Did Humans or Climate Change Cause the Extinctions of Pleistocene Eurasian Megafauna?

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Did humans wipe out the Pleistocene megafauna? This is a question that can be asked separately for each area of the world colonized by Homo sapiens. It is also a question that engenders sometimes heated debate. A new paper coming out in the Journal of Human Evolution concludes that many Pleistocene megafauna managed to go extinct by themselves, but that humans were not entirely uninvolved.

The paper by Pushkina and Raia ("Human influence on distribution and extinctions of the late Pleistocene Eurasian megafauna") examines sources in the literature and a number of databases for Eurasian localities. The researchers attempt to measure "species commonness" as the proportion of sites of a given time period for which a particular species is present, for about 30 species. "Commonness is a proxy of abundance of the species remains in a fossil locality or assemblage, because it is likely that within a given region a species abundant in some sites will be present in most of them..." These data were further analyzed for uneven sampling across time and other biases in the fossil record.

An important part of this analysis is the temporal framework for human presence in the region, which the authors summarize as follows:

Long before 100,000 years ago, humans coexisted with the megafauna without causing any extinction. In western Europe, there is archaeological evidence of human occupation as early as about 800,000 years ago ... The Acheulean cultures are known from the Caucasus from about 583,000 years ago ... Humans were present in northern Eurasia (Eurasian Plains) at about 45,000-40,000 years ago .. Anatomically modern humans inhabited western Europe at about 34,000-36, 000 years ago ... The earliest modern human occupation or early Late Paleolithic occupation for southern Siberia is recorded at 43-39,000 yrs ago and they appear to have occupied all of northern Asia by 13,000 yr ago ...

An overarching pattern seen in this study is that many of the megafaunal species did not overlap totally with human habitation. Hominids, being essentially tropical, kept to warmer areas while many of the famous Pleistocene megafauna were found in cooler habitats. In the mean time, humans tended to hunt the most abundant prey. As this relationship evolved, the researchers believe that many of the megafauna suffered from habitat loss due to climate change, and became rare (or went extinct) primarily because of this transition.

The relative commonnes of the large mammals of Eurasia were influenced by human activity to some extent. People became increasingly able to hunt abundant prey species, many of which, however, are still living. Humans became able to exclude large carnivores from their sites or defend their homes. By the latest Late Paleolithic populations of large mammals of the "mammoth-steppe" were already suffering from the deterioration and contraction to the north of their preferred habitat, while humans appeared to show little interest in the now-extinct species, even when a conservative archaeological approach was used that should have favored finding human influence on extinct fauna. Only the extinct steppe bison appears to have been negatively influenced by humans. Our findings are mainly consistent with the climatic explanation of the late Pleistocene extinctions in Eurasia.

PUSHKINA, D. (2008). Human influence on distribution and extinctions of the late Pleistocene Eurasian megafauna. Journal of Human Evolution DOI: 10.1016/j.jhevol.2007.09.024

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Very interesting; I'll have to check this one out (that is, if I ever get through the pile I already have stacked up!). I've always thought the overkill hypothesis was too narrow by itself, so it's good to see some research taking a bit of a broader perspective.

There is unequivocal evidence for extinctions of large birds and reptiles on newly-settled Pacific islands within (bearing in mind the fuzzy date resolution) 100-200 years of first settlement, correlating very well with the earliest archaeological dates (yet found).

There is similar evidence from North America and Australia. Eurasia might be a bit different, because humans and large animals had already survived together for a very long time, as in the case of Africa, where large animals still survive.

This kind of report reminds me of the very similar studies showing that dinosaurs were already dying before Luis Alvarez' comet.

There will always be someone who doubts a 'Sudden-Death' theory, which makes it all the more interesting, but not necessarily wrong.

By Richard Parker (not verified) on 26 Jan 2008 #permalink

It is my contention that when early humans moved into a territory they would prey on the local animal populations. The animals would not know enough about humans to know that they should be afraid of them and so they would be "easy meat".
The animals in Africa, where humans evolved, would already know this, they knew enough to run away. Those in other areas with large populations would eventually learn by experience.
It is interesting to note, (as a birdwatcher), in areas of the world where birds are not shot they are quite "tame", at home where there are "sporting interests", you have to be cunning to see a bird close up.

Regarding coexistence of humans with megafauna prior to 100,000 years ago - is this the case in Asia? There seems to have been a decline in several species of large animals (Gigantopithecus, stegodont elephants etc) from about the time that H.erectus showed up. As this was probably the first species in our lineage to be a more or less full time hunter of big game, I would have thought there would have been some effect.

I'm sorry but this is just absurd. There is no proof that humans preyed or even hunted a good majority of the megafauna of North/South America and Australia. The only reason why people or even scientists assume it was humans is the dates of humans arrival and the very few kill sites that has very few megafauna bones. No matter how much bitching people do the only reason why people want to think it was our ancestors fault is because of the recent extinctions of the past 600 years and the extinctions of the moa in New Zealand and a few large sloths that inhabited Madagascar. Everyone wants some type of justification for the megafauna demise but there is not a shred of proof that a populaton of a few thousand aboriginals with only rocks and primitive spears hunted every animal to extinction. It is also absurd that people think that primitive humans killed every creature that was bigger than them in N/S America within a thousand years or so. Like WTF are you talking about, yes humans killed a particular species like mammoths or mastodons and others but to say a population of 4-5 million people, man, woman, and child with an life expectancy of 35-40 years at best, generation after generation to kill off every living thing they see just for the fuck of it?! It is not even ethical nor is it even gullible to sit here and say that our ancestors were stupid. They must have known the probability to kill a giant creature and how successful they could or could not get the creature to go down. I apologize for the bickering but this grap needs to end, it was climate change, climate change, climate change. What proof to you have besides reading off an article that says they have evidence it was humans when most of it is pure speculation and in the end, until there is proof, it is just another hypothesis brought up with only claims that don't even have proof to back up the claims. Anyone who believes it was humans and humans alone are only acting like cry babies because they want to put blame on something that we're use to and know about. The extinctions of the past 500+ years and other dates previous to that obviously coincide and was impacted by human activities. Another reason why people are so fixated on the idea that humans did it is because they learned it from a young age and if someone literally said that it was climate change and vegetation change alone and actually had proof, those people would still believe in what they believed before. It is a natural way of thinking but it is stupid for people to 'assume' this and that because scientist A and scientist B says something different. And even if it was our ancestors, and that's a big IF, then what's to say they did it to survive. Blame yourselves and all but none of you wouldn't be here if it weren't for them. I mean for god's sake even if they were around today I'm sure the majority of you wouldn't care much about it. You only know the greatest value of something or living creature until it is actually gone. It sucks but that is survival everyone. Just because a renowned scientist finds markings on bones of extinct animals made by man and radio-carbon dating techniques develops the idea/theory of overkill, is a good theory I will say, but it is purely "speculative". Overall, there is no evidence nor proof that humans was the reason for these extinctions, and even if they were responsible, it was out of pure survival. The only things you should be bitching about is the extinctions of the past 700 years. So shut the fuck up about it and eat yourself some noodles and be grateful humans has survived through some of the hardest times in earth's history