Dear keikileo-ga;
Thank you for allowing me an opportunity to answer your interesting question.
Not only is there a continuing trend toward earlier menarche, but
there is also a measurable difference between ages at which Caucasian
girls and girls of black African heritage reach this level of
maturation. Today, girls begin menstruating about nine months earlier
than their ancestors did 20 years ago. In studies conducted between
1973 and 1994 it was found that black girls were 40% more likely to
begin menstruating before the age of 11, but on average menstruation
began for them three months earlier than white girls, who generally
reach this stage of maturity at the age of 12.
SOURCE: October issue of ?Pediatrics?
Researchers are unclear as to why this trend is occurring, but what
they do know is that it can be traced to the 19th Century when
physicians first began to note the earlier menarche trend. Since that
time girls have consistently begun menstruating at earlier and earlier
ages; a trend that appears to be continuing in more recent
generations. Some theorize that it is perhaps one of many early signs
that certain as-yet-to-be-identified exposures of our progressively
modern environment are adversely affecting human fertility, and as
such the biologic capacity of men and women to reproduce. Of course
this is just a theory and there are many factors which need to be
considered and studied more closely such as dietary factors, hormonal
factors and environmental agents just to name a few (environmental
estrogens, like those found in hair care products, and pesticides are
both suspect).
Along those same lines of course are issues related to obesity, as
this is a known risk factor for early puberty and perhaps early
menarche. While studying the obesity gene researchers discovered a
byproduct called leptin and suspect that this might determine the age
at which menarche is reached in young girls. Again, it is only a
theory, but they believe that better quality foods beginning the 19th
Century when the trend was first noted and continuing on to this day
are responsible for the role that leptin, which in turn has an impact
in the time frame for the commencement of puberty in females, has on
the historical cycle.
SOURCE: ?The Journal of Clinical Endocrinology & Metabolism? Vol. 82,
No. 10 3239-3245
When will it stop? Logically, the trend will cease eventually. Humans,
like all other creatures undergo minor and subtle biological changes
which halt in time and can carry on in that manner for millions of
years. This is just one of the many changes we, as humans, have
undergone since we first crawled out of our caves and it only seems
odd to us now because were are actually here witneseesing it rather
that studying it as something from our distance past. Perhaps in time,
after you and I are long gone, it will be discussed in classrooms when
students ask the question, "Why was it that girls from the 19th
Century to the 21st Century did not reach menarche *UNTIL* age
twelve?" and the concept, for them, will be just as odd.
Below you will find that I have carefully defined my search strategy
for you in the event that you need to search for more information. By
following the same type of searches that I did you may be able to
enhance the research I have provided even further. I hope you find
that that my research exceeds your expectations. If you have any
questions about my research please post a clarification request prior
to rating the answer. Otherwise, I welcome your rating and your final
comments and I look forward to working with you again in the near
future. Thank you for bringing your question to us.
Best regards;
Tutuzdad ? Google Answers Researcher
INFORMATION SOURCES
WEB MD HEALTH
http://my.webmd.com/content/article/51/40737?src=Inktomi&condition=News_and_Events
AGE OF FIRST PERIOD CONTINUES TO DECREASE: REPORT
http://pub39.ezboard.com/fhuntforplanetxfrm41.showMessage?topicID=16.topic
MENSTRUATION: HEAVY BLEEDING (MENORRHAGIA)
http://www.ucdmc.ucdavis.edu/ucdhs/health/a-z/80Menorrhagia/doc80full.html
THE JOURNAL OF CLINICAL ENDOCRINOLOGY & METABOLISM
?LEPTIN IS INVERSELY RELATED TO AGE AT MENARCHE IN HUMAN FEMALES?
http://intl-jcem.endojournals.org/cgi/content/full/82/10/3239
SEARCH STRATEGY
SEARCH ENGINES USED:
Google ://www.google.com
SEARCH TERMS USED:
Menarche, menstruation, earlier, trends, 19th century, leptin, puberty |
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