The brain sits snugly inside the skull, but it's not a completely flush fit - there is still a layer of fluid between bone and soft tissue that serves as a natural shock absorber. Some shocks, however, can't be absorbed, and when the head gets clobbered too hard, the brain can twist or torque or rattle around inside its skeletal casing.

The golden child may be the oldest one, unless it's the youngest. It may be the toughest one, unless it's the most sensitive. It's not even necessary that Mom and Dad have the same favorite - and typically they don't.

Jellyfish serve as a model for bioengineers for the same reason yeast were once so valuable to geneticists: they're simple to deconstruct.

Identical twins are ideal lab specimens for studying the difference between learned and inherited traits since they come from the womb preloaded with matching genetic operating systems. Any meaningful differences in their behaviors or personalities are thus likely to have been acquired, not innate.

Sisters have ways of socializing brothers into the mysteries of girls. Brothers have ways of socializing sisters into the puzzle that is boys.

As with real reading, the ability to comprehend subtlety and complexity comes only with time and a lot of experience. If you don't adequately acquire those skills, moving out into the real world of real people can actually become quite scary.

Older fatherhood isn't all bad: testosterone rates drop about 1% per year as men age, making them less reactive and more patient, and a professionally established middle-aged man is likely to have more time and money to devote to his kids than a twenty-something who's just getting started.