Quoting Fan et al. (2017): “Group-level manual laterality in
humans is related to hemispheric functional lateralization and cognitive
functions”.... Just kidding, sometimes hand and brain stuff can sound very
complex and confusing, we know! So here's the lowdown just for you:
The intricate and detailed connections in
primates between how our brains function and how our hands work IS really
complex. And it’s REALLY cool too! Because when you take a moment to pause and
appreciate how amazing it is that you can think a thought in your mind with your
imagination and then actually bring that idea to life in the physical world by
using your hands, it’s an astonishing reminder of just how amazing our human bodies really are.
Your dog can’t do that. Nor can your cat, or the bird flying
by outside. Not even that raccoons who manage to pull the lid off the garbage
cans no matter how hard you try to stop them from getting in there, can use their brains and hands the way we do.
Human hand use is pretty special, and so are our complicated
brains, but it hasn’t always been this way for us and in fact, it took many
years of evolution coordinating our hand use and brain development together to create
the fine tuned finger movements and complicated brains we have today.
Across the globe, researchers who have studied hand use in
humans have found that all humans have a greater tendency to be right handed
over left handed, but even more importantly – essentially all humans prefer to
use one hand more often than the other, rarely preferring both equally - and
that special preference in humans has been linked to our complex brains.
(That’s what that first sentence of this post says 😊)
Even though our brain may look like one big lump of
scrunched up tissue in the photo, different parts of our brains actually
control different sets of skills we use everyday as we move about in the world.
The cells at the back of the brain, for example, control our eyesight and
vision, while the cells in the centre on the left side control our tongue during
speech. This allows humans to do many things at once, like carry on a
conversation while preparing a meal – walking, talking, carrying and cutting up
vegetables all without skipping a beat to stop and think about it.
Complex hand use has been linked to complex tongue movements,
and these body parts and movements are controlled by a specific area of the
brain, leading researchers to suggest that language and tool use may have
evolved together over human history.
Gibbons, like humans, have complex communication skills.
They are also some of our closest living relatives, preceding orang-utans,
gorillas, chimpanzees, and bonobos. So when researchers are trying to figure out
how humans developed preferences for hands to begin with (a key trait that may
have led us down the path of developing complex brains over time) – looking at
our ape cousins is a good place to start. If gibbons demonstrate hand
preferences, like other apes and humans do, then we could infer that preferring
to use one hand when doing things like reaching for a tasty fig in a tree top
or reaching for a tasty apple out of the fridge, is likely the result of our
old lifestyle habit of hanging in the trees.
Our ancestors, like gibbons today, likely lived in the tree
tops, but instead of walking on top of branches on all four legs like monkeys
do, their bodies were designed to swinging below the branches – meaning they
would hang from one arm while reaching out to the tips of tree branches to get
the best tasty fruits to feast on.
A recent study published in the journal Primates by
Morino et al (2017) suggests that siamangs and gibbons tend to
be left-handed when performing tasks! And this is a big deal, because it
tells us that way, way back in evolutionary history; before apes got bigger
bodies (like orangs and chimps), before humans started walking on two feet
(like we do today), before we started crafting tools to manifest our imaginations
through cultural objects, the hand-brain connection was developing in history –
laying the groundwork for our hands and brains to get more and more complicated
as time progressed.
Understanding the relationship between handedness and brain
function, and learning about the development of these skills in our
closest living relatives is key to helping scientists understand a wide range
of seemingly unrelated issues such as dyslexia, stuttering, developmental
neurobiology, and the origins of human language and tool use. Ultimately, it helps us to understand ourselves better, as well as the similarities and
differences that make us who we are, and connect us to all the other valuable living species with whom we share this magnificent and
fascinating world.
It's super cool most gibbons appear to be left-handed.
The closer we look, the more we discover - we are all more alike than we are different.
The closer we look, the more we discover - we are all more alike than we are different.
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