Chimpanzees: They're just like us!
A study following 20 chimpanzees on the Ivory Coast found that lady chimps put out more often for male chimps who have shared meat with them, as opposed to the ones who did not share meat. (We're talking about food here, not using any euphemisms.)
This correlation was noticed because the researchers watched the chimps over a long-term period, rather than just tracking immediate behavior.
So how did they know that simple friendship wasn't the motivation for sharing the meat?
By tracking association patterns between pairs, the scientists found that males didn't just give meat to females they hung around with often. They specifically gifted food to those that they ended up copulating with. Additionally, factors such as rank and age also did not explain the connection between giving away meat and mating success.
Behaviorial ecologist Cristina Gomes explains further, "They can keep track somehow of what they have received or given in the past. It doesn't mean they're aware of this. It could be emotional. In humans, you don’t even really know how many coffees someone has bought for you in the past, you just generally feel that this person is nice to you. It creates a positive feeling toward that person."
Related: