In the passage the writer tries to ----.

As a branch of learning, prehistory deals with the
earliest history of man and is therefore part of human
history. However, it comes very close to the natural
sciences and is indeed the bridge between geology
and history. It is much concerned with periods of
time, which are also the concern of the geologist and
the natural historian. Moreover, it uses a great
number of research techniques which essentially
belong to the natural and physical sciences.
Therefore, one may refer to it both as a science and
as the earliest phase of historical study.