Analysis of sex specific genetic material, the non-recombining portions of the Y chromosome and mitochondrial DNA, show evidence of a prevalence of female-biased dispersal as well; however, these results could also be affected by the effective breeding numbers of males and females in local populations. Evidence of female-biased dispersion in hunter-gatherers is not definitive, with some studies supporting the idea, and others suggesting there is no strong bias towards either sex. In orcas, both sexes mate non-locally with members of a different pod but return to the pod after copulation. Demographic data shows that a females mean relatedness to the group does increase over time due to increasing relatedness to males. While less well-studied, there is evidence that short-finned pilot whales, another menopausal species, also display this behavior. However, mating behavior that increases local relatedness with female age is prevalent in non-menopausal species, making it unlikely that it is the only factor that determines if menopause will evolve in a species. Mother hypothesis
The mother hypothesis suggests that menopause was selected for humans because of the extended development period of human offspring and high costs of reproduction so that mothers gain an advantage in reproductive fitness by redirecting their effort from new offspring with a low survival chance to existing children with a higher survival chance. Grandmother hypothesis
The grandmother hypothesis suggests that menopause was selected for humans because it promotes the survival of grandchildren. According to this hypothesis, post-reproductive women feed and care for children, adult nursing daughters, and grandchildren whose mothers have weaned them.
Because of this, measurements of these hormones are not considered to be reliable guides to a womans exact menopausal status.Menopause occurs because of the sharp decrease of estradiol and progesterone production by the ovaries. After menopause, estrogen continues to be produced mostly by aromatase in fat tissues and is produced in small amounts in many other tissues such as ovaries, bone, blood vessels, and the brain where it acts locally. The substantial fall in circulating estradiol levels at menopause impacts many tissues, from brain to skin. In contrast to the sudden fall in estradiol during menopause, the levels of total and free testosterone, as well as dehydroepiandrosterone sulfate (DHEAS) and androstenedione appear to decline more or less steadily with age. An effect of natural menopause on circulating androgen levels has not been observed. Thus specific tissue effects of natural menopause cannot be attributed to loss of androgenic hormone production.Hot flashes and other vasomotor and body symptoms accompanying the menopausal transition are associated with estrogen insufficiency and changes that occur in the brain, primarily the hypothalamus and involve complex interplay between the neurotransmitters kisspeptin, neurokinin 3B (NK3B) and dynorphin, which are found in ‘KNDy’ neurons in the infundibular nucleus.Long-term effects of menopause may include osteoporosis, vaginal atrophy as well as changed metabolic profile resulting in increased cardiac and metabolic disease (diabetes) risks. Ovarian aging
Decreased inhibin feedback after hysterectomy is hypothesized to contribute to increased ovarian stimulation and earlier menopause. Hastened ovarian aging has been observed after endometrial ablation.