Life on Earth is led by chance

Photo: Jörg Bittner Unna / Wikimedia Commons, CC BY 2.0

Prinse Hamlet he spent much time meditating on the nature of chance and probability in William Shakespeare’s tragedy. In the famous speech “To be or not to be”, he observes that we are helplessly confronted “with the plows and arrows of scandalous luck” – although a little earlier in the play he states that “there is a special providence in the fall of a sparrow”. everything happens because God wants it to be so.

We can hardly blame the prince for holding two seemingly contradictory views on the nature of the event; after all, it is a puzzle that has upset mankind over the centuries. Why are we here? Or to give the question a slightly more modern rotation, what sequence of events brought us here and can we imagine a world in which we did not reach the stage at all?

Faith biologist Sean B. Carroll has found a way to take a puzzle that could easily fill volumes (and probably It has filled volumes) and presents it to us in a thin, non-technical and fun booklet, A series of lucky events: the chance and creation of the planet, life and yours.

Carroll (not to be confused with physicist and writer Sean M. Carroll) receives the ball with an introduction to the key concepts of probability and game theory, but quickly moves on to the problem at the center of the book: the role of evolution. Here we meet a key historical figure, the French biochemist of the twentieth century, Jacques Monod, who won a Nobel Prize for his work in genetics. Monod understood that genetic mutations play a critical role in evolution and was impressed by the random nature of these mutations.

Carroll quotes Monod: “Pure chance, absolutely free and blind, right at the root of the amazing edifice of evolution: this central concept of modern biology is no longer one of the other possible or even imaginable hypotheses. Today is unique hypothesis to be conceived, the only one that matches the observed and tested facts. “

Sean B. Carroll
A series of lucky events: the chance and creation of the planet, of life and of you.
Princeton University Press, 2020

“There is no scientific concept in any of the sciences,” concludes Monod, “more destructive of anthropocentrism than this.”

From there, it’s a short step to the realization that we humans could never have evolved. As Monod put it, “Man has been the product of countless fortuitous events.” For those who still believed that God is responsible, who manages the events of the universe, this came as a heavy blow. Carroll quotes an American theologian, RC Sproul, who wrote that “The mere existence of chance is enough to snatch God from his cosmic throne.” If we accept that chance plays a role, “it leaves God not only obsolete, but also in a workplace.”

But genetic mutations are just a kind of coincidence; there are many others that nature sends us. Take asteroids: they usually surround the sun harmlessly between the orbits of Mars and Jupiter – but sometimes one of them hits Earth. This was the case at the end of the Cretaceous period, killing dinosaurs and paving the way for the growth of small fur mammals – some of whom were great-great-great-grandparents (plus several ancestors).

The asteroid’s story has been told many times, but Carroll adds another, less discussed angle: the asteroid hit Earth right at the “right” point: an area in the Yucatan Peninsula of Mexico rich in hydrocarbons and sulfur, so the impact atmosphere huge amounts of soot and aerosols that deflect sunlight. Carroll calculates: Given the Earth’s rotational speed, he observes that the object would have hit 30 minutes earlier or 30 minutes later would have hit the Atlantic or Pacific Ocean; another colossal explosion, but not the kind that would have necessarily given mammals an advantage over dinosaurs. (What if this genre is fun, but maybe a little arbitrary; for example, why focus on the Earth’s rotation rather than orbital motion – or the countless other factors that had to be “just like that” because the impact to happen where and when did it?)

The belts and arrows continued after the asteroid; organisms continued to evolve, their destinies being shaped by genes, environment and natural selection. Carroll explains in detail how Darwin’s theory took shape and how it provoked the dominant view of the world in which different species were supposed to be created individually by God. In this new image, there is no guiding hand; events take place simply according to the laws of nature. Carroll sums it up: “Look around you at all the beauty, complexity and variety of life. We live in a world of mistakes, ruled by chance. “

But if the event dominates the day, how do complex organisms appear? This is the difficult part, and now we understand much better than Darwin how genetic mutation and natural selection work together in a kind of cumulative step-by-step process – what Carroll calls the “evolutionary ladder.” (Carroll is not the first to describe these processes; Richard Dawkins, for example, devotes much of his 1996 book, “Climbing Mount Improbable,” to the question of how evolution produces complexity.)

There’s a bit of microbiology here – Carroll is interested in the nuts of the mutation – but the historical details are what’s left for me. Like the Russian biologist Ilia Ivanov, who, in a project funded by the Soviet Communist Party, tried to create a human-chimpanzee hybrid (a “humanized”). (The Communists were eager to show that religion was outdated and that the universe was just a matter that interacted with matter to the end.) The Pasteur Institute in Paris also supported the project. Ivanov eventually managed to inseminate three chimpanzees with human semen, but they did not become pregnant.

So humans and chimpanzees are not as close as Ivanov imagined, but they are still very close – close enough that viruses that infect one species often jump to the other. Get HIV, the virus that causes AIDS. Carroll explains how a single mutation in the simian immunodeficiency virus (SIV) allowed him to make the leap from chimpanzees to humans – eventually killing more than 32 million people. Random events have brought us here, but random events can kill us. This is followed by a chapter on cancer, with a detailed exploration of how the effects of cancer involve a mixture of genetic and environmental factors – and, again, good luck.

If the book has a central message, we must thank our lucky stars that we are not here at all. But instead of turning to philosophy, Carroll chooses levity; its final section is a cleverly imagined conversation staged between Monod, Albert Camus, Kurt Vonnegut and no less than six comedians – with himself as moderator. And as he gives his final word, I’ll end with what Ricky Gervais says just in advance, when asked why we’re here: “We’re not special, we’re just lucky,” he says. “We didn’t.” of 14 and a half billion years. Then we are 80 or 90 years old, if we are lucky, and then we will never exist again. So we should make the most of it. “

This article was originally published on Undark. Read the original article.