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When it comes to evolution, people often talk about the survival of the fittest, but a new study in the journal Science suggests biologists might be overlooking an important factor - luck. NPR's Jonathan Lambert has more.
JONATHAN LAMBERT, BYLINE: Within a population, individuals differ in traits that make some a bit better at getting food or finding mates than others. Ultimately, this creates some winners and some losers in terms of survival and reproduction, says Matthew Zipple, a biologist at Cornell University.
MATTHEW ZIPPLE: Everywhere we look, outcomes across populations are unequal. And in natural populations, there's a huge amount of variation in starting position in terms of an individual's environment and its genetics.
LAMBERT: Biologists usually focus on the genetic causes of that variation since genes of the winners get passed on to the next generation. But sometimes, creatures just get lucky. That made Zipple and his colleagues wonder...
ZIPPLE: What is the role of luck and what is the role of competition in leading to those inequalities in adulthood?
LAMBERT: Often, a lucky break is just a one-off. But other times, a bit of early luck can launch future success, says biologist Michael Sheehan, also at Cornell.
MICHAEL SHEEHAN: Individuals who start succeeding early tend to keep succeeding.
LAMBERT: While some inherent trait might account for this early success, in many cases it's contingent on luck or factors that an animal can neither control nor predict, like it just so happens to get to prime territory before a competitor. But figuring out how much of that success stems from luck, genes or an organism's environment is tricky since all vary so much in nature. So, says Zipple...
ZIPPLE: We wanted to know, what if we create a society where everyone starts out with the same genetics, had access to the same resources and the same environment in early life? When those individuals grow up into adults, do they look different? Do we see that inequality develop?
LAMBERT: The team created the society using genetically identical mice, which they tracked from infancy through adulthood in outdoor enclosures. But there was one key variable.
ZIPPLE: Males in our system compete with each other to form territories, and females, as far as we can tell, do not compete to exclude each other from space in that same way.
LAMBERT: The researchers found that when competition for resources is high, getting lucky early in life really matters.
SHEEHAN: The males, they pretty early on start to diverge into really high-quality and low-quality males, or males that are gaining access to resources and males that are being excluded from resources. But we don't see that same pattern pan out for the females. They kind of all stay about the same quality the whole time.
LAMBERT: Females also get lucky, but that luck doesn't make or break an individual's fitness like it does when competition is high. That's a really exciting finding, says Robin Snyder with Case Western Reserve University.
ROBIN SNYDER: As you dial up competition, it's amplifying the effect of these small moments of coin flips. Did you get it? Did you not get it? Did you manage to gobble up all the resources and then that allows you to continue to gobble up all the resources (laughter)?
LAMBERT: It's hard to say exactly what these results mean outside of the context of this experiment, but for Snyder, it underlines an important point.
SNYDER: Even if you have something special about you - you're particularly vigorous, you have great genes or whatever - that is a necessary but not sufficient trait to have. To be exceptionally successful, you also have to be lucky.
LAMBERT: Acknowledging and studying that luck and when it counts might lead researchers to a fuller understanding of how evolution works. Jonathan Lambert, NPR News.
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