Explore the concept of collective intelligence in human societies through this 21-minute conference talk presented by Michael Muthukrishna at IPAM's Mathematics of Collective Intelligence Workshop. Delve into the paradox of diversity within collective brains, examining how societal size, information transmission fidelity, and cultural trait diversity impact innovation rates. Discover the challenges and benefits of diversity in organizational and societal contexts, and learn about the framework of 'cultural evolvability' as a potential solution. Gain insights into the implications of this research for entrepreneurship, polarization, and the nuanced effects of diversity on collective intelligence.