Life on Earth Reigns Accidentally

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

PHamlet rinses spent much time reflecting on the nature of chance and probability in William Shakespeare’s tragedy. In the famous speech “To be or not to be”, he notes that we helplessly face “the throws and arrows of scandalous fate” – although a little earlier in the play he states that “there is a special providence in the fall of a sparrow.,. “Suggesting that everything happens because God wants it to be that way.

We can scarcely reproach the prince for having two seemingly contradictory views on the nature of chance; after all, it is an enigma that has dismayed humanity over the centuries. Why are we here? Or to give the question a slightly more modern spin, what sequence of events brought us here, and can we imagine a world in which we have not arrived at the scene at all?

To the credit of biologist Sean B. Carroll he found a way to take a puzzle that could easily fill volumes (and probably has filled volumes), and presenting it to us in a slim, non-technical and fun libretto, A Series of Lucky Events: Chance and Creation of the Planet, Life and You.

Carroll (unlike physicist and writer Sean M. Carroll) gets started with an introduction to the key concepts in probability and game theory, but quickly moves on to the topic at the core of the book: the role of chance in evolution. Here we meet a key historical figure, the 20th-century French biochemist Jacques Monod, who won a Nobel Prize for his work on genetics. Monod understood that genetic mutations play a critical role in evolution, and he was struck by the random nature of those mutations.

Carroll quotes Monod: “Pure chance, absolutely free and blind, at the very root of the marvelous building of evolution: This central concept of modern biology is no longer among other possible or even imaginable hypotheses. It is today the alone an imaginable hypothesis, the only one that agrees with an observed and proven fact. “

Sean B. Carroll
A Series of Lucky Events: Chance and Creation of the Planet, Life and You
Princeton University Press, 2020

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

From there, it’s a short step to the realization that we humans may never have evolved in the first place. As Monod said, “Man was the product of an innumerable number of fortunate events.” For those who still believed that God was responsible for micromanipulating the events of the universe, that came as a heavy blow. Carroll quotes an American theologian, RC Sproul, who wrote that “The mere existence of chance is enough to tear God from his cosmic throne.” If we accept that chance plays any role, “it leaves God not only old-fashioned, but without work.”

But genetic mutations are just one kind of random occurrence; there are many others that nature sends us. Take asteroids: Usually they orbit the sun safely 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 the dinosaurs and paving the way for the rise of small fur mammals – some of which were our ancestral ancestors (add additional ancestors) grandparents.

The story of asteroids has been told many times, but Carroll adds another less-discussed angle: The asteroid hit Earth exactly the “right” place: an area in the Yukatan Peninsula rich in hydrocarbons and sulfur, so the impact ejected huge amounts of soot. and sunlight-deflecting aerosols into the atmosphere. Carroll makes the calculation: Considering the rotational speed of the Earth, he realizes that the object hit 30 minutes before or 30 minutes after it hit the Atlantic or Pacific; still a colossal explosion, but not one that would necessarily give the mammals an advantage over the dinosaurs. What if-things are fun but perhaps a little arbitrary; for example, why focus on the Earth’s rotation instead of its orbital motion – or the myriad of other factors that had to be “only” for the effect to occur where and when did it happen?)

The projectiles and arrows lasted post-asteroid; organisms continued to evolve, their destinies formed by genes, environment and natural selection. Carroll explains in some detail how Darwin’s theory was formed, and how it challenged the prevailing worldview in which various species were thought to have been created individually by God. In this new image, there is no guiding hand; events simply unfold according to the laws of nature. Carroll sums it up: “Look around you at all the beauty, complexity and diversity of life. We live in a world of error, ruled by chance. “

But if chance rules the day, how do complex organisms arise at all? This is the hard part, and we now understand much better than Darwin how genetic mutation and natural selection work together in some kind of gradual, cumulative process – what Carroll calls “the ladder of evolution.” (Carroll is hardly the first to describe these processes; Richard Dawkins, for example, dedicates much of his 1996 book, “Climbing Mount Unlikely” to the question of how evolution gives complexity.)

There’s a bit of microbiology here – Carroll is interested in dumb nuts – 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 hybrid of human chimpanzee (“humanity”). (The Communists wanted to show that religion is obsolete, and that the universe is only matter interacting with matter to the end.) The Pasteur Institute in Paris also supported the project. Ivanov finally managed to inseminate three chimpanzees with human sperm, but they did not conceive.

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. Take HIV, the virus that causes AIDS. Carroll explains how a single mutation in the monkey immunodeficiency virus (SIV) allowed it to make the leap from chimpanzees into humans – ultimately killing more than 32 million people. Random events have brought us here, but random events can also kill us. Following is a chapter on cancer, with detailed research on how cancer effects involve a mix of genetic and environmental factors – and, again, good luck.

If the book has a central message, we should thank our lucky stars that we are here. But instead of spotting philosophy, Carroll chooses recklessness; his final section is a cleverly staged imaginary conversation between Monod, Albert Camus, Kurt Vonnegut, and no less than six comedians – with himself as moderator. And while he’ll give himself the last word, I’ll end with what Ricky Gervais says just before, on the question of why we’re here: “We’re not special, we’re just lucky,” he says “We didn’t” exists of 14 billion and a half years. Then we are 80 or 90 years old if we are lucky, and then we will never exist again. So we have to take advantage of it. “

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