The battle of the sexes over the distribution of male surplus

Female primates carry and nurse the fetus, and thus have the first responsibility for rearing the offspring. Assuming males are at least equally adept at obtaining food, males might either share surplus food with females or consume the food themselves. The distribution of this surplus is the subject of a battle of the sexes. If females succeed in obtaining a large share of the surplus, then there is little size dimorphism between males and females; otherwise males might use the surplus themselves to become larger and stronger, and to engage in sexual competition with other males. Besides competing with males, females may compete with each other. Dependency may coincide with sexual competitiveness (sexiness). This paper introduces these ideas in a game theoretic setting and derives a simple bound, called the ‘female condition, on the male ‘sexiness’ required for a nonsupportive strategy to be worthwhile.EVOLUTION ; BATTLE OF THE SEXES ; MALE PARENTAL SUPPORT ; SEXUAL SIZE ; DIMORPHISM ; FEMALE DEPENDENCY ; POLYGYNY

Female competition, evolution, and the battle of the sexes

As female primates carry and nurse the fetus, it naturally falls on them to rear the offspring. On the assumption that males are at least equally adept at obtaining food, it follows that they generate a surplus which they might either share with females or consume themselves. This choice lies at the heart of an evolutionary battle of the sexes. If females succeed in obtaining a large share of the surplus, there is little scope for size dimorphism between males and females; otherwise males can use the surplus to sustain larger and stronger bodies, which are advantageous in sexual competition with other males. Besides competing with males, females may compete with each other. Moreover, dependency may coincide with sexiness and such dependency can persist. This paper examines these ideas in a game-theoretic setting.

The battle of the sexes over the distribution of male surplus

Female primates carry and nurse the fetus, and thus have the first responsibility for rearing the offspring. Assuming males are at least equally adept at obtaining food, males might either share surplus food with females or consume the food themselves. The distribution of this surplus is the subject of a battle of the sexes. If females succeed in obtaining a large share of the surplus, then there is little size dimorphism between males and females otherwise males might use the surplus themselves to become larger and stronger, and to engage in sexual competition with other males. Besides competing with males, females may compete with each other. Dependency may coincide with sexual competitiveness (sexiness). This paper introduces these ideas in a game theoretic setting and derives a simple bound, called the alpha male condition, on the male 'sexiness'' required for a nonsupportive strategy to be worthwhile.battle of the sexes

Eradication-resolution dynamics with stochastic flare-ups

In infectious disease as well as in cancer, the ultimate outcome of the curative response, mediated by the body itself or through drug treatment, is either successful eradication or a resurgence of the disease (“flare-up” or “relapse”), depending on random fluctuations that dominate the dynamics of the system when the number of diseased cells has become very low. The presence of a low-numbers bottle-neck in the dynamics, which is unavoidable if eradication is to take place at all, renders at least one phase of the dynamics essentially stochastic. However, the eradicating agents (e.g. immune cells, drug molecules) generally remain at high numbers during the critical bottle-neck phase, sufficiently so to warrant a deterministic treatment. This leads us to consider a hybrid stochastic-deterministic approach where the infected cells are treated stochastically whereas the eradicating agents are treated deterministically. Exploiting the fact that the number of eradicating agents typically decreases monotonically during the resolution phase of the response, we derive a set of coupled first-order differential equations that describe the probability of ultimate eradication as a function of the system's state, and we consider a number of biomedical applications

On a general theoretical foundation for endocrinology

Hormones are messenger molecules that distribute across all tissues and thus operate on the whole-organism level. Moreover, a given hormone typically affects a number of different biological processes. As such, hormones coordinate concerted cooperation between the cells and tissues of an organism, a phenomenon that has been termed ‘organismal harmony’. Furthermore, a concept that has recently been gaining traction is that hormones mediate or represent life history trade-offs, which are ultimately moulded by evolutionary pressures. Here, this concept is extended to include all ‘decisions’ or ‘choices’ that are made at the organismal level. A formal framework is sketched to explore the proposition that organismal biology, together with the ‘fitness landscape’, suffices in principle to determine minimalistic dynamics of the endocrine system

Inceptions of biomathematics from Lotka to Thom

Mathematical biology occupies a special place at the interface between the physical, mathematical and life sciences. Is this interface merely a meeting point for dabblers venturing out of their own proper domains to work on problems of mutual interest? Or is it an incipient science in its own right, with its own particular character, principles, and practices? The past century has seen vast advances in the application of mathematical and physical ideas and techniques to biological problems, in the process transforming many of them almost beyond recognition. Nonetheless, the question of a biomathematics as a new kind of science remains open, despite several fascinating, if sometimes problematic, attempts

Darwin endures, despite disparagement

Evolution lies at the heart of the life sciences, and Charles Darwin is a towering historical figure within evolutionary science. One testimony to his lasting influence is that declaring Darwin to have been wrong all along remains a provocative way to command attention. The present paper discusses various strands of “Darwin was wrong” partisans and their divergent views and motives: some are looking to Darwin to justify or condemn the political ideologies that they support or reject; others are concerned with the corrupting influence that the bleak cosmic outlook of evolution is deemed to exert on the moral or religious rectitude of impressionable minds, or regard Darwinism as a direct assault on religion; philosophers question the very coherence of the entire enterprise; and certain biologists aspire to go down in history as even greater than Darwin. It is sobering to reflect that this diverse group is united only by their poor grasp of Darwin’s theory of natural selection

Regulation of the upstream petroleum industry. A comparative analysis and evaluation of the regulatory frameworks of South Africa and Namibia

Includes bibliographical referencesControversy surrounds the upstream petroleum industry. Although the benefit of petroleum resources is beyond dispute, the exploitation of petroleum resources comes at a price, as history has shown time and again. Not only does petroleum exploitation have detrimental effects on the environment, but host countries often are worse off than countries with little or no petroleum resources. This "resource curse" is partially the result of flawed regulatory frameworks for petroleum resource extraction in host countries. This thesis identifies three elements that must be present in a country's regulatory framework for petroleum extraction if the resource curse phenomenon is to be avoided and benefit s from petroleum are to be maximised. These elements are: transparency, accountability and a balance of interests between the petroleum companies and the host nation. Namibia and South Africa are not yet major players in the international upstream petroleum industry. There is accordingly not much academic engagement with petroleum law in these two jurisdictions. The courts have also not yet had the opportunity to scrutinise the legislation regulating the upstream petroleum industries of South Africa and Namibia. There are, however, indications that both countries may possess viable quantities of petroleum resources. In anticipation of the possibility of finding commercially viable quantities of petroleum, South Africa and Namibia have enacted legislation to regulate the upstream petroleum industry, but the efficiency of the legislation, specifically how it reflects the elements of transparency, accountability and balance of interest, have not yet been considered. The research for this thesis is driven by the question of how the regulatory framework for petroleum exploitation in South Africa and Namibia embraces the elements of transparency, accountability and balance of interest. The purpose of this thesis is to examine the regulatory frameworks for upstream petroleum resources in South Africa and Namibia in anticipation of the demands that will be placed on law as the sectors grow. In doing so, this thesis scrutinises the legislation in South Africa and Namibia to determine the extent to which the three crucial elements of transparency, accountability and balance of interest between the petroleum company and the host nation are reflected in the regulatory frameworks for petroleum resources

Co-receptor CD8-mediated modulation of T-cell receptor functional sensitivity and epitope recognition degeneracy

The interaction between T-cell receptors (TCRs) and peptide epitopes is highly degenerate: a TCR is capable of interacting productively with a wide range of different peptide ligands, involving not only cross-reactivity proper (similar epitopes elicit strong responses), but also polyspecificity (ligands with distinct physicochemical properties are capable of interacting with the TCR). Degeneracy does not gainsay the fact that TCR recognition is fundamentally specific: for the vast majority of ligands, the functional sensitivity of a given TCR is virtually null whereas this TCR has an appreciable functional sensitivity only for a minute fraction of all possible ligands. Degeneracy can be described mathematically as the probability that the functional sensitivity, of a given TCR to a randomly selected ligand, exceeds a set value. Variation of this value generates a statistical distribution that characterizes TCR degeneracy. This distribution can be modeled on the basis of a Gaussian distribution for the TCR/ligand dissociation energy. The kinetics of the TCR and the MHCI molecule can be used to transform this underlying Gaussian distribution into the observed distribution of functional sensitivity values. In the present paper, the model is extended by accounting explicitly for the kinetics of the interaction between the co-receptor and the MHCI molecule. We show that T-cells can modulate the level of degeneracy by varying the density of co-receptors on the cell surface. This could allow for an analog of avidity maturation during incipient T-cell responses

Holling Type I versus Holling Type II functional responses in Gram-negative bacteria

We consider how the double-membrane structure of the cell envelope of Gram-negative bacteria affects its functional response, which is the mathematical relationship that expresses how the nutrient uptake flux depends on environmental conditions. We show that, under suitable conditions, the Holling Type I functional response is a plausible model, as opposed to the Holling Type II (rectangular hyperbolic, ‘Michaelis–Menten’) response that is the default model in much of the literature. We investigate both diffusion-limited and capacity-limited regimes. Furthermore, we reconcile our findings with the preponderance in the established literature of hyperbolic models for the growth response, which are generally assumed to be valid, for both Gram-negative and Gram-positive bacteria. Finally, we consider the phenomenon of dynamic adjustment of investment of molecular building blocks in cellular components, and show how this will affect the functional response as observed by the experimenter