The Search for Origins
VIRTUALLY ALL the organic matter in the living world can be summarized symbolically, if not euphonically, by the formula CHNOPS, which stands for carbon (C), hydrogen (H), nitrogen (N), oxygen (O), phosphorus (P), and sulfur (S). These six elements, in myriad molecular combinations, make up the bulk of living matter. They were the main actors in the chemical birth of life as well.
In order to reconstruct this momentous event, we must find out in what form the six biogenic elements were present on the primitive Earth and how, driven by the special physical-chemical circumstances that prevailed, they were first caught in a spiral of increasing complexity out of which life was born. First, what do we know of the setting in which life arose?
The Earth, four billion years ago, was beginning to recover from the battering by celestial bodies that accompanied its violent birth.1 It had cooled sufficiently for water to condense on its surface. Islands were rising in the primeval oceans and starting to merge into continents. The lands were barren and the waters lifeless, but the scene was far from calm. Still in the throes of intense volcanic activity, the young Earth was pitted by red-hot craters spewing thick clouds of dust and fumes. It was ravined by deep cracks through which water seeped down to the molten core, later to erupt back up again, pressurized, super-heated, and laden with vapors extracted from the seething lava. Think of Yellowstone National Park, or of the solfataras of Sicily, the Hekla region in Iceland, the flanks of Mount Fuji in Japan, or the hot springs of Rotorua in New Zealand. One memory invariably comes to mind: the smell! The all- pervasive stench of rotten eggs, the characteristic odor of hydrogen sulfide. Indeed, there is every likelihood that the cradle of life reeked of hydrogen sulfide. This fact has rarely been taken into account in origin-of-life scenarios. It deserves to be.