Scientists from Oxford University and the University of Tennessee, Knoxville, examined the impact that genes 'knowing' which parent they come from -- a process called 'genomic imprinting' -- has on how selfish or altruistic they want their carriers to be.

A report of their research is published in the journal Evolution.

They found that because, historically, women moved about more than men, and so are less related to their neighbours, our paternal and maternal genes are in conflict over how we should behave -- with our paternal genes encouraging us to be altruistic whilst our maternal genes encourage us to be selfish.

'When women disperse more during their lifetime than men, as seems to be the case for ancestral humans, this leads to you being more related to your neighbours through your father than through your mother,' said Dr Andy Gardner of Oxford University's Department of Zoology, an author of the report.

'This leads to conflicts over social behaviour: the genes you receive from your father are telling you to be kind to your neighbours, whereas the genes you receive from your mother, like a demon sat on your shoulder, try to make you act selfishly.'

Mutations in imprinted genes have previously been linked to growth disorders in infants and, more recently, it has been suggested that they could underpin neurological disorders such as autism and psychosis. This study reveals how such disorders of the social brain can evolve by mutations favouring the expression of paternal genes (favouring altruism) or maternal genes (favouring selfishness).

Dr Gardner said: 'What our research reveals is that the popular idea of someone battling their psychological 'demons', that are telling them to behave in a selfish way, has some basis in our genetic makeup -- we are all coalitions of conflicting genes.'

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Oxford.

Journal Reference:

1. Francisco Úbeda, Andy Gardner. A Model for Genomic Imprinting in the Social Brain: Adults. Evolution, 2010; DOI: 10.1111/j.1558-5646.2010.01115.x

Abstract

Genomic imprinting refers to genes that are silenced when inherited via sperm or via egg. The silencing of genes conditional upon their parental origin requires an evolutionary explanation. The most widely accepted theory for the evolution of genomic imprinting —the kinship theory— argues that conflict between maternally-inherited and paternally-inherited genes over phenotypes with asymmetric effects on matrilineal and patrilineal kin results in self-imposed silencing of one of the copies. This theory has been applied to imprinting of genes expressed in the placenta and infant brain determining the allocation of parental resources being the source of conflict parental promiscuity. However, there is growing evidence that imprinted genes are expressed in the post-infant brain where parental promiscuity per se is no longer a source of conflict. Here we advance the kinship theory by developing an evolutionary model of genomic imprinting in adults, driven by intragenomic conflict over allocation to parental versus communal care. We consider the role of sex differences in dispersal and variance in reproductive success as sources of conflict. We predict that, in hominids and birds, parental care will be expressed by maternally-inherited genes. In non-hominid mammals we predict more diversity, with some mammals showing the same pattern and other showing the reverse. We use the model to interpret experimental data on imprinted genes in the house mouse: specifically, paternally-expressed Peg1 and Peg3 genes, underlying maternal care, and maternally-expressed Gnas and paternally-expressed Gnasxl genes, underlying communal care. We also use the model to relate ancestral demography to contemporary imprinting disorders of adults, in humans and other taxa.