Naked Science Forum
Life Sciences => Physiology & Medicine => Topic started by: stana on 23/06/2008 20:13:47
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Just wondering..
are the dates of menstruation hereditary?
thanks
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A possible explanation for synchronised menstruation ...
The McClintock effect, also known as menstrual synchrony or the dormitory effect, is a theory that proposes that the menstrual cycles of women who live together (such as in prisons, convents, bordellos, or dormitories) tend to become synchronized over time.
It is thought to be analogous to the Whitten effect, which is the synchronization of the estrous cycle and has been noted in small animals such as mice and guinea pigs. In contrast to the Whitten effect, which is driven by male pheromones, the McClintock effect is postulated to have only female pheromonal involvement.
http://en.wikipedia.org/wiki/McClintock_effect
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I believe there's been work done involving dabbing the sweat of a woman at one stage in her menstrual cycle under the nose of a woman at another stage of hers, and that it resulted in a measurable shift in the cycle towards synchronysing. Sadly I read this years ago and have no idea of the reference/how good the study was/etc.
In terms of girls starting their periods I know that in our biology lessons in about year 7 we were told that girls generally start at about the same age as their mothers... I imagine there's a whole load of heritable effects which would influence that.
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There are definitely environmental factors too, one big one seems to be the presence of a father. The abstract below is from research showing that in households with no father, periods started 3 months earlier. They've identified a chemical mechanism for this in mice, but not yet confirmed it in people.
Family composition (e.g., the absence of a father) is associated with pubertal timing in women, although the socioendocrinology of the human primate is poorly understood. To better understand social influences on sexual maturation, retrospective data were collected on menarcheal age and family composition from a sample of approximately 1,938 participants from a college population. Absence of a biological father, the presence of half- and step-brothers, and living in an urban environment were associated with earlier menarche. The presence of sisters in the household while growing up, especially older sisters, was associated with delayed menarche. Menarcheal age was not affected by number of brothers in the household, nor was there an effect of birth order. Body weight and race were also associated with menarche. The present findings advance the literature as they are suggestive of putative human pheromones that modulate sexual maturation to promote gene survival and prevent inbreeding, as occurs in rodents and nonhuman primates. Am. J. Hum. Biol. 18:481-491, 2006.
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The study Rosy's referring to was published by Kathleen Stern and Martha McClintock in the late 1990s in Nature. They showed that, as Rosy says, underarm body secretions collected on absorbent pads worn by women at various stages of their menstrual stages were applied beneath the noses of a second group of women. This latter group showed changes in the lengths of their menstrual cycles by up to 14 days and, depending upon where in her cycle the "donor" was, the recipient's cycle either lengthened or shortened. Extrapolating this to a group of co-habiting non pill-using females, one can see why they synchronise, menstrually, eventually.
Chris
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An interesting read:
ABSTRACT:
Several exogenous influences on the human female's menstrual cycle length have recently been demonstrated. Previously, sexual behavior and pheromonal influences have been described. This report evaluates lunar cyclicity patterns. A relationship is demonstrated between the onset of menstruation, among women who have 29.5 + 1 day menstrual cycles, and the onset of full moon. Four separate prospectively gathered sets of data are presented from different years and seasons. It is demonstrated that these women tend to menstruate in the full of the moon with a diminishing likelihood of menses onset as distance from full moon increases.
http://www.athenainstitute.com/lunarmpl.html
Periods and Moons
Women's periods have been tied to the moon and the lunar cycle for literally thousands of years. Before modern science came along to explain that a woman menstruates because of her changing hormones, it was generally accepted that a woman's periods followed the lunar cycle. After all, the moon controls the ocean, why not women's bodies? As a result, some believe that it is possible for a woman to have two fertile times during her menstrual cycle: the first occurring when she ovulates and the second according to her lunar phase fertility period.
To the Moon
The theory of lunar phase fertility is generally credited to Dr. Eugene Jonas. In the 1950s, Dr. Jonas tried to find an explanation as to why so many women became pregnant despite faithfully practicing the rhythm method. The fact that these women were becoming pregnant at a time when they weren't suppose to be fertile lead Dr. Jonas to reason that maybe women had more than one fertile period during a month. Since Dr. Jonas was very much into astrology, and since the original ways of charting a woman's period were based on the lunar cycles, he turned his attention heaven ward.
Not surprisingly, Dr. Jonas was met with quite a bit of skepticism from the medical and scientific world. Since his theory cannot be proven by modern-day scientific reasoning, many choose to dismiss the idea of having two fertile times as nonsense. However, a British study done on lunar phase fertility found that men's sperm counts significantly increased during their lunar fertility period. Another study showed that women who practiced abstinence during both their biological and lunar fertile period were 98% effective in preventing pregnancy. This is a pretty significant increase from the 75% effectiveness rate of being abstinent only during your biological fertility period.
http://www.epigee.org/menstruation_lunar_fertility.html