[jamesqf]

Originally Posted by IamIan

I was asking what evidence the number you come up with is based on .. what evidence did you use to come to the 500 Million number ??? why didn't you go with 500,000 or 5 Billion ... etc ... you picked a number ... what is the data that choice is based on?

Basically, extrapolation from population levels at the time when there appear not to have been major adverse effects on ecosystem sustainability. Which means I leave out things like the human-caused mass extinction of North American megafauna, since the post-extinction ecosystem seems to have been equally sustainable.

In fairness, let me ask you where you're getting your data from, as well.

FYI ... if those 500Million humans are ~90% calories from meat eaters ... your 500Million are consuming more planetary resources than 13 Billion 100% vegan plant eater humans.

I don't see how you conclude that. For a counter-example, a small population getting their meat from sustainable hunting & grazing has no effect on sustainability, a large vegetarian population supported by industrial agriculture is not.

Under that logic the failing/changing ecosystem of the dinosaurs was the fault of too many humans on the planet ... even though there were ZERO humans on the planet at that time.

Not so. Of course, major external events like asteroid impacts are really not included in sustainability. To use your spaceship example, it's the difference between quietly travelling between stars, and being attacked by the Klingons.

Except the word maximum does not carry with it the restriction of ( likely , easy , etc ) ...

But we aren't talking about absolute maximum (or at least I'm not), we're talking about sustainable maximum; the number that could be carried, not for a generation or two, but indefinitely. So to get that number, we have to consider all the internal things that could go wrong.

If meat carried with it it's actual cost ... ie being 34x the $ of planet calories...

I have to question that number.

The question was about utilization of the space for the purpose of maximum sustainable human population...

Yes, and the point here is that you're trying to build your spaceship by maximizing passenger load at the expense of life support systems, without really knowing how your life support systems work.

I notice you dodged the point about subterranean going lower .. building higher up ...

Running out of time & energy is not 'dodging'. But since you ask, that has a little impact, but not much, since humans living in such spaces still need surface area for their life support systems.

Unless it is impossible for humans to sustainably survive without the musk ox...

But that's the real question, isn't it? Do you KNOW with absolute, total certainty that humans can sustainably survive (again, not for a few generations, but for thousands) without the musk ox? How about all the other species in the Arctic ecosystem, or the oceans, or deserts? How many pieces can you pull out before the whole thing collapses?