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If you have read Jared Diamond's works, you already know the question.

There is a coincidence between planetary scale climate change, human settlement and megafauna extinctions. From giant kangaroos in Australia to elephant birds in Madagascar, from New Zealand and Hawaii in the Pacific to North and South America most of the species that lived outside Eurasia and Africa and weighted more than about 30kg became extinct in the recent past.

People argue about what was the cause: over hunting, difficulties adapting to the new environment, humans carrying new diseases/pests or altering the environment by using fire.

This is a nice place where to start, but: where do I continue? Are you aware of any recent development in the field and/or of a summarizing work about state of the art research?

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Interesting that I can read that first sentence, and not come away feeling more context is needed...but I can. –  T.E.D. Oct 22 '12 at 19:33
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...oh, and I created a prehistory tag for this. Perhaps not a perfect solution, but much better than ancient-greece :-) –  T.E.D. Oct 22 '12 at 19:39
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This isn't remotely under the banner of history. Not even close. –  choster Oct 23 '12 at 19:00
    
"Not even close" is excessive, I think. It certainly falls under the banner of prehistory. It also stretches well into historical times, for some species. Peace –  astabada Oct 24 '12 at 8:53
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We could have a discussion (probably best on meta) about if anything that happened to human beings in pre-literate area/times is on topic. However, if the answer is in the negative, rather a lot of our existing questions will need to be closed. Still, a line probably ought to be drawn somewhere, unless we want to start fielding questions about continental drift and the big bang. –  T.E.D. Oct 24 '12 at 15:08
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1 Answer 1

First of all let me say that this is an excellent and well researched question. A quick recap from Wikipedia is handy:

Outside the mainland of Afro-Eurasia, [...] megafaunal extinctions followed a distinctive landmass-by-landmass pattern that closely parallels the spread of humans into previously uninhabited regions of the world, and which shows no correlation with climatic history [...]. Australia was struck first around 45,000 years ago, followed by Tasmania about 41,000 years ago (after formation of a land bridge to Australia about 43,000 years ago), Japan apparently about 30,000 years ago, North America 13,000 years ago, South America about 500 years later, Cyprus 10,000 years ago, the Antilles 6000 years ago, New Caledonia and nearby islands 3000 years ago, Madagascar 2000 years ago, New Zealand 700 years ago, the Mascarenes 400 years ago, and the Commander Islands 250 years ago. Nearly all of the world's isolated islands could furnish similar examples of extinctions occurring shortly after the arrival of Homo sapiens, though most of these islands, such as the Hawaiian Islands, never had terrestrial megafauna, so their extinct fauna were smaller.

Other than over-hunting, several other causes have been advocated.

Climate change This is ruled out both by the bigger and clearer picture that we have (which includes extinctions over 50.000 years) and by several examples were extinctions did not occur necessarily with climate change (the best example being the survival, until mid Holocene, of a Mammoth in an Alaskan island, see. Guthrie R. D., 2004, Nature, 429, 746). Indicators of global climate change do not show any correlation with extinction patterns.

Over-hunting Over hunting is the other hypothesis, and currently the most accepted one. The survival of megafauna in Eurasia and Africa to present day is explained by the fact that these animals co-evolved with our ancestors over 2 million years, and had time to develop means to defend themselves. On the other hand, megafauna in the other landmasses was naive to unknown and relatively small sized humans, which might have proved fatal. The lack of killing sites is explained with the exceptional rapidity of the extinctions. In New Zealand, for instance, the extinction of Moas was more rapid in the North than in the South Island, because of different human population densities. Accordingly, in the North it's more difficult to find butchery sites, whereas in the South more than 100 have been found already.

Other causes are summarized in Burney and Flannery 2005.

Burney D. A. and Flannery T. F., 2005, TRENDS in Ecology and Evolution, 20, 395

In their recent study, Turvey and Fritz 2011 claim that their results:

are generally consistent with the hypothesis that large mammals have been disproportionately vulnerable to extinction since the end of the last glaciation.

Turvey S. T. and Fritz S. A., 2011, Phil. Trans. R. Soc. B 366, doi: 10.1098/rstb.2011.0020

Johnson 2002 studied the effect of body mass and reproductive rate in relation to megafauna extinctions, in the Americas, Australia, Madagascar and North-Eastern Eurasia. He finds that there is indeed a trend with body mass (higher body masses more likely to go extinct) but also with reproductive rates (low reproductive rates more likely). Because the two are related (this is an assumption he derives from extant species) it is impossible to disentangle them.

Among the extant species (remember that we are talking about specific areas of the world), some are massive enough and had low enough reproductive rates that they should be extinct according to the patterns discovered. The traits they share shelter(ed) them from human contact; they are one or more of: - nocturnal - arboreal - alpine - live at high latitudes - live in closed habitats (e.g. dense jungle)

Johnson C. N., 2002, Proc. R. Soc. Lond. B 269, doi: 0.1098/rspb.2002.2130

The best evidence so far is to be found in Rule et al. 2012. They analyze the occurrence of Sporormiella fungal spores (which derive mainly from the dung of megaherbivores) in mud cores spanning the last 130000 years from Lynch’s Crater in Queensland, Australia. Their data showed that megafauna happily survived two major changes in regional climate, only to disappear about 41000 years ago, when climate changes were minimal. The Sporormiella spores disappear before the increase in charcoal and the transition from rainforest to fire-tolerant vegetation, supporting the idea that hunting alone eliminated the megafauna, and that the subsequent change in the flora was a consequence of the elimination of browsers and an increase in fires.

Rule S., Brook B. W., Haberle S. G., Turney C. S., Kershaw A. P. and Johnson C. N., 2012, Science, 335, 1483, doi: 10.1126/science.1214261

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