We Eukaryotes

Part 7 - Fire, Speech and Trade

Three seminal events in human history separated us from other animals and defined what we became. The control of fire was arguably the most significant, as it literally changed the course of evolution and made us physically what we are. The second event was the evolution of articulate speech and third was the adoption of trade which eventually gave us unimaginable wealth and modern civilization.

Fire.

Hominids were probably able to control fire between 1.8 million and 2.3 million years ago. Savannah grass fires, caused by lightening strikes, would have been common and, like all animals, hominids were fearful of fire and lightening. But they must have eventually realized that wildfires could be avoided by crossing rivers or moving upwind and that rain would extinguish a fire and cool the ground.

When burned over areas were re-occupied, hominids would have found still glowing embers and many small animals cooked in their burrows. Curiosity must have tempted children to play with burning sticks and they found that they could build small fires and put them out by knocking the sticks apart or burying the fire with earth.

They would have learned to set small fires to flush out and drive animals toward hunters. Slowly they learned how to keep fires to deter predators, cook food and provide light during dark nights.

Fire was so valuable that our ancestors found ways to make fire by rapidly rubbing or rotating a dry stick against a small piece of dry wood in a nest of kindling (pieces of easily ignited vegetation). They discovered that striking flint (a form of the mineral quartz) against rocks of pyrite (FeS2) would produce sparks hot enough to ignite kindling.

During this time, between 1 million and 800 thousand years ago, judging from the ancient hearths, earth ovens, burnt animal bones, and flint (used to start fires) uncovered by archeologists, our ancestors were cooking food.

Cooking radically changed the evolution of hominids because they no longer needed big teeth and powerful jaws to chew, and large intestines to digest, raw food. Cooking converted inedible tubers into food and permitted hominids to consume more calories required by the evolution of larger brains while permitting smaller teeth and thus more space within the skull for brains. It killed parasitic worms and other organisms found in scavenged meat that might cause sickness or death. Cooked food did not decay as quickly as fresh meat and could be preserved by repeated cooking or drying. And, as a bonus, less time chewing allowed more time for other activities such as tool making.

Before the discovery of cooked food, hominids needed to forage and eat almost continuously during daylight simply to obtain enough energy for survival. (Modern gorillas and orangutans eat for nine hours a day).

Speech.

Communication probably began more than 2 million years ago but it was largely non verbal in the form of facial expressions, gestures and grunts or howls. Chimpanzees and human babies still communicate in this way.

The lungs, larynx, tongue and lips evolved to permit breathing and eating while preventing food, water or foreign objects from entering the bronchial tubes. This required a large part of the evolving brain to sense tastes and textures of food entering the mouth, to manipulate food in the process of chewing and to cough and sneeze.