Recently I’ve been reading these three books, Power, Sex, Suicide: Mitochondria and the Meaning of Life by Nick Lane; Cosmos by Carl Sagan; and Mendel’s Demon Mark Ridley.
In his brilliant book Power, Sex, Suicide: Mitochondria and the Meaning of Life, Nick Lane argues that the single most revolutionary event in the history of life on Earth was not the origin of life itself, but something that happened roughly two billion years later: the moment one bacterium engulfed another and, instead of digesting it, struck up an intimate partnership. That engulfed bacterium became the mitochondrion, the power plant of every complex cell.
For almost four billion years, nothing like it had ever happened before, and nothing like it has happened since. That one-time symbolic event single-handedly broke the energy bottleneck that had kept life simple and prokaryotic. With mitochondria providing orders of magnitude more energy per gene, cells could finally afford to grow big, divide labor, and become the vast coordinated societies we call eukaryotes. In one audacious leap, the ceiling of biological complexity was shattered, and the stage was set for plants, animals, fungi, for everything we normally think of as “life”.
Carl Sagan, in Cosmos, posits complexity as a cosmic story with ever-ascending chapters. It begins with simple replicating molecules, moves to the universal common ancestor (LUCA), then to bacteria, eukaryotes, multicellular organisms, vertebrates, brains capable of learned behavior, and finally to creatures that invent language and writing. Each step dramatically increases the amount of information a lineage can store, transmit, and built upon.
First, the scale is measured in the length of the fidelity of DNA (or RNA).
Then culture and oral tradition push complexity beyond the genome.
Finally, writing (and later printing, libraries, the internet) allows information to be stored almost without limit and transmitted almost without loss. Humanity alone crossed that threshold, and complexity leapt again.
Mark Ridley, in his wonderful (and sadly under-read) book Mendel’s Demon, fills in a crucial missing piece between the prokaryotic world and the eukaryotic explosion. For genomes to grow large enough to support complex life, copying errors had to become extraordinarily rare. Early replicators probably had error rates around 1 in 10,000 (10^-4). That’s fine for tiny genomes, but fatal for anything bigger. The invention of sophisticated DNA-repair enzymes dropped the error rate to about 1 in a billion (10^-9 in mammals, even lower with proofreading). Suddenly genomes could safely expand by two full orders of magnitude. Only then did the energy demands of mitochondrion-equipped cell become genetically feasible.
Sex comes next, and with it, a ruthless new tool. Meiosis and recombinations expose harmful mutations to selection in every generation, letting populations purge bad variants that would otherwise accumulate like rust. With deleterious mutations under control, genomes could keep growing, experimenting, specializing. Only then could life sprint toward vertebrates, nervous systems, and eventually minds capable of wondering about their own origins.
So here we are. Every major increase in biological complexity looks, in hindsight, almost inevitable; yet each depended on astonishingly improbable breakthroughs separated by hundreds of millions, sometimes billions, of years:
- High-fidelity DNA repair
- Mitochondrial endosymbiosis
- Sexual reproduction
- Neural crest cells and brains
- Language
- Writing
The staircase of complexity has awfully long landings between steps.
And now we stand on the latest landing.
Is Artificial Intelligence the next improbable invention that will shatter today’s ceiling the way mitochondria once did? Or will the next leap still belong to biology; to some future symbiosis, some new kind of cell, some post-human lineage we can barely imagine? who, or what, would be the protagonist of the next chapter?
They are the same kind of questions our single-celled ancestors never needed to ask, right before everything changed forever.
Recently, I watched Pantheon.
From a conceptual standpoint, the idea of uploading brains to the cloud has been around for a long time. When I was in middle school, I often pondered this question. If we set aside the debate of whether a human brain (without a body as a medium, without the bacteria, cells, gut microbiome, and endocrine structures of the body) can represent the person themselves, and assume that people achieve biological upload, expressing life through information and algorithms, then this would be another leap in complexity. Life could iterate at an electronic pace.
This show, very provocatively, assumes humans can achieve immortality this way (which theoretically makes them another dimension of species, but let’s assume it’s still ‘humanity’), and asks the question: What does infinite life mean for ‘humans,’ and should humans even desire infinite life?
Again, these are cliché questions. In my past conversations with others about this, I often received the answer: “Life has meaning precisely because it ends, because of death; it is because of death that people cherish life.” We’ll set aside whether life has meaning for now, as that involves philosophical questions that could fill dozens of pages. My personal answer to that question is: Death cannot bring meaning to life.
As for the latter point, “it is because of death that people cherish life,” I simply disagree.
Yes, because we know that one day we will face death, and we instinctively fear death, we should cherish our lives and time. However, there are so many people, the vast majority even, who, despite knowing they will die one day, squander their own lives, squander the lives of others, easily end their own lives, torment themselves and waste their time over unworthy things, easily dismiss the affairs of others, and fill their lives with resentment and regret without an ounce of gratitude, even though we all know that every day we waste is the tomorrow that those who died yesterday yearned for. If there is one thing humans are best at, it is not cherishing life, but wasting it. So, you see, death does not make people cherish life, because people do not constantly remember that they will die one day. Whenever I encounter such arguments, I maintain a critical attitude; they do not convince me.
Immortality is appealing to me; I am honest about my thoughts and feelings.
It wasn’t until watching Pantheon this time that Maggie brought up a very interesting point. She said that people need death because death allows them to grow. Assuming immortality exists, imagine throughout your entire life, your parents always exist, and their parents always exist, and your grandparents’ parents also always exist. In that scenario, a person would never truly grow up and become an independent individual. This touched me because it made me realize the limitations of my own perspective. My previous perspective was focused on my own future, as if I were the first immortal individual, and from then on, I might or might not have descendants. But when I am born as a descendant into a world where my ancestors will always exist, that would be a terrifying thing. I think this is my biggest takeaway from the show so far.
Indeed. When the first cancer cell appeared, it thought it had found the secret to immortality. At first, it just wanted to live forever.
