Just remember, that those 1-in-a-billion odds are based on a number of assumptions. For starters there were, if I recall correctly, at least a half-dozen different species of "humans" that evolved on this planet from early proto-humans. Virtually all whales are candidates for being intelligent life, though very different from our own. They're undeniably tool users, though the lack of grasping appendages severely limits tool-making. Elephants are pretty damned smart as well. Parrots have been documented making custom tools to solve specific problems, while ravens are downright unsettlingly smart. And I could list dozens more. And those are only among the 1% of species that exist today.
As we look back into antiquity we're finding evidence of tool-users that predate our understanding of the emergence of human intelligence by many hundreds of thousands of years - we *assume* that those early tool-users were human, but I don't recall any evidence that would specifically suggest that was the case in the absence of a presupposition that pre-humans were the only intelligent species on the planet.
Go back further, say to the age of dinosaurs, and you could have had vast technological civilizations, and all their technology would have long since degraded into unrecognizablity. Just as if we don't make it through the next few centuries, then in a few million years the only evidence that we ever existed will be the geological disruption of our deep-earth mining activity and maybe a few fossils. And even the dinosaurs are relative newcomers - reptiles and proto-mammals covered the surface long before them, and before that insects the size of automobiles ruled the land and sky unchallenged for millions of years. And of course the seas were rich with wildly varied with life long before anything ventured on to land. This planet has had a half-billion years of complex life teeming on its surface, only a tiny fraction of which ever made it into the fossil record, to assume that we're the first intelligent species, or even the first technological one, is an assumption with no evidence behind it.
Perhaps as we colonize the moon we'll find evidence of previous intelligences - certainly there's a much better chance it would be preserved on an inert rock than a living planet. And then there's all those anomalies which have been found in Google Maps Mars - all coincidence, or evidence of previous technological residents? Heck, even if life didn't arise there it might have been colonized by Earthers - after all geological evidence suggests it may well have been a wet world as recently as 10 million years ago, it was probably a far more inviting world when saurians ruled the Earth.
