Homo erectus was the
first species in our line of evolution to expand their range beyond
tropical and subtropical environments into temperate climatic zones
of the Old World where they encountered relatively cold winters.
This evidently occurred by at least 1/2 million years ago in Asia
and a bit earlier in Europe. It was made possible mainly by
the success of new inventions and new subsistence strategies.
The most important change may have been increased meat consumption
as a result of hunting and more successful scavenging. The
greatest difficulty living in temperate areas was probably not the
cold weather but obtaining something to eat during the winter when
fresh plant foods are scarce. It is in that season that meat
would have been the most important calorie source. The
ability to create and use fire for cooking and heating may also
have been significant. However, the first convincing evidence
of regular fire use does not come until 400-300,000 years ago, when
the Homo erectus were evolving into archaic Homo
sapiens.
Implications
The cultural
developments of Homo erectus essentially began a new phase of our
evolution--one in which natural selection was altered by cultural
inventions. This has been referred to as biocultural
evolution. Culture can affect the direction of human
evolution by creating non- biological solutions to environmental
stresses. This potentially reduces the need to evolve genetic
responses to the stresses. Normally, when animals move into new
environmental zones, natural selection operating on random
mutations causes evolution. In other words, the population's
gene pool is altered as a result of adapting to a new environment.
When late Homo erectus moved into temperate environments,
nature should have selected for biological adaptations that were
more suited to cooler climates. Such things as increased
amounts of insulating body fat and insulating hair covering most of
the body would be expected. Homo erectus evidently achieved
much of the same adaptation by occupying caves, creating fires, and
becoming more capable at obtaining meat. By using their
intelligence and accumulated knowledge, they remained essentially
tropical animals despite the fact that they were no longer living
only in the tropics. However, natural selection continued to select
for increased brain size and presumably intelligence. This
pattern of culture altering natural selection accelerated
dramatically with the evolution of modern humans. Today, most of us
live in cities and towns that are essentially unnatural
environments and the rate of culture change has accelerated
dramatically. We have occupied most environmental zones on
land, and yet we are still essentially tropical animals. As a
result, we perish rapidly if our cultural technology is taken away
from us in environments in which the temperature drops to
freezing.
