Because this must needs be recorded for posterity:
The inimitable Mr. Tea presents:
The most prolific breeder in the animal world is not my brother, it's the tapeworm. Some species can lay over a million eggs in a day. Most of these, of course, will never reproduce themselves; their life cycle is convoluted, and hitting the right chain of events is a matter of chance. Nonetheless, with so many starters, the next generation is pretty much assured.
Stable populations need to give its members about even odds of replacing themselves. That means that the number of offspring a fertile female can produce is inversely proportional to the odds of survival of any one of them. It's no doubt apparent too that if you have thousands of young, you won't be tucking them all in at night. You spawn, leave them to go their merry way, and hope that a couple of them won't wind up getting eaten.
At the other extreme, of course, you can have only a few offspring, but lavish enough care and attention on them that their odds improve dramatically. This can mean a massive investment. White-winged choughs, birds native to Australia, have chicks so demanding that a mated pair isn't enough to bring up baby. They need other family members - siblings, former young who've reached adulthood - even members of other chough extended families that they've lured away - to help meet the needs of their chick.
In such species, parents offer a lot to their offspring: food, protection and shelter are the obvious benefits. But where animals have taken this option, the young also have the chance to learn from their parents. It's a hallmark of predators, whose parents teach them how to hunt. Opportunists have a lot to learn too, of what's good to eat, where to find it and how to secure it once found. Some animals can master technical skills like using tools, and they need to pick it up from the previous generation. Egyptian vultures are one of my favourite examples. They use rocks to break into ostrich eggs. This isn't instinctive - they need to learn how to do it from other vultures. What is inherited is the capacity to learn this trick. Other vultures in the region never even attempt it, not matter how often they witness their technologically advanced cousins.
Primates top the scales in learning, of course. It's not just technical competence in dealing with their environment that needs to get passed on. Primates tend to be social animals - and it takes skill to navigate the social complexities of the group. Where lions, deer and kangaroos secure their breeding rights by tests of strength, and peacocks by tests of awesomeness, for baboons and chimps, if you want to get any action then you'd better know your politics.
At the apex is Homo sapiens - our technical learning literally fills libraries, we live in larger social groups than any other primate, with more complex customs and mores; and we are born more helpless than any other, incapable even of raising our heads. Our childhood is long, rich and (for the parent)demanding indeed.
All of which explains why, as with the emperor penguin, Biyi and I have decided to take it one at a time. We're expecting our first child at the end of April next year.