Paragraph 2
The researchers conducted an
into injuries on the
. They said the injuries were caused by weapons such as
and spears. It is likely they happened during a
of conflicts over several decades. The researchers believe
tribes competed for food and water that were in
supply because of dramatic changes in climate. Ice covered a
of the Northern Hemisphere. Flooding caused major
to the availability of
. A researcher said: "People had to survive these
, which were brutal."
