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Science Forum Index » Anthropology - Paleo Forum » Age of weaning decipherable, infant tooth enamel...
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| caldervangogh at (no spam) gmail.com... |
 Posted: Thu May 29, 2008 2:39 pm |
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http://www.sciencenews.org/view/generic/id/31782/title/Teeth_chronicle_infant_diet
By Sid Perkins May 5th, 2008 Web edition Enamel can reveal when
children switched from mother's milk to solid foods
Chemical analyses of teeth, possibly including fossilized ones, can
provide clues about the age at which a child was weaned, a milestone
in life that may reveal information about how the human species and
its predecessors evolved.
Unlike living bone, which contains a substantial amount of protein
such as collagen, tooth enamel is about 98 percent mineral. Therefore,
atoms in the enamel — especially those deep within a tooth — don’t
tend to swap with those in the environment as they fossilize, says
Louise T. Humphrey, an anthropologist at the Natural History Museum in
London. Studies have shown that changes in the ratios of various
isotopes in teeth record evidence of nutritional stress, movement from
one location to another and exposure to heavy metals such as mercury,
she notes.
Recently, Humphrey and her colleagues scrutinized baby teeth that had
been shed by modern-day children to see if the effects of significant
changes in their diet had been preserved. Some of the children had
been fed formula from birth, others had been breastfed exclusively and
others transitioned from mother’s milk to formula or other foods when
they reached a few weeks or months of age.
Because various foods have differing ratios of calcium, a major
component of tooth enamel, and strontium, the dietary changes should
show up in teeth, the researchers had speculated.
Even though baby teeth haven’t yet erupted through a child’s gums at
birth, they have been forming deep within the jaw tissue, says
Humphrey. A feature that forms in the tooth around the time of birth,
called the neonatal line, is a landmark that allows scientists to
distinguish enamel that forms before birth from that which forms
during infancy, she notes.
In two infants fed formula from birth, the strontium-to-calcium ratio
in the tooth enamel that formed immediately after birth was much
higher than that recorded in prenatal enamel, the researchers found.
In contrast, strontium-to-calcium ratios in the postnatal enamel in
three of four newborns that were breastfed exclusively were
significantly lower than those found in enamel that formed before
birth. In the fourth child, who was breastfed for only five weeks, no
such change in isotope ratio appeared — probably because of the
relatively short duration of breastfeeding, says Humphrey. She and her
colleagues report their findings in an upcoming Proceedings of the
National Academy of Sciences.
The same technique should work on other teeth as well. The first
permanent molar, which begins forming a month or so before birth and
is retained throughout life, is a likely target, says Humphrey.
“There’s an archive of childhood preserved in your mouth,” she notes.
The new findings, which could be applied to fossil teeth as well, “are
really exciting for anthropological research,” says Debra Guatelli-
Steinberg, a physical anthropologist at Ohio State University in
Columbus. Gaining insight into the weaning age of ancient humans is
interesting, she notes, because humans typically wean their offspring
much later than other animals do.
Gary T. Schwartz, a physical anthropologist at Arizona State
University’s Institute of Human Origins, in Tempe, agrees: Determining
the timing and pace of important milestones in an organism’s life,
such as the age at weaning and the spacing between births, “can help
scientists sketch out a roadmap of how ancient species developed.”
“This is truly an impressive piece of work,” says Wendy Dirks, an
anthropologist at Newcastle University in Newcastle upon Tyne,
England. Because breastfeeding tends to suppress ovulation, weaning
children more quickly enabled ancient humans to reproduce more
frequently, thereby allowing populations to soar. “Early weaning is
how humans took over the world,” she notes. |
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| rmacfarl... |
| Posted: Thu May 29, 2008 10:07 pm |
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caldervangogh at (no spam) gmail.com wrote:
Quote: http://www.sciencenews.org/view/generic/id/31782/title/Teeth_chronicle_infant_diet
By Sid Perkins May 5th, 2008 Web edition Enamel can reveal when
children switched from mother's milk to solid foods
Cool! Nice article. Thanks... |
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