How Evolution and the Scientific Process Work
The most interesting thing about evolution is how simple beginnings and time are all that's necessary for complicated and diverse creatures.

Richard Dawkins is well-known for his religious criticism, but that reputation has distracted from his poetic science writing. The Greatest Show on Earth is a clear outline of the evidence in favor of evolution and clear explanations of how evolution works.
For those of you who know Dawkins from his atheism, you’ll find barbs against creationists. They ignore his life’s work for a living, after all. However, the focus is on describing the natural world. This a chance to see Dawkins’ awe of nature and the poetry of reality passionately defended.
There are many explanations of techniques like carbon dating and the robustness of the fossil record. But one of the most interesting experiments is the Lenski experiment.
Watching Evolution Unfold in Real Time
Dawkins begins his section on the Lenski experiments by pointing out how quickly bacteria can replicate. Whereas something like a lizard can take two to three years to reproduce, bacteria can produce six to seven generations each day. Richard Lenski and his team at Michigan State University took advantage of these quick generational changes to observe evolution first-hand.
Lenski began by putting the same E. coli bacterium into 12 flasks of glucose. Every day for 20 years, Lenski and his team would put some of the bacteria into a new flask to see how they would change. This resulted in about 45,000 generations of organisms with genetic codes small enough to monitor.
One of the most startling results was how uniform evolutionary changes were. All 12 “tribes” of bacteria became larger. Even more interestingly, two of them became larger in the same way:
“The astonishing result they [the research team] found was that 59 genes had changed their levels of expression in both tribes, and all 59 had changed in the same direction. Were it not for natural selection, such independent parallelism, in 59 genes independently, would completely beggar belief. The odds against its happening by chance are stupefyingly large…And the explanation, of course, is that it did not happen by chance, but because gradual, step-by-step, cumulative natural selection favoured the same — literally the same — beneficial changes in both lines independently.”
Dawkins has a section near the end of the book where he explains that most mutations are harmful. There are more ways to break the delicate machine that is an organism than there are to improve it. With so few ways to improve, it’s less surprising that beneficial changes are expressed similarly, whether the same genes are changed or not.
The Bacteria Learned to Eat New Foods, Too
The other big evolutionary change caught Lenski and his team by surprise. One of the tribe’s populations spiked. It increased by a factor of six after the 33,000th generation.
Each flask was primarily made of glucose, the food that E. coli normally ate. But there was also a little bit of citrate. Any bacterium that could figure out how to consume that would be able to take fuller advantage of its environment and support a larger population. A study of that bacterial tribe, Ara-3, revealed how this bacteria “learned” to consume a new substance:
“The magic moment turned out to be approximately generation 20,000. Thawed-out clones of Ara-3 that dated from after generation 20,000 in the ‘fossil record’ showed increased probability of subsequently evolving citrate capability. No clones that dated from before generation 20,000 did.”
Ara-3 couldn’t consume the new food without undergoing multiple changes. The genetic change necessary to consume it wasn’t enough. First, Ara-3 had to evolve a gene that allowed the mutation for consuming citrate to work:
“…After generation 20,000, Tribe Ara-3 were ‘primed’. Only they were able to take advantage of ‘mutation B’ when it turned up — as it probably did in several of the other tribes, but to no good effect. There are moments of great joy in scientific research, and this must surely have been one of them.”
This insight was hard-won from a study of forty trillion E. coli cells from Lemski’s lab. One of his students was the one who proved that the bacteria’s ability to feed on citrate required multiple mutations.
This detailed analysis of evolution, natural selection, and how we understand other related fields makes this a rich resource for anyone who wants to understand how we ended up with the diverse ecosystem of animals we enjoy today.
Scientific Theories and Snarky Footnotes
“…a good theory, a scientific theory, is one that is vulnerable to disproof, yet is not disproved. Evolution could so easily be disproved if just a single fossil turned up in the wrong date order. Evolution has passed this test with flying colours. Sceptics of evolution who wish to prove their case should be diligently scrabbling around in the rocks, desperately trying to find anachronistic fossils.”
Throughout this book, you’ll be able to follow the experiments for evolution and understand how they would have to be disproved. There’s a level of detail in Dawkins’ writing that’s hard to find anywhere else. You’ll be hard-pressed to find more clarity elsewhere.
If you do pick this book up, don’t neglect the footnotes. Many of the scientific books have rabbit holes the authors want to go down but can’t because they have to maintain the book’s focus. Dawkins is particularly active in all his books’ footnotes. The best one is a quip he remembered about “well-educated” people:
“‘Well-educated’ reminds me of Peter Medawar’s wickedly astute observation that ‘the spread of secondary and latterly of tertiary education has created a large population of people, often with well-developed literary and scholarly tastes, who have been educated far beyond their capacity to undertake analytical thought.’ Isn’t that priceless? It is the kind of writing that makes me want to rush out into the street to share with somebody — anybody — because it is too good to keep to oneself.”
Dawkins’ enthusiasm for sharing ideas permeates his work, and it’s strongest in his science writing. Anyone who doesn’t want to make the same basic mistakes about evolution that Dawkins’ critics make should pick this up and enjoy the knowledge as much as Dawkins’ passion for the world we get to experience.