Kin selection and local competition in a heterogeneous community.

When should an individual be willing to pay a cost in order to help or harm another individual in its community? Kin selection suggests that relatives should help each other, while competition for limited resources may select for harming behaviour against neighbours. This study considers social interactions between two individuals. For actions influencing non-dispersing reproduction, a condition is derived for selection to favour helping or harming, as a function of the actor's relationship to the rest of its community and to the recipient.

Time to pregnancy: a computational method for using the duration of non-conception for predicting conception.

An important problem in reproductive medicine is deciding when people who have failed to become pregnant without medical assistance should begin investigation and treatment. This study describes a computational approach to determining what can be deduced about a couple's future chances of pregnancy from the number of menstrual cycles over which they have been trying to conceive. The starting point is that a couple's fertility is inherently uncertain.

Consent agreements for cryopreserved embryos: the case for choice.

Under current UK law, an embryo cannot be transferred to a woman's uterus without the consent of both of its genetic parents, that is both of the people from whose gametes the embryo was created. This consent can be withdrawn at any time before the embryo transfer procedure. Withdrawal of consent by one genetic parent can result in the other genetic parent losing the opportunity to have their own genetic children.

Individual and social discounting in a viscous population.

Social discounting in economics involves applying a diminishing weight to community-wide benefits or costs into the future. It impacts on public policy decisions involving future positive or negative effects, but there is no consensus on the correct basis for determining the social discount rate. This study presents an evolutionary biological framework for social discounting.

Duration of courtship effort as a costly signal.

We consider a male and a female in a courtship encounter over continuous time. Both parties pay participation costs per unit time. The game ends when either one or other of the parties quits or the female accepts the male as a mate.

Costly but worthless gifts facilitate courtship.

What are the characteristics of a good courtship gift? We address this question by modelling courtship as a sequential game. This is structured as follows: the male offers a gift to a female; after observing the gift, the female decides whether or not to accept it; she then chooses whether or not to mate with the male. In one version of the game, based on human courtship, the female is uncertain about whether the male intends to stay or desert after mating.

To age or not to age.

According to the antagonistic pleiotropy theory of ageing, natural selection has favoured genes conferring short-term benefits to the organism at the cost of deterioration in later life. The 'disposable soma' theory expresses this as a life-history strategy in which somatic maintenance is below the level required to prevent ageing, thus enabling higher immediate fertility. It has been argued that a non-ageing strategy will always be bettered by a low but non-zero rate of ageing, because the costs of such ageing will be felt only in the distant future when they are of negligible importance.

Augmented discounting: interaction between ageing and time-preference behaviour.

Discounting occurs when an immediate benefit is systematically valued more highly than a delayed benefit of the same magnitude. It is manifested in physiological and behavioural strategies of organisms. This study brings together life-history theory and time-preference theory within a single modelling framework.