A 4,000-year-old skeleton discovered in India is the oldest known archaeological evidence of leprosy. The fact that the skeleton survived suggests the person was an outcast: Hindu tradition calls for cremation, and only those deemed unfit were buried.
Before this skeleton was found, there was a question where the disease originated.
The latter half of the third millennium B.C. was a period of social complexity in this civilization, characterized by urbanization, a system of writing, standardized weights and measures, monumental architecture, and trade networks that stretched to Mesopotamia and beyond.
The presence of leprosy in India toward the end of this period indicates that M. leprae existed in South Asia at least 4000 years ago, which lends support to the idea that the disease migrated between Africa and Asia during a period of urbanization, increasing population density, and regular inter-continental trade networks.