Page 88 - The Restless Earth Fossils

Fossils in the human Family 7

humans also ventured out of Africa during a warm spell, with
one branch developing into the Neandertals of Europe. It is
hard to imagine the comings and goings of species that existed
so long ago and for stretches of time that dwarf all of modern
history, but these humans, like people today, moved to wherever
they could best survive and prosper. During times of cool cli-
mates, when lots of seawater lay frozen in glaciers to the north,
sea levels fell and new territory opened up. In warm, wet times,
forests expanded. People followed the dictates of their stomachs
and slowly hunted, fished, and otherwise ate their way around
the world.
How did these various hominins interact? Could they and
did they interbreed? Did they fight or avoid each other? Scientists
now debate such details, and others, as new fossil evidence
comes to light and genetic studies of modern human populations
continue.
It is important to remember that scientists debate the details
of human evolution, not the fact that it occurred. Evolution by
natural selection serves as the cornerstone of biology the way
Newton’s laws of motion anchor our understanding of physics.

out oF aFrica—again
Paleontologists and anthropologists (scientists who specialize in
the study of human remains, both physical and cultural) pretty
much had the study of human prehistory to themselves until
chemists realized that the DNA tucked into each and every one
of our cells represents a fantastic library of past events—specifi-
cally mistakes (mutations) in copying DNA from generation to
generation. While such goof-ups are usually bad news, mutations
provide gene variations that sometimes have survival value. They
create evolutionary change. Not only that, the mutations hang
around to serve as markers that can show when some populations
split from others.
In January 2008, for example, European scientists discov-
ered that a specific mutation in the gene that codes for the dark

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