Street Life

Pigeons. Rats. Lizards. In Cities, Their Evolution Has Quickly Diverged From Their Country Cousins, Letting Them Thrive In A Hostile Habitat. If Researchers Can Figure Out How This Happens, It Could Help Other Creatures—including Us—adapt To Climate Change.

- Brendan I. Koerner

The northwest corner of Newark Bay is the kind of place comedians have in mind when they mock New Jersey as a cesspool. The grim industrial coast the bay shares with the Passaic River is lined with the hulks of old chemical plants that treated their surroundings like a toilet. The most infamous of these facilities produced nearly a million gallons of Agent Orange, the toxic defoliant whose extensive use during the Vietnam War has caused generations of suffering. The Agent Orange plant discharged unholy amounts of carcinogenic dioxin—so much, in fact, that New Jersey’s governor declared a state of emergency in June 1983. Though the Environmental Protection Agency has announced a $1.4 billion cleanup effort, the waters closest to Newark’s Ironbound neighborhood remain highly contaminated; there are few worse spots in America to go for a swim.

And yet upper Newark Bay is not devoid of life. Beneath its dull green surface teems a population of Atlantic killifish, a silvery topminnow that’s common along the Eastern Seaboard. These fish are virtually indistinguishable from most other members of their species, save for their peculiar ability to thrive in conditions that are lethal to their kin. When killifish plucked from less polluted environments are exposed to dioxin levels like those in the bay, they either fail to reproduce or their offspring die before hatching; their cousins from Newark, by contrast, swim and breed happily in the noxious soup.

Eight years ago, while he was an associate professor at Louisiana State University, an environmental toxicologist named Andrew Whitehead decided to find out what makes Newark’s killifish so tough. He and his research group collected sample fish from an inlet near the city’s airport and began to deconstruct their genomes, sifting through millions of lines of genetic code in search of tiny quirks that might explain the creatures’ immunity to the ravages of dioxin.