About a month ago a recent anti-evolutionary post caught my eye. It neatly demonstrates two major misconceptions about evolutionary biology, and gives an ideal opportunity to talk about some powerful proofs of evolution provided by molecular genetics.
The basic thrust seems to be that Rick Perry is by far the superior candidate for the GOP Presidential nomination, due to his “acknowledgement of the holes in evolution theory”. However, Mr Casey also takes the opportunity to air his own feelings about “why evolution will never be considered a fact”.
Mr Casey makes two staggeringly erroneous points in this piece: that evolution cannot be considered a fact because it cannot be observed (the moral of his match-and-candle parable); and that “not even Richard Dawkins, a leading evolutionary biologist from Oxford University, could name a single mutation that has added beneficial information.”
Just one of many examples of observable evolution is provided by the Long Term Evolutionary Experiment (LTEE) by the Lenski lab, an investigation into the evolution of 12 separate colonies of the bacterium Escherichia coli over 45,000 generations. Usually each colony would grow, use up the glucose in the growth medium, and begin to die out; however, one colony of bacteria evolved the ability to survive on citrate (also present in the medium), and could therefore grow more. The genetic basis of this ability has been tracked to two mutational events, one for each step in breaking down citrate, each adding beneficial information.
The globin gene family provides an even more detailed example of a suite of abilities provided by genetic mutation. The original gene duplicated approximately 1.1 billion years ago, producing two copies. One copy became the ancestor of all vertebrate haemoglobins, which bind oxygen in red blood cells, providing oxygen to the vast majority of cells in the body. The other became the ancestor of all vertebrate myoglobins, which bind and store oxygen in muscle cells, allowing aquatic mammals to dive for extended periods (20 minutes in the case of Weddell seal). We know the exact DNA sequence of these genes, and how mutation has added beneficial information (for more information, see sequencing studies here, here and here, as well as this previous BAB post). Professor Dawkins is presumably aware of the globins, as he detailed their evolution in his book The Blind Watchmaker (p. 175 of the 2006 edition).
Skepticism is healthy in science, but rejecting an explanation when you lack a basic understanding of its proofs is not skeptical, but pure ignorance.
Blount, Z.D., Borland, C.Z. and Lenski, R.E. (2008) Historical contingency and the evolution of a key innovation in an experimental population of Escherichia coli. PNAS 105: 7899-7906
Campbell, N.A. and Reece, J.B. (2005) Biology (Seventh Edition). Pearson Benjamin Cummings
Dawkins, R. (2006) The Blind Watchmaker, p.175. Penguin
Goodman, M., Pedwaydon, J., Czelusniak, J., Suzuki, T., Gotoh, T., Moens, L., Shishikura, F., Walz, D. and Vinogradov, S. (1988) An evolutionary tree for invertebrate globin sequences. Journal of Molecular Evolution 27: 236-249
Hardison, R. (1998) Hemoglobins from bacteria to man: evolution of different patterns of gene expression. Journal of Experimental Biology 201: 1099-1117
Hoffman, F.G., Opazo, J.C. and Storz, J.F. (2011) Whole-genome duplications spurred the functional diversification of the globin gene superfamily in vertebrates. Molecular Biology and Evolution, Advance Access