Theres no way any organism is going to start out at 1 - 1.
Humans as we are know today are descendants from Cromags{sp} who lived before us preceding the ice age. They survived the Ice age but then for some unknown reason died off. We were spawned from them some 30,000 years ago if I remember correctly. Upright walking "men" have been around for over a million years on earth. Even them would not have started out 1-1. The first land creature to come out of the sea would have started animals on land, and we would have come from that. Organisms develop and this would have taken thousands of years to create a few hundred "monkeys" (their not monkeys, but there were a bunch of "monkey" type races before humans but I can't reember any of the names of them right now) wich would eventually develop into the Cromags and then into us. There's no way that 1 -1 theory could work. It's scientifically impossible.
If your interested, I suggest "Walking with Cavemen". This is a great look at our existence from a scientific perspective, that is impossible to dispute no matter what you believe. Its a mini series that was aired last year. Very cool stuff.
http://www.bbc.co.uk/science/cavemen/
As for the incest thing, even if it was 1-1 after thousands of year that wouldn't have mattered. you start out with 1-1 and maybe until you reach a few thousand people after maybe a few hundred years those will be effected by it, but I doubt much after that. I can gurantee that if we were started like that, we would not be suffering the effects 30,000 years later. those things weed themselves out over time.