Over at 500 Startups we see a substantial number of founders and founding members who are in their 30s and 40s, and even some in their 50s and beyond.

This topic resurfaces every so often. Google will produce various articles and studies on the topic. Here's a study from HBR using Crunchbase API, LinkedIn, WSJ-

https://hbr.org/2014/04/how-old-are-silicon-valleys-top-foun...