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.

Older siblings get more total-immersion mentoring with their parents before younger siblings come along. As a result, they get an IQ and linguistic advantage because they are the exclusive focus of their parents' attention.

There are a lot of obstacles in the way of our understanding animal intelligence - not the least being that we can't even agree whether nonhuman species are conscious. We accept that chimps and dolphins experience awareness; we like to think dogs and cats do. But what about mice and newts? What about a fly? Is anything going on there at all?

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.

I was born in the U.S., my wife was born in Mexico and emigrated here when she was in college, and my daughters were born in New York City. That makes them passport-carrying, natural-born, eligible-to-run-for-president Americans. But they're also Mexicans and they like that just fine.

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.

Suffering is always hard to quantify - especially when the pain is caused by as cruel a disease as Alzheimer's. Most illnesses attack the body; Alzheimer's destroys the mind - and in the process, annihilates the very self.