I agree with Blake that this is a false and quite nonsensical statement.
This is again misleading. As you have repeatedly been informed, there is a strong scientific consensus that megafaunal extinctions in many areas, including North America, were largely due to the impact of humans (especially hunting). You have been provided with cites on this (in particular Barnosky et al., Science 2004, which you yourself have cited after I first mentioned it, although I am not convinced you have ever read anything beyond the abstract).
We’ve been over this ground so many times that I’ve pretty much given up trying to discuss it with you.
Consensus does not equal facts. Whats the consensus on what caused the extinction of the dinosaurs? Once we get to 51%, then the other scientists are thereby wrong?
Here’s a abstract of the article you cite: http://www.sciencemag.org/cgi/content/abstract/306/5693/70 "Assessing the Causes of Late Pleistocene Extinctions on the Continents
Anthony D. Barnosky,1 Paul L. Koch,2 Robert S. Feranec,1 Scott L. Wing,3 Alan B. Shabel1
One of the great debates about extinction is whether humans or climatic change caused the demise of the Pleistocene megafauna. Evidence from paleontology, climatology, archaeology, and ecology now supports the idea that humans contributed to extinction on some continents, but human hunting was not solely responsible for the pattern of extinction everywhere. Instead, evidence suggests that the intersection of human impacts with pronounced climatic change drove the precise timing and geography of extinction in the Northern Hemisphere. The story from the Southern Hemisphere is still unfolding. New evidence from Australia supports the view that humans helped cause extinctions there, but the correlation with climate is weak or contested. Firmer chronologies, more realistic ecological models, and regional paleoecological insights still are needed to understand details of the worldwide extinction pattern and the population dynamics of the species involved."
*
Let me bold one part again “**but human hunting was not solely responsible for the pattern of extinction everywhere. Instead, evidence suggests that the intersection of human impacts with pronounced climatic change drove the precise timing and geography of extinction in the Northern Hemisphere.”
**
Now, that sez that humans and climate caused the extinctions in NA, does it not? How does that =“…were largely due to the impact of humans (especially hunting).”
Is Barnosky et al incorrect as they accept climate change as a significant cause of the extinctions? Or- are they part of the consensus?
Here’s part of another abstract:
"There is intense debate over the causes of these extinctions, especially regarding the extent to which humans were involved. Most previous analyses of this question have focused on chronologies of extinction and on the archaeological evidence for human-megafauna interaction. Here, I take an alternative approach: comparison of the biological traits of extinct species with those of survivors. I use this to demonstrate two general features of the selectivity of Late Quaternary mammal extinctions in Australia, Eurasia, the Americas and Madagascar. First, large size was not directly related to risk of extinction; rather, species with slow reproductive rates were at high risk regardless of their body size. This finding rejects the ‘blitzkrieg’ model of overkill, in which extinctions were completed during brief intervals of selective hunting of large-bodied prey. "
Note that first sentence “There is** intense debate** over the causes of these extinctions, especially regarding the extent to which humans were involved.” “Intense debate” doesn;t sound like consensus to me.
Or this article: http://www.pnas.org/content/99/23/14624.full
“*The cause of the extinction of giant birds, reptiles, and mammals in the late Pleistocene is, for palaeobiology, what Fermat’s last theorem was for mathematics (1): a long-standing scientific puzzle that has captured the imagination of specialists and nonspecialists alike (2). Debate about the possible cause of the extinction has continued for over 150 yr (3–5), stimulated by new fossil finds, dating techniques, and modes of analysis. *” Again- debate- NOT consensus.
"Inferring robustly the cause of the extinction of the Pleistocene megafauna is a remarkably complicated problem that is very sensitive to assumptions concerning the analysis and interpretation of existing data. Although great progress has been made, it is premature to suggest (12, 16) that the problem has been cracked. " Complicated problem… not been cracked. Consensus?
So, you claim to have provided me with consensus, but I have never seen it. Your own cite agrees that climate change is an important part of the model.
The other cites also agree there is much debate and no consensus. Although few would deny that humans had no part at all, their role in the NA extinctions is simply not known, and there is no consensus.
Again, I’m not going to debate this with you. We have been through this discussion multiple times, and it appears you are impervious to learning anything from it. And you still have never read the Barnosky et al. article, only the abstract.
I think someone recommended it upthread already - if you really want to learn more about the prevailing theories on this issue you should read Guns, Germs, and Steel by Jared Diamond for an entertaining explanation of the current research.
Since the end of the most recent Ice Age was a period of extinction and there’s debate over the role of climate change, I had a side question: How did the most recent glaciation effect eastern Asia, especially what’s now China? Are any megafauna die-offs documented there? Both North America and Europe were strongly impacted by the climate change associated with glaciation and its retreat, but on Wikipedia at least I could find surprisingly little about conditions in mid-latitude Asia. Is the history of eastern Asia in the early Holocene in fact poorly known?
But indeed I have. However, I can only link to the abstract, and of course posters here would need to subscribe to read more
OK,I’d like to be convinced. Find me a cite in a "prestigious, peer reviewed journal’ that claims scientists have reached consensus on this debate. Oh, and that the consensus is “that megafaunal extinctions in many areas, including North America, were largely due to the impact of humans (especially hunting).” Note that I have no doubt you can find cites that agree with “megafaunal extinctions in many areas, including North America, were largely due to the impact of humans (especially hunting)”, but find us a cite that thereby concludes the debate is over, consensus having been reached.
If there is consensus, a cite should be easy to find. Every cite I have found sez that there is *anything *but consensus.
Consensus doesn’t mean the debate is over in the sense that every scientist would agree, merely that the weight of the evidence is for a particular conclusion. And if you have actually read Barnosky, you haven’t learned anything from it.
To reiterate, I’m not going to debate with you, because it’s pointless.
Then don’t, just post the cite. Just one cite, stating what the consensus is. Weight of the evidence? Ok, maybe. But who is doing the weighing? Read the article from Brook and Bowman I provided. “Quantitative modeling can investigate various scenarios by integrating existing knowledge in a logical, structured, and transparent way, but it must be accepted that the output of these models is a product of explicit and implicit assumptions. … These caveats should be borne in mind when making claims about the causes of past extinctions, particularly given the way such debates can influence current environmental management policy” That’s not my opinion. If you disagree with the authors, there’s a link at the bottom of the cite I provided. Same with my other cites- I am not giving my opinion here, I am simply quoting various “prestigious, peer reviewed journals”. Perhaps they are wrong- but you can’t say I am- as I am simply quoting them. Of course, if they are incorrect, there should be “prestigious, peer reviewed journals” where they are refuted. Those should be easy to find and cite. If you wish to debate- why it’s simple to write an article for one of those "prestigious, peer reviewed journals’.
Look, if we were talking about the K-T extinction event (Dinosaurs, folks), we’d all know there’s no consensus. Even if Bakker posted here himself and said the Alvarez hypothesis (big asteroid in the Yucatan, again for the laymen) was the “consensus” - he’d be wrong. There just ain’t no consensus on what caused the various Major extinction events*. And- you know that full well. So do you, Blake.
Now sure, if you said “among my colleagues, there’s a large majority that agree it was xxxxx” OK, then. But there ain’t no consensus. But hey- it’s easy to show I am wrong- just provide a cite- I have provided 5 of them.
that’s why they are all hypothesis as opposed to *theories. *
I am currently the curator in charge of a major museum exhibition on the Great Biotic Interchange between North and South America, which includes discussion of the reasons for megafaunal extinctions in the Americas. In writing the script for the exhibition, I have read dozens of peer-reviewed articles and books about the subject. I have also personally interviewed several of the leading experts on the paleontology of the two continents. The exhibition script, which describes the consensus I have mentioned, has itself been peer-reviewed by several experts. My opinion that such a consensus exists is based on this rather thorough professional review of the subject. So I’m going to go with “my post is my cite.”
