Just want to add a couple of words to this
discussion. About 6 years ago, I read an article
in the New York Times (unfortunately, I didn't save
it) reporting some research on rats and whatever the
rat equivalent is to menarche. It seems that rats
that were artificially fed as infants reached
sexual maturity earlier than those that were
nursed.
It has been assumed for a long time that early
menarche was related to better nutrition in general
and this research seemed to give indication that
breastfeeding (or breastmilk) has some elements
that delay menarche (at least in rats) I don't
know where that study was published or if further
research has been conducted on humans, but I
remember that it seemed like a logical and fascinating
theory.
Does anyone know any more about this study?

Naomi Bar-Yam