F. Phylogenetic analysis:
Sequence conservation across evolution

evolution = mutation of DNA sequences

two species that have genes that are similar in sequence are more closely related than are two species that have less sequence similarity.

First, not all DNA sequences mutate at the same rate: protein coding regions mutate more slowly than non-coding regions.

Second, some positions in protein coding DNA sequences are more free to mutate than others

Beyond this lie the religious wars between adherents of parsimony vs. maximum likelihood methods of measuring distance.

             +---------------------------------------Mouse
             !
   +---------4                            +------------------Orang
   !         !                    +------3
   !         !                    !      !       +---------Chimp
---6         +--------------------1      !  +----2
   !                              !      +--5    +-----Human
   !                              !         !
   !                              !         +---------Gorilla
   !                              !
   !                              +-------------------Gibbon
   !
   +-----------------------------------Bovine