I always find it interesting that people expect Human existence, and therefore the environment for its emergence, is somehow atypical. I don't know the math, but I would have thought by definition, one would wager on it being typical.
Let's say sapient life is very common and the vast majority of such species live on fairly similar planets in similar galaxies. In that situation, you would expect a random sample of one species to be typical.
On the other hand suppose typical planets in typical systems are generally very hostile to evolving sapient life. Only very unusual circumstances can lead to suitable conditions, but there are many, many different ways that can happen and different untypical conditions that can lead to sapience arising. Well, then a sample of one simply can't tell you anything about typical sapient species, because there's no such thing.
Looking at our conditions, I think there are worrying signs that out specific conditions are actually very unusual. Almost none of the extra-solar planetary systems we've found look much at all like our solar system. Furthermore we have a weirdly large moon relative to the size of our planet, which has had a huge effect on the tectonic and atmospheric development of our planet. Historically our global climatic conditions have oscillated quite widely, but always somehow managed to escape falling permanently into an extreme state. All of this seems to be very unlikely and atypical.
Probably the reason most marketing works :)