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That’s because individual knowledge is narrow. We retain what we need to guide our actions and forget much of the rest of what we learn. This is why teaching high-school students personal finance is almost completely ineffective at fostering positive financial behaviors later in life—if you don’t use it, you lose it.
So how is society able to accomplish so much if each of us knows so little? The answer is that we divide up cognitive labor. We each have our narrow area of expertise, and we each make a small contribution. By combining our knowledge, we can tackle complex problems. For example, surgery requires a whole team of experts: pre- and post-operative care nurses and technicians, scrub techs, anesthesiologists, assistant surgeons, and nurses. Further afield but also critical are the scientists at medical-research labs who develop the newest techniques and therapies, the designers and engineers who create medical devices, and the administrators who figure out how the procedure gets paid for. They each play a vital role; no individual has anything approaching the knowledge required to understand it all.
This ability to jointly pursue complex goals is central to what makes us human. An influential evolutionary theory contends that our large brains developed to cope with the increasing size and complexity of our social groups. As our social groups grew, we developed the mental machinery to share knowledge, which in turn allowed us to respond to our environment in more complex and adaptive ways. Research in comparative psychology supports this story. One of the key skills that sets people apart from other primates is the ability to share intentions with others and jointly pursue goals.
