Saturday, October 22, 2005

Refuting "Irreducible Complexity"

Bernadette and I attended a fascinating seminar at AAAS on Thursday entitled, "Evolution of Biological Complexity". It was part of AAAS's Dialogue on Science, Ethics and Religion (DoSER) lecture series. The speaker was Chistoph Adami, a professor of Applied Life Sciences at Keck Graduate Institute and a researcher at Cal Tech.

Prof. Adami discussed his most recent research on the Avida software, which simulates Darwinian evolution in silico. The Avida group has managed to show how complex adaptive traits can evolve using only the Darwinian algorithm via the accumulation of mutations. This is a stunning (although, in evolutionary camps, not unexpected) breakthrough in theorectical evolution.

A quick summary of the problem and its recent solution goes like this: Intelligent Designists say that certain biological features are far too complex to have been evolved using Darwin's algorithm. They (especially Lehigh University biochemistry professor Michael Behe) have claimed that since very complex structures (say, for example, the eye) rely on the simultaneous activation of many (tens, hundreds, thousands) of genes, they could not possibly evolve by successive single mutations. This is known as "irreducible complexity", because the complex nature of the structure is not thought to be reducible into a series of single mutations. Adami and Avida have shown otherwise.

Avida has been used to evolve a set of computer programs which compete for CPU time in a race to find solutions to mathematical problems. Adami presented an example of the equality operator, evolved from a series of NAND operations, which required the simultaneous activation of some 20 "genes". He then went on to dissect the history of the evolved operator, showing that it was not active until the last (single gene) mutation, but all the intermediate states were, in fact, functional. Several simpler operators (e.g. AND) were evolved and then lost on the way towards EQU. Surprisingly, the evolutionary train of mutations included several mutations which were downright harmful to the program, severely reducing its fitness. These deleterious mutations survived just long enough to pass on their genes to an offspring which was then mutated in a positive manner. Thus, an examplar structure which met all criteria for "irreducible complexity" was shown to be, in fact, both evolable and emminently reducible.

Importantly, this breakthrough specifically refutes the argument most commonly used by proponents of "Intelligent Design"; that Darwinian evolution cannot account for complex biological features. I hope that this new knowledge can be brought to bear on the recent debates regarding the teaching of evolution in US schools.


  1. I've commented on the Lenski/Adami stuff here.

  2. Anonymous8:09 AM

    still too many ifs and buts. science also teaches us that the simplest answer is usually the correct answer, except; when we don't get the answer we want