Born to run
We humans have to move a lot to stay he althy - in contrast to our closest relatives in the animal kingdom. The reason for this lies in our evolutionary past.
On a hazy morning in Uganda 20 years ago, I suddenly saw a group of sleeping chimpanzees in the lush treetops above me. Our team-three researchers and two field assistants-had been up for an hour. Sleepy, in rubber boots, with hastily laced backpacks and equipped with headlamps, we had tormented ourselves over muddy paths. Well, at our destination, we turned off our lights and tried not to make any noise lest the apes above us wake up. They puffed and rolled in their nests of leaves 100 feet up as the dark ocean of trees enfolded us.
As a young PhD student researching the evolution of great apes, I was traveling in Kibale National Park that summer to study how much chimpanzees climb every day. At the time, I assumed that the energy that the animals have to expend for this must be an important selection criterion and that evolution had certainly worked towards changing the physique of the chimpanzees in the direction of more efficient climbing. That-or so I believed-would lower the calorie expenditure required for body movement, thus freeing up more resources for reproduction and other vital tasks. Sitting at my desk at Harvard University, I had imagined monkeys constantly struggling to survive, struggling to the utmost every day.
That summer, however, as I watched chimpanzees intensely and followed them from dawn to dusk, I came to a different conclusion. I found that the animals spend a lot of time lounging. And it would be many more years before I realized what this says about human evolution…