Life on earth is ruled by chance

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

P.Prince Hamlet spent a great deal of time pondering the nature of chance and probability in William Shakespeare’s tragedy. In the famous speech “To be or not to be” he states that we are helplessly faced with “the slings and arrows of unheard of luck” – although a little earlier in the play he explains that “there is a special providence in the case of a sparrow, which suggests this that everything happens because God wants it to.

We can hardly blame the prince for holding two seemingly contradicting views on the nature of chance; After all, it’s a mystery that has vexed humanity over the centuries. Why are we here? Or to give the question a more modern touch: what sequence of events brought us here, and can we imagine a world in which we were not there at all?

It is thanks to biologist Sean B. Carroll that he found a way to solve a puzzle that could (and probably do) easily fill volume Has filled volumes) and present it to us in a slim, non-technical and funny little book, A Series of Happy Events: Coincidence and the Origin of the Planet, Life and You.

Carroll (not to be confused with the physicist and writer Sean M. Carroll) introduces the key concepts of probability and game theory, but quickly moves on to the topic at the heart of the book: the role of chance in the Evolution. Here we meet a key historical figure, the 20th century French biochemist Jacques Monod, who received a Nobel Prize for his work on genetics. Monod understood that genetic mutations play a crucial role in evolution, and he was impressed with the randomness of these mutations.

Carroll quotes Monod: “Pure coincidence, absolutely free and blind, at the root of the amazing evolutionary structure: This central concept of modern biology is no longer one of other possible or even conceivable hypotheses. It is that today sole conceivable hypothesis, the only one that agrees with observed and tested facts. “

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

“In none of the sciences is there a scientific concept,” Monod concludes, “that makes anthropocentrism more destructive than this.”

From there it is a short step to the realization that we humans may not have developed at all. As Monod put it, “Man was the product of an incalculable number of random events.” For those who still believed that God was in charge and micromanaging the events of the universe, this was a major blow. Carroll quotes an American theologian, RC Sproul, who wrote: “The very existence of chance is enough to tear God from his cosmic throne.” If we accept that chance plays a role at all, “it not only makes God obsolete, but also makes him unemployed.”

But genetic mutations are just a kind of random occurrence; There are many others that nature sends us. Take asteroids: they usually orbit the Sun harmlessly between the orbits of Mars and Jupiter – but the occasional one of them slams onto Earth. This happened at the end of the Cretaceous Period, when the dinosaurs were killed and the way was paved for the rise of small furry mammals – some of which were our great-great-great-grandparents.

The asteroid story has been told many times before, but Carroll adds another, less discussed point of view: The asteroid hit Earth in exactly the “right” spot: an area on Mexico’s Yucatan peninsula that is rich in hydrocarbons and sulfur. The impact threw enormous amounts of soot- and sunlight-deflecting aerosols into the atmosphere. Carroll does the math: Given the rotation speed of the earth, he determines that the object would have hit the Atlantic or the Pacific 30 minutes earlier or 30 minutes later; still a colossal explosion, but not the kind that would necessarily have given mammals an advantage over dinosaurs. (What-ifs of this kind are entertaining, but maybe a bit arbitrary. For example, why should one focus on the earth’s rotation rather than its orbit – or on the multitude of other factors that “just had to be” for the impact where could take place? and when ??)

The slingshots and arrows continued after the asteroid; Organisms continued to develop, their fate was shaped by genes, the environment and natural selection. Carroll explains in detail how Darwin’s theory took shape and how it challenged the prevailing worldview that believed that different kinds of God were created individually. There is no guiding hand in this new picture; Events just unfold according to the laws of nature. Carroll sums it up: “Look around you how beautiful, complex and diverse life is. We live in a world full of mistakes that is ruled by chance. “

But if chance rules the day, how do complex organisms come about? This is the hard part, and we now understand much better than Darwin how genetic mutation and natural selection work together in some sort of step-wise, cumulative process – what Carroll calls “the staircase of evolution.” (Carroll is hardly the first to describe these processes. Richard Dawkins, for example, devotes a large part of his 1996 book “Climbing Mount Improbable” to the question of how evolution leads to complexity.)

There’s some microbiology here – Carroll is interested in the nuts and bolts of mutation – but the historical details impressed me. Like the Russian biologist Ilia Ivanov, who tried to create a human-chimpanzee hybrid (a “Humanzee”) in a project funded by the Communist Party of the Soviet Union. (The communists really wanted to show that religion is out of date and that the universe is just matter that interacts with matter until the end.) The Pasteur Institute in Paris also supported the project. Ivanov eventually managed to inseminate three chimpanzees with human sperm, but they did not get pregnant.

So humans and chimpanzees aren’t quite as close as Ivanov imagined, but they’re 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 simian immunodeficiency virus (SIV) made the leap from chimpanzees to humans, ultimately killing more than 32 million people. Random events got us here, but random events can kill us too. A chapter on cancer follows with an in-depth look at how the effects of cancer involve a mix of genetic and environmental factors – and luck again.

If the book has a central message, we should thank our lucky stars for being here in the first place. But instead of turning to philosophy, Carroll chooses recklessness. His last section is a cleverly staged imaginary conversation between Monod, Albert Camus, Kurt Vonnegut and no less than six comedians – with yourself as the moderator. And while he’s giving himself the last word, I’ll end what Ricky Gervais said a short time ago by asking why we are here: “We’re nothing special, we’re just lucky,” he says. They have been around for 14.5 billion years. Then we’ll have 80 or 90 years, if we’re lucky, and then we’ll never exist again. So we should make the most of it. “

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