The genetic equidistance result has been called, rightly in my opinion, by the biologist Mike Denton as “one of the most astonishing findings of modern science” in his 1986 book “Evolution, A Theory in Crisis”. No one had expected the result or could have guessed it and all would be shocked by it. Nearly all scientists today either don’t know it or have no idea about what it means. In fact, it has been mistakenly interpreted ever since its discovery, which has unfortunately misled the field of molecular evolution and population genetics into the wrong path. It was the reason for the universal molecular clock idea and the junk or neutral DNA idea.
The genetic equidistance result was originally discovered by Margoliash in 1963, who states:
“It appears that the number of residue differences between cytochrome c of any two species is mostly conditioned by the time elapsed since the lines of evolution leading to these two species originally diverged. If this is correct, the cytochrome c of all mammals should be equally different from the cytochrome c of all birds. Since fish diverges from the main stem of vertebrate evolution earlier than either birds or mammals, the cytochrome c of both mammals and birds should be equally different from the cytochrome c of fish. Similarly, all vertebrate cytochrome c should be equally different from the yeast protein.”
Margoliash E (1963) Primary structure and evolution of cytochrome c. Proceedings of the National Academy of Sciences of the USA 50: 672–679.
Half of a century later with numerous genomes sequenced and compared, we all know that Margoliash is correct in noticing the equidistance result. Indeed, all vertebrate cytochrome c are approximately equally different from the yeast protein, or the bacteria protein for that matter. However, one could have just as easily used common sense to interpret the equidistance result in the following alternative way by changing a few words in the above Margolaish version:
“It appears that the number of residue differences between cytochrome c of any two species is mostly conditioned by the species with lower organismal complexity. If this is correct, the cytochrome c of all mammals should be equally different from the cytochrome c of all birds. Since fish has lower complexity than either birds or mammals, the cytochrome c of both mammals and birds should be equally different from the cytochrome c of fish. Similarly, all vertebrate cytochrome c should be equally different from the yeast protein.”
Typical textbooks mention nothing about the original equidistance result and only present the Margoliash interpretation, known as the molecular clock. For example, Dan Graur and Wen-Hsiung Li in their “Fundamentals of Molecular Evolution” (2000) said this:
“In their comparative studies of hemoglobin and cytochrome c protein sequences from different species, Zuckerkandl and Pauling (1962, 1965) and Margoliash (1963) first noticed that the rates of amino acid replacement were approximately the same among various mammalian lineages.”
In other words, these scientists noticed that the equidistance result could be interpreted to mean a universal molecular clock that all mammalian species, or all species for that matter, have approximately the same substitution rate for any given protein. However, another person could have noticed the alternative that the equidistance is a result of lower complexity species having more tolerable sequence variations. This alternative is the maximum genetic diversity (MGD) hypothesis.
So, which is right? The universal molecular clock has now been proven invalid, as acknowledged by nearly all in the field. The only other alternative is the more intuitive MGD interpretation, which has yet to encounter a single piece of contradicting data. The molecular clock has led to nonsensical ideas such as neutral or junk DNAs as if an organism is like a junk yard or a dead body, but the MGD theory has led to the exact opposite.