Such cross-pollination at Norris has helped Shibata find a new way to learn about how tumors grow. Shibata peers backwards in time by using information stored in individual tumor cells. In the same way anthropologists use genetics to trace the evolutionary relationships between different groups of humans, he uses genes to reconstruct the history of particular tumors.
Most tumors become evident to physicians after surreptitiously existing for some time.
When pathologists finally examine the tumor cells, they find little information about the tumor's history. But just as paleontologists can learn about dinosaur behavior by looking at fossils, Shibata and his colleagues learn about a tumor's growth and development by examining the genetic changes that have accumulated along the way. The entire tumors are the continents and the individual tumor cells are the people living there. The best way to do this is to look at the small, heritable changes that occur in cancer cell genes as a tumor grows. The changes, or mutations, serve as markers, just as blood type or eye color serve to identify different groups of people.