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Anthropogenic Mass Extinction. Homo sapiens and the Evolution of the Biosphere since the Pleistocene. Kyle Burchett University of Kentucky. Mass Extinctions of the Past. → Unavoidable Prolonged Geologic Events. Cosmic Collisions. Mass extinctions are normal events for Earth’s life forms.

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Anthropogenic Mass Extinction

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Anthropogenic mass extinction

Anthropogenic Mass Extinction

Homosapiens and the Evolution of the Biosphere since the Pleistocene

Kyle Burchett

University of Kentucky

Mass extinctions of the past

Mass Extinctions of the Past


Prolonged Geologic Events

Anthropogenic mass extinction

Cosmic Collisions

Anthropogenic mass extinction

Mass extinctions are normal events for Earth’s life forms.

(Erickson 2001:78)

The fittest of the fittest

The Fittest of the Fittest

  • Microscopic organisms such as bacteria show up in the fossil record for at least four billion years.

  • They are virtually indestructible and immune to the mass extinction events which regularly befall more ‘complex’ species.

An objective view of mass extinction

An Objective View of Mass Extinction

“In a sense we are like fruit flies, which live but a few weeks and cannot experience most seasonal changes, much less a year. We cannot know from experience the history of planet Earth. Most of it is destined to be as abstract to a layperson as the dimensions of the universe” (Martin 2005:54).

Anthropogenic mass extinction

The Pleistocene Puzzle

  • Approximately 50,000 years ago, the Earth’s megafauna began to exhibit an unusual extinction pattern.

    • Almost exclusively largeanimals – megafauna – rapidly began to disappear around the world.

    • 65%of mammal genera whose members weighed morethan97pounds were utterly extirpated.

    • 97of150genera of megafaunabecame extinct.

    • Plantsand marinelife were largely unaffected.

  • Previous mass extinctions evenly affected all types of organisms, including animals of all sizes, plants, and marine life.

  • (Barnosky et al. 2004; Lyons et al. 2004; Martin 2005; Nogués-Bravo et al. 2010)

  • Three compelling hypotheses

    Three Compelling Hypotheses

    • Climate Change

      (Generally construed as non-anthropogenic)

    • Overkill


    • Hyperdisease

      Anthropogenic or otherwise

    Climate change

    Climate Change

    (Nogués-Bravo et al. 2010:2444)

    Anthropogenic mass extinction

    Extreme climate changes radically alter the possible biotic composition of ecosystems.

    (Delcourt and Delcourt 2004)

    Extinction may be the only possible response for some species.

    Competition for limited available resources increases drastically both within and across species.

    If access points to alternate habitats are cut off, migration is not an option.

    (Boulter 2002:119)

    Climate change alone however is insufficient

    Climate change alone, however, is insufficient. . .

    • Climate-induced mass extinctions should not show discrimination for large body size or exclude plant and marine life.

    • 20 glacial-interglacial periods / 2 million years

      • A mass extinction pulse only shows up at the end of the Pleistocene (andcontinuestoday).

        • 50% of plant and marine life are currently threatened with extinction.

    (Boulter 2002:51)

    Invasion overkill extinction

    Invasion → Overkill → Extinction


    (Martin 2005:7)

    A smoking spear

    A Smoking Spear?

    • 76 North American Clovis sites reviewed

      • 14 contained extinct megafaunal remains

        • 12 – mammoths

        • 2 – mastodons

          (Grayson and Meltzer 2002)

    Anthropogenic mass extinction

    Mass extinction inevitable – even with moderate human population growth and hunting practices(Alroy 2001:1895)

    Buffalo jumps

    Buffalo Jumps

    • Entire herds driven over cliffs

      (Burroughs 2005:187)

      • Bone layers as deep as 20 feet

    • Historical mass killing of megafauna

    The passenger pigeon

    The Passenger Pigeon

    • Modern example of overkill

    • At the beginning of the 19th century, flocks stretched across North American skies for up to 500 kilometers.

      • In less than a century, this seemingly ineradicable species was utterly extirpated.

    Na ve species meet invasive omnivore species

    Naïve species meetinvasive omnivore species

    • Historical and modern extinctions in isolated / island ecosystems

      (Boyer 2008; Martin 2005)

    Overkill alone is likewise insufficient

    Overkill alone is likewise insufficient. . .

    Extinctions prior to invasion of Homosapiens

    Long duration of coexistence

    • Loss of naïveté

    Europe and Northern Asia

    (Hofreiter and Stewart 2009:R589)



    • 113 North American mastodon skeletons / various geographic regions

      • 52% exhibited signs of tuberculosis

        (Rothschild and Laub 2006)

    • Infection evident 34,000 – 10,000 years BP

    • Populations greatly weakened

      • More susceptible to climate change / overkill

    (Rothschild and Laub 2006:562)

    Historical validation

    Historical validation

    • 1st recorded extinction by infection in a free-ranging wildlife species

      • Sharp-snouted day frog

  • 1 other historical case of extinction by infection (in a remnant captive population)

    • Polynesian tree snail

      • (Schloegel et al. 2006)

  • Anthropogenic mass extinction

    European introduction of diseases such as measles and smallpox reduced Native American populations by perhaps as much as 95 percent (Dobyns 1993).

    Hyperdisease alone insufficient

    Hyperdisease alone insufficient. . .

    • 20 glacial-interglacial periods / 2 million years

    • Many opportunities for novel pathogen introduction

      • Mass extinctions only occur near the end of the Pleistocene and only in large land animals

        • No known analogous pathogens (such as West Nile virus) demonstrate such size selectivity

          (Lyons et al. 2004b)

    A multicausal approach

    A multicausal approach

    Climate Change + Infection + Keystone Invasive Species = Mass Extinction Event

    with Homosapiens tipping the scale. . .

    Homo sapiens

    Homo sapiens

    . . . an invasive species

    with life-negating metaphysical beliefs

    about. . .

    The inexhaustibility of natural resources

    The inexhaustibility of natural resources

    Homo sapiens as quasi divine

    Homo sapiens as quasi-divine

    fundamentally separable from all other life forms that have ever existed on the Earth

    Anthropogenic mass extinction

    • Entitled to:







    with little regard for the consequences

    Behold the rational animal

    Behold the Rational Animal. . . .

    Man has been educated by his errors: first, he saw himself only incompletely; secondly, he endowed himself with fictitious attributes; thirdly, he placed himself in a false rank order in relation to animals and nature; fourthly, he invented ever new tables of goods and for a time took them to be eternal and unconditioned . . . .

    Nietzsche, GS 115 (1882)

    Current extinctions

    Current Extinctions

    One species every 20 minutes.

    This rate is more than one thousandfold greater than the natural background rate (Pimm et al. 1995, Wilson 1992).

    (Gorke 2003:1)

    Anthropogenic mass extinction

    Even though human-induced species extinction presently seems to rank low on people’s attention scale compared to other political and societal topics, this does not mean that its significance in earth history or its ecological consequences have diminished in any way. It must repeatedly be made clear that if current trends continue, within the next one hundred years half of all our planet’s species will most likely have become extinct. Thus, members of today’s generation are witnesses and also perpetrators of the greatest catastrophe in the history of life since the disappearance of the dinosaurs 65 million years ago.

    - Martin Gorke, 2003

    Anthropogenic mass extinction

    Nonhuman megafauna s loss of habitat and access to migratory routes

    Nonhuman megafauna’s loss of habitat and access to migratory routes

    due to Homosapiens’ expanding invasion of ‘novel’ ecosystems

    Anthropogenic mass extinction

    Amazon deforestation in the state of Rondônia in western Brazil, 07.30.2000

    Anthropogenic mass extinction

    Amazon deforestation in the state of Rondônia in western Brazil, 08.21.2009

    Anthropogenic mass extinction

    The fragmentation of natural habitats essentially creates isolated ‘islands’ where species’ vulnerability to extinction is heightened as the ecosystem processes and services they depend on for survival are disrupted by biodiversity reduction, competition with invasive species over a shrinking resource base, pathogen dispersal, pollution, and numerous other anthropogenic factors.

    The megafauna du jour

    The megafauna du jour

    Anthropogenic mass extinction

    Consumption patterns of industrialized nations are not ideals for which the ‘developing’ world should strive.

    • based on short-term ‘profit’ and convenience for a ‘wealthy’ minority

    • ignore effects on biodiversity and the long-term survivability of megafaunal species such as our own

    Over consumption of toxic and limited resources

    Over-consumption of toxic and limited resources

    Anthropogenic mass extinction

    If India alone adopted the consumption pattern typical in the US, the global ecological impact would be as if the world’s population had doubled to 13.2 billion (Cox 2008:114).

    The inexhaustibility of natural resources1

    The inexhaustibility of natural resources. . .

    A false and ultimately life negating premise

    . . . a false (and ultimately life-negating) premise.

    Hubris today characterizes our whole attitude towards nature, our rape of nature with the help of machines and the completely unscrupulous inventiveness of technicians and engineers.

    - Friedrich Nietzsche, GM (1887)

    Ecosystems eventually bounce back

    Ecosystems eventually ‘bounce back’. . .

    Anthropogenic mass extinction

    . . . but not always on an anthropocentric timescale.

    Anthropogenic mass extinction

    It usually takes 10 million years for Earth’s multicellular biodiversity to ‘return’ to pre-mass-extinction levels. It took 100 million years after the end-Permian event (Benton 2003:155).

    Anthropogenic mass extinction

    The duration of Homo sapiens’ tenure depends on future consumption practices.

    Anthropogenic mass extinction

    Homosapiens is part of the natural world and is just as susceptible to extinction as Earth’s other organic beings.

    The x factor

    The X Factor

    Earth is becoming less biodiverse as a result of the escalating global invasion and consumption practices of Homosapiens.

    What kind of biosphere are we creating? Will it support the continued existence of organisms such as ourselves?

    The dreams of science fiction will not save our species from extinction

    The dreams of science fiction will not save our species from extinction.

    There is only one Earth.

    Anthropogenic mass extinction

    Blessed are the meek. . .?

    The post human earth

    The Post-Human Earth

    It’s a small world, after all. . . .

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