Your best guess. Just ballpark it.
Despite the impossibility of the question you were game enough to take it seriously and think about a response! One of your many POSITIVIE attributes m'dear which offsets your Devil's Advocating on occasion. Just thought I'd toss that in for the heck of it! So about a billion? Okay. If there were only a billion of us would the earth have been much better off? The fewer the homo saps to crap it up the cleaner and clearer and healthier things would be.
SO. Would we be facing this crisis now if there had been MANY FEWER OF US? Thank you for your reply Walt! :)
Reminds me of a news story I heard the other day.
Climate Change is threatening the Emperor Penguins' habitat.
The US is talking about making them an Endangered Species.
Except, you know, it's virtually impossible to get to their native habitat.
So will the US push change to slow Climate Change? Probably not.
Just another instance of "feel good" legislation that has no real effect.