Traditionally, experts studying the evolution of dogs believed that domestication was a conscious effort of humans. Biologist Raymond Coppinger disputes this theory.

Molecular biologist Peter Savolainen of the Royal Institute of Technology in Stockholm, Sweden, and his colleagues have studied the origins of domestic dogs using hair samples and mitochondrial DNA.

(Airs Sunday, May 31) About 8,000 years ago, the relationship between cows and man began with the revolutionary advent of domestication in Mesopotamia, the Indus River Valley, and Africa.