Did Humans Survive an Extinction Level Event?

November 30, 2019  Topic: History  Region: Europe  Blog Brand: The Buzz  Tags: EvolutionHumansExtinctionAnthropologySurvival

Warfare became a check on population growth, perhaps the most important one.

Nine human species walked the Earth 300,000 years ago. Now there is just one. The Neanderthals, Homo neanderthalensis, were stocky hunters adapted to Europe’s cold steppes. The related Denisovans inhabited Asia, while the more primitive Homo erectus lived in Indonesia, and Homo rhodesiensis in central Africa.

Several short, small-brained species survived alongside them: Homo naledi in South Africa, Homo luzonensis in the Philippines, Homo floresiensis (“hobbits”) in Indonesia, and the mysterious Red Deer Cave People in China. Given how quickly we’re discovering new species, more are likely waiting to be found.

By 10,000 years ago, they were all gone. The disappearance of these other species resembles a mass extinction. But there’s no obvious environmental catastrophe – volcanic eruptions, climate change, asteroid impact – driving it. Instead, the extinctions’ timing suggests they were caused by the spread of a new species, evolving 260,000-350,000 years ago in Southern AfricaHomo sapiens.

The spread of modern humans out of Africa has caused a sixth mass extinction, a greater than 40,000-year event extending from the disappearance of Ice Age mammals to the destruction of rainforests by civilisation today. But were other humans the first casualties?

Human evolution. Nick Longrich

We are a uniquely dangerous species. We hunted wooly mammoths, ground sloths and moas to extinction. We destroyed plains and forests for farming, modifying over half the planet’s land area. We altered the planet’s climate. But we are most dangerous to other human populations, because we compete for resources and land.

History is full of examples of people warring, displacing and wiping out other groups over territory, from Rome’s destruction of Carthage, to the American conquest of the West and the British colonisation of Australia. There have also been recent genocides and ethnic cleansing in Bosnia, Rwanda and Myanmar. Like language or tool use, a capacity for and tendency to engage in genocide is arguably an intrinsic, instinctive part of human nature. There’s little reason to think that early Homo sapiens were less territorial, less violent, less intolerant – less human.

Optimists have painted early hunter-gatherers as peaceful, noble savages, and have argued that our culture, not our nature, creates violence. But field studies, historical accounts, and archaeology all show that war in primitive cultures was intense, pervasive and lethal. Neolithic weapons such as clubs, spears, axes and bows, combined with guerrilla tactics like raids and ambushes, were devastatingly effective. Violence was the leading cause of death among men in these societies, and wars saw higher casualty levels per person than World Wars I and II.

Old bones and artefacts show this violence is ancient. The 9,000-year-old Kennewick Man, from North America, has a spear point embedded in his pelvis. The 10,000-year-old Nataruk site in Kenya documents the brutal massacre of at least 27 men, women, and children.

It’s unlikely that the other human species were much more peaceful. The existence of cooperative violence in male chimps suggests that war predates the evolution of humans. Neanderthal skeletons show patterns of trauma consistent with warfare. But sophisticated weapons likely gave Homo sapiens a military advantage. The arsenal of early Homo sapiens probably included projectile weapons like javelins and spear-throwers, throwing sticks and clubs.

Complex tools and culture would also have helped us efficiently harvest a wider range of animals and plants, feeding larger tribes, and giving our species a strategic advantage in numbers.

The ultimate weapon

But cave paintingscarvings, and musical instruments hint at something far more dangerous: a sophisticated capacity for abstract thought and communication. The ability to cooperate, plan, strategisemanipulate and deceive may have been our ultimate weapon.

The incompleteness of the fossil record makes it hard to test these ideas. But in Europe, the only place with a relatively complete archaeological record, fossils show that within a few thousand years of our arrival , Neanderthals vanished. Traces of Neanderthal DNA in some Eurasian people prove we didn’t just replace them after they went extinct. We met, and we mated.

Elsewhere, DNA tells of other encounters with archaic humans. East Asian, Polynesian and Australian groups have DNA from Denisovans. DNA from another species, possibly Homo erectus, occurs in many Asian people. African genomes show traces of DNA from yet another archaic species. The fact that we interbred with these other species proves that they disappeared only after encountering us.

But why would our ancestors wipe out their relatives, causing a mass extinction – or, perhaps more accurately, a mass genocide?

13,000-year-old spear points from Colorado. Chip Clark, Smithsonian Institution

The answer lies in population growth. Humans reproduce exponentially, like all species. Unchecked, we historically doubled our numbers every 25 years. And once humans became cooperative hunters, we had no predators. Without predation controlling our numbers, and little family planning beyond delayed marriage and infanticide, populations grew to exploit the available resources.

Further growth, or food shortages caused by drought, harsh winters or overharvesting resources would inevitably lead tribes into conflict over food and foraging territory. Warfare became a check on population growth, perhaps the most important one.

Our elimination of other species probably wasn’t a planned, coordinated effort of the sort practised by civilisations, but a war of attrition. The end result, however, was just as final. Raid by raid, ambush by ambush, valley by valley, modern humans would have worn down their enemies and taken their land.

Yet the extinction of Neanderthals, at least, took a long time – thousands of years. This was partly because early Homo sapiens lacked the advantages of later conquering civilisations: large numbers, supported by farming, and epidemic diseases like smallpox, flu, and measles that devastated their opponents. But while Neanderthals lost the war, to hold on so long they must have fought and won many battles against us, suggesting a level of intelligence close to our own.

The Conversation————————————————————————————————————–

Nick Longrich, Senior Lecturer, Paleontology and Evolutionary Biology, University of Bath

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Image: Reuters

I Hate That I’m Human

Well, that’s not entirely true or altogether accurate. I’m not really the type who goes around hating myself or each and every member of the species homo Sapiens I happen to meet. I just hate what said species is has done (and is still doing) to the planet and I hope that the Earth can survive in spite of us. If She does, it will have been a close call. The life-ways of our species has warmed up the atmosphere in ways unmatched since the last mass extinction. And at a pace unrivaled.

But then, the Earth has made it through at least five other mass extinctions and lived to tell the tale. What’s really going to be sad is how many amazing non-human beings that will end up having to go along with us when we, the out-of-control, evolved-beyond-our-own-good yet ethically-underevolved carnivorous-hominid species, goes.

Being a human being myself, the only way I can live with myself is by not taking part in most of the actions that define people these days:

Number one, I never reproduced. (Making love to a woman for mutual pleasure is not the same as going through the motions and hoping to impregnate someone to bring another human into this critically overcrowded world.)

Secondly, for the past two decades I’ve refused to take part in animal-eating of any kind. No mammal meat nor fish nor fowl—nothing that had a heartbeat. As it turns out, it’s been the best way to live for climate-health as well.

Even while living in the heart of a “sportsman’s paradise” I didn’t fall prey to the lure of murdering Bambi for my dinner.

Years before I’d even heard of global warming or the notion of a climate crisis, I lived in the mountains miles beyond power and basically, learned to live without it. For 20 years, I was never tempted to run a generator and join the “modern world.” I could have done it, but where would it have gotten me. (I still don’t own a cell phone, in part to protest all those cell towers going up everywhere).

No one was even talking about climate change back then so, for those decades at least, I was able to live in my own little world like so many still do today.

Anyway, it helps me to know that my carbon footprint isn’t as gargantuan as it would be if I’d have lived in the “real world” for all those years. It makes me wonder, though, how those bigfoots can live with themselves.

US and Canadian Bird Population Dropped by Nearly 3 Billion in 48 Years

America’s birds have taken wing. Ornithologists calculate that in the past 48 years, total U.S. bird numbers, reckoned together with Canada’s, have fallen drastically. There are now 2.9 billion birds fewer haunting North America’s marshes, forests, prairies, deserts and snows than there were in 1970. That is, more than one in four has flown away, perhaps forever.

Birds are one of the better observed species. Enthusiastic amateurs and trained professionals have been carefully keeping note of bird numbers and behaviour for a century or more.

A flock of avian scientists reports in the journal Science that they looked at numbers for 529 species of bird in the continental U.S. and Canada to find that while around 100 native species had shown a small increase, a total of 419 native migratory species had experienced dramatic losses.

Swallows, swifts, nightjars and other insectivores are in decline, almost certainly because insect populations are also in trouble.

Grassland birds are down 53%: more than 720 million fewer. Radar records of spring migrations suggest that these have dropped by 14% just in the last decade. More than a billion birds have deserted the American forests.

The 529 species studied were spread across 67 bird families, and of these 37 were less abundant than they had been. Where there had been concerted efforts at bird conservation, numbers were on the increase, especially for waterfowl and some of the raptors, such as the bald eagle, but while the gains are measured in millions, the losses are counted in billions.

“Multiple, independent lines of evidence show a massive reduction in the abundance of birds,” said Ken Rosenburg of Cornell University’s ornithology laboratory, who led the study.

“We expected to see continuing declines of threatened species. But for the first time, the results showed pervasive losses among common birds across all habitats, including backyard birds.”

That America’s birds are in trouble is not news. Nor is the loss of the planet’s living things confined to the U.S.: researchers have warned that, worldwide, a million or more species of plant and animal face extinction.

Pest Control

Climate change creates unexpected hazards: as northern hemisphere springs get ever earlier, migrant birds may arrive too late to take full advantage of supplies of caterpillars, aphids or other foods. Birds have an important role in ecosystems: they control pests, they disperse seeds and they are themselves food for other predators.

The researchers argue that all is not lost: conservation action and legislation has been shown to work, but as ever more natural habitat is destroyed, as sea levels rise to damage coastal wetlands, as global temperature rises begin to change local climates, there needs to be much more urgency in response.

“These data are consistent with what we are seeing elsewhere with other taxa showing massive declines, including insects and amphibians,” said Peter Marra, one of the authors, once of the Smithsonian Museum and now at Georgetown University in the U.S.

“It’s imperative to address immediate and ongoing threats, both because the domino effect can lead to the decay of ecosystems that humans depend on for our own health and livelihoods – and because people all over the world cherish birds in their own right. Can you imagine a world without birdsong?”