What Cordain said ( from paleodiet list April 2 1997)

During this period, which presumably coincided with increasing
technological development and increasing human populations,  South
America lost 46 out of 58 genera (80%) of mammals exceeding 44 kg;
Australia 15 out of 16 (94%); North America 33 out of 45 (73%).   For
Europe and Africa the figures are considerably lower (7 out of 24 - 29%)
and (2 out of 44 - 5%) respectively.   These mass extinctions affected
large terrestrial mammals exclusively, whereas invertebrates, small to
medium terrestrial vertebrates, plants and marine vertebrates continued
almost unscathed.

Ray Audette suggested that many of the mammals that became extinct
during this period were those which stored the most adipose tissue, and
hence were selectively preyed upon.    Although, we have no way of
determining the body composition of extinct animals, it is likely that
high northern and southern latitude mammals probably had to store fat
similar to modern mammals living in seasonal climates to survive through
the winter.    Given modern man's preference for fat, it is no less
likely that our ancestors did not seek out fat and fatty animals as
well.   Further, because of selective utilization of animal tissues
(both pre-historically and in present day hunter-gatherers), the fat
content of the human diet could have easily exceeded estimates of 15-20%
of the total caloric intake which have been widely used as a model for
the paleolithic diet.