R M Cullen MD MSc MFM BA DipStats DipProfEthics

january 2016

what is evolution? What is it that is evolving?

The definition of evolution has changed over the last fifty years and would not be recognised by Darwin.

In The Greatest Show on Earth (it is on p33 of the "Dogs, Cows, and Cabbages" chapter in my paperback copy) Professor Dawkins writes "There is no intrinsic tendency in gene pools for particular genes to increase or decrease in frequency. But when there a systematic increase or decrease in the frequency with which we see a particular gene in a gene pool, that is precisely and exactly what is meant by evolution."

This is not evolution. Nothing of Darwin survives in the Dawkins definition

First, natural selection, absolutely central to the Darwinian account of evolution is not required. Artificial selection will do. For example, according to Professor Dawkins, Hitler's attempts to breed a master race by breeding tall, athletic blond haired blue eyed Aryan males with similar Aryan females and sterilising "inferior" breeds, counts as human evolution. Dog breeding counts as dog evolution.

Second, such an increase or decrease in gene (technically, allele) frequency may reflect natural selection in response to a temporary change in the environment (for example an ice age). It may even represent a period of increased mortality in a particular population with a patchy distribution of a certain gene. For example, it may be that blue eyed tuits tend to live near the top of a volcano. Should the volcano enter an active phase lasting a century or more, then the proportion of blue eyed tuits in the population may fall as the blue eyed sub-population has an increased mortality due to molten lava running into their burrows periodically. However, once the volcano settles down it may be that a century of flooding causes causes many of the tuits living by the lakeside, who are predminantly green eyed, to die.

None of the ice age, the volcano, or the floods are what we mean by "evolution"

Evolution is something quite different. Species evolve, not genes. Evolution is descent with modification.

Species evolve by developing new inherited features which become characteristic of the species. Using humans as an example, if one human in a million could fly, that would not represent evolution until one human in a million could not fly. The exact proportion is not important. What is important is the appearance of something new, and inherited, which comes to be present in almost all members of the species

The second thing we want from evolution is extinction and branching. Using humans as an example once again, we expect humans to become the (extinct) common ancestor of two future species, neither of which can breed with the other, and neither of which could breed with humans (if there were any left)

Just because natural selection is occuring does not not mean that a species is evolving. The classic example in evolutionary biology is the pepper moth. The following quote is lifted from the Wikipedia entry 'peppered moth evolution' (http://en.wikipedia.org/wiki/Peppered_moth_evolution).

The evolution of the peppered moth over the last two hundred years has been studied in detail. Originally, the vast majority of peppered moths had light colouration, which effectively camouflaged them against the light-coloured trees and lichens which they rested upon. However, because of widespread pollution during the Industrial Revolution in England, many of the lichens died out, and the trees that peppered moths rested on became blackened by soot, causing most of the light-coloured moths, or typica, to die off from predation. At the same time, the dark-coloured, or melanic, moths, carbonaria, flourished because of their ability to hide on the darkened trees.

Since then, with improved environmental standards, light-coloured peppered moths have again become common

Another well known example are Darwin's finches. These birds show variabilities in beak morphology. In wet years, slender beaks are better as seeds are small and soft. In drier years tougher beaks have a (reproductive) advantage as seeds are tougher and need to be cracked. The prevalance of 'beak type' genes changes with medium term weather patterns. But this is mere bouncing round some long term average. It is not evolution

The false definition of evolution has arisen for two reasons. First, it allows population biologists into the church of standard evolutionary theory. Second, gene frequencies do change, and if this is all that there is to evolution, then evolution is correct (and creationism is wrong).