Research background

Organisms across a wide range of taxa, including our own, live together in complex family groups. Family living paved the way for more sophisticated, cooperative social behaviour to emerge (e.g. cooperative breeding or division of labour). Therefore, if we are to understand these complex social behaviours, we first need to understand the origins and evolution of family life. Current explanations for the evolution of family groups rely heavily on kin selection as the selective force that maintains the cooperative relationships upon which stable aggregations are based. For kin selection to operate, individuals must be able to distinguish kin from non-kin. That way they can preferentially direct cooperative behaviour toward close relatives. The mechanism proposed to facilitate this is called kin recognition. As groups become more complex (e.g. increasing size and/or formation of dominance hierarchies), misidentification of relatedness could potentially become more likely and more costly. Therefore, to ensure reliable discrimination, kin recognition should theoretically become more refined as groups become more complex.

This idea led to the hypothesis that kin recognition is crucial for the initial emergence of social organisation. It allows the display of simple social behaviour (e.g. tolerance or reduced aggression towards offspring) towards related individuals, which can increase inclusive fitness. As a next step, kin recognition can then become co-opted and refined as group structure becomes more complex and members start to cooperate with each other. However, very little is known about the evolution of kin recognition and its co-evolutionary relationship with the origins and elaboration of family life.

Within my PhD, I focus on one specific trait that could play a key role in the evolution of kin recognition: live birth. During evolutionary history there have been many transitions from ancestral egg-laying to live-bearing. As one can imagine, such a transition requires a series of major morphological, physiological and even behavioural changes to occur. Broadly, it caused dramatic changes to the social environment in which development takes place by increasing the duration and extent of mother–offspring interactions. With live bearing, the entire development process occurs internally rather than largely externally inside an egg. Additionally, there are fewer barriers between mother and offspring because of the lack of a hard eggshell and (often) presence of a placenta. Within the context of the evolution of kin recognition and sociality, this provides increased opportunities for selection to operate on interactions between mother and offspring. Simply put, live birth has the potential to strengthen the bond between a mother and her offspring.