Sunday, 28 October 2012

All Creatures Great and Small (are important considerations in the megafauna extinction debate)

I came across an interesting journal article the other day about introducing a behavioural economics perspective to megafauna extinction. This journal is interesting not only to me as an Economics and Geography student, but also because it suggests the value of an inter-disciplinary perspective to environmental geography.   In the 2005 paper ‘Megafauna Extinction: A Paleo-economic Theory of Human Overkill in the Pleistocene’, Bulte et al argue that previous scientific models of overkill concentrated only on megafauna as prey for humans, while ignoring the entire opportunity set facing the human hunters, which is the presence of substitute foods and behaviours. One of these is hunting small animals or minifauna.

Bulte et al have designed a model which suggests that counter intuitively, hunting minifauna was essential to the overkill hypothesis. Minifauna supported human populations and allowed humans to reach critical densities which were large enough to wipe out megafauna. Besides, hunting minifauna enabled more chance encounters with megafauna. Complementing last week’s post, they suggest that the harsh environmental conditions of the late Pleistocene may have triggered humans to engage in minifauna hunting rather than more benign activities like agriculture.  Minifauna did not go extinct because they breed much more quickly than slow-breeding megafauna.

This echoes modern day poaching behaviour in Africa. Poachers often hunt both rhinos and elephants, and not only the more valuable rhino ivory alone, because the probability of encountering rhinos is much smaller, making sole rhino hunting a loss-making activity. Thus, poachers also hunt the relatively more abundant elephants, taking rhinos as a bonus. Thus, elephant hunting is what economists call a ‘complementary’ activity to rhino hunting, in the same way as hunting minifauna was complementary to hunting megafauna for early humans.  

Although the authors of this journal are economists rather than paleo or megafauna experts, they do make an important point about considering the behavioural incentives facing early human hunters and not simply portraying them to be the mechanistic 'superpredators' of most overkill models.


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    1. Hi! I do agree that we should consider the effect of hunting minifauna on the overkill hypothesis when considering megafauna extinction. However, I think that regardless of the behavioural incentives facing early human hunters, the proposition that they mainly hunted minifauna and in the process of doing so, hunt megafauna (by extension from your analogy) still poses Man as 'superpredators' and does not exonerate Man from the blitzkrieg hypothesis.

      Do you happen to know if there were any changes in the extinction rates for minifauna across the pleistocene and if there were any evidence of human impact on minifauna biodiversity?

  2. Hi Fung,

    My aim in posting this paper on Man hunting minifauna is not to exonerate Man from the blitzkrieg hypothesis. I just intend to show that species should not be viewed in isolation as ecosystems and extinction events are extremely complex! While minifauna is not within the scope of my blog, I do know what minifauna extinction certainly happened as climates changed. However, the late Pleistocene extinction event was unusual in its rapidity and species selection (i.e. megafauna was most affected). Perhaps I should do a blog post to explain this species selectivity soon!