Human adiposity, longevity and reproduction features as consequences of population bottlenecks

A model of the origin of modern humans through several population bottlenecks caused by glacial cycles and cold-arid periods was used as a frame for describing occurrence of unique physiological characteristics. Occurrence of regular evening food sharing among the hominid group members improved their chances of finding food the next day. It allowed slow emergence of a gracile and energy efficient phenotype. Improving chances of group survival in the harsh environment included these traits: - The menstrual cycle occurrence in the common ancestor of human and great apes. - Single pregnancies only in women with sufficient fat reserves. Ovulations stop during the food shortage seasons, or longer periods of starvation and during lactation. - Women prone to obesity sooner become pregnant, passing the obesity trait as an advantage. - Seldom pregnancies separated by several years of anovulation made a strong pressure toward the longevity of women and man. - Menopausis improved the group survival through preventing pregnancy of women to old to deliver and raise children without significant risks. The modern times food abundance results in high incidences of adiposity, diabetes and metabolic syndrome. Continuos ovulations from puberty to menopausis except during seldom pregnancies and lactations is considered responsible for the occurrence of estrogen induced breast and endometrial cancers. The combination of longevity with decades of androgen secretion is the main cause of prostate cancer.