The Pleistocene and the present don’t compute


March 15, 2025, For Immediate Release:

“Rest assured, Pleistocene Parks Inc. is doing everything possible to recapture our escaped ice age megafauna. Please back away slowly from any African lion you encounter. Keep pets and children away from cheetahs. Do not approach camels, as they may kick, spit and bite. Unless you are in a convertible, remain on the floor of your vehicle if an elephant in the rutting frenzy called ‘musth’ attempts to sit upon the roof.”

All the critters mentioned above and more will be released in large swaths of the West if America follows the advice of 12 eminent conservation biologists. Ten years ago, when I read their proposal in the respected journal Nature, I checked to see if the issue was dated April 1. It wasn’t. The co-authors were serious. I confess that back then, the plan struck me as a crackpot idea.

“This ‘Pleistocene re-wilding,’” they explained, “would be achieved through a series of carefully managed ecosystem manipulations using closely related species as proxies for extinct large vertebrates, and would change the underlying premise of conservation biology from managing extinction to actively restoring natural processes.” They went on to predict that the alien conglomeration would create a cascade of tourist dollars.

I’ve followed the debate about Pleistocene re-wilding for a decade now. I still think it’s a crackpot idea, but it does not follow that the coauthors are crackpots themselves. Led by Josh Donlan, and his then advisor, renowned Cornell ecology and evolutionary biology professor Harry Greene, all have done superb work for wildlife.

I’ve avoided the subject for two reasons: I have tremendous admiration for the coauthors, most of whom have helped me with writing projects. And I thought their proposal would fade away. It hasn’t. The popular press seems increasingly enamored, lauding it as “interesting,” “novel,” “bold,” “fascinating,” even “delicious.” The Smithsonian hosted a panel discussion about it at the National Museum of Natural History on March 31.

The scientific community is less effusive. In Conservation Biology, Luiz Oliveira-Santos and Fernando Fernandez accuse the coauthors of promoting “Frankenstein-like ecosystems.”

Michael Hutchins, former CEO of the Wildlife Society and now with the American Bird Conservancy, defines Pleistocene re-wilding as “a huge mistake and distraction.” Since the Pleistocene extinctions, “there have been enormous changes in ecological systems,” he told me. “Neo-ecologists have basically said the Anthropocene (the age of human-caused mass extinctions) is inevitable, that alien species are not so bad and that we should accept them. If that’s the way we’re going, we’ll lose vast numbers of native species.”

In addition to unleashing extant African animals in North America, Pleistocene re-wilding proponents favor “de-extinction” -- a process whereby long-gone species would be genetically resurrected, eventually to replace their African stand-ins. Writing in Yale Environment 360, Paul Ehrlich, president of the Center for Conservation Biology, likens the scheme to the movie Jurassic Park, calling it “an awful idea” that would “divert us from the critical work needed to protect the planet.”

The concept of Pleistocene re-wilding is rooted in the notions of one of the original 12 coauthors, Paul Martin, who died in 2010. In his book, Twilight of the Mammoths, Martin hypothesized that the large-mammal assemblage of the Pleistocene was eradicated by humans shortly after they arrived from Asia. This led him to conclude that “the Bering Land Bridge should not be shut down forever in the interest of imagined faunal purity.”

So if Paleolithic humans caused these ancient extinctions, modern humans should try to reverse the process, right?

Wrong. Even if de-extinction becomes possible, Pleistocene conditions and habitats can’t be resurrected. What’s more, many paleontologists are highly skeptical of Martin’s thesis, noting that it’s unlikely that Pleistocene people could have wiped out anything. They were far too few. They hunted with spears. They didn’t even have horses. Martin glossed over the more likely cause -- climate change.

On the website of the Center for Humans & Nature, Greene suggests that while superimposing African lions on the American West “can’t precisely replace the ones we lost,” it’s no less justified than peregrine falcon recovery with “an amalgam of seven subspecies, four of them Eurasian.” But all peregrines belong to a single extant species. We had no choice but to use nearly identical races that fit into an existing niche emptied by DDT a mere half-century ago.

Pleistocene megafauna species died out millennia ago. They are gone for good reason. They need to stay gone.

Ted Williams is a contributor to Writers on the Range, a column service of High Country News. He writes about wildlife and conservation issues and lives in Massachusetts. For the proponents’ perspective, see “Pleistocene Rewilding: An Optimistic Agenda for Twenty-First Century Conservation” at:

Note: the opinions expressed in this column are those of the writer and do not necessarily reflect those of High Country News, its board or staff. If you'd like to share an opinion piece of your own, please write Betsy Marston at [email protected].

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