The Path Book 1: Origins

Our comparatively long and gradual childhood allows modern human brains to fully mature and absorb the lessons necessary for functioning in modern societies, but the brutal era of Homo erectus afforded no such luxuries.

Turkana Boy wasn’t an ape, but a very early, true human. He had a more primitive skull than ours, with a lower forehead and significantly smaller brain. The decay of his jawbone indicates he had an infection that was likely fatal. Had he survived to adulthood, Turkana Boy would have reached about six feet - and needed a lot of calories to sustain such mass. This required high calorie food - meat.

The transition from hominoids to Homo was central to human evolution: legs grew thinner and longer, arms shortened, and brains expanded in the transition from apelike bodies to human ones. Homo erectus were the first hominins with the body proportions of modern humans – long legs and short arms compared to the torso, adaptations to a terrestrial life.

Endocasts show the species had brains twice the size of chimpanzees 1.8 million years ago. They would go on to become the longest-lived of the humans, colonizing all of Eurasia and reigning as one of the planet’s most successful predators for two million years - about nine times as long as the modern human race’s entire existence.

So how did a comparatively puny creature like Turkana Boy feed its massive, caloriedevouring brain?

Homo erectus had been faced with a dilemma: how does one kill a huge, dangerous animal, full of meat and fat, without dying in the process? The answer lay in two key innovations - endurance running and high activity in mid-day heat.

Originally scavengers, Erectus eventually evolved into fleet, carnivorous big-game hunters, working cooperatively in packs. They had thick, pronounced facial features, and the shape of their femurs shows they were swift - elite runners on par with modern Olympic athletes. Says Stony Brook University’s Dr. John Shea, “If they were around today, chasing people around, we’d be in trouble. These guys were like wolves with knives.”

Homo erectus had evolved to run, just like modern humans. When these early humans had shed their primate body hair, and evolved the ability to cool by sweating, it enabled a new technique for capturing prey: persistence hunting.

Because they’re covered in fur, most animals run at a disadvantage in the midday African sun, and quickly overheat if they don’t periodically stop to rest and cool down by panting. This limits their running to short sprints - ten to fifteen minutes at a stretch.

But hairless skin allows air to circulate freely, cooling the body as sweat transfers thermal energy into the air by evaporating. This feature makes humans excellent longdistance runners, among the best on the planet – if we need to, we can run nonstop, potentially even for days at a time.

299