Human brain development aligns closely with other primates

The results of a study led by University College London (UCL) are challenging long-standing beliefs about the development of human brains in newborns compared to other primates. 

According to the research, the idea that human newborns have underdeveloped brains is a misconception. The experts found that the brains of newborns are at a development level typical for primates.

False impression

Human brains grow so much larger and more complex than other species after birth. This creates a false impression that newborns are underdeveloped, or “altricial.”

“This new work changes the overall understanding around the evolution of human brain development,” said study lead author Dr. Aida Gomez-Robles.

“Humans seem so much more helpless when they’re young compared to other primates not because their brains are comparatively underdeveloped but because they still have much further to go.”

Human brain development 

The research modifies the conventional view that human brains are less developed at birth due to evolutionary compromises, such as the need for babies’ heads to fit through the birth canal.

Traditionally, scientists have assessed brain development across species by comparing brain sizes at birth with adult brain sizes. This suggested that humans are born with a smaller percentage of their adult brain size compared to other primates, leading to the belief in their relative underdevelopment. 

However, the UCL study indicates that other measures of human brain development align closely with other primates like chimpanzees, bonobos, gorillas, and orangutans.

Study implications 

The study also addresses the implications of these findings for the concept of brain plasticity in human evolution. It has been suggested that the perceived underdevelopment at birth results in greater brain malleability and sensitivity to environmental stimuli during early life, contributing to human intelligence. 

The researchers clarify that while human brains do take longer to reach full capacity, this does not stem from significant underdevelopment at birth. Thus, while brain plasticity remains critical in human evolution, it is unlikely to be a result of being less developed at birth than other primates.

How the research was conducted

To conduct this analysis, the team examined the brain development of 140 different mammal species, including modern primates, rodents, carnivores, and the fossils of early humans and ancestral hominins. 

The researchers compared fetal gestation lengths, the relative size of newborn brains and bodies to adult sizes, and overall brain size at birth and adulthood across these species. 

The findings revealed that while there are considerable variations in brain development at birth among different mammal species, primates, including humans, show a consistent pattern of development.

This research, supported by the National Science Foundation and the National Institutes of Health in the US, marks a significant shift in the understanding of human brain development and its evolutionary trajectory, challenging long-held assumptions in the field of anthropology and neurology.

The study is published in the journal Nature Ecology & Evolution.

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