On the probability of extraterrestrial intelligence

On the face of it, the question of whether there exists extraterrestrial intelligent life within the Milky Way galaxy may seem as presently unanswerable as profound in its bearing upon our understanding of humanity’s place in the greater cosmos. To the contrary, however, the significant body of astronomical and paleontological knowledge amassed over centuries of inquiry can be shown well sufficient to support confident conclusions in such regard. In point of fact, all that is required is (1) a fair estimate of the relative age of our species in comparison to the galaxy, (2) a general understanding of the timing and phases through which life has progressed on Earth, and (3) a recognition that present rates of technological advancement will very shortly (relative to evolutionary timescales) propel humankind outward into the rest of the galaxy—the consequent inference being that the substantially advance advent of any extraterrestrial second species of similar intellect would have precluded our own through preemptive colonization of our planet. Hence, two such species may only coexist within the galaxy if evolved essentially in close, and probabilistically quantifiable, synchrony. The same model can further be applied to gauge galactic incidence rates of life in different stages of evolutionary development.