The impact of this new perspective is profound. On the Origin of Species 7 . A 0 giving rise to two lineages that are prevented from further interbreeding. Most similarities between present-day species are due to their common ancestry. Turning this around, the most similar species today tend to be those that share the most recent common ancestry.
More distinct species tend to have more remote common ancestry.
This is true in classifying organisms, as well. If we classify by an arbitrary criterion, then knowing an organism's placement within the classification can be remarkably uninformative. We cannot begin to guess whether it is pathogenic, whether it makes food taste good, or whether it enhances the growth of our lawn. In the case of organisms, we can do much better than an arbitrary classification. Ideally, we wish to base our classification on the relationships of the organisms, that is, on their genealogy or phylogeny.