In this study, the roles of MCPH genes in the evolutionary enlargement of human brain size was explored through molecular evolutionary analysis of eight newly identified microcephaly genes; CEP135, ZNF335, PHC1, CDK6, SASS6, MFSD2A, CIT, and KIF14. Sequence data from 48 eutherian species was employed to investigate the signatures of episodic positive selection and diversifying selection during mammalian evolutionary history. This evidence concerns the gene KIF14 and microcephaly.