Isn't there at least one language where the shape of an object modifies the verb or something?
In Chinese, the -article- (more or less) of a noun is determined by its shape (or by some other concept you have about it). The generic one is "ge," which just means, like, "unit," so we get "yi ge ren," which translates to "a person" but is more literally "a unit of person." The "ge" bit is called a "measure word." You get loads of bizarrely specific measure words, like "yi ben shu," which means "a book" but is literally "a book-shaped thing of book" (or something, I've never encountered another word that takes ben as its measure). A picture is "yi zhang zhaopian," with "zhang" loosely meaning "flat thing." You have one flat thing of picture. It's like grammatical gender gone mad.
And, entertainingly, while they do have plural, they tend not to use it. The Chinese equivalent of adding an S to the end of a word is to append the syllable "men," but I've mostly heard it used when addressing groups of people to acknowledge the inclusivity of the speech. Generally, you just say "two book" (or "two book-shaped thing of book"). And there's no conjugation at all, and a totally bizarre system of tense markers that--
Anyway. You get the picture. There's practically nothing a language -has- to have. I think the linguistics people (whom I do not trust, the ivory tower monoglots that they are) tend to say that all languages have pronouns, and even that's been disputed.