It seems like economics is a purely human invention, far removed from the jungle. But scientists say our ancestors were spending and investing for millions of years. So our behavior when we manage our portfolio or climb the corporate ladder resembles nothing so much as the interactions of apes or monkeys. In the latest installment of Clever Apes, we consider how our financial activity has deep parallels in the primate world. And furthermore, many of our most important financial decisions come from even more primitive impulses, deep in our lizard brains.

The University of Chicago’s Dario Maestripieri is a professor of comparative human development, evolutionary biology, neurobiology and psychiatry and behavioral neuroscience. (I usually abbreviate titles, but his makes me happy). He studies the intersections among our minds, our primate cousins, and evolution. In his new book Games Primates Play, he details how the mechanisms of economics have their origins in our deep past.

Apes and monkeys play the market by choosing whom to groom and whom to attack, whom to sleep with and what food is worth risking a fight for. As Yale psychologist Laurie Santos explains, the psychology that governs those decisions didn’t begin with humans. So we see monkeys making the same kinds of classic mistakes that humans make, like “loss aversion,” where we work harder to avoid losses than to achieve equivalent gains. (check out her TED talk for a great explanation.)

We’re also subject to the same quirks of biology as many non-human primates. Biologists have found that monkeys with high levels of testosterone and lower levels of the brain chemical serotonin tend to take more risks: taking longer leaps between trees, challenging unfamiliar males, and so on. Maestripieri and his colleagues set up a similar experiment with business school students. There too, those with higher levels of testosterone were more likely to make long-shot investments or go into a riskier profession.

Finally, we check in with neuroeconomist Camelia Kuhnen of Northwestern University. She finds that our investment decisions are heavily influenced by some of the most ancient parts of our brains. She and a colleague did an experiment where they activated the brain’s reward center using something that had nothing to do with money – in this case, it was sexy pictures. In males, anyway, this led them to make riskier bets in an investment game. Just the whiff of reward was enough to make these guys high-rollers … something we can thank our reptilian ancestors for.