There is no evidence that polar bears survived the warmth of the Eemia because they were not yet completely dependent on ice • Watts Up With That?
Is evolution mostly fast or slow? It takes hundreds of thousands of years or a few years generations to create new species? ignore vast evidence by contrast, most geneticists emphasize that evolutionary change is slow and unnoticeable. one of them are using this misconception to support the narrative of human-caused climate change.
For polar bears, the question is: can brown bears (aka grizzly bears) survive hundreds of thousands of years living in an entirely different habitat – the frozen world of Arctic sea ice. permanently – before significant biological changes take place? I think the answer is no. Furthermore, if I am correct that polar bears arise ca. 140,000 thousand years ago (140kya) during the height of the extreme ice age, fossil evidence concurs. Analysis of fossil remains shows that as late as 115-130kya (perhaps after 10 thousand years), polar bears mainly ate seals like their modern counterparts and their bones have lost their bones. special features of grizzly ancestors.
But that’s the maximum timeframe: research on other animals shows that such important changes almost certainly took place long before that, in the first few generations of life on Earth. sea ice. If the coordinated changes had not happened very quickly, within Ecological time, brown bears simply cannot survive the harsh life on the Arctic sea ice.
An essay published earlier this month by Ned Rozell (June 1, 2023), ‘Polar bears of the past survived the warmth,’ includes an interview with experienced polar bear geneticist Sandra Talbot (e.g. Heaton et al. 1996; Talbot and Shields 1996a, 1996b). Basically, she told Rozell that the reason polar bears survived for thousands of years without ice in the summer during the Eemian Ice Age (about 115-130kya) was because they still looked like grizzlies. and can therefore spend large amounts of time on land eating terrestrial food.
“The Eemian’s warm period may have come at a time when polar bears were not such an expert on ice,” Talbot said.
This is an extraordinary claim because Talbot is a co-author of one of the papers providing evidence to the contrary (Ingolfsson and Wiig 2009; Lindqvist et al. 2010). Isotope analysis of the jawbone (jawbone) of Eemia-age fossils found in Svalbard (see image below) confirmed that the animal ate a diet similar to that of modern polar bears. Another paper that clearly describes the fossil states that the overall size and shape of the bones, as well as the shape of the cheek cavities, suggest an animal that closely resembles a modern male polar bear.
“...our results clearly demonstrate that the jaws belonged to an individual with a feeding ecosystem similar to today’s polar bears, at the top of the Arctic marine food chain..” [Lindqvist et al. 2010:5055]
“Morphological analyzes of the lower jaw suggest that it came from a fully mature male similar in size to extant male polar bears.” [Ingolfsson and Wiig 2009:455]
And as the drawings below show, it’s not just the lower jaw that differs between polar bears and polar bears. There are also major differences in the skull, which means that all of these changes can happen at the same time. Not shown are changes in the rest of the skeleton, from the vertebrae to the metatarsal bones.
With her statement, Sandra Talbot is telling readers that it takes hundreds of thousands of years to create a new species because she thinks the process is driven by the accumulation of many random genetic mutations. She, like most geneticists and many evolutionary biologists, holds this view.
However, there is a lot of evidence that this timeframe is incorrect and that a species can mutate into a new distinct form in 10 generations or less. It is a little-known fact that modern biologists cannot explain exactly how a distinct species, such as the grizzly bear, could mutate into a single entity. polar bears) through randomly accumulated genetic mutations. This is known in the field of evolutionary biology as the “Species Problem” (Crockford 2004, 2023).
However, I have developed a reasonable, testable theory to explain it well (Crockford 2003, 2004, 2023a, 2023b). my new book introduced this concept in detail because understanding how a polar bear rapidly evolved in response to their invasion in the extremely harsh new environment of mobile sea ice explains most of the How other speciation events can also occur.
The understanding that polar bears must have arisen very rapidly from grizzly ancestors also disproves Talbot’s suggestion that polar bears may have survived thousands of years through the ice-free summers of the Eemian because they had not really ‘polar bear’.
Curiously, the Rozell work ends with implied Talbot that polar bears may not be locked into a sea ice lifestyle and may face extinction because returning to land (perhaps due to lack of sea ice due to global warming) is currently blocked by the presence of humans determined to kill them.
“We cannot predict whether the polar bear is too far away (in its evolution toward life on ice), she said. “It is interesting to have a few examples of crossbreeding (between a polar bear and a brown bear). It’s something to watch.”
It is possible that polar bears are trying to adapt to life on land, but one species has blocked that evolutionary path. Polar bears that roam the land, especially near human settlements, tend to get shot. And humans – who didn’t roam out of Africa until about 45,000 years ago – were not at the edge of the sea ice when polar bears first made it their home.
“We didn’t influence them then the way we do now,” says Talbot.
These are extremely irresponsible and misleading statements. The notion that polar bears may not be fully adapted to life on sea ice is not one that I have encountered before from a polar bear biologist. And there is absolutely no evidence that recent hybridization events represent polar bears “trying to adapt to life on land”.
Moreover, the fact that over a some rare occasion, a polar bear that has been able to mate with a grizzly bear and produce fertile offspring does not negate the polar bear’s unique species status, as many insist. This belief is based on an inaccurate, oversimplified definition of a species that don’t take into account large number of genetic, morphological, physiological, behavioral, and life-historical differences between polar bears and brown bears (Cronin and MacNeil 2012).
“These genetic data…support the recognition of polar bears and brown bears as distinct species in terms of biological species, genetic species and phylogenetic species.” [Cronin and MacNeil 2012:879]
Key point: Geneticists often have a limited grasp of the evolutionary literature outside of their expertise, and some of them are making misleading public claims about polar bear evolution. in an effort to support the story of man-made global warming. There is no evidence that polar bears survived the warmth of Eemia because they are not yet completely dependent on ice, or that future polar bears could live on land like grizzlies if the ice were in the Arctic sea. disappear completely at every season of the year. Fortunately, there are no climate models that predict that elevated CO2 levels would make that scenario happen.
Presenter
Crockford, SJ 2003. Thyroid hormone rhythms and hominid evolution: A new model implicating rhythmic thyroid hormone secretion in trait changes and adaptations. International Journal of Comparative Biochemistry and Physiology Part A 135, 105–129. https://doi.org/10.1016/S1095-6433(02)00259-3
Crockford, SJ 2004. Animal domestication and vertebrate speciation: A model for the origin of species. Ph.D. thesis. Victoria University, Canada. http://hdl.handle.net/1828/542
Crockford, SJ 2022. Archaeological and fossil records of polar bears from the Pleistocene and Holocene epochs relate to the extent of sea ice and open water polynyas. Quaternary open 8(7): 1-26. https://doi.org.10.5334/oq.107
Crockford, SJ 2023. Polar bear evolution: A model of how new species arise. Amazon Digital Services, Victoria. https://www.amazon.com/dp/1778038328
Cronin, MA and MacNeil, MD 2012. The genetic relationship of brown bears survives (Ursus arctos) and polar bears (Ursus maritimus). Genetic magazine 103(6): 873-881. doi: 10.1093/jhered/ess090 http://jhered.oxfordjournals.org/content/103/6/873.abstract
Lindqvist, C., Schuster, SC, Sun, Y., Talbot, SL, et al. 2010. The complete mitochondrial genome of the Pleistocene jawbone reveals the origin of polar bears Proceedings of the National Academy of Sciences of the United States of America 107:5053-5057. open access http://www.pnas.org/content/107/11/5053.abstract
Heaton TH, Talbot SL and Shields GF 1996. An ice age refuge for large mammals in the Alexander Islands, southeastern Alaska. Quaternary Studies forty six:189–192. https://doi.org/10.1006/qres.1996.0058
Ingolfsson, Ó and Wiig, Ø. 2009. Late Pleistocene fossil found in Svalbard: oldest remains of a polar bear (Ursus maritius Phipps, 1744) was ever discovered. Polar research 28(3):455-462. https://doi.org/10.1111/j.1751-8369.2008,00087.x
Talbot, SL and Shield, GF 1996a. Phylogeny of bears (Ursidae) is inferred from complete sequences of three mitochondrial DNA genes. Molecular Phylogeny and Evolution 5:567-575. https://doi.org/10.1006/mpev.1996.0051
Talbot, SL and Shields, GF, 1996b. Phylogeography of brown bears (Ursus arctos) of Alaska and paraphyly in Ursidae. Molecular phylogenetics and evolution 5:477-494. https://doi.org/10.1006/mpev.1996.0044
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