There is something about a trilogy that is somehow uniquely satisfying. From Tolkien's 'Lord of he Rings', E R Eddison's 'Zimiamvian Trilogy'*, Mervyn Peake's 'Gormanghast' and even Wagner's 'Ring' should be seen as a trilogy, where 'Das Rheingold' serves as merely a prologue, an appetiser, to the events which foreshadow 'Götterdämmerung' and an implicit Ragnorök. So, in keeping with this mood of triads, triplets, I give you a post which follows on to the most recent two posts about man-made extinctions; perhaps the most inglorious of humanity in all its history, although the individuals or societies could little have guessed how they would affect the ecosystems into which they marched, blind and unthinking.
The history of the planet is littered with 'mass extinction' events; the 'Permian-Triassic' (P-Tr), in which 95% of all known species died out and the Cretaceous-Paleogene (K-Pg) or, to give it its more common name, the Cretaceous-Tertiary (K-T) boundary, which saw the extinction of the last remaining large dinosaurs, to name but the most famous. Such extinction events are only to be found after a cataclysmic disaster of global proportions; whether by the release of vast pockets of methane gas buried below the oceans, massively increased vulcanism or an asteroid strike may never be known with any degree of certainty, there is evidence to support many competing theories. However, man, at least, can have had no place in any event prior to their own evolution around 500,000-1,000,000 years ago.
Much of what follows is predicated upon a simple hypothesis, the so-called 'Out of Africa hypothesis'. This 'hypothesis, in support of which there is a good deal of evidence from the fossil record and from genetics, is that mankind first evolved in Africa and subsequently spread out over the globe, whether by one or more than one migrations from its basal root. In doing so, Homo Sapiens Sapiens supplanted whatever previous incarnations of the hominid 'bush' which had gone before it; Neanderthal man is perhaps the best known example. Within a few tens of millennia, Homo Sapiens had reached the far corners of the known world; we spread like locusts from the jungles of South East Asia, even reaching Australasia, to the plains of Southern Africa; from the steppes of Mongolia to the glaciers of northern Europe, we swept all before us.
Fifteen thousand years ago, the northern hemisphere was slowly beginning to creep out of the ice-age which had enveloped the continents for millennia. Contrary to popular belief, Europe, continental Russia and the the northern USA was not immersed in a climate akin to the the arctic, a barren wilderness of snow and ice with only fish and sea mammals to provide food. The ice-age had caused massive climate change, driving weather systems far to the south and in their wake had left dry but prosperous grasslands beyond the ice sheets. Wherever new environments spring up, nature has an uncanny ability to evolve animals, fish, insects to take advantage of such circumstances; mankind was not the least product of this last throw of evolution's dice. Herds of huge mastodons, woolly mammoths, woolly rhinoceros, glyptodonts**, musk oxen, reindeer evolved to feed at the very edges of the ice sheets.
With so much of the world's water bound up in the carpet of ice which swathed the land, sometimes ice that was more than a mile thick, it is little wonder that sea levels plummeted. Britain was joined to Europe by a land bridge over which people and animals could cross (which is why you can find fossils of woolly rhinoceros in southern England) but the most important of these land bridges was the one that connected Kamchatka and Alaska, what is now the oceanic Bering Strait. Over a few millennia, Homo Sapiens migrated out of the Mongolian and Siberian plains and across into Alaska; from there they migrated throughout the length and breadth of the Americas.*** Into a land where people had before never trod, there came the incessant waves of human beings in search of, to use Hitler's words, Lebensraum.
A primary reason for the rapid spread of humanity throughout the continent was the abundance of large prey. Armed as they were with primitive man-made stone and bone tools, the giant herbivores fell easy prey to human hunters. However it is difficult to conceive that a rag-tag. motley wave of human hunters, armed with such primitive weapons, could eradicate entire species in the course of a few thousand years. However, recent research into the the behaviour of the ice-age fauna's nearest living relatives suggests a possible mechanism.
Elephants and rhinos, unlike the fellow inhabitants such as oxen, reindeer or elk, breed only slowly and there is every reason to suppose that the mammoths and the mastodons were no different in that respect. Therefore, it is likely that they were more susceptible to the pressures of hunting, even on a modest and small scale, than other animals. However, more importantly, is what happens to elephants in the wild if the largest animals are killed; the mature bulls who command the most mates. Sub-mature and recently mature males end up fighting amongst themselves to fill the gap left by the 'alpha bulls'; with disastrous consequences. Essentially, they end up killing each other and breeding slows to a crawl, insufficient to make up for the animals that die. No doubt, human hunters would choose the biggest of the animals to kill; more meat for your spear!
Battles will rage in the scientific press about exactly how much impact human predation had on the fauna of the last ice age but like the large dinosaurs before them, these mammals were already under significant pressure from climate change and loss or changes to their habitat. Like the triceratops and the hadrosaurs. and their predator, T-Rex****, all it needed was one final push to tip them over the edge to oblivion. In the case of the dinosaurs, it was likely an asteroid impact; for the mammoth and the mastodon, it was human predation.
* Like the author's 'The Worm Ouroborus', it deals with a 'traveller' to a distant world, who is conveniently forgotten in the tale that follows. It is no less dense, with a love of arcane language, than its predecessor; it makes for a book which is not to be given to any but the most accomplished of English speakers.
** A type of giant armadillo.
*** Evidence? Appearances alone would support the hypothesis; Native Americans both north and south quite clearly have 'mongoloid' features. You scarcely need genetics to confirm it.
**** The sabre-toothed cats went the same way; without prey to hunt or scavenge, they starved to death
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