In an earlier entry-thread, mmcirvin said:
It's possible, I just don't like betting too much on our finding the toolkit. I'm hoping we can manage it with a 10- or 12-billion person Earth, because that's what we're likely to end up with at some point.
Now, I know we do feed a lot more people with fewer inefficiencies (like Ireland in the 1840s) than we did a century ago. The premature death rate due to starvation is half what it was in the 19th century and I would imagine a lot of what we do see is due to political and moral factors, not an inherent inability of the Earth to grow enough food.
This article appears to take a somewhat optimistic stance, although it links to one that does not. Of course, projections of future growth could be wrong, which leads me to a question that should be easy enough to answer: just counting the food we currently produce, and assuming a health diet for each person, how many people can we feed?
Wikipedia lists the current production of major crops here. Anyone out there care to make an estimate of how many balanced diets that mix of crops represents?
We could use the UK's WWII rationing system as a guide (nicked from wikipedia again):
* 1s 2d (approximately 1 lb 3 oz or 540 g) of meat (offal or sausages 1 weren't rationed)
* 4 oz (113 g) bacon or ham
* 3 pints (1.7 l) of milk per week or 1 packet of milk powder per month
* 2 oz (57 g) butter
* 2 oz (57 g) margarine
* 2 oz (57 g) fat or lard
* 2 oz (57 g) loose tea (teabags were not used widely in the UK)
* 1 egg per week or 1 packet (makes 12 “eggs”) of egg powder per month
* 2 oz (57 g) jam
* 3 oz (85 g) sugar
* 1 oz (28 g) cheese
* 3 oz (85 g) sweets
* plus, 16 "points" per month for tinned and dried food.
Other foods that were rationed were onions in 1943 (approximately 2lb (907g) per week).
Rather annoyingly, this gives me no guide to how to dole out cereal crops.
I note that based on this, we could feed 44 billion people their necessary weekly meat ration based on current output of meat and assuming any meat will do where the UK used bacon or ham.