\n<\/p>\n
Big hands might mean big feet, but it seems long thumbs are linked to large brains \u2013 at least in primates.<\/p>\n
Researchers say the results suggest the brain co-evolved with manual dexterity in such mammals.<\/p>\n
\u201cWe 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,\u201d said Dr Joanna Baker, lead author of the research from the University of Reading.<\/p>\n
\u201cAnd 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.\u201d<\/p>\n
Large brains and manual dexterity are both thought to have played an important role in human evolution, with opposable thumbs a key feature that enabled a greater ability to grip and manipulate items \u2013 including tools.<\/p>\n
However, with some other primates having partly opposable thumbs, questions have remained over whether other changes in the hand \u2013 such as thumb length \u2013 could also be important in the evolution of tool use.<\/p>\n
\u201cIn general terms, you can say that the longer the thumb you have, the more motion you have to pick up and control small objects,\u201d said Baker.<\/p>\n
To explore the issue Baker and colleagues studied the estimated brain mass and thumb length of 94 primate species, from five of our ancient hominin relatives to lemurs.<\/p>\n
The results, published in the journal Communications Biology, reveal humans and most other hominins have thumbs that are significantly longer than would be predicted based on the hand proportions of primates as a while. However, further analysis revealed an intriguing pattern.<\/p>\n
\u201cWhen you have longer thumbs relative to your overall hand, that tends to come in conjunction with overall increased brain size,\u201d said Baker.<\/p>\n
Indeed, once the size of our brains are considered, humans and their close relatives are no longer outliers among primates.<\/p>\n
\u201cWe\u2019re not saying we don\u2019t have exceptionally long thumbs. We do. And we\u2019re not saying we don\u2019t have exceptionally large brains. We do. But given the relationship between the two, that\u2019s happening across all primates,\u201d said Baker. \u201cSo if you have a longer thumb, you have a larger brain, regardless of what species you are.\u201d<\/p>\n
Only the early hominin A<\/em> sediba<\/em> broke the trend, with a thumb that was longer than expected, even after accounting for brain size \u2013 something Baker said is probably related to a life lived in the trees and on the ground.<\/p>\n Further analysis revealed that it is the neocortex, a brain region involved in cognition, sensation and planning of actions, that is larger in primates with longer thumbs.<\/p>\n \u201cThe fact that it isn\u2019t one of the other very important parts of the brain associated with motor control [such as the cerebellum] was really surprising,\u201d said Baker.<\/p>\n However, the study does not support the idea that thumb lengths alone can be used to identify tool use, with the relationship to brain size constant across all primates, regardless of whether they used tools.<\/p>\n \u201cWhilst not completely surprising, we did expect that there might be some marked shift in hominins that we just didn\u2019t see,\u201d said Baker.<\/p>\n Dr Fotios Alexandros Karakostis, a group leader and senior researcher in biological anthropology at the University of T\u00fcbingen who was not involved in the work, said the study suggested that hand and brain adaptations probably co-evolved.<\/p>\n But Karakostis said the study also noted that thumb length and brain size alone could not fully explain or represent human-like manual dexterity or the evolution of our brains.<\/p>\n \u201cA fuller understanding will require integrating other key hand anatomical traits, biomechanical model simulations, and further experimental research on the specific neural mechanisms linked to manual dexterity and human-like tool use,\u201d he said.<\/p>\n","protected":false},"excerpt":{"rendered":" Big hands might mean big feet, but it seems long thumbs are linked to large brains \u2013 at least in primates. Researchers say the results suggest the brain co-evolved with manual dexterity in such mammals. \u201cWe imagine an evolutionary scenario in which a primate or human has become more intelligent, and with that comes the<\/p>\n","protected":false},"author":1,"featured_media":17896,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[58],"tags":[2176,2569,7832,189,333,10869,3141,10871,10870],"class_list":{"0":"post-17895","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-science","8":"tag-bigger","9":"tag-brains","10":"tag-evolution","11":"tag-finds","12":"tag-longer","13":"tag-primates","14":"tag-research","15":"tag-tend","16":"tag-thumbs"},"_links":{"self":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/posts\/17895","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=17895"}],"version-history":[{"count":0,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/posts\/17895\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/media\/17896"}],"wp:attachment":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=17895"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=17895"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=17895"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}