The Greatest Show from Darwin to Dawkins - 8

8. Forty-five thousand generations in the laboratory



With such a grandiose promise, Dawkins begins a story about a laboratory experiment on E. coli. Indeed, what could be more exciting than being able to trace the path of evolution from an ape to the intelligent being that we consider ourselves to be. Let this be a rather conditional approximation, but this way we can better understand how natural selection worked, tracking thousands of imperceptible changes that led to the emergence of our species.
I will not describe the experiment in detail. All the information is in the original source, the facts from which I do not question, I accept completely and unconditionally.

I can only say that Richard Lenski created ideal Darwinian conditions for bacteria in his laboratory. The flask with nutritious broth was infected with Escherichia coli bacteria. The bacterial population began to grow rapidly until the food supply ran out. Hunger was beginning. At this moment, a sample was taken from this flask and placed in the next one filled with nutritious broth.
One cycle took a day and was strictly repeated every day. As Dockins emotionally notes: "there are excellent conditions for evolution and, moreover, the experiment was conducted in twelve separate lines in parallel."

Why 12 lines? Yes, so that, without wasting time, we can trace the evolutionary path of bacteria in parallel, covering the largest number of possible variations that can arise in equally ideal Darwinian conditions.
The experiment has not been completed and by the time of writing the book lasted more than twenty years, which was equivalent to forty-five thousand generations of bacteria (an average of six to seven migrations from test tube to test tube per day).

"To imagine — if we went back 45,000 human generations, it would be about a million years ago in the past, at the time of Homo erectus, Homo erectus."
In such a subtle way, Dawkins warms up the reader, promising to reveal the absolutely grandiose results of the experiment. Judge for yourself, our prehistoric ancestors had to experience such radical conditions, which were created in Lenski's laboratory, hardly several times. They, of course, had to starve, but it is unlikely to die out almost completely in each generation. The population was slow, with some dips, but it grew steadily.

And in the laboratory, "the bacteria went through the same daily recurring cycles of abundance, accompanied by starvation, from which a happy hundredth part was saved and transferred in a glass Noah's Ark to a new one."
In this figurative quote, we dare not suspect Dawkins of believing in the reality of the events of the "Old Testament". In the laboratory, yes, a small part of the population was miraculously saved every day. In life, each generation would need its own Noah, saving an evolved family from a regular World Flood.

So, what was going on in the lab? The broth contained glucose, and it was a limiting resource. "Under these conditions, the Darwinian expectation was that if any mutation arose that would help an individual bacterium use glucose more efficiently, natural selection would favor it, and it would spread through the flask, since mutant individuals would be ahead of non-mutant individuals in reproduction."

This is exactly what happened in all twelve tribes. All twelve lines have improved, and have become better at using glucose as a food source. Populations grew faster in successive flasks, and the average bacterial body size grew in all twelve lines, reaching the largest size by generation 2000. Then the growth process slowed down, but with less or more success it continued for another 18,000 generations.

Dawkins' gift as a writer is so great that the tension increases with each new turn of events. Very figuratively, he reports on intermediate "amazing results", about "step-by-step cumulative natural selection" and that "the chances are staggeringly great..." And he, according to the rules of the detective genre, saved the most important turn for the very finale.
"So far, we have seen a beautiful demonstration of evolution in action: evolution right before our eyes, documented by comparing twelve independent lines, as well as comparing each line with "living fossils" that literally, and not just metaphorically, come from the past.

However, a long-term experiment has thrown up one striking exception.
Shortly after the 33,000 generation, something absolutely wonderful happened.
One of these twelve lines, called Ara-3, suddenly went berserk."
I don't know about you, but I, driven to the extreme by the intrigue, jumped up at this point with a shout:

- They say!?
Perhaps this inappropriate display of feelings caused someone to smile. But what else could be expected after such statements? It's not for nothing that Dockins so subtly hinted at a parallel with a man walking upright?
Yes, I understand that the original species are not initially equal in their development, but after all, the conditions of a laboratory experiment are incomparably more favorable for an evolutionary breakthrough than those in which our tailed ancestors had to develop.

What really happened? It turned out that one knee of Escherichia coli, and only one, suddenly acquired the ability to eat not only glucose, but also citrate. Two mutations led to this breakthrough.
"You'll be glad to hear," Dawkins reports, "that this is exactly what Lenski's student, Zachary Blount, discovered while conducting a tedious series of experiments using approximately forty trillion — 40 000 000 000 000 — E. coli cells of all generations".

Well, we would be glad. If we hadn't been told before about the experiment with the relocation of Podarcis sicula lizards from island to island. Eighteen generations of these lizards were able to go through a path in which, in addition to gaining the ability to eat cellulose, a lot of interesting things happened. Eighteen generations in normal conditions versus forty-five thousand in ideal Darwinian conditions!

Yes, I remember that we considered the lizard case a misunderstanding caused by a silly joke of cheerful naturalists. But this is only an assumption that the esteemed Professor Dockins would hardly agree with. For him, both experiments are absolutely serious. At the same time, he evaluates the results of the second as: "there are moments of great joy in scientific research, and this, of course, should have been one of them."

Such healthy scientific optimism leaves no doubt about the significance of the results of the experiment. So maybe it's the bacteria themselves?
As for bacteria, the author of the bestseller reassures: "If we assume that the probability of a gene mutation during any act of reproduction of a bacterium is only one in a billion, the number of bacteria is so enormous that almost every gene in the genome mutates somewhere in the world every day."
But if there is nothing wrong with the bacteria, then perhaps something is wrong with the conditions created in the laboratory. Otherwise, the difference in the number of mutations per generation would not be so egregious.
Well, let's not look up to lizards. We will look up to those whom Dawkins himself suggested - an upright man. And in order not to bother with mathematics, let me remind you that everything has already been calculated for us: "45,000 human generations, it would have been about a million years ago in the past, at the time of Homo erectus."

It's just a stone's throw from Australopithecus afarensis, those of our ancestors who spent a significant part of their lives in trees. I cannot name the exact number of transformations necessary to bridge the gap from Homo erectus upright to us, but I very much doubt that this difference is only in the diet.

Correct me if I'm wrong, but purely arithmetically, if the conditions of Lenksi's experiment were followed by nature, then there is a high probability that Professor Dawkins and I discussed the stunning results of this experiment while sitting on different trees.
Although, what am I talking about? What is there to discuss? Ventriloquism!
After all, the appearance of the ability to speak and think logically is not the same as eating citrate.

* - I apologizes for my English. I would be grateful for the corrections.

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