Tuesday, August 12, 2008

Overkill in the 6th Mass Extinction

Research led by UK and Australian scientists sheds new light on the role that our ancestors played in the extinction of Australia's prehistoric animals. The study, published this week in the journal Proceedings of the National Academy of Sciences of the USA, provides the first evidence that Tasmania's giant kangaroos and marsupial 'rhinos' and 'leopards' were still roaming the island when humans first arrived. The findings suggest that the mass extinction of Tasmania's large prehistoric animals was the result of human hunting, and not climate change as previously believed.

Scientists have long argued over the reasons behind the worldwide mass extinctions that took place towards the end of the last ice age. The main culprits are generally thought to be climate change or some form of human impact. People only arrived in Tasmania around 43,000 years ago, when the island became temporarily connected by a land bridge to mainland Australia. None of Tasmania's giant animals, known as 'megafauna' were known to have survived until this time. This appeared to clear humans of any involvement in the disappearance of the island's large megafauna.

This new international study reports the discovery of giant kangaroos surviving in Tasmania until people arrived, placing humans back on the list of likely culprits for the subsequent extinction of the megafauna.

There are three candidates for the 6th mass extinction's cause right now. The first is that the climate changed and all the megafauna like the wooly mammamoth and sabre toothed tiger died from that. The second hypothesis was that mankind wiped them out. The third is that there was, at least in NorAm, a comet crash that did in a number of species.

The problem with the first hypothesis is that there were numerous times between glacials and interglacials that the climate swung more wildly than now. This puts a damper on the idea that the climate, which the megafauna had survived just fine previous, suddenly warmed so much so fast that it killed them all this time.

The second hypothesis seems more likely to me and at some point in the future, we'll talk about this in depth after I do the KT (K-Pg, Julia, right?) Mass Extinction in depth like I have the others.

The final hypothesis is actually advocated by my colabbies. The primary problem is that their proposed impact over the Canadian Arctic, iirc, would only effect NorAm...not SoAm or Eurasia. The mass extinctions were pretty severe there too.

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