- The major trajectory upgrade happens for two reasons. Each generation can learn a lot more new things when they can talk to each other, compare notes, and combine their individual learnings (that’s why the blue bars are so much higher in the second graph). And each generation can successfully pass a higher percentage of their learnings on to the next generation, so knowledge sticks better through time.
Knowledge, when shared, becomes like a grand, collective, inter-generational collaboration. Hundreds of generations later, what started as a pro tip about a certain berry to avoid has become an intricate system of planting long rows of the stomach-friendly berry bushes and harvesting them annually. The initial stroke of genius about wildebeest migrations has turned into a system of goat domestication. The spear innovation, through hundreds of incremental tweaks over tens of thousands of years, has become the bow and arrow.
Language gives a group of humans a collective intelligence far greater than individual human intelligence and allows each human to benefit from the collective intelligence as if he came up with it all himself. We think of the bow and arrow as a primitive technology, but raise Einstein in the woods with no existing knowledge and tell him to come up with the best hunting device he can, and he won’t be nearly intelligent or skilled or knowledgeable enough to invent the bow and arrow. Only a collective human effort can pull that off.