Good science is hard; good science communication may be even harder. During my publishing career I was the editor or managing editor on quite a few university-level texts, and I usually found the “Introduction to …” textbook authors to be better communicators and classroom teachers than the authors of “upper division” specialized texts. Ironically, the best-selling intro text authors may get zero academic credit at their home schools for their work when it comes to their tenure evaluations. The top-tier universities want “original research” instead, while “making a hard subject easier” does not count. It should.
The recent book by Sean B. Carroll called A Series of Fortunate Events: Chance and the Making of the Planet, Life, and You (Princeton University Press, 2020) is “hard science made easier” in the best sense of that phrase. In a brief 225 pages, including endnotes, the author takes you all the way from the “really big” of cosmology down through the evolutionary biology that produced you, and further on to the “really small” quantum mechanics of DNA molecules, all with a running theme of the tiny probabilities of events that radically shaped, and continue to shape, that journey.
Sean B. Carroll has had a long and distinguished career as an evolutionary biologist at the University of Wisconsin and the University of Maryland. Not coincidental to the tenor of this book, he currently leads science education efforts for the Howard Hughes Medical Institute, which is the largest private supporter of science education in the U.S. 
The unlikely collision
Carroll starts his journey with the mid-1970s discovery of a strange band of clay lacking fossils, but appearing in multiple strata of rocks around the world at the same geological point in time, 66 million years ago. Now called the Cretaceous-Paleogene Boundary (K-Pg for short), this layer marks the point where three-quarters of all living creatures on the Earth died out, including the large dinosaurs. We now know for quite certain that an asteroid about six miles wide, which had likely begun its own journey around the sun more than 4 billion years earlier, collided with Earth, creating a crater some 100 miles wide off the Yucatan Peninsula in modern-day Mexico. What were the odds of this unfortunate event?
Or fortunate event, because some very small early mammals survived this apocalypse, and with the larger reptiles gone from the ecosystem, larger and larger mammals evolved to “take up the empty space” in the new ecology of post-asteroid Earth. Then, a continuing series of improbable events that Carroll zips us through slowly shapes continents and weather patterns, altering the evolutionary path of these mammals until one day, through another sequence of low-probability happenings, you show up on this planet in baby form.
A recurring theme in this blog is that no matter what your favorite theology (or lack of it), you need to account for the prevalence of the natural laws of probability (or at least what looks and smells like it) in human history and our daily lives. In one of my earliest posts I visited the topic of one form of cancer whose age-adjusted rate of occurrence in Florida did not deviate much at all from 14 per 100,000 in a decade. Sean Carroll devotes much of a chapter demonstrating how most cancers require a sequence of six or seven sequential-but-random mutations to cells in order to “take off” in a human body.  The basic statistical concept of the Central Limit Theorem kicks in here to make the rates of most types of cancers amazingly predictable in total (to the joy of insurance company actuaries), but yet quite unpredictable for you, specifically.
Quantum probability in your DNA
The most fascinating revelation to me in Sean Carroll’s book is his discussion about how those mutations happen in DNA in a seemingly random pattern, but one that is very predictable in the very long run of millions of years. This stochastic rate of mutation allows us to “date” very old DNA quite accurately, and place long-extinct species on branches of the evolutionary “tree of life” that connects all living things on Earth.
Carroll then demonstrates how just two chemical bonds connecting two of the four chemical “bases” making up our DNA “ladder” differ only by a shift of one hydrogen electron, moving from one side of the molecular bond to the other and thus altering the DNA a tiny amount. This shift appears to happen relatively infrequently in molecular time, and it also appears to be a function of quantum randomness, the probability function of how an electron’s orbital shifts quantum states.
That apparently random event is the beginning of a single cell mutation. But the vast majority of those mutations occur in the numerous “nonfunctional” segments of the DNA chain, and so most of our genetic mutations, pass quietly by, like the thousands of threatening near-Earth objects that we never knew existed until better telescopes broke our blissful ignorance.
That rare, quantum-level, probabilistic DNA mutation is responsible for all of life. “Mutation, then, is a feature, not a bug in DNA,” Carroll states. And so, without acknowledging it, the author appears to throw a monkey wrench into Albert Einstein’s cosmological quip that “God does not play dice with the universe.” The rise of life on Earth, and the evolution of that life into the myriad of forms we see today, certainly appears to have had significant branch points with “roll of the cosmic dice” factors.
And so, where does determinism fit in?
My major disappointment with Carroll’s book is that he stayed completely away from the philosophical “black hole” of Einstein’s determinism argument against probability “dice” in the universe. An avowed determinist sees the universe through the lens of Laplace’s demon, a conjecture named after French polymath Pierre-Simon Laplace (1749–1827). According to Laplace, if someone (his “demon”) knew the exact location and momentum of every atom in the universe, then the future values of those atoms for any given time could be calculated from the laws of classical (Newtonian) physics.
To take that conjecture to a more practical level, if you knew the exact location and momentum of every ball bouncing in a lottery draw, you could theoretically predict where each ball ended up when the barrel stops. Good luck.
The classical equations do not take probability into account. The atoms making up a second large asteroid are currently somewhere on a trajectory to repeat that big dinosaur-destroying collision, the event with which Carroll starts his book. Those atoms began their journey, according to Laplace’s demon, shortly after the beginning of the universe, and their arrival is a deterministic fait accompli unless something else wipes us out first. That second collision may occur ten million years from now, or it may be today. Yet, here we are, and it’s a nice day here in Florida.
I refer to this view of history as the hidden Calvinist theology of predestination lurking in determinist physicists. French/Swiss theologian John Calvin (1509–1564) posited that an “omniscient” (all-knowing) God knows from the beginning of time how it will ALL end up, including whether you personally will wind up in Heaven or Hell. And where those lottery balls will fall (“God chose me to win the lottery today!”). I have often wondered if Laplace consciously figured out how to make this theology palatable to atheist physicists 200 years after Calvin.
And yet both Calvinists and physicists worldwide do get up every morning and select that first cup of coffee from the Starbucks menu as if they are making their own personal choices for their day. So do I. Explaining that contradiction to ourselves both with or without “God” has been a human pastime, and wager, for many thousands of years.
At any rate, I recommend Sean Carroll’s book. There is a good chance that you will enjoy learning something from it.
- Sean B. Carroll should not be confused with Caltech physicist Sean M. Carroll, also the author of several great books, such as The Big Picture: On the Origins of Life, Meaning, and the Universe Itself (Dutton, 2016).
- Page 124.
- Page 85.
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