"We will now discuss in a little more detail the Struggle for Existance. -- Charles Darwin "

Study of various segments of the globin gene clusters in several organisms has indicated the presence of non-functional sequences that are nearly homologous to normal globin genes. The sequences are called pseudogenes, and are considered to be relics of evolution, dereivatives of once-functional genes that were duplicated. Presumably a mutation occured at one time that inactivated the gene product. Since at least one functional copy remained, there would have been no selective pressure to eliminate the mutant gene, therefore additional mutations would have have accumulated. pseudogenes are wide spread in gene clusters.

An example of pseudogenes lies in Odorant Receptor genes. Half of human odorant receptor genes appear to be pseudogenes, where as in rodents all odorant receptor genes are functional. In primate O.R. genes, the fraction of disfunctional O.R. pseudogenes is greater the more closely the primate is related to humans.