In today's excerpt--Fritz Haber, whose 1909 development of a process to synthetically manufacture nitrogen was perhaps the most important invention of the twentieth century, since it enabled the synthetic manufacture of gunpowder, thus enabling wars of the unprecedented scope of World Wars I and II, and also allowed the manufacture of artificial fertilizers, thus enabling the growth of world population from under two billion in 1900 to almost 7 billion in 2000. Haber's story embodies the paradoxes of science: the double edge to our manipulations of nature, the good and evil that can flow not only from the same man but the same knowledge:

"The discovery of synthetic nitrogen changed everything--not just for the corn plant and the farm, not just for the food system, but also for the way life on earth is conducted. All life depends on nitrogen; it is the building block from which nature assembles amino acids, proteins, and nucleic acids; the genetic information that orders and perpetuates life is written in nitrogen ink. But the supply of usable nitrogen on earth is limited. ... Until a German Jewish chemist named Fritz Haber figured out how to turn this trick in 1909, all the usable nitrogen on earth had at one time been fixed by soil bacteria living on the roots of leguminous plants (such as peas or alfalfa or locust trees) or, less commonly, by the shock of electrical lightning, which can break nitrogen bonds in the air, releasing a light rain of fertility. ...

"Before Fritz Haber's invention the sheer amount of life earth could support--the size of crops and therefore the number of human bodies--was limited by the amount of nitrogen that bacteria and lightning could fix. By 1900, European scientists recognized that unless a way was found to augment this naturally occurring nitrogen, the growth of the human population would soon grind to a very painful halt. ... "This is why it may not be hyperbole to claim that the Haber-Bosch process (Carl Bosch gets the credit for commercializing Haber's idea) for fixing nitrogen is the most important invention of the twentieth century. [Geographer Vaclav Smil] estimates that two of every five humans on earth today would not be alive if not for Fritz Haber's invention. We can easily imagine a world without computers or electricity, Smil points out, but without synthetic fertilizer billions of people would never have been born.

"Fritz Haber? No, I'd never heard of him either, even though he was awarded the Nobel Prize in 1920 for 'improving the standards of agriculture and the well-being of mankind.' ... During World War I, Haber threw himself into the German war effort, and his chemistry kept alive Germany's hopes for victory. After Britain choked off Germany's supply of nitrates from Chilean mines, an essential ingredient in the manufacture of explosives, Haber's technology allowed Germany to continue making bombs from synthetic nitrate. Later, as the war became mired in the trenches of France, Haber put his genius for chemistry to work developing poison gases-ammonia, then chlorine. (He subsequently developed Zyklon B, the gas used in Hitler's concentration camps.) On April 22, 1915, Haber was on the front lines directing the first gas attack in military history.

"His 'triumphant' return to Berlin was ruined a few days later when his wife, a fellow chemist sickened by her husband's contribution to the war effort, used Haber's army pistol to kill herself. Though Haber later converted to Christianity, his Jewish background forced him to flee Nazi Germany in the thirties; he died, broken, in a Basel hotel room in 1934. Perhaps because the history of science gets written by the victors, Fritz Haber's story has been all but written out of the twentieth century. Not even a plaque marks the site of his great discovery at the University of Karlsruhe."

Michael Pollan, The Omnivore's Dilemma, Penguin, Copyright 2006 by Michael Pollan, pp. 42-44.