In a complex world where plants and animals and everything else are duking it out to survive,
an organism stands to gain from becoming more complex.

Life on earth began some 3.5 billion years ago, not all that long after the planet itself first formed, and for 1.5 billion years it chugged along, single-celled creatures self-replicating, dividing, diversifying. Remarkably, it took that long – 7,500 times longer than all of human history – for the first multicellular life to emerge, and still longer for it to evolve into life as we know it. Despite that, the question many researchers ask isn’t what took so long, but rather why complex life would have evolved in the first place. Consider this: single-celled organisms make up more than half of the biomass on earth, and even one of the tiniest organisms – Y. pestis, better known as bubonic plague – can effortlessly, thoughtlessly kill you. Nature, it seems, doesn’t need you. Indeed, there isn’t any obvious reason it would go to the trouble of creating something as complex as a human being, complete with its differentiated organs and top-down control systems. And yet, despite four billion years of Nature’s great “meh,” here you are, alive, multicellular, complex – even intelligent enough to ponder your own existence.