Megafauna Extinction Rewrite

Greetings!  After three years of sharing rough draft sections, I’ve begun rereading the book from page one, and cleaning it up.  The first 70 pages went pretty smoothly.  Then came the discussion related to megafauna extinctions (samples 18 to 21).  It needed attention.  The following is a shorter and clearer rewrite.

MEGAFAUNA EXTINCTIONS

This morning, during your invigorating walk to work, school, or wherever, you probably didn’t worry about being devoured by a hungry saber-tooth cat.  Did you see a single cave bear or woolly mammoth?  As the human herd has expanded, the population of wild megafauna has sharply declined, and many species have gone extinct.  Megafauna are mammals weighing more than 100 pounds (45 kg).  Megafauna critters include herbivores, carnivores, and omnivores — both wild and domesticated.  You are a megafauna, and so am I.

Large herbivores have played a starring role in our ancestors’ evolutionary journey, because they enabled the survival of our lineage.  Look in the mirror.  Look at the folks on the sidewalk.  Our bodies are far different from our closest relatives, the chimps and bonobos.  We have the bodies of persistence hunters, folks who can run for hours in pursuit of a hot lunch, folks skilled at killing large animals.  These hunting skills gave us the ability to colonize six continents, and radically alter their ecosystems.

Before we proceed, please understand that prehistoric dates and extinction counts are estimates.  Different sources present different numbers.

Blitzkrieg Overkill

Paul Martin is essentially the poster boy for megafauna extinction.  He sparked intense controversy with his theory that many of the extinctions in North America essentially took place during a thousand year “blitzkrieg” (lightning war) of overhunting.  Most estimates date the North American extinction spasm somewhere around 13,500 to 10,000 years ago. 

In 1956, Martin’s research involved visiting caves in multiple locations and analyzing piles of ground sloth turds.  As he dug through the dung, he focused his attention on the pollen and fungal spore contents in each layer.  As he dated his findings, he noticed an odd pattern.  Sloths in Arizona had disappeared several centuries earlier than in South America.  Also, on the islands of the West Indies, they survived an additional 3,000 years longer than in mainland regions (hunters didn’t have boats at first).  Dates of extinctions indicated how hunters had colonized the New World — from Alaska, they migrated southward, to Central America, and then throughout South America. 

By 1966, a daunting new hypothesis had hatched in the space between Martin’s ears.  Megafauna extinctions were not just an American thing, they had happened around the world.  In this updated hypothesis, extinctions began more than a million years ago in Mother Africa, the original hominin homeland.  Then, like a gradual cascade of falling dominos, they moved on to Australia, Eurasia, North America, and finally South America. 

Australia lost 15 out of 16 genera of vertebrate megafauna, including giant reptiles and marsupials.  Europe lost 21 of 37 genera of megafauna, Asia lost 24 of 46, North America lost 45 of 61, and South America lost 58 of 71.  What’s a genera?  It’s the plural of genus.  A genus is a category of closely related species.  For example, the Homo genus includes Homo sapiens, Homo neanderthalensis, Homo erectus, and so on (12 different species). 

Australia and the Americas got hit especially hard because the megafauna had not lived for thousands of years along with humans, Neanderthals, or other hominins.  They had not coevolved with humans, and learned that we were dangerous.  Martin created a chart showing the correspondence between human colonization and extinctions.  [LOOK] 

Fernando Fernandez described the bottom line.  “About two thirds of all animal species larger than 50 kg (the so-called megafauna) were extinct from the late Pleistocene onwards, starting in Australia at about fifty thousand years ago and following humans’ footsteps in their expansion throughout Eurasia and the Americas.”  In the era between 50,000 years ago and 500 years ago, at least 97 of 150 genera of the world’s large terrestrial mammals blinked out forever.  The scope of his paper did not include the earlier extinctions in Africa, which were also severe (more on them below).

For mentally alert critical thinkers, it’s difficult to imagine folks with spears and arrows, traveling by foot, in a roadless wilderness, wiping out all the horses, mammoths, saber-tooth cats, and so on, across an entire continent.  Martin’s theory can sound utterly ridiculous — until you evaluate the less compelling alternative theories.  It’s very important to understand that few, if any, extinctions were quickies, many took more than a thousand years.

Native Americans were especially offended by Martin.  The overkill hypothesis implied that their ancestors had foolishly hunted way too hard.  His theory was racist, hateful, and wrong.  Today, anyone can see that the ultimate champions of furious destruction were the civilized settlers who stole their ancestral homeland, and went totally berserk on the ecosystem.  In his book, Red Earth, White Lies, Lakota historian Vine Deloria described, with righteous vigor, why Martin’s overkill hypothesis was absolutely wrong.

Native Americans are also not fond of the notion that their ancient ancestors originally came from the Old World.  In their traditions, America has been their home forever, since the dawn of creation.  Similarly, the white settlers remain extremely uncomfortable with the notion that the roots of their family tree lie deep in Mother Africa.  For many thousands of years, most generations of their ancestors had beautiful brown skin and curly hair (gasp!).

Obviously, Native Americans lived far more simply and gently.  In the good old days, they had no horses, wheels, or iron.  Early white colonists were astonished by the vitality of New World ecosystems, with their expansive forests, clean water, and fantastic abundance of wildlife.  But Lewis and Clark, and other pioneers, mentioned events when natives killed more game than they needed, wasting meat and hides.

Dan Flores wrote that the Cree tribe believed that the numbers of bison were essentially infinite, and that the animals they killed in no way diminished their abundance.  William Dobak mentioned an Assiniboine legend that the bison will live as long as the people, and there will be no end of them until the end of time.  Shepard Krech wrote that the Powhatan tribe hunted throughout the year, and killed animals regardless of their age, sex, or breeding state.  The Cherokee believed that every deer they killed was reanimated, each would be replaced.

William Hornaday wrote about the American bison (commonly nicknamed buffalo).  Genuine buffalo live in sub-Saharan Africa and south Asia.  In the good old days, white observers described bison herds 25 miles wide, and 50 miles long (40 by 80 km), that took five days to pass — maybe 480,000 animals.  In 1889, when the bison were close to extinction, he wrote, “No wonder that the men of the West of those days, both white and red, thought it would be impossible to exterminate such a mighty multitude.  The Indians of some tribes believed that the buffaloes issued from the earth continually, and that the supply was necessarily inexhaustible.  And yet, in four short years the southern herd was almost totally annihilated.”  He wondered if elk, moose, caribou, mountain sheep, mountain goat, antelope, and black tail deer would still exist in 25 years. 

Baz Edmeades noted that the fantastic number of bison on the U.S. prairie in the 1840s was made possible by the fact that bison didn’t have to share the grassland with 12 species of large herbivores that went extinct earlier.  Charles Mann suspected that bison numbers exploded as a result of the sharp decline in the number of Native American hunters.  Smallpox travelled westward far faster than the white settlers, arriving on the plains by the 1730s.  Indians had no immunity.

For more than 40 years, many disgruntled experts have worked hard to disembowel Martin’s overkill hypothesis.  Todd Surovell and team, writing in 2016, were surprised to see that such a radically unusual idea could survive so many years of intense scrutiny.  But, for the most part, it has. 

It was a wacky-sounding idea, but it was lucky to be less wacky than the alternatives.  It’s vital to bear in mind that this isn’t a story about a few generations of fanatically insane exterminators (like U.S. bison killers).  Indeed, a thousand year process can take a very long time.  What were your ancestors doing a thousand years ago?  Where did they live?  What did they hunt? 

Imperceptible Overkill

Brook and Johnson, studying Australia, disliked the notion of “blitzkrieg overkill.”  They thought that “imperceptible overkill” was a much fairer description.  They created a computer model to analyze possible extinction paths for the giant marsupial, Diprotodon opoptatum.  The extinction process could have been very slow.  “We show that remarkably low levels of exploitation of juveniles (the equivalent of one or two kills per 10 people per year) would have been sufficient to drive these large species to extinction within centuries, as a consequence of their ‘slow’ life-histories.”

Martin’s notion of blitzkrieg overkill can only be seen as speedy when it is viewed from the mountaintop perspective of geological timeframes that span many thousands of years, even millions of years.  From the perspective of living hunters around a campfire, it’s possible that the megafauna extinctions may have never been noticed by the passing generations.  “Imperceptible overkill” is a more open-minded label, and it doesn’t have the stinky scent of Nazi invasions (“blitzkrieg”).

J. B. MacKinnon wrote about “shifting baseline syndrome,” or ecological amnesia.  Each of us tends to perceive the world of our childhood as the “normal” state of the ecosystem.  In the Florida Keys, photos of fishermen in the 1950s show the biggest fish as being as long as wide as the fishers.  Photos from 2007 show that most fish are about a foot long (30 cm).  We have “change blindness.”  We don’t notice changes that we aren’t paying direct attention to. 

Farley Mowat compared five centuries of old journals that mentioned wildlife.  Based on this, biologists concluded “that biomass — the total weight of living things — off North America’s east coast may have declined by 97 percent since written records began.”  Five hundred years ago, cod grew to seven feet long (2.1 m), and weighed up to 200 pounds (91 kg).  In 1984, the average cod was 6 pounds.  The fishery blinked out, and has never recovered.  No generation knows the land as their grandparents knew it. 

Fernando Fernandez noted that “the extinctions were a long process that took several millennia to occur in most continents.  …Killing large animals just slightly above their fertility rate could wipe them out over the passage of centuries.”  It wasn’t so much about the intensity of the hunting as the fragility of the hunted.  Prey often had no instinctive fear of humans.  Over a thousand years, and many generations of hunters, extinctions may have been essentially invisible.

Elizabeth Kolbert noted that modern elephants do not reach sexual maturity until their late teens, each pregnancy takes 22 months, and there are never twins.  Because they reproduce so slowly, mammoths could have been driven to extinction by nothing more than modest levels of hunting.  Doug Peacock estimated that taking only 4 or 5 percent of a slow breeding species could put them on a gradual path to extinction.  Peter Ward calculated that if hunters had regularly taken just two percent of the mammoths each year, the extinction process would have taken 400 years — too slow for each generation of hunters to notice.  Regardless of climate conditions, hunting alone would have wiped them out.

While the front lines of human colonization advanced, the yet to be explored human-free regions remained wild, free, and happy.  Small isolated bands of people were living in a vast wilderness, unaware of the current conditions in every surrounding hill and valley.  There was no way they could accurately monitor the populations of game animals.  When hunting was bad, they couldn’t know exactly why.  Was it a temporary dip, or time to move?

As long as the hunting was good, folks could stay where they were, and enjoy the delicious abundance.  Later, when the hunting eventually wheezed, the solution was to wander into the unmolested frontier and resume the feasting.  This was the engine of colonization.  They followed their stomachs.  For thousands of years, during the era of our species’ dispersal, few could foresee that they would eventually reach the end of wild abundance.

By the twentieth century, the wide open wild frontier was a distant memory.  There were now limits, boundaries, and regulations.  To carefully survive, if possible, tribes had to live with acute foresight and mindfulness.  Richard Nelson spent time with the Koyukon people of Alaska, and learned that moose, caribou, and salmon numbers varied from year to year.  When deer numbers declined, they stopped hunting them for several years, and ate other critters instead.  Also, when game was abundant, they would stop hunting in a portion of their domain, creating a refuge where game could get a break from hunting, and recharge their numbers. 

Megaherbivore Decline

Beware!  The science jargon now gets a bit slippery.  Megafauna weigh 100+ pounds (45+ kg).  A subset of megafauna is megaherbivores, plant eaters that weigh more than a metric ton: 2,200+ pounds (1,000+ kg).  Megaherbivore extinctions have rocked every continent.  

Alfred Crosby concluded that the human colonization of the world caused a general disaster among the rest of the family of life.  “Nothing this devastating had happened in millions of years.”  It was especially hard on huge animals.  “When the die-off ended, all land mammals of one metric ton or over, of which there had been numbers of species — mammoths, mastodons, ground sloths, woolly rhinos, giant kangaroos, and more — were gone, except in southern Asia and sub-Saharan Africa.”  These megaherbivores were the most desirable critters to kill, because they were slow, easy to find, and provided lots of meat. 

In the good old days, the megaherbivores’ massive body size and strength had boosted their ability to survive.  Then came the humans with projectile weapons.  We are the only predators that use atlatls, which allow us to kill from a distance, at far less risk of personal injury and premature death.  A modern hobbyist with an atlatl can hurl a dart right through a car door.  Darts can break elephant bones.  In 1961, Colin Turnbull wrote, “The Pygmies today still kill elephants single-handed, armed only with a short-handled spear.”  So, because of this advanced technology, jumbo body size lost much of its defensive advantage.  It became a disadvantage, often a death sentence, a trap door to extinction.

As the world’s megaherbivores blinked out, so did the carnivores that specialized in hunting the giants.  For example, several large cat species had long upper canine teeth or fangs.  These saber-tooth and scimitar-tooth cats were specialized for killing huge herbivores with very thick hides.  As their traditional large prey declined, the cats’ long fangs may have become a handicap for hunting smaller varieties of prey.  They were doomed by overspecialization, and were escorted off the stage by bad luck.

In Europe, several sites indicate that Neanderthal hunters had focused on nursery herds, consisting of mothers and their offspring.  It was much less dangerous to kill a young aurochs or steppe bison than to attack its huge and powerful daddy, who could easily splatter you into a puddle of bloody mush.

The far less dangerous way of bringing home mammoth steaks was to kill their smaller, weaker offspring.  Baz Edmeades noted that scimitar-tooth cats had a fondness for dining on youngsters.  In the Friesenhahn Cave in Bexar County, Texas, excavations revealed the remains of 33 cats, and 300 to 400 young mammoths, mostly two year olds. 

He added that the human youngsters 15,000 years ago were similarly vulnerable.  Their homeland did not sound like traffic and sirens, it sounded like moaning lions and whooping hyenas.  Wandering away from the camp at night was dangerous and dumb.  Babies instinctively cry when left alone too long.  Even our chimp and baboon cousins have been known to snatch and devour unattended infants.

Climate Shifts?

Native Americans aren’t the only group that is not fond of Martin’s overkill hypothesis.  Lisa Naagaoka and team pointed out that lots of archaeologists are also unconvinced.  Where is the compelling “smoking gun” crime scene evidence?  There isn’t much.  There aren’t even many sites where extinct megafauna and humans were found in the same region at the same time.  Martin pointed out that the archaeological record is not thorough and complete.  For the most part, it’s essentially an impressive collection of holes and gaps. 

In academia, specialists often work in closed circles, isolated from ideas buzzing around in the outer world.  Archaeologists hang out with archaeologists, and primarily read journals focused on their field.  Experts from a wide variety of specialties rarely gather together at the same pub every night, and engage in lively mind-expanding discussions until sunrise.  Naagaoka mentioned five theoretical reasons for the extinctions: hunting, climate change, disease, manmade landscape changes, and a combination of factors.  Archaeologists mostly vote for a combination, with climate being the primary suspect. 

Ice core research in Greenland has provided lots of information on climate trends going back 122,500 years.  It indicates that the extinct megafauna, and their human hunters, had managed to survive multiple super-frigid climate periods.  There is not a pattern of extinction surges corresponding to the ups and downs of glaciation cycles.  When temperatures got colder, cold adapted species expanded, and heat loving species migrated to warmer locations (and vice versa).

There isn’t specific overwhelming evidence linking frigid eras, disease, or landscape change with megafauna extinctions.  So, the general thinking, outside of the archaeology club, is that hunting played a role in every extinction spasm, and climate change may have played a secondary role, sometimes, maybe.  If climate change had been a primary cause of extinctions, then plants and small animals would have also been affected.  Martin noted that there is no evidence of this.  The most common victims everywhere were animals that had “low reproductive potential” — not species that bred like bunnies.

Ross MacPhee noted that the one possible exception is the extinctions in Sahul, the landmass of Australia, New Guinea, Tasmania, and neighboring islands when they were joined together by low sea levels.  In Sahul, evidence of early human activities is quite scarce.  It’s possible that climate change may have been a primary factor.  Amos Esty added, “Unlike other parts of the world, nothing in Australia’s fossil record proves that humans hunted megafauna.”

Alfred Crosby wondered why the alleged super-deadly climate shifts did not strike fast and hard, like an asteroid.  Why did they selectively zap nearby regions at different times — mainlands first, and offshore islands much later?  Why did extinctions tend to coincide with the advance of colonization: (1) humans arrive, (2) megafauna blink out?  Why did harsh climate events display little interest in hammering small critters, while almost exclusively focusing on megafauna?

Crosby wasn’t absolutely convinced that overkill was the one and only cause of the extinction spasms, but he was certain that humans are very unusual critters.  During every extinction event, humans are present, and play a major role.  Humans have become exceedingly clever at radical high speed change via cultural evolution — a powerful fork in the human saga.  Innovation is our middle name (and our curse).

Only humans drove herds off cliffs.  Only humans use fire to trap herds.  On a lucky afternoon, a dozen primitive hunters with atlatls can have a bloody excellent time.  Our uniqueness can also be a quirky two-edged sword.  Crosby wrote, “Homo sapiens is arguably the only species that commits genocide, which, we might note, might easily extend in practice to species suicide.”

Smoking Guns

The most compelling evidence that humans were the primary suspects turned out to be island extinctions.  Oceanic islands had a climate similar to the mainland, but extinctions came much later, when hungry hunters were eventually able to travel by boat.  For example, extinctions happened merely 4,700 years ago in Cuba, 1,500 years ago in Madagascar, 500 years ago in New Zealand, and so on.  Martin noted that on the islands of Cuba, Haiti, and Puerto Rico, ground sloths survived 5,000 years longer than on the mainland.  On the mainland, ground sloths were already extinct from Alaska to Patagonia.

Humans arrived in New Zealand between 800 and 1,000 years ago, and by 400 years ago the moas were extinct.  Moas were flightless ostrich-like birds that could grow to 10 feet (3 m) tall, and weigh 550 pounds (250 kg).  Many collections of moa bones have been found, some containing the remains of up to 90,000 birds.  Evidence suggests that a third of the meat was tossed away to rot.  Obviously, the birds were super-abundant and super-easy to kill, and the hunters had no perception of limits.

Humans arrived in Madagascar around 2,000 years ago.  The island is located east of the African mainland, and its climate is similar.  Isolated from the outer world for several million years, it has been home to a unique collection of fauna.  Seventeen species of giant lemurs went extinct, some as recently as 400 years ago.  Also gone are the half-ton elephant birds, pygmy hippos, carnivorous giant fossas, and others — a heartbreaking tragedy.

Mother Africa

Mother Africa was the original homeland of the hominin family.  Lars Werdelin, an expert on ancient carnivores, wrote: “Hominins seem to have become routine hunters between 1.8 and 1.6 million years ago.  With rapidly evolving intelligence and teamwork, hominins were able to level the playing field.”  And, “between 2 and 1.5 million years ago, the number of large carnivore species began to nosedive.  Entire groups of species disappeared.  The steep downturn was 1.5 million years ago.”

Peter Ungar noted that in the archaeological record, the quantity of animal remains and artifacts significantly increased around 2 million years ago.  At that time, there were at least four different hominin species living in Africa.  Hominins were eating antelopes, hippos, horses, giraffes, and elephants.  This indicates the promotion of bipedal primates into the elite club of large predators.

The African continent was loaded with megafauna 1.8 million years ago, but many were gone by 1.4 million years ago.  Edmeades mentioned that at the Olduvai Gorge site in Tanzania, they have found bones dating back 1.8 million years, including megaherbivores like rhinos, hippos, and elephants.  The bones were marked by signs of butchering.

He noted that in the good old days, Africa had nine species of big cats (three today), up to twelve species of elephants (one today), and at least four types of hippos (one today).  There were giant antelopes, giant hyenas, giant pigs, giant monkeys, giant baboons, and many others — all gone.  Over the course of many thousands of years, there was a significant change in the mix of players remaining on the savannah. 

Saber-tooth cats emerged in Africa around 12 million years ago.  Over time, they spread across Eurasia and the Americas.  In Africa, they went extinct 1.4 million years ago.  So did most megaherbivores (animals more than 2,200 pounds or 1,000 kg).  Coincidentally, Homo erectus emerged around 1.5 million years ago.   Erectus was the first advanced hominin, having a brain larger than average for its body size.  This era corresponds to the oldest known evidence of domesticated fire.  Today, only two percent of the original African large carnivore species still survive.

Some species that disappeared in Africa continued to survive on other continents.  Edmeades emphasized that during the African wave of extinctions, there were no similar extinction blips in Siberia, Europe, Australia, or the Americas — regions where zero hominins resided.  In these other regions, many megafauna species remained fat and happy for maybe another million years or so.

Eurasia

The Eurasian extinctions were far more gradual than those in the Americas.  This is likely because the megafauna had lived around hominin hunters for a long time.  For example, Homo heidelbergensis lived in Europe 500,000 years ago, and Neanderthals had appeared by 300,000 years ago.   

Bernardo Araujo and team studied climate models for the last 122,500 years.  For 19 regions, they compared the dates when humans arrived, with the dates when megafauna species went extinct.  They found that humans were entering Europe and Central Russia about 45,000 years ago.  In the colonized regions of Eurasia, extinction dates began about 40,000 years ago, and continued until about 10,000 years ago — the longest of the megafauna extinction cycles outside of Africa.

Araujo emphasized that our colonization of Eurasia was a significant turning point in the human colonization of the planet.  It was the first time that our fully tropical species was moving into regions that were colder than the conditions for which evolution had fine-tuned us.  It was far more challenging for humans to survive in snow country.  Cleverness was mandatory.

Fernando Fernandez reported that in Eurasia, megafauna extinctions corresponded with the arrival of human colonists, not climate swings.  Most of the extinctions occurred in two spasms — roughly from 45,000 to 20,000 years ago in the warmer Mediterranean south, and from 14,000 to 9,000 years ago in the cooler north. 

Two million years ago in Africa, our pre-human hominin ancestors were smaller, and still learning the tricks of big game hunting.  So, the extinctions were a long slow process.  The hunters who later colonized Eurasia were bigger, stronger, more skillful, and better armed.  Let’s take a brief peek at a few of the species that blinked out in Europe.  Most had been around for a long time, and survived multiple ice ages.

The elephant-like family originated in Africa, and eventually colonized the five continents, diversifying into many forms.  Mammoths emerged in South Africa about five million years ago.  By 2.6 million years ago, they had spread across Eurasia and North America. 

Woolly Mammoths emerged 400,000 years ago in Eurasia, and went extinct in Europe 10,000 years ago.  In Asia, several hundred dwarf mammoths survived until about 3,700 years ago, on Wrangel Island, off the north coast of Siberia. 

Straight-tusked elephants were in Europe by around 780,000 years ago, and vanished 30,000 years ago.

Irish “elk” were actually a species of large deer (not elk).  They could weigh more than 2,500 pounds (1,133 kg), and their enormous antlers weighed more than the animal’s skeleton.  They could spread up to 13 feet (4 m) across.  They survived for several million years, including 400,000 years in Europe.  The last ones died 7,700 years ago in the Ural Mountains.  They lived throughout Europe, east to Siberia and China, and south to northern Africa.

Cave hyenas were gone by 13,000 years ago, after 3.5 million years on Earth.  They dined primarily on horses, steppe wisent, and woolly rhinoceros.  Large hyenas could weigh up to 225 pounds (102 kg).  They inhabited northern Africa, the Middle East, and much of Europe and Asia.

Cave bears emerged about 1.2 million years ago, and vanished 29,500 years ago.  They ranged from Britain and Spain, east across much of Europe, and into Russia and Iran.

European cave lions were quite similar to the lions still alive in Africa.  The two lines diverged about 1.9 million years ago, and the European cats went extinct 13,000 years ago.  They ranged in a wide belt from Spain and southern England, to Siberia, Alaska, and the Yukon.

European hippopotamus ranged across Europe, from Spain to Britain to Greece.  They emerged 1.8 million years ago, and went extinct 24,000 years ago.

Woolly rhinoceroses were living on the Tibetan Plateau 3.6 million years ago.  They were common throughout Europe and northern Asia, from Spain to China.  They survived until 10,000 years ago.

In London, buried under the city, construction crews have discovered the remains of hippos, elephants, Irish elk, aurochs, and lions. 

The Americas

Edmeades summed it up nicely: “With its giant bears, giant beavers, giant armadillo-like species, giant tortoises, and its giant ground sloth species, North America was, without exaggeration, a super-Serengeti containing many more big-animal species than present-day Africa.”

Megafauna in the Old World had lived around humans for a very long time.  They were likely to know that we were terribly dangerous (run!).  This was not the case in the New World, where human space aliens had appeared more suddenly.  The New World was hit hardest of all.  In North America, when humans arrived, there were at least nine species of big cats, and seven species of elephants.  The biodiversity was incredible.

Fernando Fernandez reported that the North American extinctions mostly occurred between 13,500 and 11,000 years ago.  Experts still disagree when humans first arrived on the continent, suggesting dates usually ranging from 20,000 to 13,000 years ago.  By the time humans entered North America, they had already developed effective tools and strategies for succeeding in snow country.  These preparations made a faster dispersal possible.  South American extinctions mostly took place between 13,000 and 7,800 years ago.

Fernandez presented a list of arguments why climate change was not the primary cause of megafauna extinctions.  (1) The pattern of extinction spasms had little association with the preceding pattern of 31 intense glacial cycles.  (2) Many species that vanished had been around for a million years or more.  (3) Extinctions occurred first on continental mainlands, while species on isolated islands in the same region, with the same climate, survived much longer.  (4) When extinctions took place in a region, there is no evidence that plant species were zapped by climate swings at the same time.  (5) It was the large animals that blinked out (the preferred game of hunters).  Small animals did not vanish in the same era (like they might have during a climate shift). 

He did note that glacial cycles could have stressed ecosystems, making some species less resilient, but he concluded that “low reproductive potential was the main determinant of the extinct species.”  Importantly, “the pieces of the puzzle immediately fit together when we observe the clear correspondence between the dates of humans’ arrival and of megafaunal extinction in each landmass.” 

The reason why human evidence is rarely found close to mammoth remains is that mammoths spent five million years on Earth.  Most of them died without ever seeing a human.  Big bones are more likely to survive the passage of time. 

Richard Manning chatted with Paul Martin.  During the North American extinction spasm, some megafauna species survived, and some went extinct.  The survivors included the moose, bison, caribou, elk, deer, grizzly bears, black bears, musk ox, and pronghorn antelope.  Of these, the only species that originally evolved in America was the pronghorns.  They have been here for 25 million years. 

The others were immigrants from the Old World that had crossed the land bridge into the New World.  These immigrants had survived for thousands of years in regions where humans hunted them.  They were absolutely aware that humans were dangerous critters.  At first, the indigenous American megafauna had no experience with humans, and no instinctive fear of them.  They were sitting ducks. 

Evolution had provided the pronghorns with the ability to zoom across the land at 70 miles per hour (112 km/h), so they could avoid being eaten by speedy American cheetahs.  Dan Flores noted that the speedy cats had all gone extinct prior to 10,000 years ago.  Today, pronghorns are very well adapted to a reality that no longer exists.  Unfortunately, they are unable to leap fences, a fact that delights their cowboy neighbors.  In 1892, Texas homesteaders found 1,500 pronghorns trapped by a fence and killed them.  By 1900, they had declined from at least 15 million to 13,000.  Today there are maybe 700,000.

To put the North American extinctions in context, let’s take a peek at some of the evidence.  Elephant family species immigrated into America from 1 to 15 million years ago.  There were at least seven varieties (mammoths, mastodons, etc.).  They survived until 13,000 years ago, with one exception.  America’s last mammoths died 5,600 years ago on St Paul Island in Alaska’s Pribilof Islands.  This island was once part of mainland Beringia, the land bridge from Siberia to Alaska.  Later, as sea levels rose, it became an island.

Horses originated in North America about 4 million years ago, and later spread into South America, Asia, Europe, and Africa.  They were extinct in North and South America by 8,000 years ago.

Saber-tooth cats emerged in Africa 12 million years ago.  Some types could grow up to 620 pounds (280 kg).  They have been found in North America, South America, Eurasia, and Africa.  They went extinct in Africa 1.4 million years ago.  In North America they vanished 10,000 years ago.

Scimitar-tooth cats emerged in Africa about 4 million years ago.  They vanished from Africa 1.5 million years ago, from Eurasia about 28,000 years ago, and from America about 12,000 years ago.

American lions originated in Africa over a million years ago, and migrated into North America, expanding as far south as Peru.  They were 25 percent larger than modern lions.  They went extinct around 11,300 years ago.

Camels originated in North America maybe 40 million years ago.  By 2 to 5 million years ago, some had crossed into Asia, and spread into Africa.  In North America, they went extinct 10,000 years ago.  They still survive in the Old World.

Short-faced bears were abundant in California.  They were among the largest land dwelling mammalian carnivores on Earth, they could weigh over 1,500 pounds (680 kg).  The species emerged about 1.8 million years ago, and went extinct about 11,000 years ago.

Giant armadillos were mammals that originated in South America 5.3 million years ago, migrated into North America, and went extinct about 12,000 years ago.  They had an armor of bony plates.  Some weighed more than 1,000 pounds (454 kg), and were as big as a Volkswagen Beetle.

Giant ground sloths could grow as large as elephants.  They could stand erect up to 20 feet (6 m) tall, and weigh 2,204 pounds (1,000 kg). They emerged in North and South America about 4.9 million years ago, and went extinct 11,000 years ago.

Giant beavers were the largest North American rodent.  They could grow to 7.6 feet (2.3 m) long, and weigh up to 276 pounds (125 kg) — about the size of a black bear.  They emerged about 2.6 million years ago, and went extinct about 11,700 years ago.

Tapirs could grow up to 4.6 feet (1.4 m) long, and weigh up to 496 pounds (225 kg).  They emerged 20 to 30 million years ago in North America, and went extinct about 11,000 years ago in America.  In China, some survived until 4,000 years ago.

Woodland musk ox could grow to 934 pounds (423 kg).  They lived from Alaska to California, and east to New Jersey.  They emerged about 2 million years ago, and went extinct about 11,000 years ago.

Dire wolves lived in North and South America from 125,000 to 9,440 years ago.  The average wolf weighed about 150 pounds (68 kg).  Their prey included camels, bison, mastodons, ground sloths, and horses.

Perfection of Hunting

While low tech persistence hunting had worked for a very long time in our original homeland, it didn’t work well everywhere.  Up north, in temperate Eurasia, we couldn’t chase large game for hours in deep snow until they collapsed from overheating and exhaustion.  Yet these cooler regions were home to abundant large game, our favorite food — an incredibly vast treasure of precious nutrients, an irresistible temptation.

How could we hunt them?  “Necessity” (fear, desire, insanity, etc.) is the mother of invention.  We got clever.  Technology enabled new possibilities.  We figured out how to survive in temperate regions, and became experts at killing big critters.  This was a major shift away from our traditional mode of tropical living.  Cleverness was the master key to countless treasure chests, and countless disasters.  Look at us today.

Our new and improved weapons increased the risk of unintentional overhunting, and that’s exactly what happened.  Alfred Crosby wrote a fascinating and depressing book on the history of projectile technology, spanning from sticks and stones to ballistic missiles.  “Humanity equipped with atlatl and firestick was instrumental in the elimination of scores of species of megafauna.”  As our ancestors expanded into new regions, they kept learning new hunting strategies, and inventing more and deadlier tricks and gadgets.

In Greenland, Peter Freuchen and Knud Rasmussen felt sorry for the primitive Eskimos.  The two lads built a trading post so that natives could have access to the wonders of modernity.  Guns made it far easier to hunt (and overhunt).  Rifles made so much noise that they scared caribou away — they abandoned their normal migration routes, and entire communities starved.  Loud gunfire scared seals away.  Seals shot with guns often sank, and were lost.  By 1908, Rasmussen had profound regrets about the consequences of his good intentions.  The Eskimos appeared to be on the path to extinction.

Farley Mowat told stories about the Ihalmiut people who lived in the region around Hudson Bay in northern Canada.  When traders moved in, the natives learned that they could trade fox furs for stuff like guns and ammunition.  These made it far easier to kill deer, so their traditional mode of low tech hunting was abandoned.  Prior to firearms, it had never occurred to anyone that it was possible to kill too many deer.  Until then, the availability of deer was as reliable as the dance of the sun and moon.

Long ago, hunters who resided in luxurious mammoth bone huts temporarily lived very well via overhunting, but eventually starved.  Mammoth hunters had no way to undo the unintended consequences of their shortsighted progress.  Ronald Wright concluded that this mode of progress was (and is) dark juju.  Shortsighted progress can be very fun and intoxicating, for a while.  Wright called this joyride “the perfection of hunting,” and he declared it to be humankind’s first progress trap.  Like a ratchet wrench, it’s a one-way process that only moves from tight to tighter, burning each bridge it crosses, and never looking back.

Eventually, the growing number of megafauna extinctions inspired us to shift into a new progress trap, plant and animal domestication, which later led to the trap of industrial civilization.  Trap after trap has ratcheted us forward into our ghastly consumer wonderland — eight billion tropical primates devouring the broken, bleeding, crying remains of the family of life.

Pleistocene hunters spread around the world, and feasted on organic grass-fed meat for many thousands of years.  Over time, our ancestors exploded in number, from a cute and insignificant minority group, into a global horde of Earth shaking demolition experts (consumers).  Naturally, any joyride of snowballing growth will eventually slam into game changing limits.  Wright lamented, “We have already caused so many extinctions that our dominion over the Earth will appear in the fossil record like the impact of an asteroid.” 

I invite you to imagine what the world looked like two million years ago, when there were a tiny number of hominins, whilst the entire planet was a thriving paradise of immense biodiversity, abundant life everywhere!  Imagine that!  This was the incubator in which our lineage evolved.  This was the environment in which hominins felt at home, and where they lived in balance.  Look at us now.

Sources

NOTE: Links often go extinct.  The Internet Wayback Machine can sometimes find them.  Copy the dead URL, and visit https://archive.org/web/

Araujo, Bernardo, et al., “Bigger kill than chill…,” Quaternary International, November 2015.  [LINK] 

Brook, Barry W., and Christopher N. Johnson, “Selective hunting of juveniles as a cause of the imperceptible overkill…,” Alcheringa, Volume 30, 2006.  [LINK] 

Crosby, Alfred W., Throwing Fire, Cambridge University Press, New York, 2010.  [REVIEW]

Davis, Leslie B., and Brian O. K. Reeves, editors, Hunters of the Recent Past, Unwin Hyman, London, 1990.  [REVIEW]

Deloria, Vine, Jr., Red Earth, White Lies, Scribner, New York, 1995.

Dobak, William A., “Killing the Canadian Buffalo: 1821-1881,” Western Historical Quarterly, Spring 1996.

Edmeades, Baz, Megafauna: First Victims of the Human-caused Extinction, 2013, unpublished manuscript.  [REVIEW]   News at Facebook: [LINK]

Esty, Amos, “Investigating a Mega-Mystery,” American Scientist, Sept-Oct 2005.  [LINK]

Fernandez, Fernando, “Human Dispersal and Late Quaternary Megafaunal Extinctions…,” ResearchGate, July 2016.  [LINK]  (Readable & detailed)

Flannery, Tim, The Future Eaters, George Braziller, New York, 1995.  [REVIEW]

Flores, Dan, American Serengeti, University Press of Kansas, Lawrence, 2016.  [REVIEW]

Flores, Dan, The Natural West, University of Oklahoma Press, Norman, 2001.  [REVIEW]

Hornaday, William Temple, The Extermination of the American Bison, Government Printing Office, Washington D.C., 1889.  [LINK]

Kelekna, Pita, The Horse in Human History, Cambridge University Press, New York, 2009.  [REVIEW]

Kolbert, Elizabeth, The Sixth Extinction: An Unnatural History, Henry Holt and Company, New York, 2014.  [REVIEW]

Krech, Shepard, The Ecological Indian, W. W. Norton & Company, New York, 1999.

Kurtén, Björn, The Cave Bear Story, Columbia University Press, New York, 1976.

Kurtén, Björn, Pleistocene Mammals of Europe, Aldine Publishing Company, Chicago, 1968.

MacKinnon, J. B., The Once and Future World, Houghton Mifflin Harcourt, New York, 2013.  [REVIEW]

MacPhee, Ross, End of the Megafauna, W. W. Norton Company, New York, 2019.  [REVIEW]

Mann, Charles, 1491: New Revelations of the Americas Before Columbus, Alfred A. Knopf, New York, 2005.

Martin, Paul S., “Africa and Pleistocene Overkill,” Nature, October 22, 1966.  [LINK]

Martin, Paul S., Twilight of the Mammoths, University of California Press, Berkeley, 2005.

Mowat, Farley, Sea of Slaughter, Atlantic Monthly Press, Washington D.C., 1984.  [REVIEW]

Naagaoka, Lisa, et al., “The overkill model and its impact on environmental research,” Ecology and Evolution, John Wiley & Sons, 2018.  [LINK]

Nelson, Richard K., Make Prayers to the Raven, University of Chicago Press, Chicago, 1983.  [REVIEW]

Surovell, Todd A., et al., “Tests of Martin’s overkill hypothesis…,” PNAS, January 26, 2016.  [LINK]

Turnbull, Colin M., The Forest People, Simon and Schuster, New York, 1961.  [REVIEW]

Wallace, Ronald L., Those Who Have Vanished, Dorsey Press, Homewood, Illinois, 1983.

Ward, Peter D., The Call of Distant Mammoths, Copernicus, New York, 1997.  [REVIEW]

Werdelin, Lars, “Hominids, Carnivores, and the Origin of the Anthropocene,” Swedish Museum of Natural History, 50 min. video.  [LINK]

Werdelin, Lars, “King of Beasts,” Scientific American, November 2013, pp. 34-39.

Wright, Ronald, A Short History of Progress, Carroll & Graf, New York, 2005.  [REVIEW]