Is there any evidence to the subject. Also, I’ve heard that the decrease in puberty age is due to the use of hormones in food, better health, social behaviour, etc. Is there any concensus among the scientific community as to what the cause is ?
Is there any evolutionary advantage to this ?
IANAMD
If you want evidence just walk through your local mall at about 5 O’Clock. I too have noticed what you mentioned.
As for the evolutionary advantage I would say yes because the girls can produce offspring sooner.
The age of onset of puberty decreased among girls in industrialized countries since WWII but that trend seems to have ended. Age at menarche is dependent on weight and the fact that fewer girls are underweight seems to explain the decrease in average age at menarche. I don’t think there is necessarily an evolutionary advantage for humans to able to reproduce at 11 or 12 years of age but there is some evolutionary advantage for puberty delay among poorly nourished girls.
That great bastion of Western Journalism, Time magazine did a cover story on this a few years back. There is an increase in young girls (and young boys, but not quite as great in number) entering puberty at an early age. There’s no consensus as to what might be causing it, though some thing it has to do with the hormonally/antibiotically-injected meat Americans are consuming. Personally, I have a friend with a kid sister who looks to be around 16 or so (she’s almost 5’ 10", has a rather developed chest, and mild acne), but is in fact only about 12 or 13. As of yet, no one knows if those girls will develop health problems later on or if there are any other health related consequences to this (other than the ability to become pregnant at an extremely young age).
Species under stress (such as those facing extinction) often have females who reproduce at younger and younger ages.
Therefore, we can only assume that human extinction is imminent. You know, because the species has a “brain” and somehow knows this fact.
But seriously, thats the kind of thing I’d need a cite for. No offense.
So Tuckerfan, you’re saying Generation Y knows something we don’t? Should I cash in my long term investments in favor of something more imediate?
This hypothesis should be easy to verify by comparing the figures in Europe (where growth hormones are forbidden in cattle production) and in the US…If the trends are the same in the US and in the EU, then it’s unrelated with hormones in meat…
The online Museum of Menstruation has a nice plot (with ref.) of the average age of menarche. In 1830, the average age was 17 years, now it’s 13.
Puberty has been starting progressively earlier in the U.S., primarily due to better nutrition. We know that high fat levels in girls tend to trigger puberty. In addition, precocious puberty (true puberty starting before age 8 in girls and age 9 in boys) is also increasing in frequency. Concerning the issue of hormonally injected meats that Tuckerfan mentions, this site poo-poos that notion among girls:
I have also heard a theory (sorry, no cite) that artificial light may be responsible. Essentially, the cumulative effect of exposure to light signals the body to start menstruation. With hours per day spent under the lights, girls reach the threashold earlier.
Am I the only one who has heard this?
Never heard of that KenP. What I have heard most frequently is that as LadyLion says it is due to better nutrition. Same reason why people are taller in average in developed countries.
This site debunks the beef hormone link in greater detail: http://www.stats.org/statswork/puberty-latimes.htm
Hi!
I read about a twin study on evolution in Australia a while back on the Science Daily web site, but I’ll be damned if I can find it again.
Since I’ve failed there, I searched and found this article about an Australian twin study. It may be the same study. Here’s the abstract…aarrrgh!:mad: It’s a PDF file so I only get the grabby-handy-thingie and the zoom in/out. I can’t copy. Anyway, it says:
I hope that helps.
Interesting, KenP. Never heard of that, but found it interesting. I had heard some other things about a gland called the pineal body, which doctors used to think was merely vestigeal. Now we are learning more about how it responds to our environment. It is thought it may have something to do with seasonal affective disorder. People with SAD respond well to increased time under bright lights, and some research indicates that the light may stimulate the pineal body to release some minerals necessary to good emotional health. Dr. Carolyn Mein’s website also states:
“The Pineal synthesizes and releases melatonin and is activated by sunlight… It is also a key regulating factor in PMS irritability and mood swings.” (She also included some “new age-y” stuff I chose to disregard.) Perhaps then it may have other functions we are only now starting to uncover.
I think that it is pretty much accepted that the decrease in age of menarche is not related to better health per se, but rather an increase in the percentage of body fat as we get more and more under-exercised and overfed. Amoung athletes it is common for menarche to occur at the 13-15 range. Pediatricians do not even begin to think of delay in puberty in athletes until age 16, and then do not worry much.
I think that it is pretty much accepted that the decrease in age of menarche is not related to better health per se, but rather an increase in the percentage of body fat as we get more and more under-exercised and overfed. Amoung athletes it is common for menarche to occur at the 13-15 range. Pediatricians do not even begin to think of delay in puberty in athletes until age 16, and then do not worry much.
By saying that a species is under stress I suppose that you mean “survival stress”…where the individuals are less likely to live to an old age without dieing.
If thats the case, then its likely that females that mature sooner are more likely to have a chance to reproduce than those that mature later. Hence more fast maturers
But this dosen’t seem to be the case for humans as most can and do live to an old age.
What i think is responsible for the apparent increase in the amount of young but physically mature females is our perception.
Since the population is growing, theres more ppl around, since theres more ppl around, its more likely you’ll see someone who seems “different”…in this case, more mature looking.
People might say that thats not the case as you see there are more “maturity advanced” females hanging out at malls nowadays.
Well, the fact that they are “maturity advanced” makes them want to hang out more at a relatively early age.
(my 0.02 cents)
Puberty Age of girls decreasing over years ?
Do not think so - just seems that way and it is downright depressing 
…of cos with my above post i don’t debunk all prove of “Puberty Age of girls decreasing over years”…i donno the nutritional factors to this. I’m just stating that its not something thats been shaped in a sense by human’s evolution.