Life
What is life? That question became relevant to the discussion of Homo nouveau as my going in assumption during my research was that Homo nouveau would be a living human species. In my discussion in chapter 13 of What Comes After Homo Sapiens? regarding electronic evolution, I had to revisit that assumption. Would an artificial superintelligence (ASI) be considered a species? If so, could that be the answer to the question, What Comes After Homo Sapiens? An ASI would be more intelligent than Homo sapiens, engage in some form of “thinking”, creativity, and language, perhaps even have some form of “consciousness”, and it would even evolve. Why would we consider it non-living?
An ASI would not meet some of the criteria for life proposed by Dr. Daniel E. Koshland, Jr., former editor of Science Magazine. For example, it doesn’t use DNA or RNA and doesn’t have a metabolism. But that definition of life comes from a member of the Homo sapiens species. If you ask a future ASI if (he, she, it) is alive, the answer very well could be “yes” according to its own definition of life. Who will adjudicate between competing definitions of life between an ASI and humans?
In What Comes After Homo Sapiens?, I opted to take the parochial view and declare an ASI as non-living. I further accepted the evidence that life on Earth began 3.8 billion years ago. But I must admit that I completely avoided ever defining exactly what that original life was or how it came to be. I just started with the widely accepted notion that we have three domains of life: first Archaea and Bacteria, then later, Eukarya. Humans, and all other plants and animals, are a member of the Eukarya domain. Part I of What Comes After Homo Sapiens? takes us from the first Eukarya to Homo sapiens (to be fair, mostly from chimps to Homo sapiens), and Part II took us to the answers.
That question of the first life on Earth (or anywhere else) continues to nag at me. I’ve done a lot of reading about it and although the answer is still to be determined, it is getting a little less mysterious. George Church and Ed Regis in their book Regenesis: How Synthetic Biology will Reinvent Nature and Ourselves make some convincing arguments about the origin of life given the fundamental forces and thermodynamics of the universe (lets not get into how they originated). Given those fundamental forces, as the universe cooled sub-atomic particles naturally condensed into atoms, atoms naturally formed molecules, some molecules naturally formed polymers of those molecules like proteins, RNA and DNA. That is, at least getting to the building blocks of life is deterministic. Unfortunately Church and Regis did not really take it beyond that to actually hypothesize how these naturally occurring entities organized into the first Bacteria or Archaea.
Nick Lane, in my opinion, did a much better job of that in his book Life Ascending: The Ten Great Inventions of Evolution. He makes a convincing argument that ancient alkaline underwater vents were where life on Earth may have begun. He reviews the Stanley Miller-Harold Urey experiment that started with a flask of water mixed with gases thought to be prevalent 3.8 billion years go: ammonia, methane and hydrogen. After sending electric sparks, like lightning, through the mixture, some of the 20 amino acids that form the basis of all life emerged in this primordial soup! This was intriguing, but it was not life. Nothing living ever appeared in these flasks. Perhaps Miller and Urey didn’t have the soup ingredients quite right. Other gases, and elements like sulfur and iron might be needed. Those ingredients, it turns out, are present in the alkaline underwater vents whose tiny compartments lined by catalytic iron-sulfur compounds make natural organic synthesis chambers.
Lane’s answer is much more complicated than I’m describing here, involving reverse Kreb’s cycles and proton gradients and other deep chemistry components. In fact, he describes key differences in what the primordial soup had to be like within the vents compared to what would be needed for the first forms of life to leave the vents and venture into the rest of the watery world. In particular, in addition to the precursors to proteins—amino acids—there had to be precursors to RNA and DNA—nucleotides.
When all is said and done, we are still left with two difficult facts: 1) life on Earth started about 3.8 billion years ago and there is no evidence from DNA or other factors that a new cycle of life ever started again on Earth independently and 2) we cannot recreate the conditions in a laboratory that leads to a living organism from the hypothesized primordial inorganic chemicals and conditions.
Here is my hypothesis. We know that life exists today in an extreme variety of ecologies and conditions. These conditions range from those alkaline underwater vents and even more extreme hot volcanic hydrothermal vents to ordinary seawater and oxygen-rich air over land. We have aerobic and anaerobic bacteria and large complex eukaryotes both in water and on land. Thus it is obvious that there is a wide range of conditions on Earth that can sustain life. Perhaps there is only a very narrow range of conditions—maybe only one—that can initiate life from the natural physical building blocks of the universe. Maybe that condition never existed on Earth but only on another object in the universe. We know that external objects carrying water and all sorts of organic compounds constantly bombarded the early Earth. Life forms that originated somewhere else that had the magic conditions to initiate life could certainly have ridden on those objects. Once here, they found conditions that were able to sustain life, even if they couldn’t initiate it. This is not a new idea and it certainly doesn't answer how life emerged elsewhere. But it could explain why it happened only once on Earth and why we can’t reproduce it.