The sesame cake was poisoned

That's an interesting theory. It may be correct because I don't know why he'd say eat the cake one minute and not to eat it the next.

Actually, I believe it's because he knows him from past explorations. He's been looking for the lost city for a long time, and the captain says he owes money to everyone, so I think he just wanted to *beep* with him. It looks like Monroe(?) Ate some too

That would be very clever, and that's probably why it wasn't actually the case. It's a bit too convoluted for a group of people who have absolutely no qualms with blowing someone's head off. Plus, poisoning is a woman's method, and these guys like to think they're pretty macho.