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How cities redesign the evolutionary path of urban wildlife



The northwest corner of Newark Bay is the sort of place that comedians think of when mocking New Jersey as a cesspool. The bleak industrial coast that divides the bay with the Passaic is lined with old chemical plants that treat their surroundings like a toilet. The most notorious of these plants produced nearly a million gallons of Agent Orange, the toxic defoliant whose extensive use during the Vietnam War has caused generations of suffering. Agent Orange's work spilled unholy amounts of carcinogenic dioxin – so much so that the governor of New Jersey declared a state of emergency in June 1983. Although the Environmental Protection Agency has announced $ 1

.4 billion in cleanup, the waters near Newark's Ironbound district remain heavily contaminated; In America, there are few worse places to go swimming.

And yet the upper Newark Bay is not without life. Its dull green surface is teeming with a population of Atlantic killifish, a silvery topminnow found on the east coast. These fish are virtually indistinguishable from most other members of their species, except for their special ability to thrive in conditions that are deadly to their loved ones. If less-contaminated environments are exposed to plucked killifish dioxin levels as found in the bay, they may either not reproduce or their offspring may die before hatching. In contrast, her cousins ​​from Newark swim and breed happily in the harmful soup.

Eight years ago, when he was an associate professor at Louisiana State University, an environmental toxicologist named Andrew Whitehead decided to figure out what makes Newark's killifish tough. He and his research group collected sample fish from a bay near the city's airport and began dissecting their genomes. They searched millions of lines of genetic code in search of tiny quirks that could explain the creatures' immunity to the ravages of dioxin.

] In late 2014, two years after joining UC Davis, Whitehead focused on genes linked to the aryl hydrocarbon receptor, a protein that regulates a number of cell functions. When most adult killifish encounter dioxin, the signal pathway of this receptor is brought to life, hoping to metabolize the chemical invader. But anyway, the protein can not break down the insidious substance. Instead of acting as a defense mechanism, the frustrated pathway leads to devastation during development, resulting in severe birth defects or the death of embryos. "If you inappropriately activate this path in the development of your organs, you are really hosed down," says Whitehead. But this ugly destiny never hits the killifish of Newark Bay because their bodies are wise towards dioxin's cunning. The genes that control their aryl hydrocarbon receptors, whose DNA sequences differ slightly from those of other killifish, rest when confronted with the toxin.

The story that the pioneers of urban evolution are composed is obscure. [19659006] As he explained in a groundbreaking scientific work in 2016, Whitehead and his colleagues also noted that the Newark Bay killifishes are not the only ones using this clever genetic tactic to survive in polluted water. He identified similarly resistant killifish in three other East Coast cities whose estuaries were hit by industry: New Bedford, Massachusetts; Bridgeport, Connecticut; and Portsmouth, Virginia. Since killifishes are never far from their birthplace, these resistant populations must have evolved the same changes to their genomes without mingling – or, more simply, the distant fishes have all evolved in remarkably similar ways in response to it same environmental impact. This is convincing evidence for the assumption that evolution, the most sublime of the engines of nature, is not a chaotic phenomenon, but a decent one, the results of which we may possibly predict.

Whitehead's work on killifish is one of the key achievements of urban evolution, an emerging discipline that addresses the issue of why certain animals, plants and microbes survive or even thrive, no matter how much we change their habitats. People seldom think much about the creatures scurrying or crawling or romping about our blocks of flats and shopping centers, in part because we dismiss them as ordinary or less than wild. But we should instead wonder how these organisms have managed to keep up with our tireless urge to build and bundle cities. Instead of withering as Homo sapiens spreads with concrete, bitumen, and steel, a select number of species have developed elegant adaptations to cope with the peculiarities of urban life: stiffer cell membranes that can ward off heat, and digestive systems that do Can Increase sugary garbage, altered limbs and upper body, which increases the mobility on tarmac or in effluent streams of which are at the beginning of their career, are now beginning to locate the subtle genetic changes that underlie these new traits. Their clutter promises to solve a puzzle that has bothered biologists for 160 years, and to show how we can manipulate evolution to make the world's cities – which will probably host two-thirds of humanity by 2050 – resilient enough to endure the catastrophes, who are coming to you.


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