Darwin_DoubtFor the previous installments: part 1, 2, 3, 4.

Chapter 12

Scientists largely ignored the mathematicians who pointed out the seeming impossibility of creating new genes and proteins because the mathematical equations of population genetics pointed to a nearly limitless creative power of random mutations.  Given known mutation rates, population sizes, and reproduction rates, there seemed to be no end to what evolution could accomplish.  The problem with this conclusion is that population genetics is based on some assumptions that we now know to be false.

When the neo-Darwinian synthesis (the idea that evolutionary change is driven by natural selection acting on random genetic mutations) was formulated in the 1930s, biologists did not yet understand the structure of genes.  Watson and Crick would not discover the structure of DNA and the digital code it uses to build proteins until 1953 and beyond.  Prior to this, genes were only understood functionally as those entities that determine visible and selectable traits such as eye color and the number of toes on our feet.  It was assumed that single genetic mutations could alter genes in such a way so as to produce a new function, and that one gene could be responsible for building a complex structure.  Given these assumptions, it’s easy to envision an organism slowly improving one mutation at a time.  Today, however, we know that these assumptions are patently false:

  • Hundreds of proteins are often required to create a complex system. To build that system would require changes to hundreds of genes.  Furthermore, because the function of these systems depends on the coordination of several well-matched parts, these new proteins (or proteins with new functions) must arise at the same time.[1]
  • To change or improve the function of a single protein typically requires multiple, coordinated amino acid changes, which in turn requires multiple, coordinated changes in the DNA. Because the new function depends on the coordination of multiple mutations, every mutation must be present in the protein at once.

(more…)