How did life become complex, and could it happen beyond Earth?
When astrobiologists contemplate life on nearby planets or moons, they often suggest such life would be simple. Instead of there being some kind of multicellular organism on, say, Jupiter's moon Europa, scientists instead aim to find something more like a microbe.
But from such simple life, more complex life forms could eventually come to be. That's what happened here on planet Earth, and that's what could happen in other locations as well. How did the chemistry evolve to get life to where we are today? What transitions took place?
Frank Rosenzweig, an evolutionary geneticist at the University of Montana, is looking into such questions over the next five years with funding from the NASA Astrobiology Institute. His lab studies how life evolves "complex traits," factors that influence everything from lifespan to biodiversity.
"Over my career, I've been interested in what are the genetic bases of adaptation and how do complex communities evolve from single clones," Rosenzweig said. "Related to these questions are others such as how do the genetic 'starting point' and ecological setting influence the tempo and trajectory of evolutionary change."
Complex life is only known to exist on Earth, but scientists aren't ruling out other locations in the Solar System. Our understanding of life's evolution could be informed by studying the Saturnian moon Titan, whose hydrocarbon chemistry is considered a precursor to a living system. Researchers recently tried to replicate a substance in Titan's atmosphere called tholins, which are organic aerosols created from solar radiation hitting the methane and nitrogen atmosphere.
Understanding how tholins and other substances are formed on Titan could give researchers a picture of how early Earth evolved life. Also, studying how Earthly life-forms and their biochemical precursors evolved from simple subunits to successively more complex and interdependent systems could give hints of how life might evolve on other moons or planets.