why most animals have litters of babies when they give birth, but when humans give birth to twins or triplets, it’s considered rare?
In: Biology
Animals have different strategies for continuing their species. Some have lots of babies in the hope that one or two will survive, some have only a few and work harder to make sure those few make it to adult hood. Humans spend a lot of time and energy making sure that their one kid is born and survives to adulthood and is prepared to live on their own. Wild dogs, cats, and many other mammals spend not quite as much time and energy making sure that the few young they have survive to adulthood, so they have more young to increase the chances that some survive. Some animals like fish don’t spend any time taking care of their young, so they have thousands to increase the chances that a few will survive.
Also, the longer you spend taking care of your young after it is born, the less developed it has to be when born. For example: baby fish are born tiny, but completely developed. They don’t need to be cared for. But human babies are not completely developed. They can’t even walk or crawl on their own, they need to be cared for.
The more care young requires, the more intelligence and empathy a species has to have to keep their young alive. Human children need 18 years of care, and we have to be very intelligent to manage that, and we also form significant familial bonds. Kittens only require about eight months of childhood before they are completely self sufficient and can breed, so cats don’t have to be as smart and they don’t often care about their young after they grow up.
The number of young you have is an evolutionary trade off of having more or less young, to sacrifice more or less effort in raising them, to increase your chances of having surviving offspring to carry your genes.
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