Study Shows Kangaroos Are Left Handed
A new study suggests that kangaroos in the wild tend to prefer using their left hands when performing common tasks such as feeding and grooming. The researchers arrived at their conclusion after spending many hours observing multiple wild species. They found two kangaroo species and one species of wallaby displaying a left handed tendency. Other species of marsupials which walk on all fours did not display the same tendency.
The study is important
The research was undertaken by scientists from the St. Petersburg State University who collaborated with Janeane Ingham from the University of Tasmania. Ms. Ingham said some of her colleagues questioned the value of studying left handed macropods however she rejects the criticism because such study contributes to the understanding of brain symmetry and mammalian evolution.
Handedness not unique to humans
Dr Yegor Malashichev the senior author of the study said the previously it was believed that handedness was unique to humans, however research conducted over the last couple of decades shows that asymmetry in brain structure and behaviour is in fact quite wide spread. He adds that examples of handedness tend to be attached to specific actions and were not consistent across the entire population.
“As one of our reviewers pointed out, laterality is also obvious in how parrots hold their food or how your dog shakes hands. But these examples of lateralisation have not been proven at the population level.” Ms Ingram said.
Parallel evolution
The results of the study showed that red-necked wallabies, red kangaroos and Eastern grey kangaroos all consistently displayed left-handed bias regardless of whether the animals were just propping themselves up, feeding or grooming. Dr Malashichev says their discovery is an example of what he calls “parallel evolution” because handedness appears in both placental mammals as well as marsupials which are not related in the evolutionary tree.
Posture is important
The authors of the study also suggest that posture is another important factor. The tendency to be left handed is only displayed in species that stand upright on their hind legs and use their front limbs for tasks besides walking. Another possible conclusion is that as primates evolved into an upright posture they also developed handedness. It is not immediately obviously whether there are specific aspects of the brain in marsupials which were responsible for developing handedness or can explain why kangaroos tend to be left handed whilst humans are predominantly right handed.
