What difference between human and non-human biology allows for non-human animals to give birth to such large litters, versus humans who have so few, comparatively?
In: Biology
Nothing. Lost of animals have a single offspring, elephants if I understand correctly have twins a lot less the humans.
It is all about the investment in the offspring. What they need to do when born and their size relative to the adults. If they need to start moving quickly you have few, it if takes years to take care of them you have few. If you do not take care of them at all like a lot of fish, turtles, flyes, etc.
Most time when you have a lot of offspring the mortality rate is very high so few will reach adulthood. One that you take care off or many that have to fend for themself is different strategies.
It is all a compromise.
It is a sliding scale of quantity vs quality. An animal that produces the most young will spend less time and energy raising young because out of the many a few will survive to maturity. If an adult wastes more energy and time growing and raising young they will have fewer young, but by raising the young they have a better guarantee that the young will survive. Because of the amount of time and attention to raise young it’s better to focus the time and energy to a few or one.
Likewise this actually happens in human population as well. It has been shown time and again that the more likely children who make it to adulthood the fewer children a woman have.
I forgot to add that primates mainly have one offspring on a whole, though some lemurs will habitually have twins. I have heard that mammals will have twice as many nipples as normal offspring numbers.
Cats and dogs have a tube in the middle with several individual wombs branching off to the sides. Each kitten or puppy grows in its own womb and is born through the tube. Humans and other large mammals like cows and horses eg, have one womb. If they have more than one baby they all have to grow together in the same womb at the same time.
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