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Explaining human handedness: the role of parental genes.

   School of Biology

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  Prof A Gardner, Dr S Paracchini  No more applications being accepted  Competition Funded PhD Project (Students Worldwide)

About the Project

Around 10% of people are left-handed, across all cultures and ethnicities. Although sidedness is observed in most species, the strong rightward population bias of handedness is characteristic of humans. Human handedness correlates with language hemispheric dominance, which typically resides in the left hemisphere, and is thereby linked with traits related to lateralized brain function, including language acquisition, cognition, personality, dyslexia, autism and schizophrenia. Accordingly, explaining handedness holds the key to understanding multiple facets of the human experience.

Handedness has a strong biological basis and is established during foetal development. It is also clearly heritable, with the prevalence of left-handedness increasing to 19.5% and 26.1% among children born to one or two left-handed parents, respectively, and with twin-studies pointing to a heritability of ~25%. However, genomic studies have identified only a small number of genes that are associated with handedness, and these appear to account for a very small proportion of its overall heritability. Accordingly, a major challenge for handedness research is to explain the “missing heritability”.

For right-handedness to predominate while left-handers remain present at a lower – but substantial and fixed – frequency implies that there is both a basic evolutionary advantage to right-handedness and also a frequency-dependent advantage to individuals of the rarer type. Such a frequency-dependent advantage has been suggested to arise in relation to combat, whereby left-handers are able to surprise opponents that are more used to fighting against right-handers. In support of this social-evolutionary hypothesis, a left-handedness advantage has been observed in combat sports, and the somewhat higher incidence of left-handedness among men than women is consistent with combat having traditionally been a male-dominated activity.

In this social-evolutionary view of the balance between right- versus left-handedness lies a potential explanation for the missing heritability. Genes underpinning social adaptations are expected to express at different levels according to the parent from which they are inherited, yet these parent-of-origin effects – so-called “genomic imprinting” – are not considered in standard genomic approaches that seek to link genes with phenotypes. Therefore new theoretical models and analytical approaches are need to understand the biology of handedness. The project aims to identify new genes contributing to handedness, and to develop a completely novel framework for the integration of theoretical and empirical approaches in the study of social traits more generally.

This is a unique opportunity for a fully-funded interdisciplinary PhD project that will combine social evolutionary theory and genome analysis to establish the role for parental genotype in deciding an individual’s handedness. Training will be provided in both areas of the project. The PhD researcher will work under the supervision of Prof Andy Gardner (School of Biology) to develop novel mathematical models to formalise this social-evolutionary hypothesis and thereby derive explicit predictions as to patterns of gene expression for genes that promote versus inhibit the development of left-handedness. Genetic analysis on already-available datasets will be supervised by Dr Silvia Paracchini’s (School of Medicine)  

The successful applicant will have an undergraduate degree in Biology or other relevant subject, an ability for logical and creative thinking, and a passion for evolutionary genetics and multidisciplinarity. We particularly encourage applications from women and from BAME individuals.

For informal enquiries, please email Prof Andy Gardner ([Email Address Removed]) and/or Dr Silvia Paracchini ([Email Address Removed]).  

Subject areas: Bioinformatics, Evolution, Genetics, Handedness, Social Evolution.

Funding Notes

Funded by the European Research Council and the School of Biology, University of St Andrews. The studentship covers the tuition fees (Home and Overseas), a living allowance and all research costs, for a duration of 3.5 years.


Gardner A & Úbeda F (2017) The meaning of intragenomic conflict. Nature Ecology & Evolution 1, 1807-1815. [Link]
Hitchcock TJ, Paracchini S & Gardner A (2019) Genomic imprinting as a window into human language evolution. BioEssays 41, 1800212. [Link]
Papadatou-Pastou M, Ntolka E, Schmitz J, Martin M, Munafò MR, Ocklenburg S & Paracchini S (2020). Human handedness: A meta-analysis. Psychological Bulletin 146, 481–524. [Link]
Pettigrew KA, Frinton E, Nudel R, Chan MTM, Thompson P, Hayiou-Thomas ME, Talcott JB, Stein J, Monaco AP, Hulme C, Snowling MJ, Newbury DF & Paracchini S (2016) Further evidence for a parent-of-origin effect at the NOP9 locus on language-related phenotypes. J Neurodevelop Disord 8, 24. [Link]
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