Study Design: An analysis and differential diagnosis of bony alterations in the lower lumbar vertebrae of a Homo erectus boy skeleton. Objective: To analyze low back problems during early human evolution. Summary of Background Data: Back problems in modern humans are often attributed to our upright, bipedal locomotion that is thought to place huge mechanical stresses on the vertebral column. However, little is known of this situation during the course of human evolution. Methods: We analyzed the lower lumbar spine of the most complete early hominid skeleton, the 1.5 million year old Homo erectus boy KNM-WT 15000 from Nariokotome, Kenya, who died at an age of approximately 8 years. We use bony alterations as indirect evidence for disc disease in the absence of soft tissue. Results: We describe an extensive osteophytic anterior curved remodeling of the left superior articular process of L5 and formation of a new joint at the underside of the left pedicle of L4. This indicates collisional facet joint subluxation, most likely as the result of juvenile traumatic disc herniation. Conclusions: This indirect evidence of juvenile disc herniation in a Homo erectus boy skeleton represents the earliest known case of this typical human ailment that is intricately linked to upright bipedalism. The extensive bony remodeling of the articular processes of L4 and L5 suggests that the disc herniation occurred several months before his death. Disabling backache and recurrent sciatica might have at least temporarily restricted his daily activities, which indicates advanced social care and nursing in early Homo. We hypothesize that the early Homo intervertebral discs were more vulnerable to injury compared to modern humans due to a relatively small vertebral cross-sectional area.