The most significant evolutionary experiment of all time was started by Dr. Richard Lenski at Michigan State University on February 15th 1988. That experiment continues to this day. It has been argued that this experiment shows that a strain of the E. coli bacterium is undergoing dramatic forward evolution, allowing us to document in the test tube the same type of macroevolution that allows one type of life to morph into a fundamentally different type of life (such as ape-to-man evolution). Some have argued that the resulting bacterial strains have actually morphed into entirely new species. It has often been said this experiment lays to rest any doubts about macroevolution. More specifically, it is widely claimed that this experiment proves that the neo-Darwinian mechanism (random mutations plus natural selection) is fully sufficient to explain the origin of all forms of life, including man.
In this paper we will document that this experiment is indeed extremely significant, but for the opposite reasons. The bacteria have not experienced forward evolution, but rather the net effect has been reductive evolution (evolution going backwards). It is true that there has been some adaptation to the new artificial environment, but this has been primarily due to loss-of-function mutations. Such adaptive fine-tuning can at best be called microevolution, and has been accomplished through a net loss of information (broken genes/disrupted gene regulation). In all 12 experimental populations, the functional bacterial genome has shrunk - containing less total information. The resulting bacterial strains are still the same species, but have been seriously damaged. These disabled strains would quickly go extinct in any natural environment.
If any experiment could have validated large-scale macroevolution, it would have been this one. This famous experiment powerfully demonstrates that the mutation/selection process has very serious limitations. Even given huge populations and vast number of generations, all that was accomplished was a trivial amount of adaptive microevolution. Even while some superficial fine-tuning has been happening at just a handful of genomic sites, significant genetic damage has been accumulating throughout the rest of the genome, due to many slightly harmful deleterious mutations that cannot be selected away. This means that in the long run the net effect will be degeneration. This famous evolutionary experiment proves that in deep time, even given a model population that is optimal for validating evolution, populations do not evolve – but instead devolve. MORE...
APPENDIX 1: Download PDF for a detailed literature review of the major mutations that arose in the experiment and their associated fitness effects.