When talking about "humans," most equate that with Homo sapiens--the latest phase of human evolution. Homo Sapiens have actually been around between 200,000-250,000 years not 120,000. It took us a long while to migrate out of Africa moving into Europe and Asia in small groups just 40,000 years ago. At this point, we were still butting heads with Neanderthals for dominance. Then a significant glacial age occurred around 12,000 years ago. It was during that age that we began clustering in larger groups allowing for specialization of work which really helped us come out of the glacial age in good shape compared to the Neanderthals. After we eradicated our competition, we took our large groups and proceeded to become decent farmers, not only providing for the entire group but with surplus to boot. So this leads to trading (local economy) and full-fledged cities and eventually wars and countries and more wars. So 8,000 years of these machinations and you finally get some calm periods (maybe 300 years here, 400 years there) and people start doing some real neat things. Don't forget, written language is estimated to be only about 5,000 years old. It took awhile for enough people to become educated well enough to be able to properly communicate abstract concepts and ideas. A lot of credit for getting the ball rolling has to go to the Greeks given their contributions to literature, science and philosophy. And after the Enlightment in the 18th century, the pace of technological development really went exponential. To wit, the number of scientific discoveries made over the past 100 years is greater than ALL previous scientific discoveries spanning thousands of years. In keeping with this exponential growth rate (for better or worse), the scientific discoveries over the next 50 years will easily outstrip all the discoveries in existence today. The more you have, the more you can do.. . And if all of what I just wrote isn't valid (albeit a Reader's Digest version), then I'd go for...alien intervention being the reason...or, wait, how 'bout "young earth creationism"? Hmmm?