The present invention provides methods for identifying evolutionarily significant polynucleotide and polypeptide sequences in human and/or non-human primates which may be associated with a physiological condition, such as enhanced resistance to AIDS infection. The invention also provides methods for identifying evolutionarily significant polynucleotides with mutations that are correlated with susceptibility to diseases, such as ICAM 1. The methods employ comparison of human and non-human primate sequences using statistical methods. Sequences thus identified may be useful as host therapeutic targets and/or in screening assays.