Nature’s Lefties
In
a society where 9 out of 10 people are
right-handed, the pain of being a lefty using
scissors catered toward the majority falls on
deaf ears. Rumours about lefties being brainier
or better artists are offset by the hypothesis that
they are more likely to be isolated or to suffer from
psychological disorders. In some societies, left-
handed individuals have even been historically
shunned, and believed to be malicious. While a
majority of humans are right-handed, handedness
in animals is a lot less studied. Other than a myth
about polar bears being left-handed (they’re not),
it appears that aside from primates, the only other
animal with handedness is kangaroos. But how
exactly is handedness shaped in nature and why
does it exist?
Tracing back to our closest natural relatives,
primatologists confirmed that hand preference
ex i s t s i n pr imates. For example, pros imians
(a type of primitive primate) tend to be left-
handed. Primates are close to us genetically and
are approximately 30 percent southpaws (left-
handed) [1]. While reasons for these patterns
have yet to be identified, left-handedness has
undoubtedly been found in nature.
Explaining human preference for handedness
is complex. For instance, genetic makeup is not
the sole determinant of handedness. Identical
twins with the same genetic makeup have been
documented to have different preference for the
dominant hand, explained by differences in foetal
positioning in the womb [2]. Another explanation
suggests that preference is formed and influenced
by parents when they teach us how to use different
tools.
Our ancestors’ preference for handedness
is a question that requires more probing. Daniel
Abrams, As sociate Profes sor in Engineer ing
S c i e n ce s a n d App l i ed Ma t h ema t i c s a t
Nor thwestern University, suggests that aside
from genetics, on an evolutionary standpoint,
handedness is shaped by two types of pressure –
competitive and cooperative, and is responsible
for the 9:1 equilibrium between righties and lefties.
Lefties have an advantage over righties when it
comes to competitive sports or combat. Since they
are the minority, they instigate the surprise factor
and would be more prepared against opponents
who are right-handed. Evolutionarily, the group
holding an advantage would typically increase
in numbers until the advantage balances out,
known as competitive pressure. However, Abrams
explains that “human evolution has been shaped
by cooperation, as well as competition”, as seen
in tool-sharing, where tools are created catered
toward the majority – right-handers. This is known
as cooperative pressure [3].
Handedness in animals is much less common.
Howeve r, recent s t ud i es have shown that
kangaroos and wallabies were found to exhibit
handedness in comparison with other marsupial
animals (animals found in Australia such as koalas).
They suggest that animals which walk on four legs
require both “hands” to execute daily actions,
whereas kangaroos and wallabies are bipedal,
much like humans [4].
Wh i l e handednes s ex i s t s promi nent l y i n
humans, and much less so in animals, it should
be noted that handedness is a spectrum. Most
people have a preference for the left or right
hand, but some are ambidextrous, and able to
perform equally well with either hand for various
activities. Further study into handedness has the
potential to reveal the evolutionary secrets of the
human race [4].
