birth control

birth control, the voluntary limiting of human reproduction, using such means as sexual abstinence, contraception, induced abortion, and surgical sterilization. It includes the spacing as well as the number of children in a family.

Birth control encompasses the wide range of rational and irrational methods that have been used in the attempt to regulate fertility, as well as the response of individuals and of groups within society to the choices offered by such methods. It has been and remains controversial. English economist and demographer Thomas Malthus famously raised the general issue of population control in the 18th century with his theory that the number of people in the world will always tend to outrun the food supply, meaning the betterment of humankind is impossible without stern limits on reproduction. This thinking is commonly referred to as Malthusianism. Coining the phrase "birth control" was American reformer Margaret Sanger in 1914–15 and, like the social movement she founded, the term has been caught up in a quest for acceptance, generating many synonyms: family planning, planned parenthood, responsible parenthood, voluntary parenthood, contraception, fertility regulation, and fertility control.

(Read Thomas Malthus’s 1824 Britannica essay on population.)

Human reproduction involves a range of activities and events, from sexual intercourse through birth, and depends as well on a series of physiological interactions, such as the timing of ovulation within the menstrual cycle. The visible events are central to the transmission of life and have been subject to social and religious control. The invisible factors in human reproduction gave rise early on to speculation and in modern times have become the topic of scientific investigation and manipulation. New knowledge relevant to birth control has diffused at different rates through various social groups and has not always been available to those with the greatest need. Hence, the conflicts and controversies surrounding birth control have been complex and impassioned. The disagreement over birth control arises in part from the debate over what is natural and what is artificial (and, to some, unacceptable). For information on human reproduction in general see reproductive system, human, and pregnancy.

Natural fertility

At first glance the species Homo sapiens appears to have low potential for reproduction. Puberty begins late, pregnancy is long, normally only one baby is delivered at a time, and lactation can continue for several years. Yet on the global level there are many more births than deaths every year; in 2015, for example, there were 141 million births compared to just 57 million deaths. In addition, a large percentage of the world’s population lives in urban areas, often at extremely high population densities. In experiments, when mammals are placed in crowded conditions the age of sexual maturity rises, the interval between pregnancies increases, and infant mortality jumps, leading to slower growth in the population. Among humans in analogous crowded conditions, however, in the absence of artificial birth control the opposite situation arises.

In many cases ovulation does not take place in the first several cycles after the onset of menstruation (menarche). Once a woman is fertile, social factors determine whether she is exposed to the opportunity to become pregnant. In preindustrial Britain, couples were expected to form their own nuclear group upon marriage, and many a first-time bride was in her later 20s. By contrast, in contemporary Third World societies that encourage extended families, girls often marry in the early teens.

In all mammals whose reproduction is not tied to seasonal changes, physiological mechanisms ensure the optimum spacing of pregnancies. In Homo sapiens, as in other primates, breast-feeding provides the basis for nature’s own method of birth control. In the few remaining societies of hunters and gatherers, whose way of life may represent the conditions under which most of human evolution took place, women nurse their babies frequently and ovulation and menstruation are suppressed for two to three years after birth. Nomadic women of the !Kung, a group of the San people of southern Africa, use no contraceptives but have a mean interval between births of 44 months and an average of four or five deliveries in a fertile lifetime. Modern methods of birth control substitute for the control over fertility once provided by lactation and permit a degree of control over human reproduction not previously available.

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The combination of high infant mortality with relatively low fertility associated with traditional patterns of breast-feeding kept population growth in preagricultural human societies virtually static. Ten thousand years ago the world’s population may have stood at 10 million. Since that time natural restraints on human reproduction have broken down at an accelerating pace. By the beginning of the Christian Era the world’s population was perhaps 300 million. In the mid-1980s it passed the 5 billion mark. Since the Industrial Revolution, and with intensely increasing pressure in the past century, both individuals and societies have had to make important decisions about the use of birth control.