LOS ANGELES—Robert Wayne from the University of California, Los Angeles, and Olaf Thalmann of the University of Turku in Finland used 18 ancient samples from dog and wolf fossils found mostly in Europe to reconstruct their mitochondrial genomes and build a family tree. They found that most living dogs are more closely related to ancient wolves than modern ones. “The [gray wolf] population that gave rise to modern dogs is most likely extinct,” said Thalmann. Based upon mutation rates and genetic differences, they think that dog domestication began between 18,800 and 32,100 years ago in Europe. But critics point out that Wayne and Thalmann were not able to obtain suitable DNA from ancient canids from the Middle East or from East Asia, and that mitochondrial DNA is only passed down from mothers. Others argue that dogs are too interbred to solve the puzzle. “Genomic archaeology has its limitations and the dogs are testing it. It may settle one day, but don’t count on it,” commented Stephen O’Brien of St. Petersburg State University in Russia.