Phylogenetics

 Phylogenetics is the study of evolutionary history, achieved by analysing the molecular sequences of individual organisms. It tells us how different organisms are related to each other by their evolutionary history and thus, how they have descended from one another; this branch of phylogenetics is known as phylogeny. Fundamental to phylogeny is the universally accepted belief that all organisms originally descended from a common ancestor (LUCA - last universal common ancestor.) 

Evidence for phylogeny comes from various sources. These include analysis of DNA sequences, comparative morphology/anatomy (homology) amd paleontology (analysis of fossils.) 

Analysis and comparisons of DNA sequences can involve looking for nucleotide differences in a particular gene. For example, DNA sequences can be examined for any nucleotide mutations in the gene coding for cytochrome-c (a protein found in almost all living things.) The fewer the nucleotide differences in the sequence, the more closely related the organisms are to each other. One way in which genomic sequences can be observed is through Phylogenetic Footprinting.