Longevity in Human Evolution

Only available on StudyMode
  • Download(s) : 129
  • Published : November 8, 2009
Open Document
Text Preview
Diamond proposes that one evolutionary advantage that we have is longevity. Discuss the implications of this advantage in evolutionary terms.

Diamond suggests one advantage that progressed through the evolutionary tree, is longevity. We will discuss the reasons for longevity in the evolvement of the human species. Diamond addresses through chapter seven, how aging and menopause are strongly connected to longevity. Men and women have been tested in various different ways to solve the mystery behind the theory that reproduction is the cause of post-generative longevity. Another benefit Diamond writes about is how technology is a big step toward progressing how lives much further then it was one hundred thousand years ago. The one theory written progressively is one of Charles Darwin’s ‘Theory of Natural Selection’ which is one of the theories much argued about today. These topics, as well as being spoken about in Diamond’s book, are heavily argued about whether the theories are believable to endure human longevity to an increased size.

In menopause, there are two different hypotheses to state post generative longevity; these are the ‘Stopping-Early Hypothesis’ and ‘The Grandmother Hypothesis’. The ‘Stopping-Early Hypothesis’ states, since human infants are too young to live without protection or motherly aspects,’…it is beneficial for women to cease reproduction at the age at which the risk of maternal death reaches a certain threshold. In contrast, ‘The Grandmother Hypothesis’ states that survival long past the age of menopause have been selected for because grandmothers significantly improve grand offspring survival probabilities.’ (J. Beise) These two hypotheses have biological origins but have social implications; they are both tested for evolution of menopause and the evolution of post-generative longevity. Menopause and post-generative longevity are artefacts of modern life that were not present for most human evolutionary history, and are in accordance with the lack of evidence from the fossil record of human ancestors surviving to late ages. Some have argued that because modern hunter-gatherer societies have life-expectancies well beyond the mean age at menopause means that the same was probably true for historical populations with similar lifestyles. While this argument is valid, the fact remains that the ‘modern-artefact’ hypothesis can not be ruled out. Having an extended lifespan was selected for early in human evolutionary history but the primary selection was the improved status and mating opportunities that age meets the expense of men. Men achieve status with age, and reproductive opportunities. According to this hypothesis, female longevity is a by-product of selection for longevity in males but there has never been sufficient selective pressure on females to alter their reproductive lifespan.

In chapter seven, Diamond articulates that aging and menopause are crucial to today’s’ human existence as evolution is involved. Aging and menopause gives Homo Sapien Sapiens a higher advantage in the evolutionary tree when it comes to longevity. Diamond suggests that modern humans have a longer lifespan than apes because modern humans age more slowly. ‘The longer lifespan of modern humans than of apes rests not only on cultural adaptations; such as tools to acquire food and deter predators. It also rests on biological adaptations of menopause…’ (Diamond pg 117) Human female fertility rises gradually with age, peaks in the late twenties, and then begins to decrease until menopause occurs during the late forties or early fifties. At this point it is not possible for women to reproduce anymore, yet women can expect to live between another 19-22 years even in contemporary hunter-gatherer societies without modern medicine. Evidence regarding the termination of reproduction prior to death amongst primates kept in captivity, well fed and free from predation, is very mixed. Where an animal dies having not...
tracking img