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Is it possible that nearly human mammals existed before the last mass extinction dinosaurs?

Is it possible that nearly human mammals existed before the last mass extinction dinosaurs?



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From time to time I am hearing people discussing about the possibility that men and dinosaurs meeting some time ago.

The oldest mammal remains seem to be about 35 million years old, quite some time after dinosaurs have perished.

Also, it is very implausible for a primitive man to manage to survive near the dinosaurs (I think they would be very hard to handle even using current technology).

Question: is it even remotely possible for advanced mammals (nearly humans) to have coexisted with dinosaurs?


Is it possible that nearly human mammals existed before the last mass extinction dinosaurs?

Short answer

No!

Longer answer

The ancestor of all mammals lived about ~180 millions years ago (see here), so much before the Cretaceous-Paleogene extinction event (~65 millions years ago). The ancestor of all primates lived ~65 millions years ago (see here), so pretty much at the same time as the C-P extinction.

But please, don't picture the ancestor of all primates as something that is too human like. It looked more like a lemur, a tarsier or a loris, than like a human!

The first great ape lived about 14 millions years ago (see here) and the most recent ancestor of chimpanzee, bonobos and humans lived about 6 millions years ago (see here). The discovery of how to control fire happened about 1.5 millions years ago (with a pretty wide confidence interval, see the wikipedia article). The first generally considered Homo sapiens lived about 200,000 years ago (see the wikipedia article). The wheel was first invented about 5'000 years ago (see the wikipedia article).

Related: Who are humans' closest relatives, after primates?


Will Humans Survive the Sixth Great Extinction?

In the last half-billion years, life on Earth has been nearly wiped out five times—by such things as climate change, an intense ice age, volcanoes, and that space rock that smashed into the Gulf of Mexico 65 million years ago, obliterating the dinosaurs and a bunch of other species. These events are known as the Big Five mass extinctions, and all signs suggest we are now on the precipice of a sixth.

Except this time, we have no one but ourselves to blame. According to a study published in Science Advances, the current extinction rate could be more than 100 times higher than normal—and that’s only taking into account the kinds of animals we know the most about. Earth’s oceans and forests host an untold number of species, many of which will probably disappear before we even get to know them. (See pictures of 10 of the earth's rarest animals.)

Journalist Elizabeth Kolbert’s book The Sixth Extinction won 2017's Pulitzer Prize for general non-fiction. We talked to her about what these new results might reveal for the future of life on this planet. Is there any chance we can put the brakes on this massive loss of life? Are humans destined to become casualties of our own environmental recklessness?

The study that's generated so much conversation estimates that as many as three-quarters of animal species could be extinct within several human lifetimes, which sounds incredibly alarming.

Yes. That study is looking at very well-studied groups of animals. They restricted themselves to vertebrates—like mammals and birds and reptiles and amphibians—and said, OK, let’s look at what is actually happening. And they document pretty compellingly that extinction rates were already extremely elevated in [the year] 1500, and are just getting worse and worse.

They’re very high figures, and people are kind of getting inured to it. Kids who are born 10, 20 years ago—they’ve grown up their whole lives with these numbers. They don’t really think, OK, well that really is fantastically unusual. (Read about a study that says extinction rates are a thousand times higher because of humans.)

People have been debating whether we really are in the throes of a sixth mass extinction. What is your opinion?

To be honest, that’s one of those debates where I think we’re focusing on the wrong thing. By the time we have definitive answers to that question, it’s possible that three-quarters of all species on Earth could be gone. We really don’t want to get to the point where we definitively can answer that question.

What is clear, and what is beyond dispute, is that we are living in a time of very, very elevated extinction rates, on the order that you would see in a mass extinction, though a mass extinction might take many thousands of years to play out.

Are there habitats or species—or groups of animals that you think are especially vulnerable to the changes that are going on?

Island populations are very vulnerable to extinctions for a couple of reasons. They tend to have been isolated. One of the things we’re doing is removing the barriers that used to keep island species isolated. New Zealand had no terrestrial mammals. Species that had evolved in the absence of such predators were incredibly vulnerable. A staggering number of bird species have already been lost on New Zealand, and a lot of those that remain are in deep trouble.

So, places that have been isolated for a long time. Those are very vulnerable. Species that have a very restricted range, that exist only in one spot in the world, those tend to be extremely vulnerable. They have nowhere to go and if their habitat is destroyed, say, then they’re gone.

The human component of this story—the fact that we appear to be responsible for the sixth extinction—what is some of the best evidence for our involvement?

I don’t think there’s any dispute that we are responsible for the elevated extinction rates we see now. There are very few, if any, extinctions that we know about in the last 100 years that would have taken place without human activity. I have never heard anyone argue, “oh extinction rates, that’s just a natural thing that would have happened with or without humans.” It’s just pretty much impossible to argue that.

If we’re pulling the trigger, what did we load the gun with?

There are thousands and thousands of scientific articles that have been written about this. We loaded it with hunting. We brought in invasive species. We are now changing the climate, very, very rapidly, by geological standards. We are changing the chemistry of all the oceans. We are changing the surface of the planet. We cut down forests, we plant mono-culture agriculture, which is not good for a lot of species. We’re overfishing. The list goes on and on.

There’s no shortage of bullets. We have a pretty big arsenal right now. (Read about which animals are likely to go extinct first due to climate change.)

Is it still possible for us to slow down the loss of life?

All of the ways that we’re changing the planet that we just discussed—in each case, I could point to a library’s worth of reports suggesting how we could do things better. Just take dead zones in the ocean as one tiny, little example. We could change fertiliser regimens in all sorts of ways. We dump nitrogen on fields in the Midwest and the fertiliser runs down the Mississippi and into the Gulf of Mexico, and that causes these dead zones.

The sort of fundamental question is, can 7.3 —going toward 8, going to 9 billion people —live on this planet with all of the species that are now still around? Or are we on a collision course, in part because we consume a lot of resources that other creatures also would like to consume? That’s a question I can’t answer.

The other five mass extinctions – how long did it take the planet to recover from those?

To get to the previous level of biodiversity, it seems to take several million years.


Why did mammals survive the 'K/T extinction'?

Picture a dinosaur. Huge, menacing creatures, they ruled the Earth for nearly 200 million years, striking fear with every ground-shaking stride. Yet these great beasts were no match for a 6-mile wide meteor that struck near modern-day Mexico 65 million years ago, incinerating everything in its path. This catastrophic impact -- called the Cretaceous-Tertiary or K/T extinction event -- spelled doom for the dinosaurs and many other species. Some animals, however, including many small mammals, managed to survive.

"They were better at escaping the heat," said Russ Graham, senior research associate in geosciences at Penn State. "It was the huge amount of thermal heat released by the meteor strike that was the main cause of the K/T extinction."

He said underground burrows and aquatic environments protected small mammals from the brief but drastic rise in temperature. In contrast, the larger dinosaurs would have been completely exposed, and vast numbers would have been instantly burned to death.

After several days of searing heat, the earth's surface temperature returned to bearable levels, and the mammals emerged from their burrows, but it was a barren wasteland they encountered, one that presented yet another set of daunting conditions to be overcome, Graham said. It was their diet which enabled these mammals to survive in habitats nearly devoid of plant life.

"Even if large herbivorous dinosaurs had managed to survive the initial meteor strike, they would have had nothing to eat," he said, "because most of the earth's above-ground plant material had been destroyed."

Mammals, in contrast, could eat insects and aquatic plants, which were relatively abundant after the meteor strike. As the remaining dinosaurs died off, mammals began to flourish. Although representatives from other classes of animals also survived the K/T extinction -- crocodiles, for instance, had the saving ability to take to water -- mammals were clearly the main beneficiaries and they have since spread to nearly every corner of the planet.

Story Source:

Materials provided by Penn State. Original written by Nick Bascom, Research/Penn State. Note: Content may be edited for style and length.


Fact or Fiction?: The Sixth Mass Extinction Can Be Stopped

Is the planet undergoing the sixth mass extinction in its history courtesy of the human species?

The most famous mass extinction came from space, but the biggest might have been because of carbon dioxide. Cataclysms, whether the asteroid that ended the dinosaurs&rsquo reign or the volcanism that may have caused the Great Dying, drove the first five mass extinctions in Earth&rsquos history, in which 75 percent of more of the planet&rsquos life died out. The sixth mass extinction may now be beginning&mdashand the apocalypse this time is us.

During the last several centuries we have burned through eons worth of fossilized sunshine, changing the climate for our fellow species. We use more than half of the planet&rsquos unfrozen land for cities, logging or food, eliminating the habitats of our fellow animals and plants. Before we even achieved civilization, we had already helped hunt the biggest, fiercest animals&mdashwoolly mammoths, giant kangaroos and giant sloths&mdashto extinction.

Biologists and paleoecologists estimate that humans have driven roughly 1,000 species extinct in our 200,000 years on the planet. Since 1500 we have killed off at least 322 types of animals, including the passenger pigeon, the Tasmanian tiger and, most recently, the baiji, a freshwater dolphin in China. Another 20,000 or more species are now threatened with extinction according to the International Union for the Conservation of Nature, which keeps a list of all the known endangered plants and animals on the planet. The population of any given animal among the five million or so species on the planet is, on average, 28 percent smaller, thanks to humans. And as many as one third of all animals are either threatened or endangered, a new study in Science finds.

In the jargon it's an "Anthropocene defaunation," or sixth mass extinction, and one caused by humans. Scientists can't be sure of the current die-off rate, perhaps because much of it is happening to beetles and other insects that are notoriously overlooked. But according to that new study in Science, the total number of such invertebrates fell by half over the past 35 years while the human population doubled. Other recent studies suggest that the current extinction rate is roughly 1,000 times faster than the average pace in Earth's history. That makes this the fastest extinction event on record, even if it is not yet a mass die-off.

The biggest, fiercest animals still left on the planet&mdashelephants, tigers, whales, among others&mdashare most at risk. And we humans have shown no inclination to stop the activities&mdashoverexploitation for food, habitat destruction and others&mdashthat drive extinction.

And yet it's not too late. In the past few decades humans brought the black-footed ferret back from just seven individuals vaccinated and hand-reared condors to relative abundance and battled to preserve and restore populations of hellbender salamanders, to name just a few in just North America alone. According to another new analysis in Science, people have physically moved 424 species of plants and animals to protect them from extinction.

For such assisted migration efforts to succeed, careful attention must be paid both to genetics and habitat. There is no point in bringing back the baiji, for example, if the Yangtze River remains polluted and overfished. But conservation efforts can work. Fishes can rebound when fishing pressure is removed, just as Maine haddock and Washington State coho salmon both have. The reforesting of the U.S. eastern seaboard shows that when farms go away, woodlands return, and coyotes, deer, turkey and other wildlife move back in. The animals and plants of the Amazon rainforest have benefited from Brazil's efforts to curb deforestation. And in what might prove an enduring lesson in conservation, paleoecologists have shown that 20 out of 21 large mammals in India&mdashfrom leopards to muntjac deer&mdashhave survived there for the past 100,000 years alongside one of the largest human populations on the planet.

To avoid the sixth mass extinction we will probably have to employ more aggressive conservation, such as moving species to help them cope with a changing climate. Think re-wilding: reintroducing species like wolves or beavers that were once present in a given ecosystem but have since disappeared. Aggressive conservation might also mean killing off newcomer species to preserve or make room for local flora and fauna in New Zealand, rat extirpations have helped kakapos survive.

In the most extreme case aggressive conservation could involve bringing in new animals to fill the role of animals that have gone extinct. For example, European sailors ate their way through the Indian Ocean islands of Mauritius, killing off the dodo and the local tortoise species. But closely related tortoises from the neighboring Seychelles archipelago have been imported recently, and they have helped restore the island ecosystem, including bringing back the endangered local ebony trees. As a result of that success, similar projects are being considered from Caribbean islands to Madagascar. There is even some hope of bringing back entirely extinct species in the future using the new tools of synthetic biology. (De-extinction or even ecological replacement could cause some of the same problems as invasive species, so careful management is required.)

But we are not doomed to cause a sixth mass extinction, at least not yet, despite consuming our way through the world's remaining big wild animals. Based on an estimate published in Nature in 2011, we have a century or two at present rates before our depredations assure a mass extinction. Unlike an asteroid, we could choose to change course.


Humans will be extinct in 100 years says eminent scientist

Professor Frank Fenner

(PhysOrg.com) -- Eminent Australian scientist Professor Frank Fenner, who helped to wipe out smallpox, predicts humans will probably be extinct within 100 years, because of overpopulation, environmental destruction and climate change.

Fenner, who is emeritus professor of microbiology at the Australian National University (ANU) in Canberra, said homo sapiens will not be able to survive the population explosion and “unbridled consumption,” and will become extinct, perhaps within a century, along with many other species. United Nations official figures from last year estimate the human population is 6.8 billion, and is predicted to pass seven billion next year.

Fenner told The Australian he tries not to express his pessimism because people are trying to do something, but keep putting it off. He said he believes the situation is irreversible, and it is too late because the effects we have had on Earth since industrialization (a period now known to scientists unofficially as the Anthropocene) rivals any effects of ice ages or comet impacts.

Fenner said that climate change is only at its beginning, but is likely to be the cause of our extinction. “We’ll undergo the same fate as the people on Easter Island,” he said. More people means fewer resources, and Fenner predicts “there will be a lot more wars over food.”

Easter Island is famous for its massive stone statues. Polynesian people settled there, in what was then a pristine tropical island, around the middle of the first millennium AD. The population grew slowly at first and then exploded. As the population grew the forests were wiped out and all the tree animals became extinct, both with devastating consequences. After about 1600 the civilization began to collapse, and had virtually disappeared by the mid-19th century. Evolutionary biologist Jared Diamond said the parallels between what happened on Easter Island and what is occurring today on the planet as a whole are “chillingly obvious.”

While many scientists are also pessimistic, others are more optimistic. Among the latter is a colleague of Professor Fenner, retired professor Stephen Boyden, who said he still hopes awareness of the problems will rise and the required revolutionary changes will be made to achieve ecological sustainability. “While there's a glimmer of hope, it's worth working to solve the problem. We have the scientific knowledge to do it but we don't have the political will,” Boyden said.

Fenner, 95, is the author or co-author of 22 books and 290 scientific papers and book chapters. His announcement in 1980 to the World Health Assembly that smallpox had been eradicated is still seen as one of the World Health Organisation’s greatest achievements. He has also been heavily involved in controlling Australia’s feral rabbit population with the myxomatosis virus.

Professor Fenner has had a lifetime interest in the environment, and from 1973 to 1979 was Director of the Centre for Resource and Environmental Studies at ANU. He is currently a visiting fellow at the John Curtin School of Medical Research at the university, and is a patron of Sustainable Population Australia. He has won numerous awards including the ANZAC Peace Prize, the WHO Medal, and the Albert Einstein World Award of Science. He was awarded an MBE for his work on control of malaria in New Guinea during the Second World War, in which Fenner served in the Royal Australian Army Medical Corps.

Professor Fenner will open the Healthy Climate, Planet and People symposium at the Australian Academy of Science next week.


Permian-Triassic extinction - 252 million years ago

Some 252 million years ago, life on Earth faced the “Great Dying”: the Permian-Triassic extinction. The cataclysm was the single worst event life on Earth has ever experienced. Over about 60,000 years, 96 percent of all marine species and about three of every four species on land died out. The world’s forests were wiped out and didn’t come back in force until about 10 million years later. Of the five mass extinctions, the Permian-Triassic is the only one that wiped out large numbers of insect species. Marine ecosystems took four to eight million years to recover. (Find out more about the devastation of the Permian-Triassic mass extinction.)


The sixth mass extinction, explained

The populations of the world's wild animals have fallen by more than 50 percent and humanity is to blame. Here's everything you need to know:

What's gone wrong?As the human population has swelled to 7.5 billion, our species' massive footprint on planet Earth has had a devastating impact on mammals, birds, reptiles, insects, and marine life. We've driven thousands of species to the edge of extinction through habitat loss, overhunting and overfishing, the introduction of invasive species into new ecosystems, toxic pollution, and climate change. In the past 40 years, the number of wild animals has plunged 50 percent, a 2014 study found. And the World Wildlife Fund (WWF) estimates that populations of vertebrates — higher animals with spinal columns — have fallen by an average of 60 percent since 1970. The past 20 years have brought a 90 percent plunge in the number of monarch butterflies in America, a loss of 900 million, and an 87 percent loss of rusty-patched bumblebees. Only 3 percent of the original populations of the heavily fished Pacific bluefin tuna remain in the sea. "We are sleepwalking toward the edge of a cliff," said Mike Barrett, executive director at WWF.

How many species are already extinct?Scientists can only guess. Earth is home to between nine million and as many as one trillion species — and only a fraction have been discovered. Vertebrate species have, however, been closely studied, and at least 338 have gone extinct, with the number rising to 617 when one includes those species "extinct in the wild" and "possibly extinct." Recent vertebrate extinctions in the wild include the northern white rhino, which lost its last male member in 2018, and Spix's macaw, a blue parrot native to Brazil. But 99 percent of Earth's species are invertebrates, and 40 percent of the species known to have died off since 1500 were land snails and slugs. One, the Hawaiian tree snail, died out on New Year's Day, when its final member, George — dubbed "the world's loneliest snail" — passed at age 14. "I'm sad," said Rebecca Rundell, a biologist at State University of New York. "But really, I'm more angry, because this was such a special species, and so few people knew about it."

How many species are endangered?There are 26,500 species threatened with extinction, according to the International Union for Conservation of Nature (IUCN), a global network of some 16,000 scientists. That includes 40 percent of amphibian species, 33 percent of reef-building corals, 25 percent of mammals, and 14 percent of birds. There are now only 7,000 cheetahs left, and the number of African lions is down 43 percent since 1993. Only about 100 Amur leopards — often poached for their beautiful coats — are left in the wild in southeastern Russia and China. A third of insect species are endangered, and the total number of bugs on Earth is dropping by 2.5 percent every year. "There are examples of species all over the world that are essentially the walking dead," said biologist Paul Ehrlich.

Is a mass extinction underway?Possibly. Many scientists now believe humans are living through a "mass extinction," or an epoch during which at least 75 percent of all species vanish from the planet. Earth has supported life in some form for about 4.2 billion years. The previous five mass extinctions occurred over the past 450 million years the last one occurred about 66 million years ago, when the aftermath of a massive asteroid strike wiped out the dinosaurs. These prior events differed from the current one, though, in that they were triggered by a natural disaster or change in Earth's climate. This time, it's humanity that is driving the mass die-off, which is why a debate is now afoot in scientific circles over whether to rechristen our current geological epoch as the "Anthropocene Era" — from anthropos, for "man," and cene, for "new."

How fast is this happening?Extremely fast. Species extinction is an ordinary part of the natural processes of our planet in fact, 99 percent of all species that ever lived on Earth are gone. It's the pace of recent extinctions that is alarming. More than half of the vertebrate extinctions since 1500 have occurred since 1900. Generally speaking, scientists assess the current rate of extinction as somewhere between 100 to 10,000 times Mother Nature's regular pace.

What are the consequences?Potentially enormous. The loss of species can have catastrophic effects on the food chain on which humanity depends. Ocean reefs, which sustain more than 25 percent of marine life, have declined by 50 percent already — and could be lost altogether by 2050. This is almost certainly contributing to the decline of global marine life, down — on average — by 50 percent since 1970, according to the WWF. Insects pollinate crops humans eat. "This is far more than just being about losing the wonders of nature, desperately sad though that is," the WWF's Barrett said. "This is actually now jeopardizing the future of people. Nature is not ‘nice to have' — it is our life-support system."

Can extinct species be resurrected?Using DNA technology, scientists are working on recreating species that have disappeared. The technology, called "de-extinction," is likely at least a decade off, although there are a few possible ways to go about it. The first, "back-breeding," involves mating examples of a living species with traits similar to the extinct species. The second option is cloning — famously attempted in 2009 using the DNA of an extinct Pyrenean ibex and its closest living cousin, the common goat. (The offspring lived only seven minutes.) The third option is to edit the genes of an extinct species' closest living analog to obtain an approximation. Such work is now underway with the passenger pigeon and woolly mammoth. "If you're willing to accept something that is an elephant that has a few mammoth genes," said Beth Shapiro, an evolutionary biologist, "we're probably closer to that." But don't expect to see a Tyrannosaurus rex or velociraptor like the ones in Jurassic Park. De-extinction requires an extinct species' DNA, and that molecule of life only lasts about a million years before degrading. Dinosaur DNA would be far older.


18 signs we're in the middle of a 6th mass extinction

The phrase "mass extinction" typically conjures images of the asteroid crash that led to the twilight of the dinosaurs.

Upon impact, that 6-mile-wide space rock caused a tsunami in the Atlantic Ocean, along with earthquakes and landslides up and down what is now the Americas. A heat pulse baked the Earth, and the Tyrannosaurus rex and its compatriots died out, along with 75% of the planet's species.

Although it may not be obvious, another devastating mass extinction event is taking place today — the sixth of its kind in Earth's history. The trend is hitting global fauna on multiple fronts, as hotter oceans, deforestation, and climate change drive animal populations to drop in unprecedented numbers.

These alarming extinction trends are driven by one key factor: humans. According to a 2014 study, current extinction rates are 1,000 times higher than they would be if humans weren't around. A summary of a United Nations report released last month put it another way: "Human actions threaten more species with global extinction now than ever before," the authors wrote.

That report, which assessed the state of our planet's biodiversity, found that up to 1 million plant and animals species face extinction, many within decades, due to human activity.

Other recent research has led to similar conclusions: A 2017 study found that animal species around the world are experiencing a "biological annihilation" and that our current "mass extinction episode has proceeded further than most assume."

Here are 18 signs that the planet is in the midst of a sixth mass extinction, and why people are primarily to blame.


Abstract

The population extinction pulse we describe here shows, from a quantitative viewpoint, that Earth’s sixth mass extinction is more severe than perceived when looking exclusively at species extinctions. Therefore, humanity needs to address anthropogenic population extirpation and decimation immediately. That conclusion is based on analyses of the numbers and degrees of range contraction (indicative of population shrinkage and/or population extinctions according to the International Union for Conservation of Nature) using a sample of 27,600 vertebrate species, and on a more detailed analysis documenting the population extinctions between 1900 and 2015 in 177 mammal species. We find that the rate of population loss in terrestrial vertebrates is extremely high—even in “species of low concern.” In our sample, comprising nearly half of known vertebrate species, 32% (8,851/27,600) are decreasing that is, they have decreased in population size and range. In the 177 mammals for which we have detailed data, all have lost 30% or more of their geographic ranges and more than 40% of the species have experienced severe population declines (>80% range shrinkage). Our data indicate that beyond global species extinctions Earth is experiencing a huge episode of population declines and extirpations, which will have negative cascading consequences on ecosystem functioning and services vital to sustaining civilization. We describe this as a “biological annihilation” to highlight the current magnitude of Earth’s ongoing sixth major extinction event.

The loss of biological diversity is one of the most severe human-caused global environmental problems. Hundreds of species and myriad populations are being driven to extinction every year (1 ⇓ ⇓ ⇓ ⇓ ⇓ ⇓ –8). From the perspective of geological time, Earth’s richest biota ever is already well into a sixth mass extinction episode (9 ⇓ ⇓ ⇓ ⇓ –14). Mass extinction episodes detected in the fossil record have been measured in terms of rates of global extinctions of species or higher taxa (e.g., ref. 9). For example, conservatively almost 200 species of vertebrates have gone extinct in the last 100 y. These represent the loss of about 2 species per year. Few realize, however, that if subjected to the estimated “background” or “normal” extinction rate prevailing in the last 2 million years, the 200 vertebrate species losses would have taken not a century, but up to 10,000 y to disappear, depending on the animal group analyzed (11). Considering the marine realm, specifically, only 15 animal species have been recorded as globally extinct (15), likely an underestimate, given the difficulty of accurately recording marine extinctions. Regarding global extinction of invertebrates, available information is limited and largely focused on threat level. For example, it is estimated that 42% of 3,623 terrestrial invertebrate species, and 25% of 1,306 species of marine invertebrates assessed on the International Union for Conservation of Nature (IUCN) Red List are classified as threatened with extinction (16). However, from the perspective of a human lifetime it is difficult to appreciate the current magnitude of species extinctions. A rate of two vertebrate species extinctions per year does not generate enough public concern, especially because many of those species were obscure and had limited ranges, such as the Catarina pupfish (Megupsilon aporus, extinct in 2014), a tiny fish from Mexico, or the Christmas Island pipistrelle (Pipistrellus murrayi, extinct in 2009), a bat that vanished from its namesake volcanic remnant.

Species extinctions are obviously very important in the long run, because such losses are irreversible and may have profound effects ranging from the depletion of Earth’s inspirational and esthetic resources to deterioration of ecosystem function and services (e.g., refs. 17 ⇓ ⇓ –20). The strong focus among scientists on species extinctions, however, conveys a common impression that Earth’s biota is not dramatically threatened, or is just slowly entering an episode of major biodiversity loss that need not generate deep concern now (e.g., ref. 21, but see also refs. 9, 11, 22). Thus, there might be sufficient time to address the decay of biodiversity later, or to develop technologies for “deextinction”—the possibility of the latter being an especially dangerous misimpression (see ref. 23). Specifically, this approach has led to the neglect of two critical aspects of the present extinction episode: (i) the disappearance of populations, which essentially always precedes species extinctions, and (ii) the rapid decrease in numbers of individuals within some of the remaining populations. A detailed analysis of the loss of individuals and populations makes the problem much clearer and more worrisome, and highlights a whole set of parameters that are increasingly critical in considering the Anthropocene’s biological extinction crisis.

In the last few decades, habitat loss, overexploitation, invasive organisms, pollution, toxification, and more recently climate disruption, as well as the interactions among these factors, have led to the catastrophic declines in both the numbers and sizes of populations of both common and rare vertebrate species (24 ⇓ ⇓ ⇓ –28). For example, several species of mammals that were relatively safe one or two decades ago are now endangered. In 2016, there were only 7,000 cheetahs in existence (29) and less than 5,000 Borneo and Sumatran orangutans (Pongo pygmaeus and P. abelli, respectively) (28). Populations of African lion (Panthera leo) dropped 43% since 1993 (30), pangolin (Manis spp.) populations have been decimated (31), and populations of giraffes dropped from around 115,000 individuals thought to be conspecific in 1985, to around 97,000 representing what is now recognized to be four species (Giraffa giraffa, G. tippelskirchi, G. reticulata, and G. camelopardalis) in 2015 (32).


Is the Modern Mass Extinction Overrated?

A fter decades of researching the impact that humans are having on animal and plant species around the world, Chris Thomas has a simple message: Cheer up. Yes, we’ve wiped out woolly mammoths and ground sloths, and are finishing off black rhinos and Siberian tigers, but the doom is not all gloom. Myriad species, thanks in large part to humans who inadvertently transport them around the world, have blossomed in new regions, mated with like species and formed new hybrids that have themselves gone forth and prospered. We’re talking mammals, birds, trees, insects, microbes—all your flora and fauna. “Virtually all countries and islands in the world have experienced substantial increases in the numbers of species that can be found in and on them,” writes Thomas in his new book, Inheritors of the Earth: How Nature Is Thriving in an Age of Extinction.

Thomas is a professor of conservation biology at the University of York in England. He is not easily pigeonholed. He has been a go-to scientist for the media and lawmakers on how climate change is scorching the life out of animals and plants. At the same time he can turn around and write, “Wild geese, swans, storks, herons and cranes are returning as well, and the great whales, the largest animals ever to have lived on Earth, are once more plying their way across our seaways in numbers after centuries of unsustainable butchery.” Glass half empty, meet Chris Thomas.

WHY HE WRITES: “I’m concerned a lot of resources being spent on conservation are focused on trying to keep things exactly as they are, or revert to some imagined past,” says Chris Thomas (above). “As great as those aspirations might be, in the long run, they’re doomed.”

Inheritors of the Earth collects years of Thomas’ field research, illuminating plant and animal species—notably one of his specialties, butterflies—flourishing all over the Earth. Thomas also puts big ideas on display. Humans are just another animal on the planet, he wants us to know. Our actions are not outside the engine of evolution, even though we have the most horsepower. Environmentalists need to stop fencing off nature from humans, he argues, understand the mechanics of evolution better, including our role in it, and quit being such nattering nabobs of negativity. Once they do all those things, real conservation has a chance. The Sixth Great Extinction, he tells us, is premature.

There may be a bit too much of Dr. Pangloss in Inheritors of the Earth, and despite its ample footnotes, I would have liked to have learned more about how Thomas quantifies some of his general assertions about increases in species. I did ask Thomas to cite the research he has drawn from to support his views, and he responded with the names of five scientists who have influenced him. You can read his answer in a footnote at the end of the interview. 1 (I didn’t include it because it seemed kind of wonky.) In any event, Thomas was a pleasure to talk to. What is it about a wry Englishman that so enchants an American interviewer? Thomas and I had a jolly conversation, even if it got contentious at times, as I reminded him of the environmental wreckage that hung like a dark cloud over his thesis.

You write, “It is entirely possible that the long-term consequence of the evolution of Homo sapiens will be to increase the number of species on the Earth’s land surface.” That sure goes against the grain of what we have been hearing for generations.

What first caused you to you come to that conclusion?

I knew there was a new hybrid plant living in my hometown of York, England, and nowhere else in the world, and I had also heard about a new kind of fly evolving on introduced apple trees in North America. I started to reflect on the fact that so many of our crop plants started out as hybrids between different species. So I privately asked myself: How many new species might come into existence because of humans? All I needed was a pencil and the back of an envelope for my first calculation. I was gobsmacked, and eventually pleased with my preliminary answer. I reckoned that we might, very roughly, double the number of species on Earth over the next million years. Brought up on stories of extinction and environmental doom, it took me several years to believe my own answer.

Give us a convincing example of how humans boost the number of species.

The Italian sparrow is a really good example of a rapid evolution of a new species. It began when the house sparrow colonized out of Asia, following the development of agriculture. In the Mediterranean Basin, it met the Spanish sparrow. At some point, probably about 6,000 years ago, the house sparrow and the Spanish sparrow hybridized, and their offspring became sufficiently genetically distinct. Although they can interbreed with both of their parents, they basically don’t. So a new species came into existence by hybridization. I really like this example because the Italian sparrow has probably already survived for several thousand years. It’s not one of these species that come into existence and suddenly disappear.

Yes, there are monsters. Biodiversity is not a one-way street to a beautiful, happy world.

Most of the new hybrids exist because we humans have either deliberately or accidentally brought the parents—which used to live in different parts of the world—into contact with one another. This is an extraordinary feature of the modern world. There has been no time in the history of life when species have been mixed up within and between continents at the rate that’s going on at the moment. The consequence of this human-caused transport is that hybrids must be coming into existence faster than ever before.

Is there a mammal that fits your scenario? Mammals have not fared well with humans.

You are quite right. The heavyweight, large body-sized mammals are where we have most systematically exterminated other species over the last 60,000 years. There’s no doubt about that whatsoever. But hybridization is taking place in mammals too, when they’ve been introduced to new locations. In Britain, the native red deer has been mating with the sika deer. There’s some hybridization among the wapiti, or elk, and red deer. Presumably, these new populations will start to diverge with a new mixture of genes that they didn’t have previously.

In 1997, the biologist E.O. Wilson wrote, “Extinction is now proceeding thousands of times faster than the production of new species.” Is that just wrong?

At the time he wrote that, nobody had made any estimate whatsoever of the current speciation rate. It was based on a presumption that the present-day speciation rate is the same that it appears to have been in the long-term historical past. For animals, particularly vertebrates, it’s pretty clear that over the last few thousand years, the extinction rate has indeed been a lot higher than the speciation rate. However, it’s not so obvious for plants. If you take the mainland North America north of Mexican border, for which there’s good data, and mainland Europe, we know of more hybrid plant species in both of these regions that have come into existence over the last 300 years than we know of plant species that have become completely extinct.

I’m not disputing that what Wilson and others are talking about is real. What I’m saying is that, simultaneously, large numbers of biological gains are also going on, and that they are at least as worthy of scientific study as the losses. As environmental managers and conservationists, we should start incorporating these gains into our thinking of how we manage the planet, rather than taking a stance of simply trying to fight the losses.

How do we benefit by taking those gains into account?

It depends on what sort of gain you are talking about. A number of scientists have suggested the benefits of ecosystems to humans may increase with the number of species in an ecosystem. Most ecologists accept that various plants can stabilize the soil, purify water, or fix carbon from the atmosphere, and so on. If so, then why should these services not also be provided by so-called non-native species? There’s no clear evidence that the old ones are better than new arrivals at doing these ecological jobs. The fact that new species are becoming established in our new, disturbed environmental conditions, suggests that non-native species could actually be better at these jobs. If you were to say, “My standpoint is that ecosystems are degraded by the loss of the former diversity,” then you might think that the ecosystem service has declined. But that argument doesn’t follow once you take into account the balance in gains.

CLOSE UP: Look close and species are flourishing everywhere, says Chris Thomas. On his own land in York, England, “I have counted 22 butterfly species, 15 types of dragonflies and damselflies, 92 bird species, and 19 different kinds of mammals,” he writes in Inheritors of the Earth.

Tell us why you dug a hole on your property.

I live in the Vale of York, a flat area of Northeastern England. The farther down you dig, the further back you go in history. When I got down a meter or so, past layers of sand, I hit this goopy clay. It turns out this clay was laid down at the bottom of a lake that was at the edge of the ice sheets 15,000 years ago. This was a community that might have had the odd polar bear swimming in it. It would have had Arctic fish, and you could imagine early hunters might have gone fishing and tried to kill reindeer to get fur and meat. But when the climate started to warm, the ice melted, and this resulted in the whole lake draining very rapidly.

The take-home message is that every biological community that’s been on this land for at least the last 10,000 years has itself been a transient assemblage of species. As humans are changing the world and warming the climate, a new transient set of species are arriving, and they will in turn be replaced by others. The replacement of species is a normal operation of our biological planet. Species survive by moving from one place to another, not necessarily by surviving in exactly the same place in the long term. Yet many of our environmental strategies are about trying to keep things as they are. The way nature survives is often by moving around, not by staying as it is.

“Species come and go with the vagaries of the Earth’s climate,” you write. That sounds so nonchalant. Let’s look at a species that gets people fired up: the polar bear. Do we not agree its habitat is under threat from a warming planet, that its food sources are dying?

We do indeed. And I gave an assessment as to whether the polar bear should be listed as threatened as an endangered species in North America. I argued that it should. Although I’m pointing out that many species are successful, I also point out that many are not being successful, and the critical thing to do is to reduce our greenhouse gas emissions to minimize the amount of climate warming that takes place. That’s what’s going to reduce the number of species that are endangered from climate change. Everything else is like putting a sticking plaster on a gaping wound.

Couldn’t climate skeptics use your statements to defend their views that global warming is overblown?

But you’re right, the polar bear is the poster child of endangerment from climate change. What do we do about it? Well, the polar bear is a recently evolved type of bear, having come into existence during the Ice Ages of the last couple of million years. It can still hybridize with the brown bear. Let’s say, though, you want preserve the polar bear. Are you going to shoot brown bears so they don’t hybridize with the polar bears? That’s gonna be a tricky thing to do. Are you going to move them to Antarctica where they would be very happy? There would be ecological Armageddon. They would eat their way through the penguin and seal colonies.

There are going to be some types of species in the future that are probably just not going to hack it. We have to decide what resources we’re going to put into trying to keep them going. In the case of the polar bear, we know the overwhelming threat is climate warming. We know that it is a result of human-generated greenhouse gases, and we know how we can at least reduce the rate at which it declines and minimize the risk of its final extinction.

Short of arresting global warming, are you saying, “We just have to stand back and reconcile ourselves with the fact that the polar bear may hybridize into a brown bear. There’s nothing we can do about that.”

Yes. In the case of polar bears, there’s nowhere north of the North Pole they can go. They’re kind of stuffed. Fortunately there aren’t so many species that live so far north. Far more species threatened from climate change live on tropical mountains. If you were to imagine species that were restricted to mountains somewhere in Central America, one could ask, “What proportion, if any of them, would be able to establish elsewhere?” They can’t get down to the hot lowlands and then go up another mountain range somewhere else, say one which is a bit higher and cooler for them. They can’t do it on their own, so could we as humans transport a fraction of those species and reduce the extinction rate? That tends to fall outside traditional conservation thinking. They would be seen as non-native species, and potentially detrimental. But if we take this longer-term view, then we can potentially reduce the extinction rate compared to what it would be otherwise.

Do you personally think that’s a good idea?

I personally do, yes. In the long-run, the world’s ecosystems—and we—rely on the species that currently live on Earth and their descendants. Since we have no real idea what people will do to the planet over the next thousand years or so, keeping the present species alive somewhere, on the off-chance that they will be suited to the new conditions, seems like a reasonable long-term biological insurance policy. It is entirely logical that we should try to maintain as many of them alive as possible for future generations, whether or not they turn out to be important.

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Let’s stay with climate change for a second more. You write, “Given how many species live in the hottest parts of the world, it is not surprising that the average biological diversity per square kilometer of the world goes up when the climate warms.” I have to say, climate skeptics could easily use statements like that to defend their views that global warming is overblown.

So what would you say to climate skeptics who would use your book to buttress their views?

What I would say is climate change has paradoxical effects on biological diversity. It’s threatened a large number of species. There’s a strong consensus on that in the scientific community, although there is no consensus as to exactly what percentage are endangered. People seem to think it’ll be 10 or so percent of the world’s species that might be endangered, and many of these are these mountain species with nowhere to run.

However, there are more species close to the equator than elsewhere, and they will spread. Just this morning I saw a little egret fishing on the edge of my university lake in Yorkshire. It only started to breed in Britain a couple of decades ago, and it can already be seen in half the country. Southerners like the egret moving north as the climate warms. The result? The biodiversity of some areas of the world is starting to increase because the rate of arrival of new species slightly exceeds the rate of departure of those for which it is no longer suitable.

Life is just what happens, and unfortunately, or fortunately, it has no ultimate purpose.

So why should we be concerned? Well, the loss of the cold-adapted species is potentially a long-term concern, because if the climate ever becomes cooler again, and we’re still in a long-term Ice Age, these are the species that will thrive and become common in the future. They will be the key players in future ecosystems. Secondly, if we lose 10 percent of the species to climate change, then we have thrown 10 percent of the biological opportunity of the world for future generations. It’s a paradoxical thing. Gains in some places, but extinctions of others.

If extinction of whole species does not convince skeptics, I’d just say, “New Orleans and London, not to mention the farmers of Bangladesh.” They are going to be in deep trouble once the sea levels rise seriously. Although that doesn’t happen very fast within an individual lifetime, it is an inexorable process that once it has started cannot be stopped for thousands of years. Therefore we are effectively sealing the fate of humanity to live on a smaller area of land on the planet.

THE HYBRID: “The more people look, the more it seems hybridization is the norm,” Chris Thomas writes. That goes for the polar bear. “Alaskan grizzlies have polar bear genes in every cell of their bodies,” Thomas notes. Polar bears may one day breed with a bear species in a warm climate.

You tell us this loss of around 10 percent of species “falls far below the level of extinction (75 percent plus) required to match one of the previous ‘Big Five’ mass extinctions in the geological past.” Is the Sixth Extinction overrated?

Well, I agree there has been a huge acceleration of the extinction rate in the human epoch, and that if we keep up the current rate of extinction for the next 10,000 years, we end up with a mass extinction of 75 percent of species going extinct. That is equivalent to the percentage that went extinct when the dinosaurs died out. And 10,000 years or even 100,000 years is an extraordinarily short period in geological history.

But could it be that we’re spurring evolution too fast? Maybe the rate at which the change is going on now, compared to the past, is too fast for there to be corrections.

Evolution is a process. It can’t be too fast or too slow. It just happens. Under some circumstances it’s faster and slower. By and large, the faster the environment changes, the faster evolution takes place, because some lineages are lost and some are able to diversify under the new conditions. Yes, there could be a rate of change that was so fast that evolutionary adaptations were incapable of keeping up with it. But there isn’t any evidence at the moment that we are beyond some kind of tipping point beyond which evolution can’t hack it any longer. Look at how fast things evolve resistance to pesticides, or how many species manage to colonize new parts of the world that we have disturbed.

Why do you call Earth “Anthropocene Park?”

To focus our thinking on the fact that we are both the inmates of the park and its managers. And to take issue with the dream of unaffected nature. A park is a modified environment and so calling our world Anthropocene Park gets us away from thinking there are any places unaffected by us. Every decision we make, or every time we decide not to intervene, has an influence on the biodiversity of a particular place and on the planet as a whole. Like it or not, we are managing the world species and ecosystems. We have to get used to that. We are part of the system.

Are there monsters in the park?

There’s a certain pink primate in the park. Well, I don’t mean “pink” because that’s a thoroughly narrow view of the world. I would like to unsay it. I’ll say “naked” primate. But, yes, absolutely, there are monsters. There are pathogens. Biodiversity is not a one-way street to a beautiful, happy world. There are elements of biodiversity that are harmful to us and other things. I am happy to rejoice at the extinction of smallpox and other diseases that affect us and our livestock because they seriously interfere with the capacity of humans to live on the planet.

You’ve just got to get real that every biological system is modified by us.

You write, “Humans are natural within the Earth system, so anything we do is also a natural part of the evolutionary history of life.” Well, what do you mean by “natural?” That would imply there is an “unnatural.” How do you differentiate the two?

You spotted the fatal flaw! But if I’m not allowed to use the word “natural,” and I accept it has no special meaning, I would just have to say that the Earth’s system is simply what it is: It now contains the human species as well as other species. That is the system we have, but we cannot distinguish between the human parts from the inhuman parts. Humans evolve within the system, so we are part of the system. Unless you go deep into rocks or some such location, you cannot identify locations where the impacts of humans are zero.

OK, but wouldn’t you agree that a lot of the natural things we do are awfully destructive? Are you saying they’re just part of a natural way?

Sure, humans have changed the world a lot, and some of the changes do look like destruction. But destruction is a bit of a subjective word. Normally we change one type of habitat into another. You’ve just got to get real that every biological system is modified by us. I’d argue that conservationists should throw off their apparent reluctance to do so-called unnatural things. Let’s ensure that positive things happen to the natural world as well, however that might be achieved. Why tie our hands behind our backs when we try to fight for nature? The forces of industry, some of whom are less concerned about nature, are not tying their hands behind their backs.

We’re the species with the big brain. We have the technology and ability to shape the natural world to our own ends. Do you think we have an ethical responsibility to conserve nature?

Not really, but human society as a whole does tend to quite like a lot of things about wildlife and the environment. And that goes for me too. From our perspective, we would rather live in a green world full of animals and plants. Therefore we might wish to intervene to ensure that that is the case.

But I don’t feel there is any ethical duty to do this. Life is just what happens, and unfortunately, or fortunately, it has no ultimate purpose. It came into existence, it will exist for a while, and eventually it will disappear. Conservation is more about humanity’s perspective on the now and the relatively near future, by which I might mean millions of years. But in terms of conserving life in the universe, I don’t think there is any essential ethical requirement for us to do it.

Why do you say that conservation and the environmental movement are “backward-facing?”

If you want to measure how the state of the world is changing, and that’s a valuable thing to do, you need some kind of reference point. It’s natural we take some past point and monitor things into the future. But when you reference back to some time in the past to identify how things are changed, it tempts us to think that this baseline is a more idealized way the world was or should be. Then you tend to think that the environment is deteriorating, when it may just be changing.

I also think that there’s the human social perspective. Many of us are reflecting on our childhoods, or maybe things that we have read about. In England we have loads of cultural traditions about snowy Christmases because there was a string of snowy years when Charles Dickens was a child, and he wrote about them. It’s well-known in social science circles that people often imagine a time, in the relatively recent-to-medium past, that was an idealized state of the world.

The difficulty is time goes forward. The biological processes of the birth and death of individuals, the better survival of some species than others, the evolution of new genetic types—all of the biological processes that take place on the planet—are dynamic ones. The expectation that things should stay exactly as they are is not a realistic expectation of the biological systems of the world.

Looking backward is really informative. It’s extremely valuable. Don’t get me wrong. But we should also, in our aspirations, look forward to how we might make things better for ourselves, even if that “better for ourselves” and whatever we care about, such as wildlife, becomes less like it was in the past.

How did a pessimistic narrative get so ingrained in environmentalism and conservation?

Well, you may not be able to quote this, but shit happens. Species have gone extinct, and we as humans have caused those extinctions. We nearly killed off the great whales just as we killed off many of the world’s great land mammals. North America doesn’t have ground sloths wandering around in it today because our human ancestors killed them. Those bad things are really clear, and they leave a very strong impression on us. There are positive trends, but the positive trends do not generate additional inconvenience to us, so we don’t respond to them very much.

You want conservationists and science and environmental writers to do a better job. How should we?

I think we should ask, “How could I increase biodiversity or promote biological gains?” whenever we consider a question like “How can I stop something declining?” These are complementary questions. Both are valid. It’s clear to me that we also need a lot more systematic scientific analysis of the balances of gains and losses. We need to know this for different metrics of biological diversity, on different timescales and for different spatial scales, and also in different parts of the world. That information is starting to come together, but that process of bringing it together is far from complete at the moment.

This might be a shock, but every scientist is actually a human, and they come with their own personal baggage. Although we might agree on the data, very often people will disagree about the interpretation, not because of a data difference, but because of the personal lens through which they are seeing it. So science writers should always be aware of where a particular scientist is coming from.

That’s great advice. Where are you coming from?

I walked into that one. The confusing answer is from all sorts of directions at once! I still accept many of the dire messages of environmental doom. But now I hold another set of generally more hopeful views. Some of them are “as well” opinions, others have replaced what I previously thought. The first time I came to the conclusion that humans might increase the number of species in the world made me shudder—I still remember the moment—because it was so shocking to my previous beliefs. For me, both as a person and as a scientist, I’m now really happy about this. Changing my mind on all sorts of previously cherished opinions means I’ve really learned something. Whether it has led to any new clarity of thought I leave others to judge.

1. Dov Sax at Brown University has done important research. He started with the Hawaiian islands and U.S. states, where, on average, the number of species in each region has been tending to increase—more species arrive, often through human transport, than have been disappearing. In fact, the numbers of incoming species has increasing in most parts of the world. I am also aware of recent studies by Mark Vellend and Maria Dornelas suggesting that if you monitor local diversity in many parts of the world, you find that it hasn’t been going down. Which species are present in a particular location has been changing, but the actual number of species has not been declining.

Then, from the evolutionary perspective, I had been reading studies by geneticists, people like Jim Mallet and Richard Abbott, interested in the process of speciation. Ever since Darwin, geneticists have been besotted by speciation. They’ve been trying to understand the processes by which populations evolve into new species and new hybrids come into existence. People have been asking for years, “What’s the extinction rate?” Everyone knows it’s high. But they never stepped back and asked, “What’s the speciation rate?” The moment you ask that question, it becomes fairly obvious it’s increasing.


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