NEW YORK (AP) — Silicon Valley’s efforts to promote workforce diversity haven’t yielded many results — unless you count a backlash at Google, where a male engineer blamed biological differences for the paucity of female programmers.

His widely shared memo, titled “Google’s Ideological Echo Chamber,” also criticizes Google for pushing mentoring and diversity programs and for “alienating conservatives.”

Google’s just-hired head of diversity, Danielle Brown, responded with her own memo, saying that Google is “unequivocal in our belief that diversity and inclusion are critical to our success.” She said change is hard and “often uncomfortable.”

The dueling memos come as Silicon Valley grapples with accusations of sexism and discrimination. Google is also in the midst of a Department of Labor investigation into whether it pays women less than men, while Uber’s CEO recently lost his job amid accusations of widespread sexual harassment and discrimination.

Leading tech companies, including Google, Facebook and Uber, have said they are trying to improve hiring and working conditions for women. But diversity numbers are barely changing .