The progress made in science so far is truly remarkable, considering that not too long ago (in the grand scheme of things), we thought that the universe revolved around the Earth and that living things arose spontaneously from non-living matter. It was not until the insights of Darwin and others, like Alfred Russell Wallace that people began to understand the origin of diverse life forms, based on the theory of adaptation by natural selection. In 1859, Darwin published On the Origin of Species, where he proposed the theory of adaptation by natural selection. His ideas were met with outrage and disbelief. Since then, they have become foundational to our understanding of biology, but they still face some opposition today.
The persistent distrust in Darwin’s theory of evolution by some people is partially based on the misperception that it is not something that is directly observable, that natural selection is “just a theory.” In fact, even Darwin himself thought evolution is too slow a process to observe. Now we know that this is not necessarily true. Evolution by natural selection can be demonstrated experimentally. You just need to conduct the experiment on the right organisms.
On Darwin Day 2019, we were joined by Dr. Richard Lenski who told us about his 30-year-long evolution experiment that revealed the power of natural selection. His study organism is the common gut bacterium, Escherichia coli. He started with 12 identical E. coli populations and diluted an aliquot of the original culture 1000-fold with liquid media with limited glucose every day. There is also citrate in the culture media, a nutrition source that E. coli cannot utilize in its natural environment. And he was able to observe that after 30,000 generations, one E. coli population evolved to be able to live on citrate. That is, a growth environment with limited, ready-to-consume nutrients selected for mutants that can live on the alternative nutrition source. A new form of life evolved that could do things it’s ancestors could not. Natural selection!
“The best part about this experiment is how simple…how straightforward it is,” commented Dr. Lenski. With E. coli and a slightly stressful growth environment, his research bottles evolution in an Erlenmeyer flask.
If you look at a comprehensive phylogenetic tree, it would probably be difficult to find us, Homo sapiens, among the countless other hard-to-pronounce Latin names. Because the range of evolutionary entries is simply so vast, so boundless, that me, the one typing up these words, and you, the one reading them, are virtually not that different from Oryctes rhinoceros, or Danio rerio. On our own evolutionary timescale, we are the population of Escherichia coli that evolved to consume citrate under certain circumstances. But we are also the population that has wanted to understand our own origins for as long as we have existed. We have managed to do so in part because of the insights of scientists, from Charles Darwin to Richard Lenski.
If you always had lingering questions about life itself, what it means to be alive, where we come from, and where we are going, consider studying biology to join the quest, to continue the valiant work laid down by our predecessors.