I believe in evolution because I believe in time. I can not tell you anything specific about my ancestors five hundred years ago but I believe they existed. This little section of time is almost meaningless compared to the 500 Million years animal life is believed to have existed on Earth. The problems of knowing specifics about small intervals of change millions of years in the past is complicated by the increasing awareness that evolutionary change is not a constant, but rather it occurs in bursts of opportunity.
Animal Family Tree Looking Bushy in Places: Writing this week (Dec. 23, 2005) in the journal Science, a team of University of Wisconsin-Madison scientists … suggests that a branch-by-branch account of animal relationships over a vast expanse of time is difficult to reconstruct because early animal evolution occurred in bunches.
"As you go into deep time, these bursts of evolutionary origins become harder to resolve," Carroll explains. In addition to the complications of deep time, animal life sometimes has a tendency to explode in radiations as organisms exploit new or newly vacant ecological niches.
UW Madison Professor Sean Carroll is the lead author and in case you are interested his recommend reading list includes The Origin of Species (1859).
