Most animals found today are evolved forms of past species. For
example, modern man has only existed for about 12 thousand years.
However, recent discoveries have traced back human ancestry as far
as some of the first organisms to ever exist, ancient fish-like
beings. Through many, many millions of years, animals can evolve to
become very different things. Here's another one: the closest
living relative to the mighty Tyrannosaurus Rex? Domestic chickens.