No evidence polar bears survived Eemian warmth because they were not yet fully ice-dependent

Is evolution primarily fast or slow? Does it take hundreds of thousands of years or a few generations to produce a new species? Ignoring vast evidence to the contrary, most geneticists insist that evolutionary change is imperceptibly slow and one of them is using this misconception to support the human-caused climate change narrative.

For polar bears, the question is this: could brown bears (aka grizzlies) have survived for hundreds of thousands of years living in a completely different habitat–the perpetually-frozen world of Arctic sea ice–before significant biological changes took place? I contend the answer is no. Moreover, if I am correct that polar bears arose ca. 140,000 thousand years ago (140kya) during the height of an extreme glacial period, the fossil evidence concurs. Analysis of fossil remains show that by about 115-130kya at the latest (after perhaps 10k years), polar bears were primarily eating seals as their modern counterparts do and their bones had lost the distinctive features of their grizzly ancestors.

But that’s the maximum time frame: research on other animals indicate that such critical changes almost certainly took place long before that, within the first few generations of life on the sea ice. If coordinated changes had not taken place very quickly, within ecological time, brown bears would simply not have survived the harsh life on Arctic sea ice.

An essay published earlier this month by Ned Rozell (1 June 2023), ‘Polar bears of the past survived warmth,’ included an interview with experienced polar bear geneticist Sandra Talbot (e.g. Heaton et al. 1996; Talbot and Shields 1996a, 1996b). She essentially told Rozell that the reason polar bears survived the thousands of years of summer ice-free conditions during the Eemian Interglacial (ca. 115-130kya) was because they were still grizzly-like and therefore able to spend large amounts of time on land eating terrestrial foods.  

“The warm period of the Eemian might have come at a time when the polar bear wasn’t such an ice specialist, Talbot said.”

This is an extraordinary statement given that Talbot was a co-author of one of the papers that provides evidence to the contrary (Ingolfsson and Wiig 2009; Lindqvist et al. 2010). Isotope analysis of the Eemian-aged fossil mandible (jawbone) found on Svalbard (see image below) confirmed that this animal ate a similar diet to modern polar bears. Another paper describing the fossil states explicitly that the overall size and shape of the bone, as well as the conformation of the cheek tooth sockets indicate an animal closely resembling a modern male polar bear.

“...our results clearly demonstrate that the jaw is from an individual that had a feeding ecology similar to present-day polar bears, at the top of the Arctic marine food chain.” [Lindqvist et al. 2010:5055]

Morphological analyses of the mandible suggest that it comes from a fully grown male that was similar in size to extant male polar bears.” [Ingolfsson and Wiig 2009:455]

Upper: polar bear male left mandible ca. 12.9-12.4ky old from Asdal, Denmark, Geert Brovad photo, Natural History Museum of Denmark. Lower: polar bear male right mandible (mirror image) from Svalbard ca. 130-115ky old, Karsten Sund photo, Natural History Museum, University of Oslo. Middle: grizzly left mandible sketch isolated from larger drawing, Canadian Museum of Nature.

And as the drawings below show, it’s not just the mandible that differs between grizzly and polar bear. There are major differences in the skull as well, which means that all of these changes likely happened at the same time. Not shown are changes in the rest of the skeleton, from the vertebrae to the foot bones.

By her statement Sandra Talbot, is telling readers that it must take hundreds of thousands of years to produce a new species because she assumes that the process is driven by the accumulation of many random genetic mutations. She is like most geneticists and many evolutionary biologists in holding this view.

However, there is a huge body of evidence that this time frame is incorrect and that a species can transform into a new distinct form within 10 generations or less. It is a little-know fact that modern biologists cannot explain precisely how a distinct species, like a grizzly, could have transformed into a unique entity (the polar bear) via randomly accumulated mutations in genes. This is known within the field of evolutionary biology as “The Species Problem” (Crockford 2004, 2023).

However, I have developed a plausible, testable theory that explains it well (Crockford 2003, 2004, 2023a, 2023b). My new book lays out the concept in detail because understanding how a polar bear arose rapidly in response to their colonization of the extremely harsh new environment of the mobile sea ice explains how most other speciation events probably happened as well.

Understanding that polar bears must have arisen very quickly from a grizzly ancestor also refutes Talbot’s suggestion that polar bears may have survived thousands of years of ice-free summers during the Eemian because they were not yet truly ‘polar bears.’

Bizarrely, the Rozell piece ends with Talbot implying that polar bears may not be irreversibly locked into a sea ice lifestyle and could face extinction because a return to land (presumably due to lack of sea ice caused by global warming) is now blocked by the presence of humans determined to kill them.

““We can’t predict whether the polar bear is too far out (in its evolution towards a life on ice),” she said. “It’s interesting that there are a few examples of hybridization (between polar bears and brown bears). That’s something worth watching.”

Maybe polar bears have been trying to adapt to life on land, but one species has blocked that avenue of evolution. Polar bears that wander onto land, especially near a human settlement, tend to get shot. And humans — who didn’t wander out of Africa until about 45,000 years ago — weren’t present on the edge of the sea ice when polar bears first made it their home.

“We weren’t impacting them then the way we are now,” Talbot said.”

These are very irresponsible, misleading statements. The notion that polar bears may not be thoroughly adapted to a life on sea ice is not one I have ever 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.”

Furthermore, the fact that on a few rare occasions, a polar bear has been able to interbreed with a grizzly and produce fertile offspring does not negate the unique species status of the polar bear, as many people insist. This belief is based on an incorrect, over-simplified definition of a species that fails to take into account the large number of genetic, morphological, physiological, behavioural, and life-history differences between the polar bear and brown bear (Cronin and MacNeil 2012).

“These genetic data…support recognition of polar bears and brown bears as different species under the biological species, genetic species, and phylogenetic species concepts.” [Cronin and MacNeil 2012:879]

Bottom line: Geneticists often have a limited grasp of the literature on evolution outside their specialty and some of them are making misleading statements to the public about polar bear evolution in an effort to prop up the human-caused global warming narrative. There is no evidence that polar bears survived Eemian warmth because they weren’t yet fully ice-dependent or that polar bears in the future could live on land like grizzlies if Arctic sea ice disappeared completely, in every season of the year. Fortunately, no climate model predicts that rising CO2 levels could cause that scenario to occur.


Crockford, S.J. 2003. Thyroid hormone rhythms and hominid evolution: A new paradigm implicates pulsatile thyroid hormone secretion in speciation and adaptation changes. International Journal of Comparative Biochemistry and Physiology Part A 135, 105–129.

Crockford, S.J. 2004. Animal Domestication and Vertebrate Speciation: A Paradigm for the Origin of Species. Ph.D. dissertation. University of Victoria, Canada.

Crockford, S. J. 2022. Polar bear fossil and archaeological records from the Pleistocene and Holocene in relation to sea ice extent and open water polynyas. Open Quaternary 8(7): 1-26.

Crockford, S.J. 2023. Polar Bear Evolution: A Model for How New Species Arise. Amazon Digital Services, Victoria.

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

Lindqvist, C., Schuster, S.C., Sun, Y., Talbot, S.L., et al. 2010. Complete mitochondrial genome of a Pleistocene jawbone unveils the origin of polar bear. Proceedings of the National Academy of Sciences USA 107:5053-5057. Open access

Heaton T.H., Talbot S.L. and Shields G.F. 1996. An ice age refugium for large mammals in the Alexander Archipelago, southeastern Alaska. Quaternary Research 46:189–192.

Ingolfsson, Ó and Wiig, Ø. 2009. Late Pleistocene fossil find in Svalbard: the oldest remains of a polar bear (Ursus maritiumus Phipps, 1744) ever discovered. Polar Research 28(3):455-462.

Talbot, S.L. and Shields, G.F. 1996a. A phylogeny of the bears (Ursidae) inferred from complete sequences of three mitochondrial DNA genes. Molecular Phylogeny and Evolution 5:567-575.

Talbot, S.L. and Shields, G.F., 1996b. Phylogeography of brown bears (Ursus arctos) of Alaska and paraphyly within the Ursidae. Molecular Phylogenetics and Evolution 5:477-494.

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