Luck be an evolutionary lady tonight

Evolution has been known as survival of the fittest, however the fittest may also have been simply the luckiest. Though genetics are a driving force of evolution, many evolutionary changes were a result of random occurrences or being at the right place at the right time.

Survival of the luckiest

Species evolve when "individuals who are better adapted to their environment — those that manage to acquire food, escape predators, survive diseases and parasites and attract successful partners — are the ones to reproduce and pass on their traits to the next generation," said the Davidson Institute of Science Education. Many traits originally came in the form of a random genetic mutation. "Each genetic change that contributed to these traits originally appeared by chance in one individual in the population and spread through the population by helping that individual reproduce."

While this process was common knowledge, luck can also affect individuals that are identical in genes and circumstances. An article published in the journal Science found that contingent events, also known as luck, can play a significant part in developmental trajectories, especially when it comes to competition. "A male ram battling for a female's attention might face a rival that accidentally slips on a loose rock and tumbles to its death," said NPR. "A foraging bird may happen upon a bonanza of food before others, just by chance."

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To test this, researchers created an equal society of mice. "Groups of about 26 two-week-old mice and their mothers were placed in outdoor enclosures in groups that mimicked their natural environment but had identical 'resource zones' with food and shelter," said NPR. This species of mouse had males competing for resources, and females were not. Luck affected the males far more than females. "An individual male mouse might just so happen to win a fight with its identical twin over food. That lucky break would help it become bigger than its twin, setting it up to win the next fight."

The males "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," Michael Sheehan, a biologist at Cornell University and senior author of the study, said to NPR. "We don't see that pattern pan out for the females. They all kind of stay about the same quality the whole time."

An unequal distribution

Genetics and circumstances go hand in hand when it comes to evolution. "Everywhere we look, outcomes across populations are unequal," Matthew Zipple, an evolutionary biologist at Cornell University and study author, said to NPR. Even "probability and chance play a significant role in the fate of a particular gene," said the Davidson Institute. Just because a favorable gene emerges in a population does not necessarily mean it will be passed on.

This idea gave rise to the neutral theory, which is the "historically controversial idea that 'survival of the fittest' isn't the only, or even the most common, way that species change, split or disappear," said The Atlantic. Instead, the theory placed luck as one of the most significant factors in evolution. "What we're finding is that even if you have something special about you, something that's lasting — you're particularly vigorous or have great genes — that is a necessary but not sufficient trait to be exceptionally successful," Robin Snyder, a theoretical ecologist at Case Western Reserve University, said to NPR. "You also have to be lucky."