Undark: What’s in a Genome? The Quest to Decipher Human Difference


Michael Schulson


Racial categories are crude maps imposed on human biological variation. How do scientists square them with genetics?

Tina Lasisi was 19 years old, sitting in a lecture hall at the University of Cambridge, when she found the scientific question that would occupy more than a decade of her life. ‍

The instructor that day had presented a classic discovery from the study of human evolution: People with many ancestors who lived near the equator, where there’s more ultraviolet radiation, tend to have darker skin than those whose ancestors lived near the poles.

‍For Lasisi, the biracial daughter of a Bulgarian mother and a Nigerian father, the detail felt like a revelation. Suddenly skin color wasn’t about race, exactly; it was about UV light, and about how much of it her ancestors had encountered as they moved through the world. But then, almost immediately, came another question: “What about my hair?”

Lasisi had stumbled onto a puzzle — a set of puzzles, really. Human scalp hair varies by color, thickness, and structure; unlike the hair of nearly any wild mammal, it often curls. But scientists have little idea how this panoply of hair came to be.

Over the years, as she pursued a Ph.D. in biological anthropology, Lasisi amassed a collection of human hair. (Today, she estimates, she has more than 200 samples, some kept in small tubes in a walk-in lab refrigerator, others embedded in moldable plastic.) She devised rigorous methods for measuring the curvature and shape of each hair fiber. Now a postdoctoral researcher at the University of Southern California, Lasisi also studies the genetics of hair. Which genes affect the kind of hair a person has? Why is there variation at all?

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Image Credit: Ken Gonzales-Day, 41 Objects Arranged by Color, 2016