Evolution and why it matters

IN HIS NEW BOOK, STOP FEEDING US LIES, CHARLIE SPEDDING EXPLAINS HOW THE HUMAN BRAIN HAS GROWN THANKS TO RUNNING

- CHARLIE SPEDDING

GENETIC research has shown that our nearest cousins in the animal world are the chimpanzees and we both evolved from a common, tree-living ancestor about seven million years ago. Experts believe a major change in the climate caused a huge loss of trees in the African rainforest, which led to the formation of open grasslands and, because of this, our ancestors were forced to adapt and change. They stopped living in the trees like other apes and began to walk on two feet instead of four. Their diet had to change too and the groups that survived ate a variety of new foods. During those seven million years the brain of the chimpanzee has remained roughly the same but our brain has trebled in size.

The process that made us what we are today emerged about two million years ago. That is, when people evolved who were clearly like the humans of today and, with that timescale, you and I are descendants of about 100,000 generations of two-footed, humanlike mammals. An enormous amount of adaptation to the environment must have happened through so many ancestors and this information has been passed down to you and me in our genes.

What are the main changes that we have undergone in the last few million years? We have straightened our spines and hips so we stand and walk upright; we have lost our body hair and developed sweat glands so that we are very good at losing excess heat; and we have developed much bigger and better brains.

What did we do to make these changes happen? Instead of sitting in a tree reaching out for the fruit and nuts around us, we were forced to search for food when the trees disappeared. Standing up straight and walking on two feet was faster and more efficient than using all four limbs, the way chimpanzees do. As we became more upright, we became taller and could see further, which helped us to spot both food and danger.