02 September 2019

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.


Blogger Victor said...

I'm 61 1/2, so I won't be here when it's time to pay.

Sorry that I helped run up the bill...

02 September, 2019 17:44  
Blogger RO said...

As always, your brilliance makes me think about the past and wonder about things to come. I sure wish I could come back to life as a different person for just one day of each century to see how life changes and/or evolves once I'm gone. Hugs, RO

03 September, 2019 02:40  
Blogger Sixpence Notthewiser said...

Humans seem to be their own worst enemy, no?
In the name of ‘progress’ we destroy and extinguish. Just look at what Bolsonaro’s policies and ideas are doing to Brazil’s rainforest. And you know that American businesses are behind the push to create more roads to exploit the crops that will replace the rainforest.
Those big animals disappeared because of men and did not seem to affect ecosystems too much. This exploitation of the Amazon I’m sure will have more lasting effects.


03 September, 2019 03:48  
Blogger thomas.h.pickering@gmail.com said...

Good posting here! I just left a comment, and it wouldn't take it, but also, Google made changes to my computer, so something I need to work on. No, all of this is fascinating stuff. But I also read, that as we keep talking about what species we are losing, there are also new one developing. Humans have such a dominant role in shaping what will happen too, as you point out. It fascinates me, of all the bones of prehistoric sea creatures they found right here in Texas, too. It would be interesting to see the planet in several thousands of years from now. In the meantime, we can try to get computers and AI to try to paint a picture ... which is fun. I hope this goes through, this time

03 September, 2019 05:58  
Blogger The New York Crank said...

Of course, we could save a whole bunch of species if we eliminated just one: homo sapiens.

That failing, if we could reduce our global population from the current approximately 7.5 billion down to, say, half a billion, we could all drive cars, leave the air conditioners running all day, let the cows fart their heads off until we eat them, and still have a viable planet.

Humanity is a pest species.

Yours crankily,
The New York Crank

03 September, 2019 15:20  
Blogger Infidel753 said...

Victor: I'm not sure you got my point. We're looking at a pretty-much-inevitable evolutionary process here.

RO: Thank you for the kind words! Rather than coming back, I hope we'll just be able to stick around.

Sixpence: I'm not sure we're getting an accurate picture of what's going on in the Amazon -- see the last two link round-ups. But it's bad, certainly.

Thomas: Blogger may be going through a period of being glitchy with comments. A few of mine have disappeared too.

The picture at the top of this post is the excavation of a mammoth skeleton which was discovered just a bit south of Dallas (Ellis county) in 2014. It was donated to the Perot Museum in Dallas and is probably still there.

Crank: So, the Holocaust times a thousand? Whether a species is a "pest" or not depends on one's point of view, and only humans really have a point of view on issues this complex. No other animal species would ever restrain its instincts for our sake if the positions were reversed, nor for the sake of preserving the overall ecology -- if they were even able to understand the question, which they aren't. No other animal species will ever launch an interplanetary probe or make a snarky YouTube video. We won the intelligence race fair and square. It's our planet now.

04 September, 2019 04:17  
Blogger The New York Crank said...

Infidel: No holocaust needed. Simply stop reproducing so fast (and meanwhile let's stop chopping down forests, burning fossil fuels, and dumping crap into the oceans anyway.)

However, if we don't clean up our act, Mom Nature will create a holocaust for us. No human effort required. She'll drown anybody currently living near the ocean, freeze and starve others, huff and puffs and blow your house down, turn fertile fields to deserts, spread more and new antibiotic-resistant diseases, create wars between nations struggling for increasingly scarce resources, and the list of dire consequences go on.

Nature is a hanging judge, and humanity, that alleged winner of the intelligence race, just climbed up to the top of the scaffold and put a rope around its own neck. That's all I'm saying.

Yours crankily,
The New York Crank

04 September, 2019 06:16  
Blogger Infidel753 said...

Stop reproducing so fast? Birth rates are already below replacement level in the majority of the world. It will still take generations for population to drop substantially, even if life expectancy doesn't continue to increase, which it probably will, very dramatically.

As for the rest, I don't believe any of that is going to happen. See the post.

04 September, 2019 06:34  

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