Breeding 2,000 Generations of Bacteria May Have Solved This Major Debate in Biology

Since the dawn of genetics, biologists have debated if evolution is driven by chance or by the original diversity in the genes.

Having a lot of genetic options to choose from might make natural selection move a lot faster at the beginning, but do the genetic changes that happen over time contribute more to survival?

Researchers at Michigan State University have tested the adaptive ability of 72 different populations of Escherichia colibacteria over the course of two thousand years.

At the beginning of the experiment, each population ofbacteria was engineered to have a different amount of genetic diversity.

On the other side of the spectrum, the population was bred from a single clone, so every cell was the same.

Populations were grown from a single pre-existing population ofbacteria.

The maximum amount of genetic diversity could be achieved by mixing a few pre-existing populations together.

At the beginning of the experiment, each population was given a meal of sugar. To test the ability of thesebacteria to adapt to a different growth environment, they were given the D-serine instead of the sugar.

The populations were tested for their ability to compete for nutrition resources against a common competitor.

The Long-term Experimental Evolution Project was started in 1988 by one of the co-authors on the recent paper.

The more genetically diverse the population, the better it was.

The early stages of the experiment showed the importance of the genetic diversity in the initial population.

The authors wrote in their preprint that the diversity at the start of the experiment was no longer important because the new mutations were large.

There were no differences in fitness by the 500th and 2,000th generation.

The researchers say that any benefit of pre-existing variation in asexual populations may be short-lived.

This result may close the book on the longest-running argument in evolutionary biology when it comes tobacteria, as it is yet to be scrutinized by others in the scientific community and published in a peer reviewed journal.

There is no right answer to the question of the relative importance of standing variation in nature.

They say that scientists tend to emphasize one or the other source of genetic variation.

The diversity of the gene pool is the main source of evolutionary capacity because it isn't practical to wait around for hundreds of years for new genes to be created.

The major source of evolution for those studyingbacteria andviruses are the changes in genes.

Both forces can contribute to the process of adaptation by natural selection.

The preprint can be found on BioRxiv.