My dentists, whose service I'm very happy with, are telling me misaligned teeth are much more prone to decay than the straight ones.

Reasons being: certain parts of the dental periphery are more vulnerable since they are supposed to be covered by gums or neighboring teeth.

My dentists keep saying that our teeth are highly specialized in every meaning of the word, and every deviation from the beaten path is heavily penalized with decay and a number of other conditions.

:(

The average human lifetime has more than doubled in the past few hundred years.

But average is a useless statistic since many people who survived childhood lived to a similar age as today.

Only if you eat a modern diet. You can't blame our teeth for being ill prepared to handle coca cola.

The fact that we grow one set of bones, lose them, and then grow another set has always been weird for me to think about.

Well, both sets actually start growing before birth, so your timeline is a bit off. The primary teeth start to come in after half a year or so after a child is born. The permanent teeth continue to develop until they absorb the roots of the primary teeth beginning around 6-7 years old, causing them to fall out and making room for the new teeth.