Revolution - another excerpt from the second chapter of Mario Livio's book "Genius Errors"

to the first part of the episode

revolution
The first edition of Darwin's On the Origin of Species was published in London on November 24, 1859, and the face of biology changed forever that day. Figure 2 shows the title page of the first edition; Darwin called her "my child" when she was published. But before going to review the main arguments on the origin of species, it is important to understand what the book does not deal with. Darwin did not say a single word in it about the actual origin of life, or about the evolution of the universe as a whole. Moreover, contrary to popular belief, he did not deal at all with the evolution of man, except in one paragraph, prophetic and optimistic, near the end of the book, where he wrote: "For the future, I see fields wide open for the most important studies [alternative translation: for important studies] more]. Psychology is guaranteed to be built on foundations... [new, i.e.] that every mental talent will be acquired gradually. Much light will be shed on the origin of man and his history." It was only in a later book, The Descent of Man and Selection in Relation to Marriage, published a dozen years later, that Darwin decided to make it clear that he believed his ideas about evolution should also apply to man. In fact, he was much more specific, concluding that man is the natural descendant of ape-like creatures that probably lived on trees in the "Old World" (Africa):

"From this we learn that man is a descendant of a hairy and tailed four-legged creature, apparently a tree-dweller in his habits and a resident of the Old World. This creature, if naturalists had examined its structure as a whole, would have been associated with the series Quadrumana [four-armed primates, such as apes], with a degree of certainty equal to that of their even earlier ancestor of the Old World and New World monkeys. "

But most of the hard intellectual work on evolution was already done on the origin of species. In one fell swoop, Darwin got rid of the concept of design, shattered the idea that species are eternal and unchangeable, and proposed a mechanism by which adaptation and versatility can be achieved.

Put simply, Darwin's theory includes four pillars that all rely on one and only one impressive mechanism. The pillars are: evolution, gradation, common descent and differentiation. The essential mechanism that drives everything, and fuses the various elements into one cooperative entity, is natural selection, which as we know today, is somewhat pushed aside by several other mechanisms of evolutionary change, some of which could not have been known to Darwin at all.

I will briefly present these distinct components of Darwin's theory. The description will mainly outline Darwin's own ideas, rather than the current modern versions of these components. Despite this, in some places it will be practically impossible to avoid presenting the evidence that has accumulated since Darwin's time. But as we will see in the next chapter, Darwin made one serious mistake, which could have completely contradicted his most important insight: natural selection. The source of the error was not Darwin's fault - in the nineteenth century, no one understood what genetics was - but Darwin did not understand that the theory of genetics that he used directly contradicted the concept of natural selection.

The first mainstay of the theory is evolution itself. Some of Darwin's ideas about evolution did indeed have an old genealogy, but the French and English naturalists who preceded him (and among them the names of personalities such as Pierre-Louis Moreau de Maupertoil, Jean-Baptiste Lamarck, Robert Chambers and Darwin's own grandfather, Erasmus Darwin) failed to provide a convincing mechanism for the operation of evolution. This is how Darwin himself described evolution: "The view that was accepted by most naturalists and also by me up to this point, is that each species was created for itself without relation to others - by a fundamental mistake. I wholeheartedly believe that species are not immutable; But those who are members of this thing, which in our language is called a genus, are the relatives of other species, most of which are extinct." In other words, the species we encounter today did not always exist. Rather, they are the descendants of some previous extinct species. Biologists today usually distinguish between microevolution and macroevolution. Microevolution is concerned with small changes (such as those we sometimes find in bacteria), which are the result of the evolutionary process in relatively short periods of time, usually in local populations. Macroevolution is the results of evolution on long time scales, usually between species - and it may also include mass extinction events, such as the one that wiped out the dinosaurs. In the years that have passed since the publication of the Origin of Species, the idea of ​​evolution has become the guiding principle of all research in the life sciences - so much so that in 1973 Theodosius Dobzhansky, one of the most important evolutionary biologists of the twentieth century, wrote an essay titled "Nothing in biology is comprehensible but in the light of evolution". Towards the end of his article, Dobzhansky noted that the philosopher and Jesuit priest Pierre Thiers de Chardin "was a creationist, but understood that creation is realized in this world through evolution."

Darwin drew the idea embodied in the second pillar, gradualism, mainly from the writings of two geologists. One of them was the eighteenth-century geologist James Hutton, and the other was Darwin's contemporary, who later became his best friend, Charles Lyle. The geologic record shows patterns of horizontal stratification covering large geographic areas. This fact, in combination with the finding of different fossils in these layers, indicates the progress of a change to Shivarin. Hatton and Lyle were mainly responsible for formulating the modern theory called uniformitarianism: the idea that the rate at which processes such as weathering and sedimentation are conducted in the present is similar to the rate that prevailed in the past. (We will return to this idea in chapter 4, when we deal with Lord Calvin.) Darwin claimed that just as geological action changes the surface of the earth slowly but surely, so the evolutionary changes are the results of transformations that span hundreds of generations, or thousands. Therefore, one should not expect to be able to see significant changes in less than many years, except perhaps in organisms that reproduce very frequently, such as bacteria; These, as we now know, are able to develop resistance to antibiotics in a remarkably short time. But contrary to the uniformitarian position, the rate of evolutionary change is generally not uniform over time in a single species, and may also vary from species to species. As we will see later, the pressure exerted by natural selection determines first and foremost how quickly evolution will take place. Some "living fossils" such as the pair Priscomyzon riniensis - a jawless marine vertebrate with a funnel-like mouth - have hardly changed in 360 million years. I will add, as a fascinating side note, that the idea of ​​gradual change was already introduced in the seventeenth century by the empiricist philosopher John Locke. He wrote, in his sharp distinction, that "the boundaries between the species, according to which man sorts them, are man-made."

The next pillar of Darwin's theory, the idea of ​​the common ancestor, became in its modern incarnation the main driving force for all the ongoing searches for the origin of life. Initially, Darwin argued that there is no doubt that all members of a taxonomic class - for example, all vertebrates - are descended from a common ancestor. But his imagination carried him on, and he went far beyond this idea. Although his theory came into the world long before anyone knew that all living organisms share certain characteristics - such as the DNA molecule, a limited number of amino acids and the molecule that goes to the trader in the production of energy - Darwin boldly ruled that "the human being may lead me one step from this And further, and this is to bring me to a rule of faith, that animals and plants all came from one prototype." And immediately after admitting, for the sake of caution, that "it is possible that the hikku may be an illusionary guide", he nevertheless concluded that "it is possible that all the organic creatures that have lived on earth since time immemorial are the descendants of one primitive type, in which the spirit of life was first exuded".

But, you may ask, if all life on earth came from a single common ancestor, how did this diversity, amazing in its richness, appear? After all, it was the first hallmark of life that we recognized as a preacher. Darwin did not shy away, but faced this challenge directly - it is no coincidence that the title of his book includes the word "species". Darwin's solution to the question of diversity was based on another original idea: branching, or in the language of biologists, differentiation. Life begins with a common ancestor, just as a tree has a single trunk, Darwin explained. Just as the trunk of the tree develops branches, which split into branches, so the "tree of life" developed in multiple events of branching and splitting, creating separate species at each splitting point. Many of these species have become extinct, much like the dead and broken branches of a tree. But since with each split the number of species descended from a given ancestor is doubled, the number of different species may grow exponentially. When does differentiation actually occur? According to modern thinking, this mainly happens when a group of members of a certain species is separated geographically from the rest of the population. For example, perhaps one group migrated to the rainy side of a mountain range, while the rest of the species remained on the dry slope. Over time, these environments, which are quite different from each other, create different evolutionary paths, eventually leading to two populations that are no longer able to breed with each other - or in other words, to different species. This seems to be the case of the Italian sparrow, as a 2011 study showed: genetically, it is an intermediate form between the Spanish sparrow and the house sparrow. The Italian and Spanish sparrows behave as separate species, but the Italian and house sparrows form penitentiary areas, where the distribution areas of these two species meet, capable of breeding with each other.

You may be surprised to hear this, but in 1945 the writer Vladimir Nabokov, famous for his books Lolita and Panin, came and proposed a sweeping hypothesis for the evolution of a group of butterflies called flutes. Nabokov, who had been interested in butterflies all his life, guessed that these butterflies arrived in the New World from Asia in a series of waves spanning millions of years. Surprisingly, a team of scientists using gene sequencing technology verified Nabokov's hypothesis in 2011. They found that the New World species share an ancestor that lived about ten million years ago, but many of the New World species were closer to Old World butterflies than to their neighbors.

Darwin duly recognized the importance of the concept of differentiation to his theory, and even included in his book a schematic diagram of his tree of life. (Figure 3 shows the original diagram, taken from a notebook he kept in 1837.) To be honest, this is the only illustration in the entire book. How fascinating, Darwin included the disclaimer "I think" at the top of the page!

In many cases, evolutionary biologists were able to identify most of the intermediate stages in the differentiation process: from pairs of species that probably split not long ago from a single species, to pairs that are right on the verge of differentiation. At a more detailed level, a combination of molecular data and fossil findings has provided, for example, a relatively well-detailed and well-dated picture of the phylogenetic tree of all mammal families living today, or recently extinct.
Here I cannot but digress for a moment and point out that from my personal point of view, there is another aspect of the concepts of common ancestor and differentiation, thanks to which Darwin's theory is unique and special. About ten years ago, while I was working on the Accelerated Universe books, I tried to identify the elements that make a physical theory of the universe "beautiful" in the eyes of scientists. In the end I came to the conclusion that two absolutely essential ingredients are simplicity, and something sometimes called the Copernican Principle. (When it comes to physics, there is also a third component, and that is symmetry.) When I say "simplicity", I mean reductionism, in the sense that most physicists understand it: the ability to explain as many phenomena as possible using as few laws as possible. This has always been, and still is, the goal of modern physics. For example, physicists are not satisfied with having an extremely successful theory (quantum mechanics) of the subatomic world, and an equally successful theory (general relativity) for the universe as a whole. They would like a single unified theory, "the theory of everything", which would explain all things together.

The Copernicus principle got its name from the Polish astronomer Nicolaus Copernicus, who in the sixteenth century moved the earth from its privileged place at the center of the universe. The theories that obey the Copernican principle do not require the human race to occupy any special place in order for it to function. We learned from Copernicus that the Earth does not stand at the center of the solar system, and all the findings of astronomy after that only strengthened our knowledge that, from the point of view of physics, man does not play any special role in the cosmos. We live on a tiny planet orbiting a perfectly normal star, in a galaxy that has hundreds of billions of similar stars. And our physical insignificance continues even further. Not only are there about two hundred billion galaxies in our observable universe, but even ordinary matter – all the stuff we are made of and all the stars and gas in all the galaxies – constitutes only a little more than four percent of the universe's energy budget. In other words, the truth is that there is nothing special about us. (In Chapter 11 I will deal with some ideas that hold that we should exaggerate our Copernican modesty too much.)
Reductionism and the Copernican principle are the two true hallmarks of Darwin's theory of evolution. Darwin explained everything, more or less, concerning life on earth - except for its beginnings - through a single unified vision.

It's hard to ask for more extreme reductionism than that. At the same time, his theory was fundamentally Copernican. Man is the product of evolution just like any other organism. In the tree analogy, all the youngest buds are distant from the main trunk by a similar number of branching nodes, and the only difference is that they turn in different directions. Similarly, in Darwin's evolutionary model, all living organisms today, and man among them, are the products of similar evolutionary paths. Man by definition does not occupy any special or unusual place in this format - we are not the masters of creation - but is the fruit of the adaptation and development of his ancestors on earth. This was the end of "absolute anthropocentrism". All the creatures of our world are members of one big family. In the words of the influential evolutionary biologist Stephen J. Gould, "Darwinian evolution is a discourse, not a ladder." To a large extent, the fuel that was poured on the fire of opposition to Darwin for more than 150 years is exactly that - the resentment against the theory of evolution that knocked man off the pedestal on which he proudly placed himself. Darwin marks the beginning of a completely new way of thinking about the nature of the world and human nature. Pay attention, in the picture where only the "fittest" survive (we will talk about this in the context of natural selection), there are legs to the claim that insects are clearly superior to humans, because their number is much, much greater. And indeed, the British geneticist Mrs. Haldane said (or at least, it is said that he said so), in response to theologians who asked him if he was able to conclude something about the Creator from the study of creation, that God "has a great affection for beetles." Today we know that even when it comes to the size of the genome - all the hereditary information - man falls far short, believe it or not, of a freshwater amoeba called Polychaos dubium. According to the report, the genome of this microorganism has 670 million base pairs of DNA, which is more than two hundred times greater than the number in the human genome!
Well, Darwin's theory fully satisfies the two criteria (somewhat subjective, I must admit) relevant to a truly beautiful theory. It should therefore not be surprising that the origin of species brought about the most dramatic change in thought, perhaps, ever caused by the power of a single scientific essay.

We will now return to the theory itself. Darwin was not content with saying things about evolutionary changes and the creation of diversity. He saw it as his duty, as his first task above, to explain how these processes took place. For this purpose he had to offer a convincing alternative to creationism, which would explain the seemingly planned nature of nature. His idea - natural selection - was, in the estimation of philosopher Daniel K. Dennett of Tufts University, "the best idea anyone has ever come up with", no less and no more.