A tug of war began, between sea and sky and land.

In the ocean, life was carnivorous and simple, a pyramid founded on the very simplest forms, the phytoplankton, which teemed in great colored tides wherever sunlight met raw materials. Of the elements they needed to grow and flourish, hydrogen and oxygen could be taken from the water, and carbon from the air. But calcium and silicon and phosphorus and nitrates … these had to be acquired elsewhere.

Some you got by eating your neighbor. But sooner or later, everything suspended in the sea must drop out of the cycle to join the ever-growing sediments below. Cold upwelling currents replenished part of the loss, dragging nutrients back up from the muddy bottoms. But most of the deficit was made up at the mouths of rivers, draining rain-drenched continents. Silt and minerals, the raw fertilizer of life, dripped into the sea like glucose from an intravenous tap.

On land, it took a long time for life to gain a foothold. And for a very long time there were just frail films of cyanobacteria and fungi, lacing the bare rock surfaces with filaments and tiny fibers. These first soils kept moisture in contact with stone longer, so weathering hastened. The flow of calcium and other elements to the sea increased.

Plankton are efficient when well fed. And so, after the breakup of Gondwanaland, when many great rivers fed shallows teeming with green life, carbon was sucked from the air as never before. The atmosphere grew transparent.

At that time the sun was less warm. And so, deprived of its greenhouse shield, the air also cooled. Ice sheets spread, covering more and more of the Earth until, from north and south, glaciers nearly met at the equator.

This was no mere perturbation. No mere “ice age.” Reflecting sunlight into space, the icy surface stayed frozen. Sea levels dropped. Evaporation decreased because of the chill. There was less rain.

But less rain meant less weathering of continental rocks … less mineral runoff. The plankton began to suffer and grew less efficient at taking carbon out of the air. Eventually, the removal rate fell below replenishment by volcanoes and respiration. The pendulum began to swing the other way.

In other words, the greenhouse grew back. Naturally. Within a few tens of millions of years the crisis was over. Rivers flowed and warm seas lapped the shorelines again. Life resumed its march—if anything, stimulated by the close call.

A tug of war … or a feedback loop … either way it succeeded. What matter that each cycle took epochs, saw countless little deaths and untold tragedies? Over the long term, it worked.

But nowhere was it written, in water or in stone, that it absolutely had to next time.

Dear Net-Mail User [EweR-635-78-2267-3 aSp]:

Your mailbox has just been rifled by EmilyPost, an autonomous courtesy-worm chain program released in October 2036 by an anonymous group of net subscribers in western Alaska. [ref: sequestered confession 592864 -2376298.98634, deposited with Bank Leumi 10/23/36:20:34:21. Expiration-disclosure 10 years.] Under the civil disobedience sections of the Charter of Rio, we accept in advance the fines and penalties that will come due when our confession is released in 2046. However we feel that’s a small price to pay for the message brought to you by EmilyPost.

In brief, dear friend, you are not a very polite person. Emily-Post’s syntax analysis subroutines show that a very high fraction of your net exchanges are heated, vituperative, even obscene.

Of course you enjoy free speech. But EmilyPost has been designed by people who are concerned about the recent trend toward excessive nastiness in some parts of the net. EmilyPost homes in on folks like you and begins by asking them to please consider the advantages of politeness.

For one thing, your credibility ratings would rise. (EmilyPost has checked your favorite bulletin boards, and finds your ratings aren’t high at all. Nobody is listening to you, sir!) Moreover, consider that courtesy can foster calm reason, turning shrill antagonism into useful debate and even consensus.

We suggest introducing an automatic delay to your mail system. Communications are so fast these days, people seldom stop and think. Some net users act like mental patients who shout out anything that comes to mind, rather than as functioning citizens with the human gift of tact.

If you wish, you may use one of the public-domain delay programs included in this version of EmilyPost, free of charge.

Of course, should you insist on continuing as before, disseminating nastiness in all directions, we have equipped EmilyPost with other options you’ll soon find out about.…