice and risk. Most choices we make in the world have ambiguous circumstances – it is equally logical to, when out for a walk, to walk left or right.(5) But people will more likely choose a direction which they are familiar with rather than explore. When it comes to choosing social groups, we also display this tendency. In any lunchroom in America, students tend to self segregate based on visual cues. Then this could also be assumed when a person makes a decision to protect children. First, protect those who you know. Then, protect those who look like your own child. Finally, protect other children.
Making the distinction of who is protected is important from a brain-behavior view because of the time delay involved in reproduction and immediacy to one's own genetic material. It is an investment for a woman to carry a child to term. It is extremely taxing on the body, dangerous, and a child requires significant resource expenditure even after birth, to which any new parent will attest. Because there is an instinctive desire to reproduce, we are willing to care for children who aren't even our own because it means that there is a greater chance that our genetic material will be passed on. Not only do we prefer our genetic kin because of subconscious genetic bias, but we prefer what we believe to be safe.
Considering these two aspects: that women have a complex balance of hormones designed for reproduction and that there are simple rules to the protection to children, we must return to the original premise: biologically, why are industrial women not having as many children? This question remains unanswered by biology, because there has not been a significant change in hormone for all industrial women. There is unlikely to be such a change because to the complex nature of these hormones. This question is also unanswered by evolutionary theory and choice biases. It is safer to have children in Western society, and mothers are likely to receive help from the state if they need it. There should be no need to defer survival of one's genetic material to anyone other than direct offspring.
Society's telling role comes into play. Women in industrialized nations are often delaying childbirth, or foregoing it all together, for careers or their own lives. The implication of this is that the desire to reproduce is strongly affected by society. One could rationalize the behavior by stating that as a whole, there is a high likelihood for one's genetic relatives to survive, so one may expend energy on other pursuits.
Regardless, the trends of industrialized nations are contrary to assumed biological mechanisms of capitalist existence. Survival of the fitness with intense personal preference is no longer the case. The two influencing aspects explored, hormones and preferences, are not enough on their own to explain the entire process surrounding the desire to have children. Yet they both stem to other causes which influence these factors. Biology and society have evolved together to have an elastic cohesion dependent on circumstance. Logic does not always fit into this relationship.
1) "Reproductive Physiology" , Resource of the overall features of reproduction
2) The Menstrual cycle, Resource explaining specifics in regards to reproduction.
3) "Hormones of the Reproductive System", Source on the specifics of reproductive hormones.
4) "Brain hormone puts brakes on reproduction", Article on study done about halting certain reproductive hormones.
5) Aronson, Elliot. The Social Animal. New York: W.H.Freeman & Co Ltd, 2003.
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