(This month’s featured image is a photo of the Carina Nebula taken by NASA’s James Webb telescope. It’s a vast cloud of gas and dust, slowly condensing, with hundreds of stars visible in the background behind it. The colorized image almost looks like orange mountains with a blue mist rising from them, set on a black background with bright, six-sided starbursts.)
Normally, when we talk about evolution, we mean what life does. It’s Darwin’s magic formula. You need reproduction. You need to pass on a copy of your genes, with a little variation, so things don’t just stay the same. Natural selection will weed out the less fit individuals, so they have fewer kids. The more fit individuals become more prevalent and, over time, life as a whole evolves to be more fit. Yet, this isn’t a very satisfying story. For one thing, how did it begin? Did life just start evolving out of the blue? I think story is more compelling if we think about evolution a bit more abstractly. In a sense, the physical universe itself evolves. It doesn’t have reproduction and inheritance, but it sure does have variation and selection, and this has caused it to change dramatically over the course of history.
For the first 370,000 years or so, all of space was filled with a boring, homogeneous cloud of energy and plasma. That universe is now extinct, and for one simple reason: it was unstable. In our universe, stability is the ultimate definition of “fitness.” What persists, exists. Patterns of matter and energy that get generated more often and stick around longer become more prevalent. Those that are rare and fragile exist only fleetingly. The plasma universe is gone because gravity causes matter to clump together. It was like a pencil, balanced on its tip. As soon as it became just a little unbalanced, it rapidly fell farther and farther away from that delicate equilibrium. Plasma condensed into molecules, gas clouds, and stars.
Of course, evolution needs variation to work. To find what’s better, you need to weed out what’s worse. For life, reproduction is the engine of variation, but that isn’t necessary if you have unimaginably vast scale. The universe started out with very little variation, but it steadily increased as matter interacted with itself. Gravity caused hydrogen molecules to group together in uneven clumps, and held them there. They sat around for millions of years, slowly growing bigger, until the force of their own weight ignited a fusion reaction. The gas clouds became stars, and in their cores new elements were born. The universe’s population gradually became more diverse.
That’s the counterintuitive thing about stability: it can generate diversity. When patterns become more numerous, and they stick around for longer, chaos starts to kick in. Every star and every planet is a little different. They have unique histories and influences and opportunities. They might be richer in this element or that one, bigger or smaller, hotter or colder, more or less affected by collisions. This diversity only compounds over time, as these objects smash together and interact in complex ways. The longer they stick around, the more they change, recombine, and become more elaborate.
So, for 13 billion years, the universe evolved. Its population became stranger and more complicated. Today we have about a hundred “naturally occurring” elements that didn’t exist at first, but had to evolve through multiple generations of stars fusing atoms, exploding violently, and gradually reforming. We have many kinds of stars, planets, solar systems, and galaxies, that support an astonishing variety of chemical processes that have had a very, very long time to develop. They produce “primordial soups,” pocket environments full of useful molecules for life, a steady energy source, and self-perpetuating chemical reactions. We think this happened at least once to seed all life on Earth, but it may in fact be very common.
I think this story is an essential foundation for understanding evolution as life does it. Because life didn’t start this process. The universe provides energy and raw materials in vast amounts. It provides the chaos and entropy that drives seemingly random variation, and the slow, continual breaking down that causes natural selection to prefer stable, commonly made forms. The laws of physics cause the universe to evolve towards stability, diversity, and complexity, at least for a while, until it starts to wind down again and settle into entropy. Life merely constrains that process, making it more efficient and productive, for the simple reason that matter that does so becomes more prevalent.
In these primordial soups, some chemical systems evolved to enclose themselves in bubbles, protecting delicate reactions from the outside world. These self-made “individuals” evolved regular cycles of reproduction, explicitly making copies of themselves rather than waiting for the right reactants to come together again by chance. They evolved DNA to constrain these copies, and make them more precise reproductions of the original. They evolved sophisticated error checking, which made the copies more robust and reliable. But this also gave life the power to manage variation across generations, and thus shape its own evolution. Life evolved sex to further manage variation, accelerating innovation by sharing genetic recipes across lineages. Life evolved an astonishing variety of sexual and reproductive practices, allowing it to evolve in different ways, with different patterns of variation and selection, each suited to a different range of environments and lifestyles.
The physical Universe evolves—in the most primitive way imaginable, but it still produces stability and complexity in a vast number of diverse forms. It generates the seeds of life, without any guidance or direction. Life evolves differently, because it constrains this process, making it discrete, digital, and managed. This started very simply, just discovering chemical reactions that isolate and maintain themselves. But perhaps this is the origin of what we think of as “intelligence” or “agency”? Without noticing, matter became “opinionated,” preferring certain forms and acting explicitly to promote them. From there, life’s “opinions” about itself only became more demanding and elaborate.
We often present evolution as one simple story, but there are many ways to evolve. Evolution is more like a general principle than a specific algorithm. Even just life as we know it, all based on the DNA molecule, has invented an astonishing variety of different and complex ways of evolving. Bacteria, fungi, plants, and animals use DNA differently. They grow, behave, and reproduce in completely different ways. How many other ways might there be to do it? When we present evolution as a single, constant thing, we limit our imagination. Evolution evolves, and it takes as many diverse forms as it makes.
Thinking with Nate 