Population growth, expressed as natural increase, is dependent upon the differential rate of births and deaths, more births than deaths results in a population increase, and of course, a decrease occurs when deaths overtake births. This section will summarize methods that have been developed to control causes of human mortality and factors that influence fertility.
Death Control. As noted above, causes of deaths in pre-industrial peoples likely centered on periodic episodes of starvation and repeated occurrences of serious injuries, from both man-made and natural events. The question as to whether compassion and care was extended to injured, physically disabled or aged persons has been addressed (Dettwyler, 1991). While it can be conjectured that behaviors were devised and selected for if they reduced the death toll from accidents and mishaps, it was probably mainly in the area of food production, storage, and distribution that most control was exerted. That is, there were attempts to reduce the vagaries of nutritional intake.
With increasing industrialization and urbanization, involving larger and more densely settled populations, infectious disease could and did rise to become the leading cause of death. The bubonic plague that occurred in Europe in the first half of the 14th century was mentioned earlier. Improvements in sanitation and recognition by Louis Pasteur of the germ theory of disease toward the end of the 19th century meant that death control over infectious diseases could advance. Pasteurization of milk and vaccination against infectious agents may be partially responsible for major reductions in morbidity and mortality. However, as shown by McKeown's epidemiological research (cited in Hertzman, 2001), the death rate from TB in England and Wales experienced a sharp drop well before the introduction of antibiotics and administering of vaccinations. The explanation seems to rest along social and economic lines. Indeed, Hertzman (2001) presents a strong argument for death control by way of psychosocial determinants (quality of the social environment), along with socioeconomic indicators, expressed in terms of a gradient of health status determined, for example, by the equality/inequality of income within a society. A steeper gradient in wealth leads to marked differences in health. Gage (2000) provides an illuminating discussion of the historical variation in mortality by making a distinction between proximate causes (the disease itself) and ultimate causes (the psychosocial support system).
The leading causes of death in America have now shifted to "lifestyle" diseases, notably heart disease and cancer. For clarification, recent genomic research has allowed scientists to claim they have discovered the "gene" for some of these chronic conditions. This too is an oversimplification in that genetic predisposition triggered by certain environmental events, including once again the social environment, combine and interact to make the risk for contracting and dying from these "lifestyle" diseases rather more complex. It is the case that a substantial portion of medical research is devoted toward finding treatments and cures, somewhat less for preventive measures. In short, Western medicine runs its course of attempting to gain as near as possible full control over the modern causes of death. Medical advancements in surgical techniques, nuclear medicine, medications, and the like do offer great promise for sustaining human life at a high level of vitality throughout the later years. Yet, if this advanced medicine is restricted to only those who can afford it, and if inequalities of health provision (Hertzman, 2001) are not addressed, then the general picture of health will not likely improve for a substantial number of humans. Beyond that, much of the world still must contend with childhood diarrhea, malaria, and infectious diseases. HIV/AIDS has reached crisis levels in some countries, while outbreaks of the ebola virus and bubonic plague are distinct threats.
Birth Control. Reproduction is of course the vital force of any ongoing population. Differential reproduction, wherein some adults are more successful at leaving offspring than others, is the hallmark of Darwin's theory of natural selection. Accordingly, some populations persist, perhaps to grow, while others undergo extinction. To be sure, the human population is among the former. As discussed earlier, ancestral human groups had the opportunity to undergo major expansions and migrations seemingly without any lasting effect of natural checks on their population growth. Indeed, highly successful adaptation as measured by reproductive output might well have been one impetus for these groups to migrate. At that time period, intentional limiting of births was not likely so relevant. Hence, natural fertility may well have been in place, but this would not preclude such practices as post-partum abstinence since this may have been done more for the health of the mother and her nursing baby (Whiting, 1964) than to deliberately limit births (Wood, 1994). Then too, the concept of natural fertility has been clarified with regard to postpartum "contact" in the Gambia (Bledsoe & Hill, 1998) while Ellison (2001) offers a different perspective regarding the role of lactation in postpartum fecundity.
There was, of course, a time when human groups did devise more or less effective measures to control the number and spacing of births, in part at least as a necessity or desire to control population growth, for both personal and communal reasons. Some traditional birth control methods that are documented in the ethnographic record include ingested noxious herbal agents, aggressive massage, ligatures and mechanical devices for aborting ongoing pregnancies. Infanticide/infant abandonment, and fatalities from child abuse or neglect, also were present. Selective survival of children born with disabilities has always been a cold fact of evolution. Birth defects would increase the risk of mortality on its own, along with added economic, medical, and social pressures on parents to provide reduced childcare investment, often manifested by neglect and abuse. However, given their relative rarity (approximately 5% of total live births), deaths due to birth defects, directly or indirectly, are not likely to have been a significant contributor to overall mortality rates.
Still later, presumably after the recognition of paternity, abstinence (through celibacy, delayed marriage, and postpartum taboos) and coitus interruptus (withdrawal) were practiced. These were followed by increasing reproduction knowledge that led to the timing of sexual intercourse—the "rhythm method." Together, the rhythm and withdrawal methods make up 15% of overall contraceptive use according to a worldwide survey (Fathalla, 1994). These methods are much more likely to be used in developed countries. The now well-studied temporary loss of fecundity or lower risk of pregnancy during lactation and breast-feeding, "postpartum amenorrhea" (Ellison, 2001; Ellison & O'Rourke, 2000; Wood, 1994) may have been partially understood for some time into the past (Ramos, Kennedy, & Visness, 1996). Some of these methods might be considered "low tech," perhaps to reflect their relatively high failure rate. Others, such as infanticide, while totally effective, must have exacted a terrible blow to emotional well-being, as well as considerable energy expenditure incurred by the mother who experienced the death of her infant.
The birth control industry has developed over time to a point where monetary costs, failure rate, ease of use, side-effects, as well as moral and religious attitudes, all leed into decisions of whether or not and which method/s to use. A brief survey of these methods follows, some will receive further attention in the Issues section.
Contraception. Preventing a pregnancy can take many forms, some of which were mentioned as part of earlier attempts at birth control such as periodic abstinence, the "rhythm" method, coitus interruptus, etc. In fact, it was not until after 1820 in England that any preventative measure other than delaying marriage (abstinence) was openly considered (Field, 1968). The next century was to see major advancements toward fertility control through contraception, notably by gaining knowledge about female reproductive hormones. By 1960, the FDA approved marketing in the United States of "the pill." Its action was based on administering progestin (an artificially synthesized progesterone) as an ovulation suppressor. Depo-Provera is an injectable form of ovulation inhibitor. Hormonal pills account for about 16% of all contraceptive use worldwide (Fathalla, 1994).
Barrier contraceptives, many accompanied by sper-micide, include the condom, diaphragm, and the cervical cap. Condoms alone make up 10% of worldwide contraceptive use (Fathalla, 1994). Of course, in addition to birth control, condoms are also used for greatly reducing the risk of contracting sexually transmitted diseases (STDs).
All of the contraceptive methods mentioned above are seen as temporary. On the other hand, voluntary sterilization (tubal ligation for females and vasectomy for males), is generally considered permanent, although limited success of reversal has been reported. On a worldwide basis, sterilization is the most frequently practiced method. For females it occurs 26% and males 10% of total contraceptive use (Fathalla, 1994). It is important to note that roughly two thirds of sterilization is done in developing countries.
Contragestin. Physical and chemical means to interrupt a pregnancy at its earliest stages define the action of contragestins, that is, they prevent gestation. One of the most prominently used devices is the intra-uterine device (IUD), while hormones that block implantation are found in Norplant and the "morning after" pill. Most recently introduced to the U.S. market is RU486, which serves as a non-surgical means of abortion, cleared by the Food and Drug Administration (FDA) for use up through about 7-9 weeks of gestation. The IUD method is practiced 19% of the time for those using some form of birth control (Fathalla, 1994).
Elective surgical abortion technically might be classed as a contragestin form of reproductive management. When applied for this purpose it is customarily carried out during the early stages of gestation, notably the first trimester. This topic will be given extended coverage in the next section.
Contranatals. As this term implies, fertility control is exerted after the child is born, by way of infanticide shortly after birth, or instances of child abuse/abandonment and benign neglect (cf. Cassidy, 1980, 1987) that result in death. Dettwyler, in her widely acclaimed book,
Dancing Skeletons, Life and Death in West Africa (1994), offers a heart rendering glimpse into how poverty and lack of some basic nutritional knowledge can be a lethal combination for a young child. It was mentioned earlier that some populations have regulated birth spacing or a desired son-preference outcome through female infanticide (Miller, 1987; Segal, 2001). As might be expected, precise numbers on contranatal practices are not readily available. One study indicated that as many as 38 million abortions are done each year in Southern countries, with perhaps 20 million of these carried out without proper medical supervision (Germain, Nowrojee, & Pyne, 1994). On the other hand, it is reported that in 25 countries, which contain about 40% of the world's population, abortion is permitted and properly performed through certain stages of gestation without requiring specific grounds (Fathalla, 1994).
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