Language, Numbers, Time, and Mind
The Pirahã use only three pronouns. They hardly use any words associated with time and past tense verb conjugations don't exist. Apparently colors aren't very important to the Pirahãs, either -- they don't describe any of them in their language. But of all the curiosities, the one that bugs linguists the most is that Pirahã is likely the only language in the world that doesn't use subordinate clauses. Instead of saying, "When I have finished eating, I would like to speak with you," the Pirahãs say, "I finish eating, I speak with you."
Equally perplexing: In their everyday lives, the Pirahãs appear to have no need for numbers. During the time he spent with them, Everett never once heard words like "all," "every," and "more" from the Pirahãs. There is one word, "hói," which does come close to the numeral 1. But it can also mean "small" or describe a relatively small amount -- like two small fish as opposed to one big fish, for example. And they don't even appear to count without language, on their fingers for example, in order to determine how many pieces of meat they have to grill for the villagers, how many days of meat they have left from the anteaters they've hunted or how much they demand from Brazilian traders for their six baskets of Brazil nuts.