Eight kids at once. The mind boggles. The mind is also pretty creeped out by the thought of one tiny baby after another coming out of a woman as if she were a mouse.

It’s basic energetics. Every individual has only so much energy. Some energy is spent staying alive – that is, finding food and not being somebody else’s food – and what’s left over can be spent on reproduction. In other words, there are limits to reproduction.

Of course, the various slices of that reproductive energy pie also vary between males and female of all species. Males don’t gestate or lactate so they pass on the most genes by flitting from female to female making as many babies as they can, and then walking away. The female reproductive pie is much more complex. There are costs to pregnancy, lactation for mammals, and then whatever else is needed to bring a kid up to sexual maturity so they can pass on genes as well.

But there are all sorts of ways, from an evolutionary point of view, for females of a species to distribute that energy and bring up babies successfully. She might have as many babies as she can in one shot, litters that is, and have them as often as possible. For that kind of female, reproduction is an assembly line of cheap production per kid. Or a female might opt for the other end of the scale and make one baby at a time and wait for a very long time to see if that one investment pays off.

Take a look at a naked woman and see for yourself how many babies a woman is designed to care for – two, at most.