Speaking from my rear, epigenetic influence on growth and development is too fundamental a force to be a random error heretofore untouched by selection. With hu

Speaking from my rear, epigenetic influence on growth and development is too fundamental a force to be a random error heretofore untouched by selection. With humans being a social, communal species, adverse conditions tend to hit populations en masse. That means that, for much of our (and our close relative's) evolutionary history, it was relatively certain that, say, all of your neighbors were suffering from the same drought you were. It would thus be "okay" for your children to grow to a smaller, more nutritionally manageable size, because the people they'd be competing with for food, territory and mates would also be smaller. Remember, if genetics are physical destiny, and they say you're going to be big, your body is going to have a go at it, and incur whatever performative costs that come from trying to nourish a 6ft body with a 5'6" diet. Who's more fit: the latter, starving, or the former, relatively well-fed? This model gives the body a mechanism for titrating aspects of development according to local conditions, across the handful or less generations it used to take for those conditions to change. I would not be surprised if this ultimately explains the global growth spurt that took place in the 20th century.