Rate variation during molecular evolution: creationism and the cytochrome c molecular clock

James R. Hofmann

doi:10.1186/s12052-017-0064-4

Abstract

Molecular clocks based upon amino acid sequences in proteins have played a major role in the clarification of evolutionary phylogenies. Creationist criticisms of these methods sometimes rely upon data that might initially seem to be paradoxical. For example, human cytochrome c differs from that of an alligator by 13 amino acids but differs by 14 amino acids from a much more closely related primate, Otolemur garnettii. The apparent anomaly is resolved by taking into consideration the variable substitution rate of cytochrome c, particularly among primates. This paper traces some of the history of extensive research into the topic of rate heterogeneity in cytochrome c including data from cytochrome c pseudogenes.

Highlights

The most egregious and widespread creationist misuse of cytochrome c sequence data is surely the spurious “equidistance” anomaly generated when amino acid sequences taken from several members of a large clade are compared to the sequence for a single member of an outgroup to that clade
The apparent anomaly generated by the 14 differences between human and O. garnettii cytochrome c amino acid sequences is resolved as part of a more general analysis of the variable rates of molecular evolution in cytochrome c
Recent analysis based upon both fossil evidence and molecular clocks place the origin of rodents at approximately 60 million years ago during the period of very high cytochrome c substitution rate

Summary

Introduction

The most egregious and widespread creationist misuse of cytochrome c sequence data is surely the spurious “equidistance” anomaly generated when amino acid sequences taken from several members of a large clade are compared to the sequence for a single member of an outgroup to that clade. More subtle molecular clock issues arise from the fact that mutations can result in variable amino acid replacement rates in proteins, especially among primates.

Results

Conclusion