Extermination, resumed

When we think of really big land animals, we think of Sub-Saharan Africa.  The elephant, the hippopotamus, the rhinoceros, and countless other huge beasts abound there, so much so that travel to see such creatures in the wild is a major basis of the region's tourist industry.  The native fauna in most of the rest of the world -- the Americas, Australia -- is not nearly as impressive.  The places with native animals comparable to Sub-Saharan Africa's are mostly fairly close by.  India has elephants too.  Lions lived wild in parts of the Middle East until recently.  Elephants survived in northwest Africa in Classical times (Hannibal's march on Rome used northwest African elephants).  Further away, such examples are far thinner on the ground.

Humans evolved in Sub-Saharan Africa, and early hominins such as Homo erectus have been spreading out into the Middle East, North Africa, southern Asia, and southern Europe for about a million years.  Humans did not spread to the rest of the world until far more recently, with the rise of anatomically modern Homo sapiens.  So the places that have most of the giant animals are also the places where proto-humans existed for the longest periods of time.  This isn't a coincidence, and the reason for the connection has some interesting implications.

Australia and the Americas formerly had an abundance of huge animals every bit as impressive as Sub-Saharan Africa's.  Australia had giant marsupials comparable in size to the great African creatures, including a huge carnivorous kangaroo, as well as lizards and snakes weighing over a ton and a 400-pound flightless bird similar to an ostrich.  These giants thrived in Australia for tens of millions of years.  But all of them died out over a relatively short period of time ending at or somewhat before 35,000 years ago -- no trace of them survives from any period later than that.  Some have argued that they were killed off by a sudden change in climate (Australia is notably prone to such changes), but this seems unlikely since they had survived countless such changes before.  But we know that the first humans to reach Australia arrived there roughly 40,000 years ago.  They were anatomically-modern Homo sapiens, the ancestors of the Australian aborigines.  And they were hunter-gatherers.

North America, too, once teemed with elephants, camels, lions, giant sloths, mammoths, and other huge creatures.  After thriving for millions of years, they too suddenly became extinct around 12,000 years ago.  It's been suggested that this had something to do with the end of the last ice age, but these animals had come through many previous ice ages just fine.  12,000 years ago also happens to coincide with the arrival of the first humans in the Americas.  In this case we actually have, for example, mammoth skeletons with spear-points embedded in them, suggesting the real reason for the mass extinction.

Why were these animals so easily killed off by primitive hunters, while their Sub-Saharan African counterparts were not?  The evolution of human intelligence, and thus of highly lethal weapons and strategies for hunting, was a slow process spanning millions of years.  As proto-humans gradually grew smarter and more dangerous, the animals of Sub-Saharan Africa had time to adapt.  To a lesser extent the same was true of animals in southern Asia and the Mediterranean world, who coexisted with proto-humans for up to a million years.

The native animals in Australia and the Americas had never needed to adapt to this danger, which did not exist in their environment.  Then, just 40,000 and 12,000 years ago respectively, they were "suddenly" (relative to evolutionary time-scales) confronted with a fully-developed threat for which evolution had not prepared them.  They probably felt no fear of the puny-looking new creatures.  Long before evolution had time to breed that fear into them, the little newcomers wiped them out.

We see the same pattern in northern Eurasia.  The woolly mammoths of Siberia died out around 20,000 years ago, around the same time as humans managed to settle that forbidding environment.  Some big animal species still survive in the Arctic, probably because that region was too barren to support human hunter-gatherer populations large enough to kill them off en masse.  The ancestors of the Maori, the first humans in New Zealand, arrived there only about 1,000 years ago, and the disappearance of animals such as the moa dates to the same period.

There are a couple of significant implications here.

First, mass extermination of whole categories of animal species due to human activity is not just a modern phenomenon.  It's been happening ever since humans began to spread beyond the region where we evolved and colonize the rest of the globe.  Hunter-gatherers armed with spears and intelligent hunting strategies built up over generations may seem primitive by 21st-century standards, but they still utterly outclassed even the biggest and toughest beasts they encountered.

Second, ecosystems seem to be a lot more resilient in the face of such extinctions than we tend to imagine.  Nowadays we constantly hear that the disappearance of this or that apparently-insignificant species will have ripple effects that will dangerously disrupt the whole web of life.  Obviously extinctions do create disruption, and some species are more important than others, but the disappearance of so many major species in Australia and the Americas (which may have taken only a century or two in any given locality, once humans first reached it) doesn't seem to have caused a general collapse of the whole ecosystem.

Modern technology has now put the entire natural world at humanity's mercy.  Which species and how much of nature itself will survive, will depend almost entirely on decisions that humans make.  In developed countries, people feel secure and prosperous enough to prioritize such issues, and governments are strong enough to effectively enforce laws to protect endangered animals and environments.  The tropics, where most of the biodiversity is, are home to generally poorer human societies where development and achieving a higher standard of living are often prioritized over ecological concerns, and in many cases governments are too weak and corrupt to enforce what laws do exist to protect nature.

In the long run, I don't think most of the big, impressive, emotionally-engaging parts of the natural world are going to survive, except perhaps in special preserves here and there.  Look what a struggle it's been to mobilize against global warming, and that's a problem which poses an imminent mortal threat to much of our own species.  Switching our energy generation systems over to solar and wind power, especially on a big enough scale to accommodate the massive surge in demand for electricity over the next twenty years as the Third World catches up economically and technologically, will require a huge investment.

In the end, I think, we'll do what we must to save ourselves -- plant hundreds of billions of trees across the global north to offset the loss of oxygen-generating capacity as tropical rain forests disappear, build geo-engineering projects to cool down the planet, create artificial systems to replace whatever essential benefits we can no longer depend on from the dying natural ecosystems of the Earth.  We'll preserve systems vital to us or, in some cases, aesthetically compelling to us.  But I just can't see humanity making similar investments, on top of all that, to save animals and plants that aren't useful to humans, in a world which increasingly will have no place for them anyway.  We care about those things, yes.  But not the way we care about our own kind.

Extinctions, including mass extinctions, have always been part of evolution.  Of all the species that ever existed on Earth, more than 99% had already died out before the first proto-humans appeared.  There's nothing sacred about the particular aggregation of animals and plants which exists in the world at this moment, any more than about that which prevailed forty thousand years ago, or forty million.

We are reconfiguring this planet from an unguided biosphere operating according to the vagaries of natural selection into a controlled and managed habitat primarily for the benefit of a single species.  That transformation may well reach its culmination within a century.  But it has been under way for tens of thousands of years, and its course was probably fixed, right down to the end, on the day the first hominin fashioned the first spear.