This quote from Matt Ridley's The Rational Optimist emphasizes the critical role of population size and connectivity in accelerating innovation and cumulative invention. The idea is that larger, well-connected populations create environments where knowledge exchanges occur more rapidly and efficiently, leading to compounded technological and cultural advancements. The comparison of Hong Kong and Manhattan islands serves as a tangible example illustrating this dynamic: both are densely populated and highly interconnected urban centers, which have historically fostered intense innovation and economic growth.

From a broader perspective, Ridley’s insight challenges the intuition that innovation is solely the product of isolated genius. Instead, it highlights the collective and collaborative nature of human progress where ideas build upon each other in a network effect. This perspective encourages investing in connectivity—be it infrastructure, communication networks, or social capital—as a means to stimulate and sustain innovation. It also underscores the significance of urbanization and globalization in human development.

In today’s increasingly digital world, connectivity extends beyond physical proximity to include virtual networks, social media, and global collaboration platforms. This reinforces the timeless relevance of Ridley's claim and suggests that as technology continues to shrink distances and amplify communication, the potential for cumulative invention will grow even further.

Ultimately, this quote inspires optimism about humanity’s capacity to solve problems and invent solutions through interconnectedness, urging policymakers and individuals alike to nurture environments that facilitate these dynamic exchanges.