The identification of ancestry from the human skeleton is one of the more difficult assessments in forensic anthropology. Most ancestry research has focused on the skull, however this is sometimes missing or unusable. Research on the postcranial skeleton has focussed on the pelvis and lower limb. The main aim of this study was to investigate the nature and extent of metric variation in the human postcranial skeleton of five ancestral groups with a focus on the Australasian region. A secondary aim was to investigate differences between two geographically separated populations of the same ancestral group. Thirty-four measurements from the clavicle, humerus, radius, ulna, femur, tibia and fibula were collected. Data were collected from male and female from the following: Australians of European descent, Australian Aboriginal, Thai, Americans of European descent and African Americans. Data were collected from physical bones as well as from CT scans. All variables showed statistically significant differences except for the sagittal breadth at the nutrient foramen of the tibia in males. Post-hoc tests showed that there were a high number of differences between the groups including the two groups of European descent. Principal Components Analyses were conducted to help visualise the differences between the five groups. The differences found were characterised by two main components, the breadth/circumference and the length of the postcranial skeleton. Discriminant Function and Random Forest analyses were conducted to determine if it was possible to correctly classify individuals into ancestral groups. Single and multiple bone analyses were conducted with separated and pooled sexes. Correct classification rates of 90-99.2% were achieved with the upper limb bones, 75-98% with the lower limb bones and 84.3-100% when all bones were used. The findings of this study expand our knowledge of postcranial variation between ancestral groups found within the Australasian region and beyond. It also highlights the differences found between two geographically separate groups from the same ancestral group. This study may also provide new tools for forensic anthropologists and may assist in the identification of unknown remains in cases of missing persons and in the repatriation of indigenous remains.