New Thinking About the Origin of Life (1): Purposes and Selves

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.

campfire (shutterstock.com)

shutterstock.com

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.

Harvard Studies the Beginnings of Life

In 2007, Harvard University launched its Origins of Life Initiative, a multi-disciplinary research effort to understands life’s origins both on Earth and perhaps on other planets as well. Here are some highlights of this work as reported by Courtney Humphries in the September-October 2013 issue of Harvard Magazine.

  • The driving question is, how does biology emerge from chemistry? “How do inorganic molecules begin to behave like living organisms?” Or as professor Jack Szostak puts it, “Where do you draw the line between life and not-life? Well, different people might have different places where they draw the line. It doesn’t really matter—what matters is getting some insight into the overall process.” And understanding how the process took place on Earth will point towards other planets that might be candidates for life.

    dna rna

    DNA is the cookbook, with recipes to make an entire organism. RNA is the cook that makes every recipe, even the one for the cookbook itself. Which came first?
    (dreamstime.com)

  • According to the article, scientists studying that process “face a chicken-and-egg problem: in modern cells, the genetic instructions of DNA are translated and carried out by RNA and proteins, which perform cellular functions—including building DNA. So how could any of these complex molecules have arisen without the aid of the others?” In the past, scientists thought DNA, the vast instruction book handed down to all living things, came first. But current opinion favors RNA, “a quick and dirty multitasking genetic molecule, able both to store biological instructions and catalyze [speed up] its own reproduction.” RNA is unstable, though, and eventually some of its tasks were taken up by DNA and proteins.
  • So how did these busy RNA molecules, candidates for recognition as the first living things, come about? We don’t know. “There is still a laundry list of problems that must be solved to create a plausible scenario for RNA formation, and several labs around the world are painstakingly working on each one,” according to the article’s paraphrase of Prof. Szostak. We’re back to getting from the chemistry to the biology.
  • Whatever the process was, the environment on earth was part of it. The earth provided geothermal vents to help “cook” the mixtures of early chemicals, as did the ultraviolet radiation that was 200 times stronger at that time than it is now. The earth provided the carbon and the nitrogen, while early photosynthetic bacteria burped out oxygen as a waste product, one that later became a requirement for animals.
  • A helpful poster showing the environmental changes on earth alongside the simultaneous stages in the history of life has been prepared by the Harvard scientists with the Howard Hughes Medical Institute in Maryland. The version below, when printed out, is legible.

The Harvard Initiative doesn’t have all the answers yet, but the process of life’s beginnings is getting clearer.

harvard poster

From the bottom up, the chronology of Earth’s environment, with geology on the left alongside the history of life
(hhmi.org)