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Biomedical subjects

Ilan Eshel

Publications and source records attributed to Ilan Eshel.

6 recordsLinked to original sources
PubMed2006

Why is stress so deadly? An evolutionary perspective.

The reaction of the body to prolonged stress has many harmful effects. Classical theory assumes that stress responses have evolved due to their short-term selective advantages ('flight or fight'), and despite their adverse long-term effects. In contrast, we demonstrate that the adverse effects of stress responses may have a selective advantage. Using an analytical model we show that a gene that causes the early death of a relatively unfit individual can increase in frequency in a structured population even if it has no positive effect on that individual. This result offers a new perspective on the relations between stress factors, stress responses and stress-related diseases.

Cultural Evolution↗
PubMed2005

Gregarious behaviour of evasive prey.

Gregarious behavior of potential prey was explained by Hamilton (1971) on the basis of risk-sharing: The probability of being picked up by a predator is small when one makes part of a large aggregate of prey. This argument holds only if the predator chooses its victims at random. It is not the case for herds of evasive prey in the open, where prey's gregarious behavior, favorable for the fast group members, makes it easier for the predator to home in on the slowest ones. We show conditions under which gregarious behavior of the relatively fast prey individuals leaves slowest prey with no other choice but to join the group. Failing to do so would signal their vulnerability, making them a preferred target for the predator. Analysis of an n + 1 player game of a predator and n unequal prey individuals clarifies conditions for fully gregarious, partially gregarious, or solitary behavior of the prey.

Algorithms↗
PubMed2005

Evolutionarily stable strategies and short-term selection in Mendelian populations re-visited.

This note concerns a one locus, two allele, random mating diploid population, subject to frequency-dependent viability selection. It is already known that in such a population, any evolutionarily stable strategies (ESS), if only accessible by the genotype-to-phenotype mapping, is the phenotypic image of a stable genetic equilibrium (Eshel, I. 1982. Evolutionarily stable strategies and viability selection in Mendelian populations. Theor. Popul. Biol. 22(2), 204-217; Cressman et al. 1996. Evolutionary stability in strategic models of single-locus frequency-dependent viability selection. J. Math. Biol. 34, 707-733). The opposite is not true. We find necessary and sufficient parametric conditions for global convergence to the ESS, but we also demonstrate conditions under which, although a unique, genetically accessible ESS exists, there is another, "non-phenotypic" genetically stable equilibrium.

Animals↗
PubMed2003

Evolutionary and dynamic stability in continuous population games.

Asymptotic stability under the replicator dynamics over a continuum of pure strategies is shown to crucially depend on the choice of topology over the space of mixed population strategies, namely probability measures over the real line. Thus, Strong Uninvadability, proved by Bomze (1990) to be a sufficient condition for asymptotic stability under the topology of variational distance between probability measures, implies convergence to fixation over a pure strategy x(*) only when starting from a population strategy which assigns to x(*) a probability sufficiently close to one. It does not imply convergence to x(*) when starting from a distribution of small deviations from x(*), regardless of how small these deviations are. It is, therefore, suggested that when a metric space of pure strategies is involved, another topology, hence another stability condition, may prove more relevant to the process of natural selection. Concentrating on the case of a one dimensional continuous quantitative trait, we resort to the natural Maximum Shift Topology in which an epsilon -vicinity of the fixation on a pure strategy x(*) consists of all mixed population strategies with support which includes x(*) and is in the epsilon -neighborhood of x(*). Under this topology, a relatively simple necessary and sufficient condition for replicator asymptotic stability, namely Continuous Replicator Stability (CRSS), is demonstrated. This condition is closely related to the static stability condition of Neighbor Invadability (Apaloo 1997), and slightly stronger than the condition of Continuous Stability (Eshel and Motro 1981).

Biological Evolution↗
PubMed2002

A long-term genetic model for the evolution of sexual preference: the theories of Fisher and Zahavi re-examined.

Long-term co-evolution of male's sexual extravagance and female's preference for it is studied. Fisher's "Sexy Son" principle is checked against Zahavi's Handicap Principle. It is shown that although both principles are equally likely to explain this sort of co-evolution in the short run, only the second one allows for a long-term evolutionarily stable females' preference for costly male's extravagance. It is shown, however, that Fisher's argument, although not sufficient on its own to explain long-term persistence of females' choice, may tacitly appear as an indispensable component for the application of Zahavi's theory to the important case of dense polygenous populations.

Animals↗