Our tendency to favor immediate rewards over long-term goals is partially rooted in our DNA, according to a recent study published in the journal Science. American Journal of Human Biology. The findings suggest that these genetic differences are also related to major milestones in life, such as how much education a person completes and when they start a family. Ultimately, this study shows that both biology and the environment shape our approach to future planning.
Psychology and evolutionary biology study how humans allocate their time and energy throughout their lives. This concept is known as life history theory. Evolutionary biologists focus on how humans balance resources between their own growth and reproduction.
Within this framework, humans face a biological trade-off between quantity and quality of offspring. A person may have many children, but invest fewer resources in each child. Or maybe you have fewer children but are invested heavily in the skills and success of each child.
Some people tend to follow a fast-life strategy, shortening their education, having children at a younger age, and placing less emphasis on long-term planning. Some people follow a slower strategy that emphasizes future rewards. This slow strategy involves extending education, delaying child-rearing, and investing more in fewer children.
Historically, psychologists have explained these different strategies by referring to a person’s environment. They suggest that early environmental conditions such as childhood adversity, unpredictability, and lack of resources drive individuals toward earlier life strategies to ensure survival. In this psychological perspective, rapid strategies are a pragmatic response to a world with an uncertain future.
Evolutionary biologists take a slightly different approach. They highlight the genetic variation and biological trade-offs that have developed through thousands of years of natural selection. Scientists conducted this new study to bridge these two perspectives.
“In our study, we asked whether genetic differences may also play a role. We used genetic data to test whether genetic predispositions (polygenic scores) to delay discounting (preference for immediate rewards) are associated with life history traits,” said study author Martin Feeder, associate professor at the University of Vienna and co-author of the paper. Not so strange after all: the changing relationship between status and fertility.
Delay discounting refers to the human tendency to devalue rewards if it takes a long time to receive them. People with high delay discounting scores prefer smaller rewards in the present over larger rewards in the future. This preference serves as an important measure of a person’s impulsivity and future orientation. By examining genetic data, the scientists aimed to test whether the natural tendency to discount delays is linked to the genetic basis of life milestones.
The discovery of a genetic link would suggest that differences in life strategies are caused by genetic predispositions and environmental factors. To explore these connections, scientists analyzed data from the Wisconsin Longitudinal Study. This is a long-term project that follows a random sample of individuals who graduated from high schools in Wisconsin in 1957.
The researchers focused on a specific group of 2,713 men and 2,980 women born between 1937 and 1940. We limited our analysis to unrelated Caucasians of European descent. This particular restriction helps prevent statistical errors that can occur when mixing genetically diverse populations in this type of analysis.
Researchers used a tool called a polygenic score to measure genetic predisposition. A polygenic score is a number that summarizes how an individual’s specific genetic variations influence a particular trait or behavior. The researchers obtained polygenic scores for delay discounting, educational attainment, age of first child, and total number of children for each participant.
First, the researchers compared the genetic scores to each other to look for molecular overlap. They controlled for participants’ year of birth and broad genetic background structure to ensure statistical accuracy. The delayed-discounted genetic scores were then compared to participants’ actual real-world life outcomes.
These real-world outcomes include the exact number of years of education completed after high school. We also included the specific age at which participants had their first child and the final number of children they had. Education is considered an important part of the slow strategy because it is a long-term investment in skills that will pay off later in life.
Scientists have discovered that there is a strong connection at the genetic level for both men and women. Genetic predisposition to higher delay discounting rates was strongly associated with lower genetic scores for educational attainment. The same genetic score for impulsivity was also associated with genetic scores for having a first child at a younger age and having a larger total number of children.
When looking at real-world life results, the pattern was in exactly the same direction. Participants with higher genetic scores for delay discounting tended to complete fewer years of education. They also tend to have their first child earlier in life and have slightly more children overall.
“Our findings suggest that trends such as focusing on immediate rewards (early life history strategies) over long-term goals may be related, at least in part, to genetic differences. These trends are also associated with important life outcomes such as education and timing of starting a family,” Feeder told SciPost.
Although genetic predispositions clearly matched real-world behavior, the actual proportion of behavior explained by genes was relatively small. Delay discounting genetic scores accounted for approximately 4.5 percent of the variation in participants’ years of education. For reproductive characteristics such as age at first birth and total number of children, genetic scores explain only 1–2% of the variation.
“The impact should be interpreted with caution,” Feeder said. “Current polygenic scores capture only a portion of the underlying genetic influences, so the results primarily show directional associations rather than the overall picture of genetic influences.”
There are some limitations to keep in mind regarding this study. Because the genetic data were obtained exclusively from people of European descent, this finding may not apply to people of other genetic backgrounds. Additionally, the original dataset did not include any direct psychological testing of participants’ actual delay discounting behavior. Because of this, researchers had to rely solely on genetic predisposition to that particular trait.
The researchers also were unable to separate direct genetic effects from indirect effects of parental genetics. Parents’ genes shape the environment in which their children grow up, which can indirectly influence their children’s life choices.
In the future, the researchers aim to expand on this work by studying a broader and more diverse population. They plan to use genetic scores built from more comprehensive DNA sequencing, which tends to give a clearer, more detailed picture of human biology. Examining other biological markers, such as hormone levels and patterns of brain activity, may also help uncover specific bodily processes that link impulsive tendencies to major life milestones.
“Genetics are particularly important in human behavior and attitudes, but their role is often underestimated,” Feeder says. “Our tendencies may not be as freely chosen as we often think.”
The study, “Genetic and Phenotypic Associations of Delay Discounting Polygenic Scores and Life History Traits,” was authored by Martin Fieder and Susanne Huber.
