The Mega Killers — Humans and the Megafauna Extinction
What killed the beasts that roamed the Earth thousands of years ago? Are the modern humans to be blamed?
The Cretaceous–Paleogene extinction event wiped out 75% of the Earth’s living species 66 million years ago¹. We know this as the event where the non-avian dinosaurs and several other species died due to an asteroid impact. The term megafauna is applied to any animal with average adult body weight of over 44 kg (97 lbs)². After the dinosaurs went extinct, the land was ruled by the megafauna, until a rather frail looking, two legged primate — Humans arrived at the scene.
The word human basically means an animal belonging to the genus Homo. From about 2 million years ago to around 10,000 years ago, there walked on the face of Earth several different species of the genus Homo — Homo Erectus, Homo Floresiensis, Homo Neanderthalensis and several others. These other humans had played little to no role in the eradication of megafauna and might well have been victims of genocide by us — the Homo Sapiens (Latin for ‘Wise Man’). In the subsequent sections, humans will mean only Homo Sapiens until specified otherwise.
Agriculture was started only about 12,000 years ago which is roughly around 10,000 BC. Before that, our forefathers were hunting and gathering for centuries. Around 170,000 years ago, humans had already evolved in East Africa and by about 70,000 years ago, they started spreading to Arabia, Europe and Asia. Although this will be covered in detail in later posts, but within few thousand years of their arrival in the new territories, other human species became extinct. These new humans were skilled hunters and ruthless conquerors, thanks to their unparalleled social skills and cooperation abilities that allowed them to work in large groups.
Megafauna Extinctions in Australia and America
As we have no written records from our hunter-gatherer forefathers, most of prehistory is based on theories proposed by scholars based on archaeological findings and evidences. One such theory suggests that 40,000 years ago humans reached Australia through the Indonesian group of islands. When humans went to sea in seafaring vessels to Australia, they were the first of all living creatures without flippers or other specialized organs for sea dwelling that were travelling through hundreds of miles of open sea. When humans landed on the 40,000 year old Australia, it might have sent a chill down their bones when they sighted the giant Diprotodon (a marsupial that weighted up to 2700 Kg), the Procoptodon (a Kangaroo of 6.6 ft height and weighted more than 200 Kg), the Protemnodon (a 170 Kg wallaby), giant flightless birds called Thunder Birds, Monitor Lizards that weighted around 1900 Kg and snakes that went up to 20 ft.
But within a few thousand years of the arrival of the humans, these extra massive species went into oblivion. A large number of smaller species were also gone. Tool inflicted damage to fossilized bones, fossilized hunting tracks and cave paintings depicting extensive hunting scenes adds to this narrative of over hunting by humans. Humans, with their dexterity in using their stone tools, spears and their fire wielding prowess combined with their phenomenal ability to work in large groups, rearranged the food chains around the island and catapulted themselves to the top rung of the food chain.
A similar story of ecological disaster unfolded in America when roaming bands of hunter gatherers reached there some 15,000 years ago. These new invaders of America had now developed new weapons and sophisticated hunting strategies that enabled them to hunt down giants like Mammoths, Mastodons, supersized Armadillos and 1000 Kg Ground Sloths.
Mind you, these forefathers of ours had evolved in the hot plains of Africa and then went on to thrive in the harsh and unforgiving weather of the Arctic and Alaska region. With time, they spread on to the forests of North America, the swamps of South America and the dry deserts of Mexico. No other species — large or small could adapt in such a variety of habitats in such a short period of time. Such exceptional adaptive abilities coupled with their top rank in the food chain, made humans the deadliest species to ever walk on the face of the Earth.
Whose is to be held accountable?
Some researchers try to absolve humans of the central responsibility, instead blaming the climate for the mass extinctions. The Earth’s climate was also undergoing rapid changes at that time. But the popular consensus is that these large animals would still have been around if humans would not have made an entrance. Also, the smaller relatives of these extinct species still thrive among us. Sloths, wallabies, smaller marsupials and elephants should also have been affected by these climatic changes and gone extinct.
Humans need not necessarily hunt down every last one of them to push a species into extinction. Humans have the nasty reputation of changing their habitat to suit their needs wherever they went. This they did by modifying landscapes through fire, settlements and later on through agriculture and now through construction. When humans used fire as their weapon and burnt down whole forests, there is little that the gigantic Mammoths or Diprotodons could do. With the herbivores gone, carnivores too followed suit and so did other small species that depended on them.
The persistence of some megafauna species in remote islands for several millennia past the extinction of their continental relatives, further cemented role of humans in the mass killings. Ground sloths had survived in the Caribbean islands of Antilles until around 1500 BC³ and mammoths resided in the Wrangel Island of the Arctic Ocean as recently as 2000 BC⁴. Isolated from the mainland for 6000 years, about 500 to 1000 mammoths lived on the island at a time.⁵ Were these remote populations not affected by the climatic disturbances? In fact, there are sufficient evidences to prove that colonization of these islands by humans coincided with the demise of these remote megafauna populations. Megafauna outside of the African continent, which did not evolve alongside humans, had higher extinction rates. This was because megafauna in the Afro-Asian landscape had evolved alongside many species of apes and had evolved to evade humans and not perish merely through over hunting. Megafauna of Australia, North America and South America didn’t evolve to develop fear for the humans and proved highly sensitive to the introduction of new predation.
The curious case of New Zealand and Madagascar
Another striking example of human over-exploitation of megafauna can be found in New Zealand which was home to a diverse assemblage of avian megafauna and particular among them were a species of large flightless birds named Moa. Nine different species of this large bird vanished following the arrival of The Māori tribe on the shores of New Zealand in the 13th century.⁶ It is well documented that the early Māori diet included an abundance of moa, other large birds and fur seals. Moas had lived there for countless generations and adapted well to all climatic changes, only to vanish when the humans arrived.
The island nation of Madagascar is home to fascinating creature endemic to the island owing to millions of years of evolution in isolation. Until around 1000 years ago, elephant birds, giant fossas and large-bodied lemurs larger than their present day relatives called Madagascar their home. In a span of few hundred years, around 1000 AD, these megafauna were nowhere to be found. New research suggests that slash and burn agriculture coupled with over-hunting and introduction of domesticated animal spelled doom for the megafauna.⁷ When multiple stressors like overkill, climate, diseases and loss of habitat befalls a population such that the birth rate dips below the death rate, extinction is inevitable.
Also, while you are reading this, we humans are actively driving the Sixth Mass Extinction event (The Holocene extinction event) that too after fully understanding its consequences. Over-exploitation of natural resources, pollution, deforestation and over-fishing provides the required impetus to this extinction event. Overuse and pollution of oceanic resources have pushed quite a number of large marine animals, which were earlier relatively unaffected from human activity, to the brink of extinction. True, we are primed for survival and are global super predators but it’s about time we wise up and sort ourselves out before it’s too late.
 Fortey, Richard (1999). Life: A natural history of the first four billion years of life on Earth. pp. 238–260. ISBN 978–0–375–70261–7
 Martin, P. S.; Steadman, D. W. (1999). “Prehistoric extinctions on islands and continents”. ISBN 978–1–4757–5202–1
 Steadman, D. W.; Martin, P. S.; MacPhee, D. E.; Jull, A. J. T.; (2005);“Asynchronous extinction of late Quaternary sloths on continents and islands”.
 Arslanov, Kh. A.; Cook, G. T.; Gulliksen, Steinar; Harkness, D.D. (1998). “Consensus Dating of Remains from Wrangel Island”.
 Shah, Dhruti (March 23, 2012). “Mammoths’ extinction not due to inbreeding, study finds”.
 Allentoft, M. E. ;Heller, R; Oskam, C. L. (2014); “Extinct New Zealand megafauna were not in decline before human colonization”.
 Ketchell, Misha; (March 30,2019). “Last of the giants: What killed off Madagascar’s megafauna a thousand years ago?”.