Geology Reference
In-Depth Information
to fully aquatic
marine mammals.
Larger than life: Giant mammals of the ice ages
Most modern mammals are somewhere in between the size of an elephant and a mouse.
During the early Quaternary ice ages, however, many species of mammals had grown un-
usually large. These large mammals are called
megafauna.
Along with the mastodons and mammoths, there were also very large species of camel,
elk, bison, ground sloths, bears, beavers, rhinoceros, and even kangaroos. The skeletons
of some of these creatures have been preserved in places like the La Brea tar pits in Cali-
fornia and frozen into the
permafrost
(frozen soil) of Alaska, Canada, and Siberia. Pre-
served in this manner, soft tissue, skin, and fur, as well as bones, are recovered to be
studied by scientists.
Scientists speculate that the large size of these animals may have been an adaptation to
the colder climates; larger animals are able to stay warm more easily than smaller ones
because they can generate more heat than they lose. Regardless, the reign of giant mam-
mals had only just begun when it was brought to an end around 13,000 years ago.
Exactly why the ice age megafauna went extinct is still being explored, but some scient-
ists propose that after humans showed up, the conditions of existence on this planet
were changed forever.
