The Tribesmen are a group of people who work for Papu Papu. Their first appearance was in Crash Bandicoot, where they did nothing more than be obstacles and enemies to get in Crash's way, by either ramming him with their shields or blocking him from proceeding forward.
Their latest appearance was Crash Twinsanity at the start of the game. They proceeded to kidnap Cortex under the orders of Papu Papu. However, Crash eventually saved him from their clutches.
Their appearance stayed relatively the same in all of their appearances in the series. By Twinsanity, they seem to be more advanced, as they are seen with binoculars and boats. This tribe practises human sacrifice, which is shown when they start chanting when Cortex falls down into the river and falls off the waterfall. If a Tribesman with binoculars see Crash they will start jumping up and down, alerting the other tribesmen and Crash will be hit with spears.
In Crash Bandicoot, when the player jumps above a tribesman, he will hold his shield above his head, leaving him vulnerable. The tribesman can then be defeated if Crash spins him while jumping on the shield.