The longest-serving adviser to President Barack Obama picked an interesting time to wade into Silicon Valley, though so far she doesn't appear daunted by the tech industry's mounting crises.

Valerie Jarrett joined Lyft's board this summer, saying she admired the company's belief that affordable transportation impacts social mobility. That was right about the time when tech companies--and the ride-sharing world in particular--became caught up in Uber's extremely messy year. Today, all sorts of startups and venture capitalists are still reckoning with the industry's rampant misogyny, racism, sexual harassment and otherwise hostile culture.

Uber's misfortunes have in part been Lyft's gain, although the smaller ride-sharing company has its own diversity challenges. A June report revealed that only 18 percent of Lyft's technical workers are women, and 70 percent of its leadership team is white.

Jarrett, who is Lyft's first black director and second woman board member, says the growing attention on the tech world's recent missteps is a good first step to fixing them.

"My sense is that, in boardrooms, this is much more of a conversation," she told me last week, after speaking at a conference in downtown New York hosted by Overture, a mission-based tech startup. "The cat is out of the bag."

However, as she points out, for companies that do want to meaningfully change their boardroom diversity, "you need at least three women." Which makes sense in boardrooms -- you need backup and allies to get anything meaningful accomplished, and one lone woman or person of color in a sea of white men has less of a chance of getting heard.

That applies beyond the private sector, of course. During Jarrett's time in the White House, women eventually made up half of Obama's senior staff, and last week she reminisced about the different tenor of staff banter during those meetings. For example, in one "we were talking about breast pumping, and then we moved onto hair," she laughed. 

Research conducted by Catalyst also shows that companies with at least three women on their boards of directors tend to outperform those with less-diverse boards, though those findings have been the subject of some recent dispute

Jarrett spoke on-stage about the call for tech companies--and businesses in general--to make their cultures more inclusive. "Talent is ubiquitous, opportunity is not," she said

A lawyer and former real-estate CEO, Jarrett also held several roles in Chicago government before heading to the White House. She worked on a wide range of issues during her eight years in the Obama Administration, and was the chair of the White House Council on Women and Girls. (That council has been effectively closed by President Trump.)

She is now writing a book and advising the Obama Foundation, as well as serving on the board of directors of Lyft and Ariel Investments.