That's partly because you most languages are related in a family, but more because you're training the attributes (memory amongst others) that you need to learn a language.
As such, it might be usefull to have similair. Either a system of complementary skills, where one skill gives a small (capped) bonus to another or a set of general knowledge attributes.
((For example, a butcher will have a very limited knowledge of anatomy, and some skill with blades. A swordsdwarf will have the same. A surgeon would have a high anatomy stat, giving him bonusses if he were to fight. Even more so, a mason would make a slightly better miner, as would an architect, because they know about rocks/ structural integrity respectively.))
The civwide anotamy knowledge is nice, but a bit strange.
Yeah, that makes sense. I would say it makes sense to have a cap. The first, basic things a doctor would learn would help the most in combat training (such as what parts of the body are vulnerable to sharp weapons), but he isn't going to use his advanced knowledge much (he won't be doing heart surgery in battle). So, you know, as he gets closer to the "roof" of the cap, the complimentary skill gain slows.