American Bison - Buffalo Field Campaign

Chapter 2 History of Bison in North America
2.1 Palaeobiology and Phylogeny
Bison have existed in various forms for more than 2,000,000
years (Danz 1997; McDonald 1981). Early forms originated in
Asia and appear in Villafranchian deposits, and in the early
fossil record in India, China, and Europe (Guthrie 1990; Shapiro
et al. 2004). Bison occupied Eurasia about 700,000 years ago
then moved across the Bering Land Bridge into Alaska during
the middle Pleistocene 300,000–130,000 years ago (Illinoin
Glaciation; Marine Oxygen Isotope Stages (MIS) 8 to 6 (Shapiro
et al. 2004). All Siberian and American bison shared a common
maternal ancestor about 160,000 years ago (Shapiro et al. 2004).
Fossil evidence indicates there was a single species, or at least
a similar large-horned form with variable species/sub-species
designations, the steppe bison, Bison priscus, throughout
Beringia (Guthrie 1990).
Plate 2.1 Skull of Bison priscus, Yukon Canada. Photo: Cormack Gates.
Steppe bison probably reached their maximum distribution and
abundance during the last glacial period (Wisconsinan, 100,000–
12,000 years B.P.; MIS 2-4 and 5a-d). These are the typical bison
fossils found in the Yukon and Alaska during that period. Steppe
bison had relatively long hind legs, similar to the European
bison (B. bonasus), and large horns with tips curved back, and a
second hump (Guthrie 1990). Analysis of ancient mitochondrial
DNA (mtDNA) (Shapiro et al. 2004) suggests that Late
Pleistocene bison, found from the Ural Mountains to northern
China, were descendants of one or more reverse dispersals from
North America. The most recent common ancestor of bison
specimens analysed by Shapiro et al. (2004) existed towards the
end of the Illinoian Glacial Period (MIS6).
Lead Authors: Ben A. Potter, S. Craig Gerlach, and C. Cormack Gates,
Contributors: Delaney P. Boyd, Gerald A. Oetelaar, and James H. Shaw
Villafranchian: a major division of early Pleistocene
time, named for a sequence of terrestrial sediments
studied in the region of Villafranca d’Asti, an Italian
town near Turin. This was a time when new mammals
suddenly appeared.
Holarctic: a term used by zoologists to delineate
much of Eurasia and North America, which have been
connected by the Bering land bridge when sea levels
are low during glacial periods.
Pleistocene: Ice Age. A division of geological
time; epoch of the Quaternary period following the
Pliocene. During the Pleistocene, large areas of the
northern hemisphere were covered with ice and there
were successive glacial advances and retreats.
Beringia: a 1,000 mile wide ice-free grassland
steppe, in Asia and North America linked together by
the “Bering Land Bridge” when sea levels were low.
Animals traveled in both directions across this vast
steppe, and humans entered the Americas from what
is now Siberia.
Glacial periods: There have been at least four major
ice ages. The present ice age began 40 million years
ago with the growth of an ice sheet in Antarctica.
Since then, the world has seen cycles of glaciation
with ice sheets advancing and retreating on 40,000-
and 100,000-year time scales. The most recent
glacial period ended about ten thousand years ago.
Marine isotopic stages (MIS): alternating warm and
cool periods in the Earth’s ancient climate, deduced
from oxygen isotope data reflecting temperature
curves derived from data from deep sea core
samples.
Ural Mountains: a mountain range that runs roughly
north and south through western Russia. They are
sometimes considered as the natural boundary
between Europe and Asia.
American Bison: Status Survey and Conservation Guidelines 2010 5