Anne Fausto-Sterling in Boston Review (Photo: Rachel Mack):
During the 1950s peanut butter came in notoriously hard-to-close pry-top jars, and an enterprising rat in my family’s home took advantage. At night, after my parents’ bedroom door clicked shut, they would hear a clatter as the rat removed the metal lid and dropped it to the floor. Eventually mom and dad poisoned the ingenious beast. My brother skinned it, tanned its hide, and nailed it to a bulletin board—a stark warning to future marauders.
Lately I’ve been thinking about that rat. How did it figure out how to open the jar? How did it learn that the coast was clear when my parents retired for the night? Did it have a lid-opening gene? A peanut butter gene? Was it predisposed to explore, or did its family and rodent companions teach it to investigate? Why did that individual, and not, for example, its twin or its sister, exploit this food source?
It is a quirky case, the condiment-thieving rat, but the question of how individual differences arise is important to us all. In his State of the Union address, President Obama made a big push for personalized medicine—based on the idea that if we know an individual’s genome, we can predict medical outcomes and tailor individual treatments—and the success of that enterprise relies on the right answer.
This is a complicated challenge because, as biologists first proposed in the early twentieth century, a genotype—all the genes in the cells of an organism—does not guarantee a phenotype—what the organism looks like and how it behaves. A vast territory links genes in their cellular starting environment to individual phenotypes. Recently behavioral biologist Julia Freund and her colleagues published a fascinating study that directly addresses this problem.