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Comment by eru | Hacker News Reader

> Interestingly, the EGG hypothesis postulates that the constraining factor is not pelvis size, but rather that neonates consume so much energy that we give birth just before a women's metabolic limits would otherwise be overrun (leading to both maternal and infant death). Based on this, the increased energy demands of our larger brains mean that we have to sacrifice neonatal motor skills or drastically improve the metabolic efficiency of adult women.

This seems weird. Fully breastfed babies require even more calories from the mother. (They are bigger than unborn babies, and they lose more heat.)

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Having gone through it, while it's true you need more calories after the baby is born (I breastfed and pumped exclusively and was told it's about 500 calories per day vs 300 or so extra prior to birth) the strain on your body is lessened because you are producing a single item (milk) going to one part of your body that's drained periodically.

In contrast, by the third trimester of pregnancy, your total blood volume has increased by approximately 50% (3-4 pounds of additional blood), not to mention an extra 2-3 pounds of retained fluid, 2 pounds of amniotic fluid, and 1.5 pounds of placenta. All told, this is another ~10 pounds on top of the baby. Additionally, the mother / placenta is performing all respiratory and blood filtration functions on behalf of the fetus (the kidneys don't really do much prior to birth other than produce urine).

> https://www.mayoclinic.org/healthy-lifestyle/pregnancy-week-...

Personally, while breastfeeding and newborn care was exhausting, it felt more akin to training for an athletic event vs having another entity symbiotically tied to my system like pregnancy.

Yes, lungs, heart, kidney and liver seem like more obvious bottlenecks than calorie intake alone.

I was mostly just remarking on the energy-demand hypothesis advanced in the comment above.

My first daughter is just in the process of weaning at the moment.

Perhaps it’s more than just calories or energy intake, but as well doing the breathing, immuno responses, digesting, filtering blood etc. for both mother and baby?

Maybe. But now we are just speculating.

> Instead, the mother delivers and the neonate’s growth rate slows relative to its fetal growth rate, keeping both the offspring’s and the mother’s energy requirements in check.

Growth rate slows after birth, so that would account for some of that. Mother’s also would not need to carry around the weight of the baby, and would be more able to provide for the child.

Women in Africa (in traditional societies), carried their babies on their backs while they worked the fields, carried water, etc.

Baby-wearing is pretty popular in modern times and other parts of the world too.

Though it's not 24/7.

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