The First Hunter-Gatherers

In this chapter, Lieberman argues that during the gradual cooling of the climate, natural selection favored hunting and gathering.  Lieberman argues that the first hunter-gatherers were from the genus Homo, either Homo habilis or Homo erectus.  The advantage of hunting and gathering is that plants are abundant, easy to find, and won’t run away.  The disadvantages are that plants often contain indigestible fiber and have a low nutrient density.  The plant based diet could have been supplemented with meat to increase the amount of calories consumed.  Stone tools have been discovered, indicating that meat was an important part of the diet.  Additionally, these tools could have been used to process food, because it’s difficult to chew tough plants and meat.  Lieberman also explains that hunting and gathering resulted in a division of labor and food sharing.  In fact, Lieberman argues that food sharing extended past immediate family to the whole community.   

Compared to Australopithecus, Homo erectus had much longer legs, and Lieberman argues that this is because longer steps are more efficient.  This is evidence for the Homo erectus hunter-gatherer lifestyle, because hunter-gatherers must walk long distances to find food.  Lieberman argues that the evolution of a large external nose in Homo erectus helped conserve water when Homo erectus was walking during the middle of the day.  Lieberman argues that Homo erectus was skilled at endurance running, and used the strategy of persistence hunting.  The basic premise of persistence hunting is that humans are able to cool down by sweating, but prey animals are only able to cool down by sweating.  Persistence hunting works if the hunters run constantly after an animal, giving it no time to cool down.  Eventually the animal will collapse from heat exhaustion, and won’t be able to run away anymore.  It’s unknown when sweat glands first evolved, but Lieberman believes that it evolved in the genus Homo or was expanded on after it emerged in Australopiths.  Lieberman believes that the increase in calories from adding meat (and the additional calories) to the diet made it possible for larger brains to evolve.