Summary: Primates with larger brains are capable of solving far more complex tasks with their hands than smaller-brained species. This greater manual dexterity, however, comes with a developmental cost: infants of large-brained primates, including humans, take longer to acquire even basic hand and finger movements than infants of smaller-brained primates.
Source: University of Zurich
Humans show exceptional manual skill — but it takes a long time to learn
Human beings are extraordinary at manipulating objects and using tools, yet many basic fine motor milestones are reached relatively late compared with other primates. For example, infants typically do not deliberately grasp objects until roughly five months of age, and mastering everyday tasks such as using cutlery or tying shoelaces can take several years of practice. By the time a human child becomes proficient at many of these skills, many other primate species have already raised offspring of their own. This raises a central question: why do humans and other large-brained primates require longer developmental periods to learn fine motor skills?
Conserved developmental order across primate species
Sandra Heldstab, an evolutionary biologist at the University of Zurich’s Department of Anthropology, together with colleagues Karin Isler, Caroline Schuppli and Carel van Schaik, addressed this question through long-term behavioral observation. Over more than seven years, their team followed 36 primate species and closely monitored 128 juvenile individuals in 13 European zoos from birth until they attained adult levels of manual dexterity. One striking finding was the consistency in the sequence of motor skill acquisition: despite broad differences among species, all primates studied learned manual abilities in essentially the same order. This suggests that neural development guiding hand and finger coordination follows highly constrained, species-spanning patterns.
Brain size is linked to fine motor complexity
Although the developmental order is conserved, adult capabilities vary markedly. Species with larger brains — such as macaques, gorillas and chimpanzees — master more intricate and versatile manual tasks than smaller-brained primates like lemurs and marmosets. Heldstab and her colleagues emphasize that advanced manual dexterity and tool use are closely tied to overall brain size and organization. In other words, a larger brain provides the neural capacity required for more complex hand movements and problem-solving with the hands.
Delayed development in large-brained species
However, this enhanced capacity appears to require a longer developmental investment. Infants of large-brained species start learning basic hand and finger movements later and take longer to reach proficiency compared with infants of small-brained species. The researchers propose that one major factor is the degree of brain maturity at birth: larger-brained primates are born with brains that are less developed relative to their adult size, so the postnatal period must accommodate extended neural growth and learning. As a result, early motor milestones emerge later, even when the ultimate skills attained are more complex.
Parental investment and the evolutionary trade-off
Extended learning demands both time and energetic support, which are borne by parents and caregivers until offspring reach independence. Learning manual skills is inherently inefficient: repeated practice over many months and years is required to refine coordination and precision. Heldstab’s team concludes that only long-lived mammals with sufficient parental investment can afford the prolonged developmental window necessary for evolving large brains and the associated fine motor competencies. This evolutionary trade-off helps explain why relatively few lineages have developed the combination of long life, intensive parental care, large brains and advanced tool use that characterize humans.
Implications for understanding human evolution and skill learning
These findings illuminate how constraints on neural development shape the timing of motor skill acquisition across primates and why humans, with their exceptional technological abilities, follow a prolonged course of early development. The conserved order of motor milestones points to deep-rooted biological programs, while variation in timing and ultimate capability highlights how life history and brain evolution interact to produce species-specific outcomes in dexterity and tool use.
Why time matters for learning
Ultimately, the study underscores that learning complex manual tasks requires time, repeated practice and parental support. Species that evolved long lifespans and extended periods of juvenile dependence provided the necessary conditions for large-brain evolution and sophisticated fine motor skills. This combination of factors helps explain the rarity of advanced tool use in the animal kingdom and why humans achieved such pronounced technological capability.
About this neuroscience research article
Source: University of Zurich
Media Contacts: Sandra Andrea – University of Zurich
Image Source: The image is credited to Karin Isler, ZOOM Erlebniswelt, Gelsenkirchen.
Original Research: The study will appear in Science Advances.