Evolution Experiments and their Results

What if we could speed up time to test the concept of evolution? A scientist can’t wait millions or billions of years to study the process of natural selection as it creates new creatures. With that in mind, science must devise evolution experiments to study many generations in a much shorter time.

More than thirty years ago, Richard Lenski, who teaches at Michigan State University, began a project to study the evolution of the bacteria Escherichia coli, commonly known as E. coli. The project is called the Long-Term Evolution Experiment (LTEE). The scientist and his assistants carefully track the naturally-occurring random mutations in succeeding generations of E. coli. The environment for the bacteria is optimized for these one-cell creatures to grow and reproduce. Mutations are often harmful, but sometimes beneficial mutations lead to an improvement in the bacteria’s reproductive ability. Natural selection removes the bacteria with harmful mutations while those with beneficial mutations become more fit and reproduce. It’s what we call survival of the fittest.

Since 1988, the evolution experiment has continued, and scientists have kept careful records of the changes. Since the generation period of these bacteria is much shorter than that of humans, the study has gone through 70,000 generations. That is equivalent to more than 1.75 million years of human generations.

Through thousands of generations, there have been billions of mutations. Beneficial mutations that have lasted and accumulated amount to dozens. It is interesting that as time passes, successful mutations become increasingly rare. What the scientists are looking for is what they call “historical contingency,” which means a succession of small, almost inconsequential changes that accumulate to create significant changes.

So how has the E. coli changed after the 70,000 generations in this evolution experiment? The latest generation of E. coli can reproduce 70% faster than their ancestors. They are still bacteria. In fact, they are still E. coli bacteria. They have not mutated into some more advanced form of life. Dr. Lenski wants to see funding made available to continue the experiment for another 30 or even 300 years in the hope of seeing more dramatic results.

The LTEE has inspired other scientists to conduct evolution experiments. There is one at Harvard experimenting with yeast. Other scientists have experimented with fruit flies (Drosophila) to study the evolution of multi-cell creatures. They have bombarded the fruit flies with radiation and chemicals, changing light levels, and changing temperatures. After thousands of generations, the result has been mutant fruit flies with extra eyes or wings that didn’t function. They were still fruit flies.

The bottom line is that multi-generation evolution experiments have not resulted in new creatures or even greatly improved old creatures. The changes resulting from mutations and natural selection are either harmful or insignificant. God created animals to adapt and change due to environmental forces. Humans can change and sometimes improve animals by selective breeding. We see that very clearly in the many and very different breeds of dogs. But the evidence seems to indicate that only God can make a Canine or a Drosophila or an Escherichia—or a human.

— Roland Earnst © 2019

You can read about the LTEE in the December 2019 issue of Discover magazine, page 49.