why animals like dogs and cats can give birth to multiple offspring at a time whereas humans can only give birth to (most of the time) one child only at a time?
In: Biology
The very short version is: We make proportionally bigger babies.
Look at a new born puppy or kitten and they’re *tiny*.
If a human could make babies that were that small, they’d be the size of your hand and part of your forearm at most.
In fact, we do occasionally birth babies that proportionally small, typically prematurely, and they have to be placed in incubators to survive.
Human babies are in fact still technically born prematurely compared to most animals, which is why they take a year or three to learn to walk, while if a baby horse isn’t walking on the same day, there’s something dreadfully wrong and it’s time to call the vet.
Humans however have large brains, and therefore large heads, which still have to get out of the mother somehow.
We birth as late as we can get away with and still be able to fit our massive heads through the mother’s birth-canal, but we’re still not really fully developed enough to be walking or crawling or able to self-feed on the same day.
So we make proportionally massive babies, and because of that the resources required to make that baby put a real strain on the mother. Imagine an extra 6lb of body-mass consuming as much of your resources, particularly protein and minerals as it can get away with. It’s literally draining resources out of the mother and it takes a lot to keep up that supply.
The most we’re normally equipped for is two or three babies, one at a time is enough to be challenging.
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