Probability. Drake's equation suggests there are millions of intelligent species in the universe (assume 1,000,000). Thus, the chances of us really being the f

Probability. Drake's equation suggests there are millions of intelligent species in the universe (assume 1,000,000). Thus, the chances of us really being the first is only 1 in a million. Taking into account that the Earth was a relatively late bloomer (the universe was around for ~10 Billion years before there was any life on Earth ...) it becomes far less likely. Similarly, the chances of evolution creating two identical 'solutions' to very different environments (or hell, even nearly identical environments) is practically nil. Even if you buy panspermia (which is perfectly reasonable ...), there were still billions of years of evolution between then and now, and we should be unrecognizable from something we 'branched' from ~4 billion years ago.