It turns out that long thumbs aren’t just handy – they may be a sign of a bigger brain. According to new research, primates with longer thumbs tend to have larger brains, suggesting that intelligence and manual dexterity evolved side by side.
This article is for general informational purposes only and should not replace expert scientific consultation. Photos are for illustrative purposes only.
Brain And Thumb Evolution Go Hand In Hand
Dr Joanna Baker and her team at the University of Reading found that primates with longer thumbs often possess larger brains. The study, published in Communications Biology, examined the estimated brain mass and thumb length of 94 primate species, ranging from lemurs to ancient hominins. The findings point to a fascinating evolutionary link between thinking and doing, specifically, between brain growth and hand control.
Smarter Hands, Smarter Minds
Dr Baker suggests that as primates became more intelligent, they developed the ability to plan and refine their movements. “Those that have longer thumbs or more ability to manipulate objects in the way that the mind can see were likely to be more successful,” she explained. Essentially, the more a primate could control its hands, the more complex its brain functions became.
Humans Aren’t As Exceptional As We Think
While humans and their ancestors do have unusually long thumbs, the researchers found that once brain size is taken into account, we’re not outliers. “We’re not saying we don’t have exceptionally long thumbs. We do. And we’re not saying we don’t have exceptionally large brains. We do,” said Dr Baker. “But given the relationship between the two, that’s happening across all primates. So if you have a longer thumb, you have a larger brain, regardless of what species you are.”
The only exception was Australopithecus sediba, an early hominin whose thumb was longer than expected even after brain size was factored in, likely due to its mixed lifestyle of tree climbing and walking.
The Neocortex Connection
The team also discovered that the brain region most strongly linked to thumb length is the neocortex – the area responsible for higher cognitive functions such as planning, sensation, and problem-solving. Surprisingly, other regions involved in motor control, such as the cerebellum, did not show the same link.
A Broader Look At Dexterity
Dr Fotios Alexandros Karakostis, a biological anthropologist at the University of Tübingen who was not involved in the study, noted that these findings suggest hand and brain traits evolved together.
However, he added that thumb length and brain size alone can’t fully explain human-like dexterity or intelligence. To gain a complete understanding, future research should consider other hand structures, biomechanics, and the specific neural mechanisms behind tool use.
The Bigger Picture
While thumb length doesn’t determine tool use on its own, this research deepens our understanding of how brain and body evolved in tandem. The ability to grasp, plan, and manipulate objects may have been as crucial to primate survival as intelligence itself – proving that sometimes, evolution really is all about having the right grip.
