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What Killed Ice-Age Animals? Lakes and Trees Provide Surprising Clues

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What are they teaching in TX schools, Jeff?

robert Hill of CA 1:53AM December 14, 2009

To answer a reader question regarding whether an axis shift of the earth could have occurred, the answer is that it is extremely well researched, and there is only a gradual shift in the axis of the earth, which correlates with major ice ages. They also consider the distance from the sun, which shifts as the orbit of the earth goes from almost circular to more ovoid and back again over very long periods of time.
As for the gravity of the earth, it does not fluctuate and is clearly fixed. If it did fluctuate, one would need to assume that the Sun's gravity fluctuates and since we are still a water-bearing planet in a stable orbit, that is clearly not happening. Mass generates a specific amount of gravitational force, and the mass of the earth is essentially fixed.
That said, size IS important... some extinction events (the Permian mass extinction) were apparently caused by the rapid decline in the oxygen level of the atmosphere, suffocating all animals but those with large lungs who were already adapted to lower levels of oxygen at high altitudes. So the general idea that large isn't necessarily good for survival is a sensible line of inquiry.
And of course, there is the clear global warming phenomenon--maybe it was just getting too hot too fast for them and they didn't adapt to the climate and the influx of new competitors as well as new predators.

Joe Burney of NJ 10:07PM December 12, 2009

I don't see the discontinuity others are claiming exists. The headline says "clues", and the article supports that well. It is straightforward--the decline was not caused by human intervention, a meteor strike, a spate of forest fires, or a change of habitat (as far as can so far be determined). The decline was gradual over 1000 years. The increase in fires and broadleaved vegetation follow the population decline. Those are profoundly different pieces of information than what has been claimed previously, and are indeed clues to why the die-off occurred.

Joe Burney of NJ 9:53PM December 12, 2009

How much research has gone into the possiblity that there was a shift in the axis of the earth? How about a change in gravity? Whether temporary or permanent. Those huge animals could likely have been crushed by a changing a gravity, we all succumb to what we have now as we age.

Jeff of TX 7:21PM December 11, 2009

A very disappointing article! The headline and the story story are not really related. At least the article draws conclusions about what did not kill the Mega Fauna but the evidence is not especially convincing.
Some years ago I wrote a term paper on this very topic. The evidence for the extinction was rather subjective then - and it appears just a elusive. I wanted to suggest a bacterial, viral or fungal infection or possibly a new parasite - that might have migrated to North America. The Mega Fauna died out in Europe first so I thought it was a reasonable suggestion BUT I was told that no physical evidence for my theory could be found so don't go there! Very unimaginative and limiting, I thought!
I keep hoping that modern forensics could find something of interest along these lines from the frozen mammoths, but so far - nothing has been published.

Karin Green 10:12PM December 06, 2009

Absolutely right! "News" articles seem to exhibit a great deal of discontinuity between headline and content. Almost as though one person is hired to write eye-catching headlines and another is hired to cobble together some drivel to fill the space before the next headline.

Zaphod of ID 12:15PM December 04, 2009

The glaciers were all melting.... Global Warming?

R.L. Schaefer of CA 12:05PM December 04, 2009

Looks like this article is a classic example of bait and switch. First they get you to read it based on the teaser that they can explain why the extinctions happened and then the actual article proves nothing. Given the broad ranges and uncertainties of carbon dating there is nothing to say that an extinction time frame of 1,000 years is not consistent with one or more mass extinction events. Did they check for iridium in the mud and dung? If a lake is covered with ice for thousands of years and then the ice cap suddenly melts, all of the accumulated dust and spores in the ice are going to come to the bottom at the same time.

Hyped Title of FL 11:02AM December 04, 2009