While the polar bear is an Ice Age species, genetic and fossil evidence suggests it barely survived the profound sea ice changes associated with the Last Glacial Maximum, one of the most severe glacial periods of the Pleistocene.
A map of sea ice extent at the climax of the Last Glacial Maximum (both perennial and seasonal ice), prepared with the help of a colleague, makes it possible to discuss what genetic and fossil evidence can tell us about the probable effects of glacial conditions on polar bears and ringed seals.
Posted in Evolution, Sea ice habitat
Tagged Arctic basin, genetic bottleneck, ice age, last glacial maximum, LGM, perennial ice, Pleistocene, polar bear, population bottleneck, population decline, ringed seal, sea ice, sea ice habitat, sea level, seasonal ice
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.
See map notes on pdf below for more details. Click to enlarge.
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]