Robert L. Dorit in American Scientist:
A simplified, and ultimately misleading, account of the evolutionary process argues that natural selection inexorably leads to optimal adaptation. According to this perspective, organisms face challenges presented by the environment, and ultimately, through the agency of natural selection, find the best solutions. From this point of view, the living world—from the three-dimensional structure of enzymes to the drag-minimizing shape of porpoises—could thus be described as a compendium of these supposedly ideal adaptations.
This perspective beguiles in its simplicity, but in the end, it trivializes the complexities of the evolutionary process. Natural selection sorts among existing alternatives, but sometimes a good-enough solution may become inextricably locked in place. Evolution is not about what’s best, but what works. Organisms do fit their environments exquisitely—and the task of contemporary evolutionary biology is to elucidate the interplay of history, chance and selection that shapes life on this planet. To be sure, we can ease our burden by downplaying the reach of history. We can even maintain that chance delays, but ultimately does not derail, the emergence of peak adaptation. And finally, we can dismiss what appears to be a suboptimal design by asserting that it simply reflects our lack of understanding of what is being optimized. But these are risky simplifications. In the end, life is more than a collection of adaptations, and evolution is more than the ascent to perfection. My job as an evolutionary biologist goes beyond simply imagining the plausible benefits that disembodied features might confer on individual organisms.
The 200th anniversary of Darwin’s birth seems as good time as any to revisit the tension between history and optimality. I want to do so, however, by focusing on two seemingly disparate evolutionary narratives: The typewriter keyboard and the genetic code.