In humans, there’s early data suggesting that mothers produce fattier milk for boys than girls. But that may be only part of the story, as Hinde has found with rhesus macaques. "Just because sons are getting better milk doesn’t mean they’re getting more. It looks like they’re getting very similar total calories."
The macaque male babies get more cortisol than the females, and cortisol in infancy makes them more adventurous later in life.
And one of the sugars isn't digestible by babies--but by some of their gut bacteria. We all knew (I hope) that mother's milk was better than formula (though kids grow fine on formula), but I didn't expect individual tailoring like this.
But one thing: where do the babies pick up the gut bacteria? From the dirt? From mother's skin? They aren't present in utero, are they?
Lots of simple things turn out to be extremely complicated.
Like dirt, if the subject change isn't too jarring. There are so many different organisms in topsoil, communicating with each other directly or accidentally, so many chemicals at work--it is hard even to figure out which are inside the organisms and which outside. Last time I asked a researcher he said they were still scratching the surface. So to speak.
From the same aggregator Texan99 linked to (Rocket Science) is a link to a report on a study of the remains of "governors of ancient Egypt" which concludes that they were often malnourished and estimates only a 30-year average lifetime.
Unfortunately the home site is in Spain and not translated, so picking out critical details is hard. But I'm a little puzzled. It seems a bit counter-intuitive that the upper class would be seriously malnourished as a general rule (unless there were some fatuous diet fads afoot). Maybe the Nile was polluted, but IIRC they made plenty of beer. The team found a disproportionate number of 17-25 year-olds and I gather they drew conclusions from that. But if this was a cemetery for the governors and their families as claimed, perhaps only the folks who died on tour were buried there, and the rest returned to be buried in their ancestral region. They find Nubian bones there too, from which they infer intermarriage (or maybe they found obviously mixed ancestry bones too; I couldn't figure that out). (Years ago I was surprised to learn that pathologists had no trouble making accurate racial estimates from just bones.)