Grammatical gender
It's said that one cannot write in most languages without revealing one's gender. English is an exception because saying "I'm tall" contains no gender information but the Spanish "soy alta" certainly does. Spanish gender indicators sit on the definite and indefinite articles, pronouns, adjectives and adverbs while in English it's only on the third person pronouns.
Hindi has another structure where the genders sit on the verbs and the genitive forms of the pronouns. Therefore, while "I'm going" in English or "voy" in Spanish contains no gender information, "main ja rahi hoon" in Hindi is a gender specific statement. At the same time, most of such strongly gendered languages including Spanish and Hindi lack the neuter gender and extend the masculine / feminine binary to abstract and inanimate things such as bus stops and universities.
Relatively few languages are almost entirely gender neutral, and my birth mother tongue Bengali is one of them. Only a few nouns have explicit genders, while verbs, adjectives, adverbs and pronouns have no gender. In other words, one cannot know the gender of a writer without being told specifically. So far as I know, Persian and Pashto share this gender neutral feature.
The question I have always found interesting is why do we ascribe such overwhelming importance to genders as to go to the extent of attributing them to things that clearly have no gender? La mesa is feminine, but why? A table doesn't look either male or female, does it? It's just an inanimate piece of furniture.
Does anyone has a clue about why grammatical genders exist?