How does a living thing differ from a lifeless one? And how might those living characteristics have emerged from the lifeless matter that preceded them?
Jeremy Sherman’s new book, Neither Ghost Nor Machine: The Emergence and Nature of Selves discusses recent thinking on these questions, especially the work of neuroanthropologist Terrence Deacon. In this post and the next, I’ll summarize highlights.
Sherman emphasizes this difference between living and non-living things: living things have purpose, non-living entities do not. Purpose here has little to do with a person’s “sense of purpose” and it has nothing to do with divine intention. It refers instead to biological processes aimed at maintaining the state of being alive. The heart’s purpose—its function—is to pump blood. The purpose of a leaf is to produce food for the plant. We take for granted that bodies and all their parts serve functions and yet it may feel strange at first to identify purpose itself as a distinguishing biological feature of all organisms, even single-cell bacteria.
Non-living stuff, on the other hand, has no such purpose or aim or sustaining function. A fire in the fireplace burns and gives off heat and carbon and other gasses, after which the fire, without more fuel, goes out. Sherman writes, “Most chemical reactions yield a proliferation of molecular products” but such reactions soon peter out. The reactions in living things, on the other hand, don’t fizzle out so easily. Through their biochemistry, living things “are self-regenerative in two senses: they maintain their own existence, and they produce new selves” (9).
New selves? Sherman, following Deacon, refers to organisms as selves. Applying self to an organism calls attention to the ways that even a bacterium as well as a human works to find food, defend its-self, repair its-self, and make more selves. Inanimate things aren’t selves. Left alone long enough, anything inanimate will become disorganized and break down; an ice cube left on a counter will melt and then evaporate, its molecules finally dispersing into the air. Another difference between selves and inanimate things: with selves, we can say that something—fuel, information, lower temperature—is good or bad or useful or significant for it. But, as Sherman puts it, “Nothing is ever functional, significant, or adaptive for sodium chloride, snowflakes, mountains, fried chicken, or even computers” (25).
But what about natural selection? Didn’t Darwin’s work explain how living things evolve? Yes, but natural selection doesn’t explain the first appearance of the selves that do the evolving. “To claim that natural selection explains purpose is like claiming that erosion explains mountains. Erosion…explains how mountains are passively sculpted, but not what’s sculpted. Likewise, natural selection explains how populations of selves are passively sculpted…[as] some lineages produce more offspring than others, but not how selves arise in the first place.” (9).
So, the question: what kinds of inanimate chemical reactions might have come together as stepping-stones towards purposeful, self-regenerative selves? Until now, that question has been explored in terms of possible ingredients. Chemical stews, viruses, RNA molecules, an iron-and-sulfur world have been among the candidates for starting points. But Terrence Deacon has asked instead what kinds of reactions, regardless of their ingredients, could sustain themselves long enough to avoid the terminal fizzle of most reactions? In the abstract, his answer is that you need not one but two reactions, each of which constrains the other before it can burn itself out. How? I’ll explain in my next post.