On The Cosmic Calendar, A Date To Remember

Carl Sagan, describing his twelve-month capsule of the history of the cosmos, summarized its lesson this way: “The world is very old, and human beings are very young.”  But a neglected date on the calendar points to a different conclusion about organic life itself.

Sagan included “The Cosmic Calendar” in The Dragons of Eden in 1977. The first voyage to Mars had lifted off two years earlier. NASA, with Sagan’s help, began listening for and sending messages to other intelligent beings who might have been out there. Sagan, while asking readers to appreciate our amazing intelligence, at the same time believed that we were not the only creatures in the universe who were so endowed. The Cosmic Calendar helped him show that because it took eons to produce human civilization, the eons might have led to similar results elsewhere.

On the Calendar, one month represents about 1.1 billion years, one day equals 38 million years, and in one brief second, 438 years fly by. The Big Bang, 13.8 billion years ago, explodes on January 1. The Milky Way takes shape around March 11 (dates are from the Wikipedia version) and our Sun first shines on September 2, with planets soon after. The first living cells stir on September 21. October features photosynthesis, the gradual oxygenation of the atmosphere, and the persistence of simple bacteria and their cousins. In November, those single cells develop nuclei, complexity, and greater energy, leading to the first multi-celled organisms in early December. From then on, the variety of life emerges swiftly: fish and land plants in mid-month, dinosaurs at Christmas, then birds and flowers, and humans in the last hours of New Year’s Eve.

 

(3.bp.blogspot.com)

(3.bp.blogspot.com)

But this late appearance of humans may distract us from another date. September 21 marks the date for the beginning of organic life itself, only a few “short” weeks (about 700 million years) after the formation of the planets. From that date on—for more than a quarter of the duration of the universe—life has existed on Earth. While humans may be newcomers, living things are not. Our chain of ancestors are long-time participants, old-timers in the cosmos. We humans are fully part of the long cosmic process, not just because our atoms are star-stuff but because our cells have their “months” of cosmic history.

What is new in us, with our nearly-New-Year’s intelligence, is that we are aware of all this. But our living spark is nearly as old as planets.

Shall we celebrate September 21 each year as the “Birthday of Life”?

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)