Elven maturation and population growth

[Michael Thayne]

In Tolkien and every edition of D&D I know of, elves don't reach adulthood until age 100 or so. This has always struck me as extremely weird. It suggests elven education for "children" could be the equivalent of dozens of PhDs, and there's a general question of how you even roleplay someone who is 100 years old but just starting their career. On the other hand, maybe this helps explain why the elven population doesn't grow any faster, and perhaps slower, than the human population. It seems like reaching maturity as fast as humans plus no aging after that is potentially a recipe for fairly fast population growth (especially factoring magical healing and such). Thoughts? There's also the general question of what keeps the elven population under control regardless, since centuries of childbearing years for women presents its own problems regardless of whether they start having children at 20 or 120.