Animal parents protect their female piglets, cubs or joeys more than their male offspring when food is scarce — so how do humans behave when economic downturns limit their ability to support their kids?

That question drove a University of Minnesota marketing professor to survey parents and test whether they favored sons or daughters in different theoretical scenarios.

Naturally, nine in 10 parents in an initial survey said they treat their sons and daughters equally. But in one follow-up experiment, parents read an article which said the economy was tanking, then drafted a fictional will in which they divided assets between a son and daughter.

Just the threat of economic ruin from one article altered attitudes. Parents were then more likely to tilt the assets in the will to their daughters.

“In general, people really strive to treat their kids the same. If they have resources to split, $100, they try to give $50 each to their boys and their girls,” said Vladas Griskevicius, the U professor who co-authored the study in the Journal of Consumer Research. “But when they feel that economic times are difficult … the girls consistently got more.”

The research also found evidence that humans share similar motivations to animals, which prioritize female offspring amid famine and starvation because females are more likely to have their own offspring if they survive.

“You’re playing it safe by betting on the female when times are tough: ‘I’d rather have a few offspring than zero,’ ” Griskevicius said. “It’s evolutionary suicide otherwise.”

Griskevicius said the proof was that parents showed equitable levels of protection in tough economic times when their children were young, but favored girls as their children neared childbearing ages.

The researchers also tested other theories for gender inequities, including that parents give more to daughters in a sexist culture in which men still earn better pay.

But those beliefs were constant among surveyed parents, regardless of their children’s age or their perception of the economy, Griskevicius said. By comparison, there was a telling increase in attitudes favoring daughters when parents believed the economy was poor and their children were nearing adulthood.