In 2016  Alexandr Wang, 20 , took time off from his graduate computer science studies at MIT. He headed to Silicon Valley to join his friend and fellow developer  Lucy Guo, 23 . Two years  earlier, Guo - a 2014 Thiel Fellow - had left her senior year at Carnegie Mellon to pursue her own tech career.  Now, little more than a year after Wang left Cambridge, the two are leading a $4.7-million startup.  Scale , “The API of Human Intelligence,” serves such giants as Alphabet, P&G, GM Cruise and more. From high school dropouts to Stanford Ph.D’s, most of the  Forbes 2018 30 Under 30 Class in Enterprise Tech  are augmenting Artificial Intelligence with indispensable human skills.  Both Wang and Guo have substantial experience in tech, including stints at Snap and Quora. So they know that despite the considerable hype AI is, as they describe it, “not ready for prime time.” And, like much of this year’s class, they took risks to create something...