David Siegel, co-founder of 35 billion quantitative hedge fund firm Two Sigma, says he's "very worried" that machines could soon cost large swaths of the workforce their jobs. "Most people in the bulk of the job market are not involved in super-high-value jobs," Siegel said Monday at the Milken Institute Global Conference in Beverly Hills, California. "They are doing routine work and tasks and it's precisely these tasks that computers are going to be better at doing," just as combustion engines replaced horses or ATMs replaced most bank tellers. The Australian mining industry already employs robotic vehicles equipped with self-driving technology to extract raw materials, instead of using truck drivers, he said. Facebook Inc. requires comparatively "zero" workers to manage a social network for more than 1 billion people, according to Siegel.