After Dean Larson’s lecture on our universe, it got me thinking about life outside of our planet. If we truly are the only life in the universe, it’s crazy to think just how serendipitous our existence is, and how many events and changes had to take place to get organisms on this planet as complicated as they are. But just how serendipitous was it? If the world were to begin again, would life as we know it evolve in the same way?

In biology class, we learned all about evolution and natural selection: organisms with advantageous traits outlive and outproduce those without those traits, allowing the dominant characteristics to be passed on to offspring and gradually build a more efficient organism.  Those advantageous traits often come about as a result of random genetic mutations, so it seems like the answer to the question of how life on earth would evolve a second time would be that it would drastically different–after all, those genes that randomly mutated couldn’t possibly mutate in the exact same way every time over billions of years. However, thanks to an unprecedented study by Harvard physicist-turned-biologist Michael Desai, the idea that life would evolve in the same manner again may not be as radical as previously thought. His lab has been growing hundreds of strains of Saccharomyces cerevisiae, a common form of yeast, in identical environments. Every 12 hours, specially designed robot arms move the strains of yeast to new environments, keeping only the strains that have grown to most efficiently over the previous time increment. They repeat this process over 500 generations, and compare the colonies’ final fitness. They also sequence the genomes of the colonies throughout the process, in order to see whether or not small genetic mutations affect the overall fitness outcome of the final generations. The results show that no matter the exact genetic pathway the generations take, they all reach the same end result. The importance in Desai’s study is the scale. Similar experiments have been done (and with differing results), but those scientists were only able to examine a few strains of yeast from a single originating source. His background in physics and statistics allowed him to systematically develop a method to put his experiments on such a large scale by tracking 640 lines of yeast that all came from the same parental yeast cell.

Is this applicable to more complex organisms like humans? That remains to be seen. But the data Desai and his lab have collected are compelling enough to warrant more research on the matter, because it also indicates that evolution at the genetic level and level of the entire organism overall may not be as connected as scientists have thought. The idea that “fitness evolution follows a predictable trajectory even though sequence-level adaptation is stochastic” is especially important as geneticists are looking into specific gene mutations as they relate to human susceptibility to diseases–it may be equally as important to examine how greater numbers of individual mutations affect each other and the organism overall.

Maybe life isn’t just happenstance. We can’t know for sure whether or not if the earth started over we’d have the same organisms that we see today, but Desai’s findings really make you wonder…