Final answer:
Physical anthropologist Douglas Owsley played a key role in the Jamestown colony case by determining that cut marks on a skull evidenced cannibalism, while Donald Johanson's discovery of Lucy expanded the understanding of human evolution.
Step-by-step explanation:
The earliest instance of a physical anthropologist being a key player in a case can be traced to the work by Douglas Owsley, a forensic anthropologist from the Smithsonian Institution. William Kelso, an archaeologist at the historic Jamestown colony, discovered a human skull with unusual markings and solicited Owsley's expertise. Owsley examined the evidence and concluded that the 14-year-old girl, whose skull it was, had been cannibalized by other settlers during a period of severe starvation in the winter of 1609-1610. This crucial involvement of physical anthropology greatly informed our understanding of the dire circumstances faced by early English settlers in North America.
Moreover, key contributions to paleoanthropology have been made by physical anthropologists, such as Donald Johanson, who discovered and examined the famous skeletal remains named Lucy, shedding light on early human ancestors. These historical findings are vital for understanding human evolution and the evolutionary process, expanding the role and influence of physical anthropologists in studying ancient human history.