As you say in your sprawling overview of our species’ headlong progress (“Noble or Savage?” December 22, 2007), “it is irrelevant to ask whether we would have been better off to stay hunters-gatherers.” Indeed. After agricultural and industrial revolutions, this is hardly an option, anyhow. Because of them both, there are too many of us already, no matter whether or not hunting and gathering used to be attractive once upon a time. But your conclusion concerning our species’ steady advance is nonetheless spurious: we have been creating and solving ecological crises all along, and there is no reason to doubt our abilities from now on. Even if we eventually reverse the build-up of carbon dioxide, as you cheerfully prophecy, will we be able to reverse every ecological crisis on our path? Surely not. If demographic pressure keeps building up with every new revolution, the planet shall stop cooperating, eventually leading to a demographic collapse. This is elementary, after all. A Malthusian future surely awaits us sooner or later. Willy-nilly, hunter-gatherers beckon.