A common theme throughout Yuval Noah Harari’s book Sapiens is the argument that Homo sapiens changed so quickly thanks to our brains that our evolution, both physiologically and psychologically, couldn’t keep up. Evolution is a slow process, but human technological and sociological change has been incredibly rapid. Our minds and bodies are still adapted to live in a world that Homo sapiens no longer inhabits.
As an example, Harari writes, “no forager needed to remember, say, the number of fruit on each tree in the forest. So human brains did not adapt to storing and processing numbers.” Math is hard, and part of the reason it is so hard is that our minds didn’t evolve to do lots of math. Our foraging ancestors had incredible brains (as we still do) capable of keeping track of the social and political alliances within groups of 50 to 250 individuals – a huge number of potential combinations of friends, enemies, or frenemies. But foragers were not collecting taxes, were not trying to hang multiple pictures of different sizes equally on a wall, or trying to quickly remember which basketball player made a jump shot at the same time that another player committed a foul and tabulate a final score.
The human mind was not evolved for remembering numbers, and that is why recording and calculating numbers is so difficult. It is why we can be so easily confused by graphs and charts that are not well organized and put together. It is part of why it is so hard to save money now to retire later, and why credit card debt can be such an easy problem to fall into. We are good at remembering about 7 digits at once in our short term memory, but beyond that we easily become confused and start to lose track of information. The Agricultural Revolution made numbers more important beginning about 70,000 years ago, but our brains have not caught up. To make up for the difficulty of storing numbers in our heads we write numbers down on paper (or stone tablets in the distant past), use calculators to crunch numbers quicker than we can by hand, and rely on tools that can save numbers and data so that we don’t have to hold it all in our heads. Our brains simply are not up to the task of holding all the numbers we need to remember, so we have developed tools to do that for us. Don’t feel bad if you can’t remember tons of numbers, and don’t make fun of others who can’t do the same.