True causes for extinction of cave bear revealed

The cave bear started to become extinct in Europe 24,000 years ago, but until now the cause was unknown. An international team of scientists has analysed mitochondrial DNA sequences from 17 new fossil samples, and compared these with the modern brown bear. The results show that the decline of the cave bear started 50,000 years ago, and was caused more by human expansion than by climate change.

"The decline in the genetic diversity of the cave bear (Ursus spelaeus) began around 50,000 years ago, much earlier than previously suggested, at a time when no major climate change was taking place, but which does coincide with the start of human expansion", Aurora Grandal-D'Anglade, co-author of the study and a researcher at the University Institute of Geology of the University of Coruña, tells SINC.

According to the research study, published in the journal Molecular Biology and Evolution, radiocarbon dating of the fossil remains shows that the cave bear ceased to be abundant in Central Europe around 35,000 years ago.

"This can be attributed to increasing human expansion and the resulting competition between humans and bears for land and shelter", explains the scientist, who links this with the scarce fossil representation of the bear's prey in the abundant fossil record of this species.

In order to reach their conclusions, the team of scientists, led by the Max Planck Institute for Evolutionary Anthropology (Germany) studied mitochondrial DNA sequences from bear fossils in European deposits (Siberia, Ukraine, Central Europe and the Iberian Peninsula, specifically Galicia), and carried out a Bayesian analysis (of statistical probability).

The scientists also made comparisons with the modern brown bear (Ursus arctos) and with fossil samples of this species of bear, and managed to show why one became extinct and the other did not. In order to demonstrate this, the study analysed 59 cave bear DNA sequences and 40 from the brown bear, from between 60,000 and 24,000 years ago for the cave bear and from 80,000 years ago up to the present day for the brown bear.

The impoverishment of ecosystems during the last glacial maximum was "the 'coup de grace' for this species, which was already in rapid decline", the author explains.

The present day brown bear did not suffer the same fate and has survived until today for one simple reason – brown bears did not depend so heavily on the cave habitat, which was becoming degraded, and this is why they did not follow the same pattern as the cave bears.

"Brown bears rely on less specific shelters for hibernation. In fact, their fossil remains are not very numerous in cave deposits", the Galician researcher says.

The definitive extinction of the cave bear "broadly" coincides with the last cooling of the climate during the Pleistocene (between 25,000 and 18,000 years ago), which may have led to a reduction in shelter and the vegetation that the animals fed on.

The cave bear inhabited Europe during the Late Pleistocene and became definitively extinct around 24,000 years ago, although it held out for a few thousand years longer in some areas, such as the north west of the Iberian Peninsula, than in other places. This ursid was a large animal, weighing 500 kg on average, and was largely a herbivore. The bear hibernated in the depths of limestone caves, where the remains of individuals that died during hibernation slowly accumulated over time.

Stiller, Mathias; Baryshnikov, Gennady; Bocherens, Herve; Grandal D'Anglade, Aurora; Hilpert, Brigitte; Muenzel, Susanne C.; Pinhasi, Ron; Rabeder, Gernot; Rosendahl, Wilfried; Trinkaus, Erik; Hofreiter, Michael; Knapp, Michael. "Withering Away-25,000 Years of Genetic Decline Preceded Cave Bear Extinction" Molecular Biology and Evolution 27(5): 975-978, mayo de 2010. doi:10.1093/molbev/msq083

Over time with the overburden of ice removed, those bodies would rebound.

Of course...and the US is still recovering from the last glaciation (durn Canadians dumping the Great Lakes onto us!). Sure, there's isostatic forebulge and there's gravitational effects, but their magnitude are insufficient to support (literally and figuratively) an ice-dam situation for a more heavily glaciated Antarctica.

This is simply more like a very large ice dam on the order of thousands of feet in height that has a wide area collapse. The water behind the dam simply pours out as fast as gravity can sustain the project. Kind of like a Johnstown Flood on steroids.

Like Bretz flooding, right? Well, where's the support for this wall that the circumpolar circulation keeps frozen? Meltwater above and saltwater below?

And don't forget you're in a divergent (polar) condition, where an MLD of a given magnitude would rapidly disperse as it moved away from the point-source. The Channeled Scablands are...channeled. Without channeling, in the open ocean, you would be dispersing this pulse of excess water.

Where are you getting these hypotheses? Has any modeling (like Komatsu's) been done to estimate this? I'd be interested in any citations. I've been out of that literature for a while now.

Thanks.

You know as fast as world temperatures rose 14000 years ago this would need to go on only a few decades at most, and it would be over in hours although the global tsunami would be traveling North at just under the speed of sound.

Here's where the idea comes from ~ years back I found that the island of Penang didn't have any dirt when the Chinese first arrived (circa 1398 or thereabouts). This was where the Ming elected to establish their base of operations for their Treasure Fleet under Admiral He.

So, how big a tsunami would it take to remove the dirt from Penang, and was that just on the plain below, or did this continue up the hills to the highest elevation of about 2400 feet.

Further research didn't reveal anything, but the Chinese had a well established regime for bringing in the materials they needed to make soil and did so.

We've all seen what just a modest tsunami can do to Indonesia as well as the entire Indian Ocean coastline. Even more recently the Andaman Islands had a fault break/slip and the tsunami warning went up ~ a modest tsunami would have washed over Penang island like it was a turtle in a pond ~ and they'd been back to "no soil".

Fortunately there was no tsunami.

So, looking at Lake Agassiz and the recurring problems with faults near/around Indonesia and what tsunami do, and the damage Lake Agassiz created when the ice dam broke, just scale that up a thousand times.

This isn't a difficult scenario to envison.

Though the glacial collapse was rapid, I think you're a bit lost on the scales, both temporal and spatial.

I admit not being familiar with that chronicle, nor that Admiral He set up base at Penang (I know he stopped at Melacca [sp?], but not that he had set up a base nearby). But I suspect you're taking the translation too literally and anachronistically, much like George Washington wasn't meaning his troops were running around Burning Man style when he spoke of them being "naked" (the term meant that their clothing was inappropriate for the weather, not that they had none). Perhaps you read "barren" and it was meant as "unproductive soils" rather than "bare of soils"?

What's most compelling to me is physical evidence. It's quite clear that Penang now has a thick residual (i.e., developed in-situ) soil cover. Though the authors of that paper are engineers--and might therefore use "soil" in the engineering sense--they quite clearly define their study as being focused on residual soils. So what you would ask us to accept is that for nearly 14,000 years, no soil developed, but then in the past 600 years, we have residual soils. Admittedly, anthropogenic fill could prevent erosion of residual soils that would otherwise be washed away, but the geography and modern observations don't support that as relevant.

Besides, you'll note that the depth to bedrock, regardless of catena, is generally greater than 5 meters....even up to 40 meters! By my rough calculation, covering the island with only 5 meters of soil would require more than 300 million dump truck trips! By comparison, the Great Pyramids would have been a preschool project. That there would be little evidence of this is inconceivable, especially considering the island was uninhabited when discovered by Europeans a couple of centuries later.

This isn't a difficult scenario to envison.

In the absence of evidence, yes. But when we look at physics involved and the actual data, we see that the hypothesis is untenable and should be rejected.

If you don't, though, you could write it up, throwing in something about this being the origin of the deluge myth--and then claim to have found a lost Velikovsky manuscript! ;-)

Note, you must be very careful to differentiate Penang, the island, from Penang, the state. Intriguingly "they" found the oldest building ever built in Penang state last year. It appears to have been some sort of business office like a tax collector would use.

BTW, the island goes up to 2400 feet. Not knowing how high a tsunami would need to be to give the Ming the idea it was "barren" let's say 500 ft would probably do the job. Hillsides could probably supply whatever else was needed for rebuilding.

Settlement in this area has been very slow to arrive ~

Note, you must be very careful to differentiate Penang, the island, from Penang, the state.

I took it you meant the island. You didn't mean the state, did you?!

And are you now saying that the tsunami didn't wash over the island like a turtle, but just lapped upon the shores?

That argument still doesn't hold water, as the mineralogy of the residual soil is documented and shows that it is formed in-situ, not brought in from the hillsides. And even in the tropical climate, it didn't form in 600 years.

With no evidence of a tsunami washing the soil from Penang, even in the lowlands, the whole idea falls apart and confirms the lack of evidence or plausible mechanism elsewhere.

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