Bill Maris doesn’t Tweet. Even at the helm of Google’s venture capital arm, he seldom attends technology conferences or networking events hosted by his own firm.

But the low public profile belies the fact that the boyish-looking, dogged investor has made a big impact on the direction of Google and on the venture capital industry that Google Ventures is shaking up.

Mr. Maris has become a conduit through which Google has made strategically important investments in companies Google has gone on to acquire (Nest Labs), may partner with (Uber Technologies) or build from scratch (Calico).

Last year, Mr. Maris, who has a degree in neuroscience, convinced Google CEO Larry Page to commit hundreds of millions of dollars to create a biotech company to fight human aging. During a recent and wide-ranging interview at Google Ventures’ headquarters in Mountain View, Calif., he says he came up with the idea for the company, called Calico, and helped lure former Genentech CEO Art Levinson to run it.