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Most of the time, when people imagine the theory of evolution, they think of events that happened in the past or millions of years ago. However, that is wrong, and evolution could actually be observed in real time. This is what scientists have done since 1988 with a set of small glass flasks filled with bacteria.
Over all those years, the bacteria have been through over 80,000 generations, which is about an equivalent of a few million years of change. This is a project that researchers call Long-Term Evolution Experiment (LTEE), an experiment that focuses on one type of bacteria known as Escherichia coli or E. coli. However, what exactly did they find out with this many generations of a species? Let’s dive deeper.
What Is the Long-Term Evolution Experiment?
The Long-Term Evolution Experiment has been running since 1988, and it has revealed how quickly life can adapt, how new abilities can evolve in a population, and how random chance can shape the path of evolution. It was started by an evolutionary biologist named Richard Lenski on February 24, 1988.
He began this experiment with 12 flasks containing E. coli bacteria. They were fed a small amount of glucose as food. Every day, what researchers did was take about 1% of each flask and transfer it to a new medium where about 6 to 7 generations live per day.
Moreover, every 75 days, scientists would store and freeze the E. coli samples to create a fossil record to which they can compare and study the future generations. In other words, every 500 generations, they will have a frozen fossil record and see how the bacteria evolve over time and with each passing generation.
Read more: Wikipedia
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How Have the Bacteria Changed Over 80,000 Generations?
The environment in which the flask of bacteria was set up was very simple and consistent. It has the same temperature, the same food, and the same routine done to them every day. But, the bacteria over time did not stay the same and have continuously evolved and changed.
Early in the experiment, in the 12 flasks, the population grew fast for each of the media, even with the limited glucose they were being fed. By generation 20,000, they are already growing about 70% faster than their earlier ancestors. Additionally, some studies suggest their fitness and health improved over time, but slowly in the latest generations. This pattern tells us that adaptation can continue indefinitely.
The bacteria also changed in more ways than one. First, their average cell size increased, with their cells becoming more round and larger than the first bacteria. Genomic studies also found that there have been over tens of thousands of mutations in their lineage, but only a few were actually advantageous to the population.
Author's Final Thoughts
While Richard Lenski started this long evolutionary experiment in 1988, by 2024 and 2025, the lab where it was being done officially moved from Michigan State University to the University of Texas at Austin under the direction of Dr. Jeffrey Barrick. Up to this day, the research has been continuing, showcasing that evolution is not just an idea derived from old fossils but rather an ongoing process that can be observed and measured.
Read next: Do Animals, Plants, and Fungi All Come From One Ancient Ancestor? — Here’s What Researchers Found
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