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The groundbreaking study has found a new link between the thumb size and brain power at least in primates. The bigger the thumb, the smarter the primate, the research suggests.
According to findings published in the journal Communication Biology, the brains of mammals co-evolved with manual dexterity.
The research also shed light on the synergy between large brains and dexterity, playing a significant role in human evolution along with opposable thumbs that enables a greater power to manipulate items and have a strong grip on tools.
Dr Joanna Baker, lead author of the research from the University of Reading, said, “We imagine an evolutionary scenario in which a primate or human has become more intelligent, and with that comes the ability to think about action planning, think about what you are doing with your hands, and realise that actually you are more efficient at doing it one way or another.”
“And those that have longer thumbs or more ability to manipulate the objects in the way that the mind can see were likely to be more successful,” Dr Baker added.
Generally, the longer thumb of a primate gives it the more motion to pick up and control small objects.
In the research study, Baker and colleagues studied a connection between brain mass and thumb size in 94 primate species from five of ancient hominin relatives to lemurs.
According to Dr Baker, “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. 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 analysis revealed that the neocortex brain region that is associated with cognition and sensation, gets larger with bigger thumbs.
However, this study also acknowledges that only a thumb size can not determine the brain capacity a primate possesses.
