Men Feeding Babies

I think that almost all of my job as a stay at home dad is pretty normal from a biological standpoint. Men have always been involved in raising their children to a more or lesser extent depending on the culture of the time. What's clear, even today, is that when men are more involved in raising their children they tend to do better. That has almost certainly been true from back in the days when an attentive dad could fend off a saber tooth tiger right up until today. The only thing that is weird about a stay at home dad in the modern sense is taking care of infants.

Utterly wonderful, yet odd.

In the past, the mother/infant was more of a single unit than something that could be separated for a day of work. There would be people around to help hold the baby while mom did something and I'm sure that dads have always helped, but you just couldn't go too far from the boobs. If you had an infant, you had to have a lactating woman around. There was no way around that. Prior to the 1920's you either needed a wet nurse or the ability to make up some sort of food with animal milk, and that didn't always work. If you had a baby and the mother died, if there wasn't another mother nursing right there, the baby often died too no matter how good a dad you had. In the 1920's the first commercial infant formulas were developed and they've been working on them ever since. It's pretty widely accepted that breast milk is always better, but at least as a dad, formula made is possible to do a job that had previously only been available to women. Breast pumps have actually been around since the 1850's, but without refrigeration widely available, you still only had a very limited time away from the boob.
Historically, it's almost certainly been more common to have women in combat, right out on the field getting shot and stabbed, then to have men at home feeding an infant. I don't think we're ever going to have a world where it's a 50/50 shot whether the mom or the dad is the primary care giver from day one. The fixed location of boobs gives some pretty dramatic advantages to a mother in the first few months at least, and always will. Anatomically modern humans evolved about 200,000 years ago. In all that time, men have only really been able to be primary caregivers to infants for the last 70 or so. Culturally, it's only been happening for maybe the last 30, and it's still certainly not widespread by any measure. It's much more common to hire out the care of a 6 week old infant then to leave them in the care of their father. No wonder seeing men with little babies still seems odd.