Roca has found a way to determine where the ivory comes from. With funding from the Division of International Conservation of the U.S. Fish and Wildlife Service, he and his collaborators have sampled elephants at 22 locations in 13 African countries to get sequences of their mitochondrial DNA (mtDNA).
mtDNA is the DNA located in mitochondria, structures within cells that convert the chemical energy from food into a form the cells can use. Most DNA is "nuclear," found in the cell nucleus. What makes mtDNA a good marker for tracing the origin of ivory is first, that it is transmitted only by females and second, the fact that female elephants do not migrate between herds.
Other researchers have found that it is possible to get fragments of mtDNA from ivory and that is possible to amplify those fragments. Roca and his collaborators wanted to match these fragments to elephants from a specific location.