Category Archives: Evolution

Amstrup grasps at straws to defend his polar-bears-are-doomed computer model

Polar bear activist Steven Amstrup made an astonishing statement in an interview earlier this week — he insisted that the current rate of warming in the Arctic is greater than anything polar bears have lived through before. He also said that optimistic comments on the future of polar bears made by geneticist Matt Cronin a few weeks ago were “incautious” and “misleading.”

Polar bear cubs in den wikipedia

Previously, I described how a new paper by Cronin and colleagues confirmed that genetic evidence indicates polar bears have been around long enough to have survived several past Interglacial periods that were warmer than today (and therefore, would have had virtually no summer ice). Cronin, not unreasonably, had some critical things to say about computer modeled predictions that polar bears could not survive in an Arctic without summer sea ice.

On Monday, the Anchorage Daily News gave Amstrup a forum to rebuke Cronin for his comments. A similar story was also carried by the Washington Post. [In the same ADN article, geneticist Charlotte Lindqvist, offered an outdated argument against future polar bear survival that I’ll deal with later]

Today, I’ll address Amstrup’s ridiculous assertion that the current rate of warming, attributed by him primarily to human activities rather than natural variation, is something polar bears have never experienced in their evolutionary history (a period of more than 400,000 years!).

Let’s start with the offending portion of the news item (published March 31, 2014):

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New genetic study confirms polar bears survived several warm Interglacials

There is a new polar bear genetics paper out in the Journal of Heredity, by University of Alaska Fairbanks genetics professor Matt Cronin and colleagues. Matt Cronin, in case you didn’t know, was the first to pick up the close genetic relationship between polar bears and grizzlies, as a result of research he and colleagues did back in the early 1990s (Cronin et al. 1991).

Figure1 from Cronin et al. 2014 (in press) showing the locations of bear samples used in their genetic study. MT, Montana; AK, Alaska; Polar bear samples were from the Chukchi, Beaufort and Barents Sea populations.

Figure 1 from Cronin et al. 2014 (in press) showing the locations of bear samples used in their genetic study. MT, Montana; AK, Alaska; Polar bear samples were taken from the Chukchi, Beaufort and Barents Sea populations.

While no earth-shattering new information was revealed in this new study, reported over the weekend by the Alaska paper SitNews (March 15), it used a more detailed method to confirm the results of previous work – that polar bears have been around long enough to have survived several past Interglacial periods that were warmer than today (with less ice in the Arctic) and are genetically distinct from grizzlies.

A feature that really set this work apart was how it was promoted.
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Eemian excuses: the warm was different then, polar bears were fine

Today I’ll discuss the response by Polar Bears International representative Steven Amstrup to a comment submitted during their recent “webchat” at The Guardian (Wednesday, November 6), which had to do with the fact that polar bears survived warm periods in the geological past, particularly interglacials.

[Here’s a pdf file of all the questions that were answered by PBI staff: PBI webchat Q&A, also available here]

This is the comment (the first portion of #4 on my list), submitted by MarkBLR:

There was a paper in Science magazine last year (link …) indicating that polar bears became a distinct species about 600kya (+/- 300k years).

This means that they have survived at least two (and possibly eight) previous inter-glacials, in particular the Eemian (130kya to 110kya), when temperatures in the Arctic were 5 to 8 degrees Celcius warmer than current temperatures for several thousand years.

Note that their numbers apparently decreased significantly during the Eemian, and slowly increased as temperatures cooled, but “climate change” was not enough on its own to make them extinct. [my bold]

[We can perhaps forgive Mark for not being able to spell “Celsius” correctly, but Amstrup (see below) has no excuse. The paper in Science Mark refers to is Hailer et al. 2012, discussed in a previous post here. Note that the actual question Mark asked is not included here because Amstrup responded to this portion of his comment only]

Amstrup tries to convince Mark and other readers that polar bear resilience through Eemian warming is irrelevant to the issue of future survival, which I’ll demonstrate is not the case at all.

Here is what Amstrup had to say:
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Polar bears cavorting with ABC brown bears not supported by geological and fossil evidence

The authors of a new paper out in PLoS Genetics (Cahill et al. 2013, entitled “Genomic Evidence for Island Population Conversion Resolves Conflicting Theories of Polar Bear Evolution”) propose to explain how and why the brown bears (aka grizzlies) of the ABC islands of southeast Alaska (Admiralty, Baranof, and Chicagof – see previous post here), got to be so genetically distinct from brown bears on the Alaska mainland and so surprisingly similar (genetically) to polar bears. The authors determined (using a model) that this genetic pattern could be explained by an ancient hybridization event resulting from female polar bears cavorting with male brown bears in SE Alaska.

I had some issues with the way the paper was promoted by some of the co-authors, which I dealt with separately here. More importantly, I found the scenario these geneticists offered to explain how hybridization might have occurred to be patently implausible. Geological and fossil evidence from SE Alaska largely refutes their scenario, although another explanation may be more tenable. It is not impossible, in my opinion, that hybridization occurred in SE Alaska during the last Ice Age, but if it did, it almost certainly did not happen the way Cahill and colleagues suggest.

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Polar bear spin reaches new heights as geneticists promote their work

A new paper out in the journal PLoS Genetics proposes that a hybridization event between female polar bears and male brown bears (aka grizzlies) occurred in Southeast Alaska at the end of the last ice age. I’ll get to a discussion of the paper itself (coming in a day or two) but first I have a few things to say about the global warming hyperbole generated by the people promoting the paper. I found it simply mind-boggling.

While the paper itself (Cahill et al. 2013: “Genomic Evidence for Island Population Conversion Resolves Conflicting Theories of Polar Bear Evolution”) contains only one short phrase that could possibly be interpreted as linking the results to future scenarios of catastrophic global warming, some of the co-authors have made statements (for the press release and in media interviews) that spin the global warming mantra right over the top. Continue reading

More evidence that the polar bear is a distinct species

Most people would not question the species status of the polar bear (Ursus maritimus). While it is true that polar bears – under certain circumstances – have successfully interbred with brown bears (aka ‘grizzlies,’ Ursus arctos)[see previous post on hybridization], there are many characteristics that distinguish each of these species as unique entities (see diagram below).

Grizzly vs polar skulls composite

Now, new genetic evidence adds weight to the balance on this issue. In this post, I’ll discuss very briefly the implications of this new paper:

Cronin, M. A. and MacNeil, M. D. 2012. Genetic relationships of extant brown bears (Ursus arctos) and polar bears (Ursus maritimus). Journal of Heredity 103 (6): 873-881. doi:10.1093/jhered/ess090 http://jhered.oxfordjournals.org/content/103/6/873.abstract

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Ancient Polar Bear Remains of the World

How does the ancient distribution of polar bears – based on finds of natural-death remains (“fossils”) and bones found in archaeological sites – compare to the modern distribution of polar bears?

I have pulled together information from all of the reports I could find that listed ancient polar bear remains and summarized them into one table and one map. A low resolution copy of the map and a simplified version of the map notes are embedded in this post but a higher resolution version of the map and map notes (with pertinent details, including references) is available as a pdf. This document has been assigned an ISBN number (which means it is copyrighted and filed at Library and Archives Canada). The pdf can be downloaded below and will also be available on the PolarBearScience “references” page.

DOWNLOAD HERE: Ancient Polar Bear Remains_Crockford 2012
[small error fixed in yesterday's version]

CITATION HERE:
Crockford, S.J. 2012. Annotated Map of Ancient Polar Bear Remains of the World. Electronic resource available at http://polarbearscience/references ISBN 978-0-9917966-0-1.

See map notes on pdf below for more details. Click to enlarge.

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Is it plausible that polar bears are 4-5 million years old? Part 3, sea ice

Last in a three-part series of my critique of Miller et al.’s (2012)
paper on the newest genetic evidence for the origin of polar bears. Part 1 here, Part 2 here.

Here is my final (I hope) comments on the claims made in that paper, suggesting why we might want to take them with a grain of salt.

These are the points regarding this paper that I think deserve a critical look. In this post, I’ll elaborate on Claims #3 and #4. [I've added one more to the original three listed].

Claim #1 Polar bears and brown bears (aka grizzlies) arose 4-5 million years old. [I countered with fossil evidence]

Claim #2 Hybridization in both directions occurred repeatedly throughout the evolutionary history of polar bears and brown bears. [I countered with full details on known hybrids]

Claim #3 Svalbard may have been an important refugium for polar bears during warm interglacial periods – and related sea ice issues related to the origin of polar bears as a species.

Claim #4 Polar bear population numbers (population size estimates) over the last one million years track changes in climate (warmer/colder periods).

Claim #3 Svalbard may have been an important refugium for polar bears during warm interglacial periods (and related sea ice issues related to the origin of polar bears as a species) [Which I'll counter with evidence on paleo sea ice]

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Is it plausible that polar bears are 4-5 million years old? Part 2, Hybridization

These are some of the points regarding this new paper by Miller et al. (2012, in press), on genetic evidence for the origin of polar bears, that I think deserve a critical look. See part 1, for my comments on Claim #1 (the fossil evidence)(see Doug Hoffman summary of the paper here).

In this post, I’ll elaborate on Claim #2. I’ve added one more to the original three listed.

Claim #1 Polar bears and brown bears (aka grizzlies) arose 4-5 million years old. [I countered with the fossil evidence]

Claim #2 Hybridization in both directions occurred repeatedly throughout the evolutionary history of polar bears and brown bears.

Claim #3 Svalbard may have been an important refugium for polar bears during warm interglacial periods.

Claim #4 Polar bear population numbers (population size estimates) over the last one million years tracked changes in climate (warmer/colder periods).

Claim #2 Hybridization in both directions occurred repeatedly throughout the evolutionary history of polar bears and brown bears [a claim also made in two other recent papers on polar bear evolution (Edwards et al. 2011; Hailer et al. 2012)].

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Is it plausible that Polar bears are 4-5 million years old? Part 1

A new genetic study (Miller et al. 2012, now in print) suggests that Polar bears arose between 4-5 million years ago and thus survived the more than 50 glacial/interglacial cycles of the 2.5 million year Pleistocene epoch. Here I’ll begin to explore some of the claims of that paper on the emergence of Arctic bears, suggesting why we might want to take them with a grain of salt.

See my introduction to this topic, which contains information on the so-called ‘ABC’ bears of Southeast Alaska (as well as some notes on my adventures in ABC bear territory a few years ago). It’s worth taking a look at Doug Hoffman’s excellent Aug. 5 summary of the original paper here. The NIPCC also has a summary here.

Here are some of the points regarding this new paper by Miller and colleagues that I think deserve a critical look. In this post, I’ll elaborate on Claim #1.
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