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BioMed Central

Boys are right-handed, girls are left...

IMAGE: Many animals show a distinct preference for using one hand/paw/hoof over another.

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Well at least this is true for sugar gliders (Petaurus breviceps) and grey short-tailed opossums (Monodelphis domestica), finds an article in BioMed Central's open access journal BMC Evolutionary Biology, and shows that handedness in marsupials is dependent on gender. This preference of one hand over another has developed despite the absence of a corpus collosum, the part of the brain which in placental mammals allows one half of the brain to communicate with the other.

Many animals show a distinct preference for using one hand/paw/hoof over another. This is often related to posture an animal is more likely to show manual laterality if it is upright, related to the difficulty of the task, more complex tasks show a handed preference, or even with age. As an example of all three: crawling human babies show less hand preference than toddlers.

Some species also show a distinct sex effect in handedness but among non-marsupial mammals this tendency is for left-handed males and right-handed females. In contrast researchers from St Petersburg State University show that male quadruped marsupials, such as who walk on all fours, tend to be right-handed while the females are left-handed, especially as tasks became more difficult.

Dr Yegor Malashichev from Saint Petersburg State University who led this study explained why they think this has evolved, "Marsupials do not have a corpus callosum which connects the two halves of the mammalian brain together. Reversed sex related handedness is an indication of how the marsupial brain has developed different ways of the two halves of the brain communicating in the absence of the corpus callosum."

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Email: hilary.glover@biomedcentral.com

Notes

1. Forelimb preferences in quadrupedal marsupials and there implications for laterality evolution in mammals
Andrey Giljov, Karina Karenina and Yegor Malashichev
BMC Evolutionary Biology (in press)

Please name the journal in any story you write. If you are writing for the web, please link to the article. All articles are available free of charge, according to BioMed Central's open access policy.

Article citation and URL available on request on the day of publication.

Please credit images to Andrey Giljov, Karina Karenina and Yegor Malashichev.

2. BMC Evolutionary Biology is an open access, peer-reviewed journal that considers articles on all aspects of molecular and non-molecular evolution of all organisms, as well as phylogenetics and palaeontology

3. BioMed Central is an STM (Science, Technology and Medicine) publisher which has pioneered the open access publishing model. All peer-reviewed research articles published by BioMed Central are made immediately and freely accessible online, and are licensed to allow redistribution and reuse. BioMed Central is part of Springer Science+Business Media, a leading global publisher in the STM sector. @BioMedCentral



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