Discoveries about a young ancestor’s teeth may shed light on the upward trend in brain size over millennia.
Bipedalism developed long before bigger brains, and the use of tools was widespread in earlier hominid branches. As a result, these elements have been ruled out as the main driving force in brain evolution, despite being essential preconditions. https://efossils.org/book/bipedalism-vs-brain-size
The recent study of the 1.77 Million-year-old remains of an 11 to 12-year-old early homo from the Dmanisi site in Georgia is relevant. phys.org/…/2024-11-fossil-teeth-childhood-prelude…. This study of dental development throws some light on another human oddity, which is our very extended childhoods. The fossil’s age places it close to the emergence of larger brains in our ancestors. A useful timeline is found here australian.museum/learn/science/…/larger-brains/
Modern Human life history is distinguished by a prolonged childhood in which mental and somatic development rates diverge. This form of ontogenesis is considered crucial for developing high cognitive abilities in a socially complex environment.
This individual experienced rapid growth in their first five years, faster than in apes. For example, their wisdom teeth emerged at 12 years of age. This rapid growth was very unexpected given the age of the fossil and its relationship to modern humans. However, the teeth did have a sequence of growth similar to modern humans. Marcia Ponce de León from the University of Zurich and co-author of the study commented “Milk teeth were used for longer than in the great apes and the children of this early Homo species were dependent on adult support for longer than those of the great apes”. She suggests that “This could be the first evolutionary experiment of prolonged childhood”.
The demands of large brains cause Humans to develop more slowly than our closest animal cousins. Energy directed toward the brain dominates the human body’s metabolism early in life, which is likely why humans develop at a rate more akin to a reptile than a mammal in early childhood. A five-year-old’s brain is a real energy monster. It uses twice as much glucose as a fully grown adult. See www.sciencedaily.com/releases/…/140825152558.htm
However, just identifying some of the forces influencing the brain’s evolution does not account for the emergence of more recent advanced technology and abstract and symbolic languages. britannica.com/…/Language-culture-and-lifeways-in… Nonetheless, the brain’s expansion was an important prerequisite for those developments.
A variety of circumstances probably influenced brain development, including contributions from diverse hominid lineages with larger brains that were previously lumped into a single smaller smaller-brained species. Ian Tattersall provides a nuanced discussion of brain size and how it relates to humanities tangled origins in this 2023 article: Endocranial volumes and human evolution, pmc.ncbi.nlm.nih.gov/articles/PMC10517302/