"My other thought along this line is that since so many people with such
conditions are surviving to reproductive ages, that we are loading our ge=
ne
pool with these genes.  It would make sense that natural selection no
longer works as effectively in this situation to keep the gene pool stron=
g."

I was recently speaking with a physical anthropologist who specialises in
secular trends in evolution about this sort of thing, directly related to
breastfeeding. The thought process went.

In the past infants of women who could not breastfeed were more likely to
die.

Sometimes the problems that cause women to not be able to breastfeed (or
less likely to) are related to their anatomy eg truly inverted nipples; or
clues were given in their anatomy eg. markers of primary lactational
insufficiency.

Some of these physical traits could be genetically determined.

Therefore since the introduction of modern formulas and hygiene protocols,
the babies of women who were unable to breasfeed have survived and passed
on the genes for these physical traits.

Thus, there may be a increasing numbers of women with these problems in the
population. Their poor genes have been mediated by modern life.


Apparently in days gone by anatomy was really important and they measured
eveything and published it. I've yet to investigate if they looked at the
anatomy of breasts or nipples. If they did last century it would be
interesting to look at whether such things as inverted nipples have
increased in frequency.

Karleen Gribble
Australia
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