Parental effects and the adaptive generation of helpers in a cooperative bird

It is often said that one day, whether we like it or not, we will turn into one of our parents. Research in both laboratory animals and humans, suggests that this is not only because of our genetic similarities with our parents, but because our early life experiences shape the way we look and behave in adulthood. However, two major uncertainties exist in the development of these patterns. First, do we simply resemble our parents because we share the same environment? Second, do parents actually shape our development through varying their levels of investment in us, and if so, when does this happen and for whose benefit is it? To answer these questions we must use an animal in which we can ethically move offspring around in a natural setting at different stages of their development and then measure their behaviour in adulthood. I will use a 50g Australian bird that lives, like humans, in family groups in which offspring are reared by a variable number of helpers in addition to parents. I have been studying ~90 breeding groups of the chestnut-crowned babbler in the arid zone of south-eastern Australia for the last 8 years. This species is perfect for the aims of this project because mothers vary tremendously in their investment in offspring, varying the timing and amount of investment in eggs, as well as the number and sex of competitors with which offspring will be reared. Similarly, mothers, fathers and helpers vary significantly in how much food they provide to offspring after hatching, with some providing almost nothing and others contributing the majority of it. Finally, the success of a group depends on how many helpers it has: the survival of offspring increases until group size reaches 8, after which there are no further increases. Because helpers are almost always offspring from previous years, a small group of babblers should try to produce helpers, whereas a large group should try to produce dispersers that go off to start a new babbler group. By moving offspring between groups of different sizes and at different stages of their development, I will provide an answer to the following questions. (1) To what degree do mothers, fathers and helpers try to create helpful versus selfish offspring, and do they all agree when this should be? (2) Do offspring ignore this 'arrangement' or benefit from it, or are they being manipulated to behave in a way dictated by their up-bringing? (3) If one's upbringing influences the way they look and behave in adulthood, when is this effect generated, is it by the mum's before hatching, is it when they receive food in the nest, or is it determined after they leave the nest and begin to fend for themselves? The answers to these questions will shed new light on how the upbringing of animals and humans shapes the way we look and behave in adulthood and help answer the long-standing questions of what makes a good mother, father and helper and who is it good for? If, from these results, we are able to predict the cooperative versus selfish tendencies of offspring given their development, we can begin to direct future studies in humans to ask whether there is a sensitive period during child development that shapes our behaviour in adulthood? When is it and what types of experiences is it most sensitive to?

For decades, developmental psychologists and evolutionary biologists have differed in answering the fundamental question of whether or not individual behaviour is governed by environment or genes. This is not a trivial question - with the advent of genetic engineering, the possibility of choosing genes for ones' own offspring and even the possible search for genes for criminality, it is now more important than ever to understand the role of early developmental conditions on future phenotype. Furthermore, there is renewed appreciation among evolutionary biologists of the profound role that the early environment can play in forming adulthood phenotype (morphology, physiology, behaviour) and influencing the rate of evolutionary change. One the most important early environments is that provided by the mother and other carers, for this is the first environment that a developing offspring experiences in the egg/womb and soon after.
Using the chestnut-crowned babbler, a 50g bird endemic to deserts of south-eastern Australia, I propose to conduct the first study investigating the role of maternal, paternal and helper investment in governing how cooperative or selfish offspring are in adulthood. Babblers, like most cooperative animals including humans, cooperate by protecting and providing food to offspring and defending their territory. Some individuals in groups contribute heavily and some do nothing at all- thus benefiting from the actions of others without paying a cost themselves. I propose that mothers (and other carers) influence the cooperative tendencies of offspring through differential allocation of resources. I expect the work outlined to benefit, both nationally and internationally:

(i) The academic community, by providing the first investigation of the role of parental influences on the evolution and maintenance of cooperation as well as individual levels of variation in their willingness to cooperate. The results of this study will be of interest to evolutionary ecologists since cooperation is an evolutionary enigma still in need of full explanation. The role of carer effects for the evolution of cooperation has not been investigated previously, and the full appreciation of the role of rearing effects for evolutionary processes is yet to be realised. The work will also be of interest to developmental psychologists who, for more than a century, have advocated the importance of early conditions for influencing individual personality in humans and animals.

(ii) Government regulatory bodies and economists, by elucidating whether upbringing helps reduce the tragedy of the commons. A tragedy of the commons arises when the selfish actions of individuals erode the cooperative or common good. The main challenges of the 21st century such as global warming, population growth and the inequitable use of resources are all tragedies of a common on a global scale, whereby each individual/community/nation fails to cooperate to avert potential disaster because of the fear that others will be selfish and fail to comply with negotiation. Understanding how animals solve the tragedy of the commons, will elucidate potential solutions to our current predicament.

(iii) The public who will benefit from understanding the importance of the rearing environment on offspring behaviour (and are as guilty as nations at committing a tragedy of the commons, albeit on a more local scale). The work will also be of general interest - the study of the evolution of behaviour is a tractable means to engage with the wider public.
This study will provide unique insights into the development of cooperative behaviour. We will provide greater understanding of the role of parents in influencing the cooperative tendencies of offspring, and as such elucidate how humans can begin to reduce the tragedy of the commons, which negatively affects the lives of all. As such this work is directly relevant to goals of the NERC, RCUK and WHO.