Replication strategies and the evolution of cooperation by exploitation

Introducing the concept of replication strategies this paper studies the evolution of cooperation in populations of agents whose offspring follow a social strategy that is determined by a parent's replication strategy. Importantly, social and replication strategies may differ, thus allowing parents to construct their own social niche, defined by the behaviour of their offspring. We analyse the co-evolution of social and replication strategies in well-mixed and spatial populations. In well-mixed populations, cooperation-supporting equilibria can only exist if the transmission processes of social strategies and replication strategies are completely separate. In space, cooperation can evolve without complete separation of the timescales at which both strategy traits are propagated. Cooperation then evolves through the presence of offspring exploiting defectors whose presence and spatial arrangement can shield clusters of pure cooperators

Rank Statistics in Biological Evolution

We present a statistical analysis of biological evolution processes. Specifically, we study the stochastic replication-mutation-death model where the population of a species may grow or shrink by birth or death, respectively, and additionally, mutations lead to the creation of new species. We rank the various species by the chronological order by which they originate. The average population N_k of the kth species decays algebraically with rank, N_k ~ M^{mu} k^{-mu}, where M is the average total population. The characteristic exponent mu=(alpha-gamma)/(alpha+beta-gamma)$ depends on alpha, beta, and gamma, the replication, mutation, and death rates. Furthermore, the average population P_k of all descendants of the kth species has a universal algebraic behavior, P_k ~ M/k.Comment: 4 pages, 3 figure

Evolutionary connectionism: algorithmic principles underlying the evolution of biological organisation in evo-devo, evo-eco and evolutionary transitions

The mechanisms of variation, selection and inheritance, on which evolution by natural selection depends, are not fixed over evolutionary time. Current evolutionary biology is increasingly focussed on understanding how the evolution of developmental organisations modifies the distribution of phenotypic variation, the evolution of ecological relationships modifies the selective environment, and the evolution of reproductive relationships modifies the heritability of the evolutionary unit. The major transitions in evolution, in particular, involve radical changes in developmental, ecological and reproductive organisations that instantiate variation, selection and inheritance at a higher level of biological organisation. However, current evolutionary theory is poorly equipped to describe how these organisations change over evolutionary time and especially how that results in adaptive complexes at successive scales of organisation (the key problem is that evolution is self-referential, i.e. the products of evolution change the parameters of the evolutionary process). Here we first reinterpret the central open questions in these domains from a perspective that emphasises the common underlying themes. We then synthesise the findings from a developing body of work that is building a new theoretical approach to these questions by converting well-understood theory and results from models of cognitive learning. Specifically, connectionist models of memory and learning demonstrate how simple incremental mechanisms, adjusting the relationships between individually-simple components, can produce organisations that exhibit complex system-level behaviours and improve the adaptive capabilities of the system. We use the term “evolutionary connectionism” to recognise that, by functionally equivalent processes, natural selection acting on the relationships within and between evolutionary entities can result in organisations that produce complex system-level behaviours in evolutionary systems and modify the adaptive capabilities of natural selection over time. We review the evidence supporting the functional equivalences between the domains of learning and of evolution, and discuss the potential for this to resolve conceptual problems in our understanding of the evolution of developmental, ecological and reproductive organisations and, in particular, the major evolutionary transitions

The evolution of assortment with multiple simultaneous games

Current theories of social evolution predict the direction of selection for a given level of assortment. What remains unclear is how to determine the direction of selection on assortment itself if this were subject to evolutionary change. Here we define and analyse a simple model that allows us to investigate the evolution of assortment. We find that there is only a positive selection gradient for increased assortment if the population is polymorphic in the cooperative trait. We further show that if the individuals in question engage in multiple cooperative dilemmas simultaneously then there may be a continued selection on increased assortment which is ultimatelysufficient to resolve severe dilemmas such as the prisoner’s dilemma

Game theoretic treatments of social niche construction: How do the conditions for cooperation evolve?

The presence of cooperation has long puzzled evolutionary biologists; the resolution to this puzzle is often attributed to population structure. While the effects of population structure on cooperation are understood, less is known regarding how population structure is itself subject to evolution. The research program of Social Niche Construction (SNC) explores these issues. This thesis presents three related papers that further our understanding of SNC and addresses a number of issues within the research program.Firstly, I demonstrate that diploid organisms under the presence of meiotic drive represents an example of SNC; where assortative mating plays the role of the social niche modifier. I thus argue that assortative mating may be an adaptation that overcomes meiotic drive.Secondly, I present a formal argument for why a gene that causes individuals to assort cannot invade a population of freely-mixed defectors at equilibrium. I present a potential solution to this problem; namely, that if individuals engage in multiple simultaneous cooperative dilemmas, then there may be a continued selection pressure for increased assortment.Lastly, I present a model for the evolution of a cooperative division of labour. Previous gametheoretic definitions assume cooperation to be a single behaviour. I argue that this is too narrow, as often the benefits of cooperation come about through the interaction of differing types. To address this issue I define a class of games; which I call Division of Labour (DOL) games, that have the property that fitness is maximised by a mixture of different types. I show that DOL games are not resolved by a positive assortment on phenotype; instead mean fitness is maximised by positive assortment on a genotype that can exhibit phenotypic plasticity; i.e. express multiple phenotypes conditionally upon social environment.Together these models broaden and deepen our understanding of how population structure evolves and how SNC transforms social dilemmas and modifies social outcomes.<br/

Hamilton’s rule in non-additive games

Recently a number of authors have questioned both the validity and utility of inclusive fitness. One particular claim is that Hamilton’s rule applies only to additive games. Additive games represent a vanishingly small subset of all games and do not capture a number of interesting qualitative behaviours which are present in non-additive games. Thus, if these criticisms were correct, inclusive fitness would be a severely limited theoretical tool. We show these criticisms are not valid by demonstrating that any symmetric game can be transformed into an additive payoff matrix in such a way that the action of selection remains unchanged. The result comes with a caveat, however, which is that terms in the payoff matrix must themselves be frequency dependent. Despite this, we demonstrate the utility of inclusive fitness by means of applying Hamilton’s rule to two such non-additive games. The central claim of inclusive fitness is that relatedness is the key to cooperation, we show that this remains true even for non-additive games

Cooperation and the division of labour

Cooperation is vital for maintaining the integrity of complex life forms. In many cases in nature cooperation manifests it-self through constituent parts performing different, but complementary, functions. The vast majority of studies on the evolution of cooperation, however, look only at the special case in which cooperation manifests itself via the constituent parts performing identical tasks. In this paper we investigate a class of games in which the socially optimal behaviour has the property of being heterogeneous. We show that this class of games is equivalent to a region of ST space (the space of normalised two-player games characterised by the ‘sucker’ and ‘temptation’ payoffs) which has previously been dismissed. We analyse, through a simple group selection model, properties that evolving agents would need to have in order to “solve” this dilemma. Specifically we find that positive assortment on pure strategies may lower mean individual pay-off, and that assortment on mixed strategies will increase pay-off, but not maximise it

Game theoretic treatments for the differentiation of functional roles in the transition to multicellularity

Multicellular organisms are characterised by role specialisation, brought about by the epigenetic differentiation of their constituent parts. Conventional game theoretic studies of cooperation do not account for this division of labour, nor do they allow for the possibility of the plastic expression of phenotype. We address these issues by extending the notion of cooperative dilemmas to account for such interaction in which heterogeneous roles are advantageous and present an extended dynamical model of selection that allows for the possibility of conditional expression of phenotype. We use these models to investigate systematically when selection will favour an adaptive diversification of roles. We argue that such extensions to models and concepts are necessary to understand the origins of multicellularity and development