Human fertility studies under field conditions. Introduction.

Abstract

Human fertility is part of biological anthropology embracing human population biology devoted to the analysis of the nature, caused, origin, and development of human variation at molecular, cellular, and whole body levels. The successful outcome of human fertility depends on the interactions of biochemical, physiological, and psychological processes whose disturbance results in slight variations in behavior and even total infertility. The Hutterites in the US have the highest average fertility with over 11 live births/women. Hunter-gatherer groups rarely have more than 4 children/woman. The case of a woman who gave birth to 67 children was recorded. Total infertility often occurs even in noncontracepting societies. The most important factor that determines the character of genetic variation within the human species seems to be comparative population growth, as this was the factor determining which populations spread and which became extinct. The study of the determinants of female fertility has attracted attention recently because pregnancy and motherhood affect daily life, and in turn, reproduction is also affected by daily life. Lactational amenorrhea plays a vital role in child spacing, but the mechanism of breast feeding is complex with factors of duration, frequency, milk production, and suckling frequency interwoven. Female reproduction comprises whole body function, nutrition, body composition (the recent debate on fat stores affecting the onset of fertility), physical work, and mental health all influencing the endocrinological state. Heavy physical labor and intensive training by sportswomen can result in amenorrhea. Beta-endorphins also play a role in lactational amenorrhea along with nutrition and body composition. Infectious and venereal diseases particularly affect fertility, yet genetics protect the placenta against falciparum malaria in sickle-cell trait women.