Transitional Fossils -- Age and Descent

Some notable SciCre-ists have asserted forcefully that when considering fossil specimens, a species known by a later specimen cannot possibly be the ancestor of a species known by an earlier specimen.

If it were true that the fossil record faithfully recorded the beginning, end, and duration of all species, and we knew that information for the species in question, then the objection given would have some weight. Unfortunately, neither of those two necessary conditions are true.

Consider the following illustration, showing an example lineage of five species. The blocks in green show the periods for which fossil specimens for each species have been collected.

Species A is the common ancestor, yet the situation of the known fossil record has the oldest fossils belonging to species B. Only species E is known entirely from more recent specimens than species A.

The sampling of fossil collections does not give us complete knowledge of the residence times of species. Without that information, it simply is erroneous to state that no later fossil can represent a species that is ancestral to an earlier fossil.