A study from the European Synchrotron Radiation Facility (ESRF) suggests that early Homo species may have experienced a longer childhood before significant brain expansion, challenging long-held evolutionary assumptions. These findings are based on the dental development of a nearly complete sub-adult Homo skull, found at the Dmanisi site in Georgia and dated to 1.77 million years ago. The ESRF team, together with the University of Zurich and the Georgian National Museum, used advanced synchrotron imaging to study the specimen’s teeth, providing unprecedented insight into the evolutionary patterns of early humans.
Dental development as a key to development
The research examined dental microscopic structures that, like tree rings, record daily growth, thus providing insight into overall physical development. Study lead author Christoph Zollikofer of the University of Zurich explains that teeth fossilize well and serve as a reliable record of childhood development. According to Paul Tafforo of the ESRF, co-author of the study, dental development is often related to broader physical development, including brain development.
The analyzes revealed a unique pattern in which the back teeth matured more slowly than the front teeth over the first five years of sampling. This pattern, combined with the observed dependence on adult caregivers, supports a hypothesis that early Homo juveniles may have been dependent on adults for extended periods, like modern humans.
Implications of the “big brain-long childhood” hypothesis
This discovery could reshape the way we understand the “big brain-long childhood” hypothesis. Previous theories believed that longer childhood development was primarily due to increased brain size. Yet, despite having a smaller brain than the great apes, this Dmanisi specimen showed evidence of long-term support by older group members, possibly indicating that communal care, rather than brain size, was the initial driver of extended evolution. Was.
David Lordkipanidze of the Georgian National Museum observed that an older Dmanisi man survived without a tooth, implying social structures where knowledge was transmitted across generations. This evolutionary framework suggests that extended childhood emerged first, allowing cultural transmission, which later promoted brain development and delayed maturation.
The findings, published in Nature, indicate that the evolution of extended childhood may have played a fundamental role in early human development and social cohesion.
