Lucky breaks in a male mouse’s youth can lead to large advantages in adulthood.
A new study titled “Competitive Social Feedback Amplifies the Role of Early Life Contingency in Male Mice” and published in the journal Science, has explored how contingency—or luck—influences individual outcomes in mice. The researchers found the effect is most pronounced in groups where there is competition—in this case, male mice—who vie for food, territory and mates.
Luck did not have the same long-term impacts on female mice, who faced less resource competition in the large, outdoor enclosure used in the experiment.
“We get these competitive feedback loops,” said Matthew Zipple, Klarman Postdoctoral Fellow in neurobiology and behavior in the College of Arts and Sciences and the study’s lead author. “You start with two genetically identical individuals who are the same, and through social competition you get divergence between animals who are consistently winning—and then are more likely to win in the future—and animals who are consistently losing—and so are more likely to lose in the future.”
Michael Sheehan, associate professor of neurobiology and behavior in the College of Agriculture and Life Sciences (CALS), is a senior author of the study.
The research team placed genetically identical infant mice and their mothers in an outdoor enclosure with equally distributed nesting materials, food and shelter. Scanners placed around the enclosure collected 7.4 million readings from radio-frequency identification tags implanted in the mice to measure 17 spatial and social phenotypes, including how much the mice moved around the environment, how many resource zones with food and shelter they visited per night, and how many male and female mice they interacted with.
“By taking advantage of the scientific resources available to study manipulable populations of lab mice in large semi-natural enclosures, the team explored links between population biology and individual outcomes, providing missing links between complex environments and physiology,” Sheehan said.
For example, Zipple said, discovering a shelter early in life might be a small win for a male mouse. When another male mouse finds that shelter, the first mouse already knows the area, making it more likely to win a fight. Winning that interaction matters for the rest of their lives.
“When two males are competing with each other, the winner of that competitive outcome now has an advantage over the other male,” Zipple said. “They might have started out approximately the same, but now through some kind of chance-based interaction, one of them is now a winner and one of them is a loser.”
Researchers found this effect was most pronounced in relation to territory-holding ability. Males who hold territory generally stay in their space, while females move around. The males without territories interact with fewer females and get fewer social benefits.
“That doesn’t have anything to do with merit,” Zipple said. “It doesn’t have anything to do with differences in genetics. It all comes down to luck. That’s not to say that things like merit play no role in our lives, but it really calls into question this idea that outcomes are the way they are primarily because of differences in merit, but instead really shows how luck, paired with competition, can lead to these levels of inequality in an animal society.”
Cornell co-authors include undergraduates Daniel Chang Kuo, Xinmiao Meng, Tess Reichard, and Kwynn Guess; Caleb Vogt, post-doctoral associate in neurobiology and behavior in the College of Arts and Sciences; and Andrew Moeller, formerly associate professor of ecology and evolutionary biology (CALS), now an assistant professor at Princeton University.
More information:
Matthew N. Zipple et al, Competitive social feedback amplifies the role of early life contingency in male mice, Science (2025). DOI: 10.1126/science.adq0579
Provided by
Cornell University
Citation:
Small wins for mice in early life can lead to inequality in adulthood (2025, January 2)
