We could probably string out 20 billion humans on a diet of 90 of rice and vegetables a day, but why? Shouldn't we be concerned about our collective quality of life?

I have this image in my head of a pre-historic hunter-gatherer who's worrying how future people can stand living in cities, with their crazy indoor plumbing and prepackaged food available in giant walk-in refrigerators etc.

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$E(X_t|F_s) = X_s,\quad t > s$

Meanwhile, just in average numbers, a unit of meat protein takes 7 times more water, 7 times more grain input, 7 times the land and creates (to use a technical term for it) a shitload of detritus, much of it not on the list of cool things to have around.

Now, I don't want to highjack this thread with a holistic rant, but it does have to do with world economics part 1. As I understand it, amino acids are amino acids, no difference between beef amino acids (and thereby, beef proteins) and vegetable amino acids (and thereby vegi-proteins.) But the stuff that comes along with modern beef production (hormones, pesticides, cutting out the bad parts instead of turning away the entire cow) and the stuff that comes along with eating beef proteins such as the great tasting fats and the cooked nitates that turn to nitrites, the aforementioned hormones and other exciting chemicals that come with the execution, the are causing cancer and other health issues that the collective pays for...a blot on our quality of life from the get-go.

I cannot extrapolate to 20 billion. Nor do I have the time to multiply out and prove that the amount of food that can be sustained without petroleum-based fertilizers is much higher than 900 calories per person well into the future. But the back of the napkin says that we can do better for everyone beyond - well beyond mere survival.

Never underestimate their intelligence, always underestimate their knowledge.

Frank Delaney ~ Ireland