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Climate change, doomsday and the ‘inevitable’ extinction of humankind

Does climate change seriously threaten to wipe out the human species if left unchecked? Examining our evolutionary past suggests it might once have been the perfect catalyst for our extinction. But now…

Of an estimated 30 two-footed ape species, we’re the last ones standing. Vermin Inc/Flickr

Does climate change seriously threaten to wipe out the human species if left unchecked? Examining our evolutionary past suggests it might once have been the perfect catalyst for our extinction. But now?

Countdown to doomsday

On January 14 of this year, the Bulletin of the Atomic Scientists moved the hands of its Doomsday Clock one minute further from midnight (it’s now six minutes to midnight), encouraged, it was announced, by the “progress seen around globe in both key threat areas: nuclear weapons and climate change”.

First published in 1947, the bulletin was founded by scientists, engineers and other experts involved in the Manhattan Project. The clock continues to serve as a metaphorical countdown to the apocalypse – the annihilation of humanity – set for midnight.

Today, the bulletin’s Board of Sponsors, comprising no less than 18 Nobel Laureates, almost every one of them a physicist or chemist, sets the hands of the clock based on their reading of “threats to the survival and development of humanity from nuclear weapons, climate change, and emerging technologies in the life sciences”.

They’ve a much wider brief now, a longer list of threats, and, I guess, more reasons to be pessimistic.

Extinction-prone apes

Around 500 million years ago, animal life was almost non-existent on Earth. Today, biologists recognise up to 6 million animal species.

Humanity – Homo sapiens – is just one among the 4,500 living mammal species; and some understanding of where we might be headed can be gleaned from where we’ve been – our evolutionary journey.

Our starting point as a group of two-footed, small-toothed, weakly-muscled, brainy “have-a-chat” apes is the ancestor we share with living chimpanzees some 7 million years ago.

(The two chimpanzee species are endangered, incidentally, because of the environmental destruction caused by us, their closest cousin).

Our evolutionary group – the hominins – diversified quickly after the split from the human-chimp ancestor, and through its multiple evolutionary iterations natural selection produced 25 or 30 two-footed ape species – undoubtedly with more to be found as anthropologists discover more fossils. All of these are now extinct, except us.

Those 7 million years represent only the last couple of minutes on a 24-hour clock of Earth’s 5 billion year history. The culling of 30 species to 1 in this short timeframe, or a more than 95% loss of hominin biodiversity, is worse than the worst mass extinction episode recorded in the fossil record: the Permian event some 250 million years ago.

But these mass events obscure the fact that, in the history of life, extinction has been a dominant theme, a continuous process. Evidence from the last 600 million years shows roughly one-third of existing animal species going extinct every 10 million years.

Seen in this context, the rate of extinction in the human evolutionary tree is striking, about three times faster than normal. This strongly suggests that we hominins are a highly extinction-prone mammal.

The blame game

Why the dramatic loss of hominin diversity? What caused all these species to disappear? These are difficult and complex questions, but the answer may in part centre on the dramatic changes in climate that provided the backdrop for much of our evolution.

The last half million years or so in particular represent an episode of especially severe climate fluctuation, with intensely cold periods followed by warm phases, flip-flopping between the two on timescales of hundreds or thousands of years – in short, the worst bit of the 2.6 million-year Ice Age or Pleistocene Epoch.

The archaeological record of Europe suggests that vast areas were largely emptied of hominins during cold phases only to be recolonised during warm periods.

Hominins, pre-dating our own species, were living in Europe at latitudes as high as 53° north by 700,000 years ago.

The 53rd parallel runs from the United Kingdom east through the Netherlands, Germany, Poland, Belarus, Russia, Kazakhstan, China (Inner Mongolia), United States (Alaska), Canada and Ireland.

Many places at this latitude today experience temperatures as low as -40° Celsius. But the climate at that time was Mediterranean in character. Soon after, the planet plunged into another cold phase lasting 100,000 years, with vast areas of Europe covered by ice.

The tyranny of chance

Biologists have identified various intrinsic features of mammal species that increase their chances of extinction. They include traits such as:

  • large body size
  • narrow ecological breadth (i.e. specialist feeders)
  • low abundance, or sparse numbers of individuals, in the landscape as well as fluctuation in population over time.

Hominins are large mammals. Estimates of mass and stature for many Ice Age species would easily qualify them for spots on the front row of a rugby team … and that’s just the females!

Large mammals are slow to mature and reproduce, and normally have one offspring at a time. While many extinct hominins were, like our own species, omnivorous, those living in cold climates relied heavily on animal food, as have recent hunter-gatherers such as the Inuit. This represents a narrowing of dietary niche on a par with many carnivores.

Estimates of population size from this period are remarkably low, with perhaps only 5,000 individuals in warm phases, plummeting to 1,000 or less during the cold stages, probably for the whole of Europe.

If around today, these individuals would be part of an endangered species, vulnerable to rapid extinction. And all of this applied to our own species as well for all but the last little bit of our brief evolutionary history.

Evolutionary game-changer

Around 10,000 years ago, something unprecedented occurred that altered the course of our evolution: we invented farming. This massive change in dietary, social and economic behavior, a cultural shift known as the Neolithic Revolution, shaped the future course of our own, and the planet’s, evolution in remarkable and unpredictable ways.

It resulted in anatomical, physiological and genetic changes that massively altered our evolution.

Our domestication of plants and animals, and the large-scale clearing of land, altered the history of many others as well. It paved the way for a rise in infectious disease, and social changes such as occupational specialisation, writing, standing armies and empires, long distance trade, money and markets.

But the most profound shift of all was an explosion in human population, the result of greatly improved food security resulting in a dramatic lowering of infant and childhood mortality.

In Europe, from a base of perhaps only 5,000 Ice Age hunter-gatherers, the take-up of farming from approximately 8,000 years ago sharply increased population growth to an estimated rate of 3% per annum, from a long-term average of zero.

This is roughly three times today’s global annual growth rate. From a population of less than 100,000 people worldwide, we have grown in less than 10,000 years to almost 7 billion.

Moments lost in time

Seen in its broadest context, the history of life on Earth soberly demonstrates that the vast majority of organisms that ever lived, perhaps 99% of them, no longer do. It also shows that mammal species normally last 1-2 million years before extinction inevitably bumps them off.

Yet, unlike most mammals, including our dozens of extinct hominin cousins, we have escaped the vulnerabilities of a small and massively fluctuating population.

The simple, but profound act, of growing our own food delivered us the food security that ensured most of our children survived and our population grew.

In effect, farming gave our species level assurance that the biological isn’t always inevitable. The odds have shifted to such a degree that we may now be, with or without climate change, extinction-proof.

Do you agree/disagree with the points made in this article? Leave your comments below.

Join the conversation

19 Comments sorted by

  1. Giles Pickford
    Giles Pickford is a Friend of The Conversation.

    Retired, Wollongong

    I agree that exctinction is unlikely. The question is not about extinction, it is about the quantum of human misery that lies in the future. Will it stay the same, or rise, or fall? That is the question.

    Giles Pickford

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    1. Fang Wilson

      logged in via Facebook

      In reply to Giles Pickford

      the drug laws are creating a new species of human homo amphetaminouse by torturing this species by drug deprivation you force it on a steeper evolutionarily curve and those that survive will be supermen by comparison .and when they finish the drug war you started it will be over in a week .you are being warned amphetamine is a drug of war and you declared a drug war on your own people if you keep our drugs from us expewct no quater for in the end there can be no quater when we live in slavery by your hand .

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  2. mixmaxmin

    logged in via Twitter

    There is no doubt we shall disappear from the face of the planet; The key question is when? If the answer is in a few million years then who cares and all is good, but if it is in the next few hundred years then some careful analysis is necessary combined with common sense which seems to be missing in many "for" and "against" arguments.
    The best analogy that I have come across is: Are we on a downward slope and is it a gentle or steep slope - in which case we can do something about slowing our descent…

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  3. Alan Harvey

    Winthrop Professor of Anatomy, Physiology and Human Biology at University of Western Australia

    Interesting and useful article, thanks - but wasn't there another 'game-changer' prior to farming...and that was the evolution of speech and language, and with it the unique, modern sentient mind?

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    1. TREVOR RIDGWAY

      MR ( I am retired now )

      In reply to Alan Harvey

      Yes...but.....wasn't there another 'game-changer' prior to all these adaptations.........and that was 'climate change' which was , has been & still is beneficial. Should we be tampering with it ? Do we know enough about it to start interfering with the very vital gas ( CO2) that sustains us all ?
      Call me a cynic or a skeptic (sceptic) but the blindingly obvious benefits seem to have been downplayed in the pursuit of an ego-driven political ideological fantasy that has 'demonised' CO2.

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    2. TREVOR RIDGWAY

      MR ( I am retired now )

      In reply to Alan Harvey

      Yes ! ...but.......preceding BOTH these 'game changers' was "climate change'"(global warming, entirely due to factors NOT attributable to man i.e. NOT AGW ! ) which was then,has been & still is now beneficial to mankind !

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    3. Byron Smith
      Byron Smith is a Friend of The Conversation.

      PhD candidate in Christian Ethics at University of Edinburgh

      In reply to TREVOR RIDGWAY

      I realise I'm late to this comment, but the obvious point is that I entirely agree: do we know enough to start interfering with the very vital gas (CO2) that sustains us all? No. Though we know enough to know that our present actions are seriously interfering with the carbon cycle and the concentration of this vital gas in the atmosphere.

      What I think you may be missing, Trevor, is the scale on which "business-as-usual" is messing with this very gas. Those concerned about anthropogenic climate change are saying "let's not meddle". The radical position is to continue to burn all the fossil fuels we can get our hands on in a grand experiment to see what happens. The conservative position is to question the wisdom of this experiment.

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    4. TREVOR RIDGWAY

      MR ( I am retired now )

      In reply to Byron Smith

      Byron , thanks for your contribution.
      I do appreciate that huge amounts of CO2 are being created by "us" in industrial processes but there are much larger amounts being released & recycled through'the carbon cycle' ( by natural processes) and I don't think " we " are being correctly informed by "scientists" about the true state of the planet.

      I think governments ( & the UN ) are determined to impose taxes on 'carbon' as a wealth-redistribution-mechanism & so the term "AGW" was invented & "scientists…

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    5. Byron Smith
      Byron Smith is a Friend of The Conversation.

      PhD candidate in Christian Ethics at University of Edinburgh

      In reply to TREVOR RIDGWAY

      The natural carbon cycle is (more or less) in equilibrium, therefore about half of the 31 billion tonnes of CO2 we are adding each year accumulates in the atmosphere. This is why our contribution is important, even though it is only a fraction of the total carbon cycle.

      You say you don't think scientists are informing us of the true state of the planet. Are they deliberately deceiving us or are they incompetent?

      Your global conspiracy theory has what evidence exactly?

      "the increased CO2 level…

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    6. TREVOR RIDGWAY

      MR ( I am retired now )

      In reply to Byron Smith

      Byron , once again , thanks for your contribution.
      Ethics is your field , but as regards competence or dishonesty amongst scientists I can only speculate on aspects of human nature. There is always in an employee "a desire to produce the required result " ( the person who pays the piper chooses the tune ) which can be enhanced by offers of further funding or even discontinuance of current funding !

      There is also quite often an ideological aspect "to be doing the right thing"which can distort even…

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    7. TREVOR RIDGWAY

      MR ( I am retired now )

      In reply to Byron Smith

      Byron , sorry , I tried to correct the spelling of ceremony ( from creemony ) & annals ( from anals ) & pushed the wrong button !
      It's a good thing I'm not in charge of one of those rockets I alluded to earlier !

      Regarding the "food production & the hydrological cycle"........this article is based on yet another......................................wait for it !!!....................................computer model !!!

      The results ARE being disputed by other , equally prominent researchers…

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    8. Giles Pickford
      Giles Pickford is a Friend of The Conversation.

      Retired, Wollongong

      In reply to TREVOR RIDGWAY

      Trevor has pointed out that some scientists are corrupt. However, it is a bit rich to deduce from that that they all are, or even that most of them are. To think this way requires an amount of cynicism which is beyond my reach.

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  4. Byron Smith
    Byron Smith is a Friend of The Conversation.

    PhD candidate in Christian Ethics at University of Edinburgh

    Very helpful paleobiological context for the debate, though I agree with Alan, that what has really set us apart is the speed with which our cultural adaptations enable us to effectively accelerate evolutionary processes. Agriculture was simply amongst the most dramatically effective of these. Given the pace of change language and culture have enabled us to pursue, parallels with previous species become a little less useful in the timescales for which most of us are most interested.

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  5. Thuong Nguyen

    logged in via email @gmail.com

    Not too worry, someone will genetically engineer a new specie of human by mixing human genes with cockroach's. Insectornoid..... Awesome!!

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    1. Andrew Glikson

      Earth and paleo-climate scientist at Australian National University

      In reply to Thuong Nguyen

      Interesting article.

      However:

      1. A fundamental transformation in human evolution was the mastery of fire, something no other species has done, with far reaching implications for survival at high latitudes, consumption of proteins, clearing of forests ... the list goes on.

      2. Humans appear to be able to worry about "one issue at a time". Climate change is an extremely serious development, will affect a majority of mammals including humans, but survivors are likely in high latitudes and high mountain…

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    2. Fang Wilson

      logged in via Facebook

      In reply to Andrew Glikson

      dolphins invented fire theroy 2 million years ago it was only a lack of opposable thumbs and a suitable environment for research that held them back .in fact if it haden't been for interspecies sex man would have never had a chance to steal the idea from them and would have died from a bad cold in the ice age.

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  6. Andrew Glikson

    Earth and paleo-climate scientist at Australian National University

    Fire was mastered by the Genus Homo long before Homo sapiens emerged, namely:

    1. Some evidence exists for the use of fire by Homo erectus some ~1.6 million years ago, although the evidence is far from conclusive and is still debated by Archaeologists.

    2. Confident evidence for the use of fire exists from about 600,000 - 500,000 years ago when Homo, including hearths containing charred bones, baked clay and so on. Fire was used by Homo Heidelbergensis and Homo Neanderthalis.

    3. Homo sapiens appeared about ~200,000 years ago and so it was not the first Homo species to use fire.

    An essay regarding the Genus Homo and the mastery of fire is available from the author.

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  7. Andrew Glikson

    Earth and paleo-climate scientist at Australian National University

    correction:

    Item 2 should read:

    "Confident evidence for the use of fire exists from about 600,000 - 500,000 years ago, including hearths containing charred bones, baked clay and so on. Fire was used by Homo Heidelbergensis and Homo Neanderthalis.

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