Friday, September 16, 2016

A World from Dust (Plus): The Rapid Emergence of Life

For a scientist, opening up a new scientific journal is a bit like opening up a present on Christmas Day. I always get a slight thrill when I look through new journal articles and find one that further confirms something I'd suspected previously. I had that sensation a few weeks ago when I read "Rapid emergence of life shown by discovery of 3,700-million-year-old microbial structures" in Nature.

I admit that most people don't have their heart leap when reading those words, but compare that title to this quote that I wrote a year or two ago, now printed on p. 87 of A World from Dust:

"Before the clues, there is the question of timeline: When did life begin? This is a bit of a surprise in its own right. I would have thought that, given all the different molecules that have come together in any living thing, this assembly should have taken a long time. Instead, most evidence implies that life formed on this planet as quickly as possible, if not sooner."

"Living processes are even harder to pin down in rocks, but various lines of evidence (including unnatural imbalances of neutrons) can only be explained by life 3.5, 3.6, or even 3.8 billion years ago. A study of phosphorus in rocks 3.5 to 3.2 billion years old finds that life was mature enough to use phosphorus in a widespread, well- defined phosphorus cycle. Evidence for life immediately follows the evidence for oceans. An energy- diverting, growing, replicating chemistry followed the presence of liquid water in a geological blink of an eye."

This is why Chapter 5 (Clues to the Origins of Life) immediately follows Chapter 4 (the formation of the oceans). Many pieces of evidence point to the quick succession of these two chapters, including the "deep genealogy" studies that project what the oldest DNA sequences were like, resulting in an age of 3.8 billion years for the first proteins, as described on pages 87 and 88. Life springs up as soon as -- or even before -- the planet cools down enough to host it. This new Nature article is one more piece of evidence that fits into the quote above with an almost-audible snap.

Some have read the Nature article as a strike against "Darwinism" in some way, because this rapid emergence of complexity is inconsistent with slow, gradual change. But one of the main points of A World from Dust is that Darwinism isn't all about slow, gradual change. It's more like a symphony, a long, moving piece of music with different parts at different tempos, all reflecting the same theme of emerging life.

If the Nature article is a strike against Darwinism, then why was I, a scientist who admires Darwin and his ideas, so excited to read that sentence? Why did I write those two paragraphs as part of a whole book about evolution before this new finding was revealed? Yes, life emerged quickly, I've been saying that for a long time. I wrote those two paragraphs a year or two ago, and they are reinforced now. (Another point of my book is that it's possible to have disagreements about the nature and meaning of evolution without throwing out the idea of evolution, as shown by how often I contest Gould's "Tape of Life" metaphor yet remain convinced that evolution was the mechanism for generating life's diversity. For one thing, I think Gould's picture of evolution is at times too slow, and that it moved faster than he gave it credit.)

In the rest of my Chapter 5 I present seven chemical ideas, each one rooted in replicable laboratory experiments, for how the origin of life could have happened so quickly. I think that we might be able to understand how it happened by investigating chemistry -- in particular, the chemistry of oceans reacting with earth in oxygen-free water.

We live in a universe where we can see back 13 billion years with physics, all the way to the Big Bang, and we can understand how that worked. It stands to reason that we may be able to see back 4 billion years with biochemistry, all the way to this "Big Bang" of life, and to also understand how that worked.

I celebrate the fact that we have been given a universe we can understand, in which, periodically, life explodes with seeming joy. Understanding the chemical reasons that explain why the explosions happened doesn't take away that joy, but rather magnifies it. As I understand just how quickly life emerged, my heart leaps a little and I participate in that same old joy, as I receive that gift.

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