Well, I'm assuming he's getting at the traditional philosophical argument for agnosticism. As you dig deeper and get further removed what the here and now, scientific explanations become more theoretical and abstract to the point that at a sub-quantum level few understand the mechanics and no one can say without a shadow of a doubt that something hasn't been misinterpreted. The conclusion being that for 99.99% of the population, it takes just as much (well, actually less, but the existence of any faith outside of actually "knowing" is all that matters) outside faith to believe that at the time of the big bang the universe was full of energy at an incomprehensibly high temperature which inevitably led to everything we know today as it does to just believe something we don't understand just thought it all up. And the .01 could easily be on the wrong track because of a false presumption somewhere around the way.
Of course, I'm probably giving him too much credit and assuming when he says "how the planet got here" he means "how the matter making up the planet came into existence" rather than how the planet was actually formed. What it comes down to is that all science is incomplete and always really will be.