Are humans the only animals that are menopausal in females? If not, which are the others? What other relevant factors do they all have in common? Does the menopause confer the same survival advantage to all of them, or is it different? Is there an evolutionary advantage behind menopause?
It is a natural process found in all primate females and is a sign of natural end of fertility. After puberty, as an animal gets older, its tissues, organs and organ systems also start getting weak and weak. In other words, age and organs or functioning of organs are inversely proportional. One of its advantages seems that when the female goes through menopause, she can focus on her talents/qualities/strengths and make full use of its energies for its offspring.
Can the menopause be correlated to an evolutionary adaptation for primates with comparatively long lifespan to avoid possible chromatic aberration which may arise in aged primary oocytes.
Natural selection requires an advantage for replicators (genes) competing against alternatives; hence selection cannot favor traits that diminish the success of genes, regardless of potential benefits at the species level.
Menopause is a complex, organized physiological process -- evidence against a simple 'breakdown' hypothesis.
Other species with analogous reproductive cessation include pilot whales and elephants. In all cases, species with co-resident maternal kin, multi-generational overlaps, long periods of juvenile development and dependence, and important functions for old females.
The evolutionary logic here is that the reproductive value of additional offspring diminishes as a female ages -- she is increasingly likely to die before the offspring has been successfully raised. Conversely, older females can be useful as helpers for older offspring, and eventually, grandoffspring. So selection favored genes for menopause in hominins (and some whales & elephants) because females that stopped having babies got more genes into future generations than those females who continued to reproduce and were less able to help their existing kin because they died sooner (cost of making additional offspring, who were unlikely to survive to reproduce).
For review see:
Flinn, M.V., Quinlan, R.J., Ward, C.V., & Coe, M.K. (2007). Evolution of the human family: Cooperative males, long social childhoods, smart mothers, and extended kin networks. In: Family relationships, C. Salmon & T. Shackelford (Eds.) Chapter 2, pp. 16-38. Oxford: Oxford University Press.
Flinn, M.V. (2011a). Evolutionary anthropology of the human family. In Oxford handbook of evolutionary family psychology, C. Salmon & T. Shackleford (Eds.), chapter 2, pp. 12-32. Oxford: Oxford University Press.
Geary, D.C. & Flinn, M.V. (2001). Evolution of human parental behavior and the human family. Parenting: Science and Practice, 1 (1&2), 5-61.
Muehlenbein, M. & Flinn, M.V. (2011). Pattern and process of human life history evolution. In: Oxford handbook of life history, T. Flatt & A. Heyland (Eds.), chapter 23, pp. 153-168. Oxford: Oxford University Press.
Here is a summary of the position of Pavelka and Fedigan on this matter from a paper I wrote: "Pavelka and Fedigan (1991) point out, however, that the phenomenon in nonhuman primates differs from that in humans in many crucial ways. First, these nonhuman primates are typically very old, near the end of the known life span of their species and at a time when many body systems are in an advanced state of decline. Only humans stop reproducing approximately halfway through the known life span and prior to the senescence of other body systems. Further, menopause is universal in humans but not in monkeys and apes. Many species of nonhuman primates have been studied and within each species some individuals do stop reproducing when they are old but others remain fertile. Finally, menopause in humans is characterized by the depletion of ovarian follicles. An envelope of cells that manufactures reproductive hormones needed to orchestrate the menstrual cycle surrounds each immature egg in the ovary. In humans, follicles (an egg with its surrounding cells) are depleted, while nonhuman primates typically do not deplete follicles. Old nonfertile primates continue to have menstrual cycles, and some who live to the end of the known lifespan of their species ovulate within days of their death." A few other species have been found that seem to have a menopause, but the general points remain.
From the same paper: I report on the work of Barry Bogin : "The human life course is unique among mammals with regard to the number of life stages, their duration, and the timing of physical changes within life stages." Also, while caring for offspring and relatives is one function that has been observed in postmenopausal women, anthropologists have found that in hunter-gather groups as well as in other societies, post-menopausal women play important leadership roles in the social structure, e.g., deciding who does what job or who marries who, which are also important functions in human groups.
Derry, P.S. (2006). A lifespan biological theory of menopause. Sex Roles, 54,393-399.
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