Humans may have inherited their propensity to gamble from chimpanzees, scientists say.
In a study, common chimpanzees were found to be more likely to take risks in seeking food than bonobos, their endangered close relative found in the Democratic Republic of the Congo.
Researchers say the results demonstrate how species' food-gathering techniques and experiences shape how willing they are to engage in risky behaviour.
In the experiment, five chimps and five bonobos at Leipzig Zoo in Germany were presented with repeated choices between two upside-down bowls, one of which consistently covered four grape halves and another covered between one and seven.
The two species diverged from a common ancestor less than one million years ago and share many characteristics, including body size and appearance.
However in the wild bonobos rely heavily on feeding from ground-based vegetation, which is a fairly consistent source of food, whereas chimps spend time foraging for fruit and hunting of monkeys - both of which take time and involve greater risk.
The researchers, whose findings are published today in the Royal Society journal Biology Letters, found the captive chimps were more likely to opt for the riskier option in the tests, while the bonobos usually played it safe.
Psychologist Sarah Heilbronner, of Duke University, North Carolina, said: "In doing so, bonobos may avoid some of the risk incurred by chimpanzees in their frugivorous foraging.
"Our results suggest that species-specific feeding ecologies can strongly influence risk preferences.
"Though humans systematically violate many of the normative principles of economic theory, few researchers have considered preferences in relation to the environment in which they evolved.
"As humans did not evolve in the context of modern economies, many of our preferences are likely tailored to providing adaptive foraging and other evolutionarily relevant decisions.
"An evolutionary approach to economic preferences can offer keen insights into the nature of decision making."