Are you the type of person who struggles to save for retirement but just wrapped up your third vacation of the year? Did you cash out that savings bond from grandma at the earliest possible moment, well before it had the chance to mature? 

According to science, your innate drive toward immediate gratification at the risk of future benefit may not be your fault. 

A new study led by UNLV anthropologist Brian Villmoare and a nationwide team of researchers, which recently published in the journal PLOS One, used mathematical models to simulate evolution over thousands of generations to find out why animals — including humans — have a tendency to prioritize short-term benefits over greater long-term returns.

Though the propensity to choose the quick win over future benefit — a term known as temporal discounting — is well established, the evolutionary processes that drive this behavior are less clear. 

“For humans (in our evolutionary past) and most animals, the future is essentially unknowable, so they cannot know that a decision prioritizing the future will be rewarded,” says Villmoare. 

Modeling Good (and Bad) Decisions

Villmoare and his colleagues wanted to determine why, from an evolutionary perspective, the risk of ignoring what’s in front of you — in terms of reproduction and basic survival — for a distant possibility was too great a sacrifice.

To find out, they created a simple mathematical model where organisms were forced to choose one of two options — a stable though lesser reward shorter into the future, or a larger though less-stable reward at various intervals into the more distant future. This model was run for thousands of generations and allowed researchers to adjust the benefits of the rewards, and the distance between the short and long-term gains, to see what it would take for organisms to opt for the more distant future returns. 

In order to choose the larger reward further into the future, reliability of that reward proved to be essential. According to the research, organisms may choose a more distant reward, but only if it’s not too far into the future and has a substantially higher payoff. Any uncertainty in the future reward almost always excluded it from being selected over a short-term payoff.

“We were surprised how large even a modestly further away reward had to be in order for the population to choose it,” says Villmoare. “For instance, a 50% or even 100% better reward wasn't enough. It really had to be multiples of the original in terms of value, including up to 20-times the reward in the more distant future. The results show how natural selection, time, and unknown future risks and rewards interact to shape an organism’s behavior.” 

Civilization Has Outpaced Human Behavior 

Humans are fairly similar to other animals in their economic decision-making, according to Villmoare. The need to have something 'now' often drives poor decisions in ways that, experimentally, are similar to what researchers see in other animals. 

“This is despite the fact that you can explain the consequences of, say, purchasing consumer goods on credit to a human,” he says. “The underlying instinct easily overwhelms the 'intellectual' knowledge of the long-term cost.”

The reason for this may be tied to the fact that the rate in which human civilizations advanced far outpaced the rate in which long-held evolutionary behaviors could evolve. 

According to Villmoare, more than 98% of Homo sapiens’ existence pre-dated sophisticated food preservation techniques and agriculture, and it would have been difficult for nomadic foragers to predict future circumstances beyond a few weeks' time. 

“It is only since the arrival of complex agricultural societies just 5,000 to 7,000 years ago that humans could make reliable 'investments' in the future for most areas of their lives,” says Villmoare. “For example, they could only store food, or, once we had invented currency, put money away for future use once we had agriculture and money-based societies.”

Study authors say that this relatively quick transition, from an evolutionary perspective, profoundly altered the ecological and social landscapes in which Homo sapiens had evolved previously. 

Evolutionary Exceptions

Though the models help explain why natural selection favors lower-value short-term rewards over more optimal distant rewards, there are some exceptions. 

One example referenced in the study from the animal kingdom is the western scrub-jay, which catches and stores worms for future consumption. In order to choose this behavior, authors suggest the bird must, in some sense, know that the food will be there when retrieved. 

“If the scrub-jay caches food and the food is stolen, or it forgets the cache location, the result . . . would likely be negatively selected against,” study authors note. “But a cache that can be reliably accessed might enable the survival of an animal during a lean winter.” 

For humans, Villmoare says the effect can also be mitigated if the cost of moving from the short-term reward to the better long-term reward is less expensive and more predictable. The key, he says, lies in making the benefits of long-term decision making more obvious. 

He pointed to reproductive decision-making, “where females are more careful because the burden on a long-term investment falls to them more than to men,” says Villmoare. 

He also cited more practical economic decisions, such as choosing a job — or keeping one — to maintain health insurance, and how predictability and cost can influence choices. 

“For example, before the Affordable Care Act, the cost of quitting a job included the potential loss of health insurance for the entire family,” Villmoare says. “By providing a way for a worker's family to remain insured, the potential 'cost' of moving to a better job or taking the risk of opening their own business decreases.” 

Publication Details

“Evolutionary origins of temporal discounting: Modeling how time and uncertainty constrain optimal decision-making strategies across taxa,” was published Nov. 12, 2024 in the journal PLOS One. In addition to Villmoare, study authors include David Klein from the University of California, San Luis Obispo; and Timothy S. McHale from California Polytechnic State University, San Luis Obispo. UNLV anthropologist Pierre Liénard (deceased) also contributed to the article before his passing in 2023.