In Twilight of Mammoths, Paul S. Martin introduces the concept of ‘overkill’, in which many extinct species pertaining to the late Quaternary period would have survived but additional survival pressures ensured their demise. Martin directly attributes the additional survival pressures that ensured the extinction of these species to the spread of humanity. In specific Martin demonstrates the ability of human civilizations to produce profuse impacts on local ecosystem without the use of advanced technology.
To begin, Martin demonstrates his ‘overkill theory’ by alluding to the appearance of the Clovis people, the first humans to inhibit America, with the simultaneous and subsequent mass extinction of two-thirds of large animals in the region. In specific, humans subjected these animals to extinction by over-hunting, habitat destruction, and introduction of aliens. Therefore, through the addition of further survival pressures, humans changed the local ecosystem, inevitably subjecting megafauna species on the verge of extinction to their demise.
Moreover, Martin demonstrates the responsibility of human activity in the extinction of species through the comparison of the relative megafauna age extinctions between
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In specific, Hibbard’s argument regarding the inability of Galapagos tortoises, modern relatives of giant tortoises that went extinct, to survive harsh condition provided a counter argument. To elaborate, if Martin’s theory was correct then Hibbard argues that Giant tortoises would have been able to survive harsh weather conditions, eventually falling victim to human predation. Yet his study demonstrates that future descendants of the Giant tortoises died upon immediate exposure to cold weather, thereby attributing climate change as the cause of their extinction; invalidating Martin’s