"Error bars for the impact event, 2013."
I think what Bystander may be trying to convey, succinctly, I'm expanding:
The duration or even the fact of a mass extinction gets muddled up after 60 million years. And. It generally gets fuzzier the further back you go in time. How long did it take for the dinosaurs to beome extinct? We can see (from our viewpoint) very clearly that at some point there were lots of fossils from certain clades of animals and plants. More recent fossils: none. So, voila, extinction. No question there. But did it happen in a week? 15000 years? That is the 'error bar' in Bystander's comments. IMO. He can certainly correct my impression.
If we can narrow down the time frame, can we tie that period of time to some causative agent(s)? That is what this paper is talking about. In this case the Deccan traps were active (do not forget the timing fuzz problem) and at some point close in time near the Chicxalub impact, the activity surged apparently by orders of magnitude. Cause and effect?
Cute micro-mammoth from Wrangel Island:
http://factday.com/2012/04/27/the-last-mammoths-died-on-wrangel-island-around-2000-2500-bce/
See:
http://www.nature.com/nature/journal/v362/n6418/abs/362337a0.html
Mammoths are extinct. Mammoths used to be in North America. So when did that happen? Supposed to be during the Pleistocene Megafauna extinction event. Robin Gibbons at Stanford: From: http://web.stanford.edu/group/journal/cgi-bin/wordpress/wp-content/uploads/2012/09/Gibbons_NatSci_2004.pdf
During the Pleistocene, the world saw a dramatic number of extinctions of very large terrestrial
species. The losses of these megafauna have been attributed to either of two different hypotheses.
One hypothesis states that global climate changes occurring during the Pleistocene caused
environmental pressures that forced the extinction of several megafaunal species. The second
hypothesis proposes that the global spread of Homo sapiens and hunter-gatherer subsistence
practices were responsible for these deaths. Examining these two theories reveals that neither
climate changes nor human overkill were likely to be individually responsible for the Pleistocene
extinctions. Instead, a synthetic model that includes both hypotheses appears to be the most
plausible explanation for the Pleistocene losses.
This is another guise of the exact same problem set being discussed here. Multiple causes and time frames. Did humans cause the extinction? Climate? or both?
Mammoths lived on Wrangel island until about 2000BC. In other words our discrete approach to extinction as an assumption: 'Wham, you're dead',
may not be the way extinctions work.
As a side note - it is very interesting that extinct beasties - we associate mammoths as 'long ago animals' - persisted well into the time of written history. Extensive writing existed in Egypt at this time. As did writing in several other places throughout the Middle East, Asia Minor, India, and China. They did not seem to be interested in dwarf mammoths in the Artic, however. Nobody wrote about them. AFAIK. But they were extant during historical times.
