Now let's move on to 2002 when Enard et al (authors include Svante Paabo & Anthony Monaco) (6) published a paper describing work that investigated the evolution of FOXP2. The first thing they note is the extremely highly conserved nature of FOXP2. We have already seen that in all cases, in all species investigated, the amino acid mutated in the KE family is identical. The major splice form of the protein encoded by the gene (it has a pair of alternatively spliced exons) is 715 amino acids long and the protein is identical with no differences whatsoever in chimpanzee, gorilla and rhesus monkey. The mouse FOXP2 differs in just one amino acid from these three species. However, human FOXP2 differs from gorilla, chimp and rhesus macaque in two further amino acids (and thus differs from mouse in three amino acids out of 715). So, in 75 million years since the divergence of mouse and chimpanzee lineages only one change has occurred in FOXP2, (and that equates to 150 million years of evolution as we don't know whether the mutation occurred in the mouse or the primate lineage) whilst in the six million years since the divergence of man and chimpanzee lineages two changes have occurred in the human lineage.
Fig 1: Silent and replacement nucleotide substitutions mapped on a phylogeny of primates. Bars represent nucleotide"
I posted this mainly for Fig 1 which shows very clearly the stability of FOXP2 until the Chimp Homo divergence.
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