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]
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.
Here is an abbreviated version of the map notes, click to enlarge:
I note 10 points of interest regarding this map:
1) The oldest dated fossil (130,000-115,000 years old, based on geological features) is within the modern range of polar bears (#46).
2) Many of the ancient remains come from archaeological sites that date within the Holocene.
3) The fossil and archaeological specimens that lay outside the modern range of polar bears are found either in the southeastern Bering Sea (eastern Aleutians and the Pribilof Islands, Alaska) or the North Atlantic (Scandinavia and the eastern UK – although the taxonomy of the UK specimen – #44 – is in dispute, see map notes pdf for details).
The ancient eastern Aleutian polar bear finds (#26) that date to 4,700-4,100 BP are about 400 km south of modern sea ice limits in the Bering Sea (which evidence from a nearby site reported by Crockford and Frederick (2007) suggest lasted until about 2,500 BP). In addition, many of the Scandinavian finds (from southern-most Sweden and Norway, and northern Denmark, dated ca. 12,500-10,000 BP) are greater than 2,000 km south of modern sea ice limits – since satellite records began in 1979, sea ice has remained well beyond the north shore of Norway in the Barents Sea (Finland yes, Norway, no – see NSIDC sea ice extent image from 1979 below).
4) As far as I have been able to determine, there are no fossil polar bear remains reported from Ireland, although it has been suggested polar bears evolved there (Edwards et al. 2011) and no archaeological remains of polar bears found anywhere in the UK or Scandinavia.
5) There are very few archaeological bones and no fossil remains of polar bears found in Hudson Bay, consistent with the geological history of this region (see previous post here).
6) Geologist Art Dyke told me (in 2007) that no natural-death assemblages of polar bears or isolated polar bears bones were found during the shoreline surveys that produced bowhead and walrus fossils in the Canadian Arctic (Atkinson 2009; Dyke et al. 1996, 1999, 2011; Dyke and Savelle 2001). So far, all remains in the Canadian Arctic except one (#42 – undated) come from mid- to late Holocene age archaeological sites.
7) The largest assemblage of polar bear bones at any one location is from Zhokhov Island in the East Siberian Sea (#30). This archaeological site was occupied between 8,200 and 8,500 years ago, when all of the New Siberian Islands were still connected to the Siberian mainland (Andreev et al. 2008; Pitul’ko 1993; Pitul’ko and Kasparov 1996). By about 8,000 BP, sea level had risen enough to create the islands almost as they are today.
The majority of the polar bear bones at this site are from adult females. It is not possible to tell whether the Zhokhov Island polar bears were taken by hunters from maternity dens during the winter or from the shore during the low ice period of late summer/early fall. What we can say from this evidence, however, is that polar bears, who could not have lived in the Arctic during the LGM because of the extreme thickness of the sea ice (Polyak et al. 2010), had colonized the farthest reaches of the western Arctic by at least 8,500 BP. [also exciting for me is that dog bones were also found at this site (Pitul'ko and Kasparov 1996:13-14) – making it perhaps the oldest, furthest north site with dogs anywhere in the Arctic].
8) There are no ancient polar bear remains of any kind found in the Sea of Okhotsk or the Gulf of Alaska in the western Arctic, although the presence of ringed seal bones dated to the LGM on Prince of Wales Island, Southeast Alaska (“On Your Knees Cave,” see my previous post on the brown bears found there) suggest there was almost certainly suitable habitat for polar bears in the Gulf of Alaska during the LGM (Heaton and Grady 2003).
9) So far, all polar bear remains that definitely pre-date the end of the LGM have come from the Northeastern Atlantic Ocean and adjacent Barents Sea. Only five of these specimens have been dated well enough to place them firmly in this time period (and even then, the identification of one of them (#44) as polar bear has been contested). Three additional specimens could be this old (#’s 40-42) but have only been described as “Pleistocene” age. This means only four (possibly five) polar bear fossils exist that are definitively older than 19,000 years.
10) As sea ice does not now extend nearly as far south as southern Sweden (see 3 above), all of the 12,500-10,000 year old NE Atlantic polar bear remains indicate that winter sea ice in the North Atlantic expanded much further south during the “Younger Dryas” cold period (13,000-11,500 BP) – and for 1,500 years or so afterward – than it did in the North Pacific. In the North Pacific, sea ice extent appears to have been at or below current limits by at least 13,000 BP (Condron and Winsor 2012 in press).
In summary, even within the past 12,000 years, sea ice conditions have been very different than they are today and this has affected where polar bears have been able to live.
Blog post references
Andreev, A. A., Grosse, G., Schirrmeister, L., Kuznetsova, T. V., Duzmina, S.A., Bobrov, A. A., Tarasox, P. E., Novenko, E.Y., Meyer, H., Derevyagin, A. Y., Kienast, F., Bryantseva, A. and Kunitsky, V.V. 2008. Weischelian and Holocene palaeoenvironmental history of the Bol’shoy Lyakhovsky Island, New Siberian Archipelago, Arctic Siberia. Boreas 38:72-110.
Atkinson, N. 2009. A 10400-year-old bowhead whale (Balaena mysticetus) skull from Ellef Ringnes Island, Nunavut: implications for sea-ice conditions in high Arctic Canada at the end of the last glaciation. Arctic 62:38-44.
Condron and Winsor 2012 in press. Meltwater routing and the Younger Dryas. Proceedings of the National Academy of Science USA. http://www.pnas.org/content/early/2012/10/31/1207381109.abstract
Crockford, S., and Frederick, G. 2007. Sea ice expansion in the Bering Sea during the Neoglacial: evidence from archaeozoology. The Holocene 17:699-706.
Dyke, A.S., and England, J.H. 2003. Canada’s most northerly postglacial bowhead whales (Balaena mysticetus): Holocene sea-ice conditions and polynya development. Arctic 56:14-20.
Dyke, A. S., Hooper, J. and Savelle, J. M. 1996. A history of sea ice in the Canadian Arctic Archipelago based on postglacial remains of bowhead whale (Balaena mysticetus). Arctic 49: 235-255.
Dyke, A.S., Hooper, J., Harington, C.R. and Savelle, J.M. 1999. The late Wisconsinan and Holocene record of walrus (Odobenus rosmarus) from North America: a review with new data from arctic and Atlantic Canada. Arctic 52:160-181.
Dyke, A.S., Savelle, J.M. and Johnson, D.S. 2011. Paleoeskimo demography and Holocene sea-level history, Gulf of Boothia, Arctic Canada. Arctic 64:151-168.
Edwards, C.J., Suchard, M.A., Lemey, P., Welch, J.J., Barnes, I., Fulton, T.L., Barnett, R., O’Connell, T.C., Coxon, P., Monoghan, N., Valdiosera, C.E., Lorenzen, E.D., Willerslev, E., Baryshnikov, G.F., Rambaut, A., Thomas, M.G., Bradley, D.G. and Shapiro, B. 2011. Ancient hybridization and an Irish origin for the modern polar bear matriline. Current Biology 21:1251-1258.
Pitul’ko, V.V. 1993. An early Holocene site in the Siberian high Arctic. Arctic Anthropology 30:13–21.
Pitul’ko, V.V. 1999. Ancient humans in Eurasian Arctic ecosystems: environmental dynamics and changing subsistence. World Archaeology 30:1–36.
Pitul’ko, V.V., and A.V. Kasparov. 1996. Ancient arctic hunters: material cultural and survival strategy. Arctic Anthropology 33:1-36.
Polyak, L., Alley, R.B., Andrews, J.T., Brigham-Grette, J., Cronin, T.M., Darby, D.A., Dyke, A.S., Fitzpatrick, J.J., Funder, S., Holland, M., Jennings, A.E., Miller, G.H., O’Regan, M., Savelle, J., Serreze, M., St. John, K., White, J.W.C. and Wolff, E. 2010. History of sea ice in the Arctic. Quaternary Science Reviews 29:1757-1778.