Book excerpt: The Life and Letters of George John Romanes is a biography about a Canadian-Scots evolutionary biologist and physiologist who laid the foundation of what he called comparative psychology, postulating a similarity of cognitive processes and mechanisms between humans and other animals. He was the youngest of Charles Darwin's academic friends, and his views on evolution are historically important. He is considered to invent the term neo-Darwinism, which in the late 19th century was considered a theory of evolution that focuses on natural selection as the main evolutionary force.