Most Indo - European languages are grammatically gendered, sometimes
all nouns, sometimes only personal pronouns (le, la, sie, er).
However, Ural-Altaic languages (Hungarian , Finn, Estonian) are devoid
of gender signals.  They are different language systems.
But what can be the sources of these diffeences in gendering?  Thanks.

Hello carmi604-ga,

This is a very interesting topic and more complex than just
differentiating between gendered and non-gendered languages.
Apparently, some languages use other classification systems as well. I
hope these links will get you started.

http://www.linguistlist.org/~ask-ling/archive-1997.7/msg00418.html
Why some languages have gendered nouns

http://en.wikipedia.org/wiki/Grammatical_gender
Grammatical gender

~ czh ~