The molecular clock

pre-printThe molecular clock uses evolutionary changes in proteins and DNA to measure the passage of time. Yet molecular evolution is clocklike only to a first approximation. Uncertainties arise because of variation in rates of molecular evolution, because of difficulty in calibrating clocks, and because we measure molecular changes only indirectly. Statistical methods now cope with all of these uncertainties. As these methods have matured and molecular data sets have increased in size, the molecular clock has grown increasingly reliable

Genetic Relatedness to Sisters' Children Has Been Underestimated

Males of many species help in the care and provisioning of offspring, and these investments often correlate with genetic relatedness. For example, many human males invest in the children of sisters, and this is especially so where men are less likely to share genes with children of wives. Although this makes qualitative sense, it has been difficult to support quantitatively. The prevailing model predicts investment in children of sisters only when paternity confidence falls below 0.268. This value is often seen as too low to be credible; so investment in sisters' children represents an unsolved problem. I show here that the prevailing model rests on a series of restrictive assumptions that underestimate relatedness to sisters' children. For this reason, it understates the fitness payoff to men who invest in these children. This effect can be substantial, especially in societies with low confidence in paternity. But this effect cannot be estimated solely from confidence in paternity. One must also estimate the probability that two siblings share the same father

Model of kin-structured migration

Journal ArticleWhen individuals disperse from one local group to another, they often do so in the company of relatives. This is known as "kin-structured migration," and its effect on genetic population structure is investigated here. It is shown that when migration is kin-structured, the ratio of between- to within-group variance is increased by a quantity that can be estimated either from behavioral or genetic data. Theoretical results indicate that kin-structured migration should be most important in populations with high mobility, and analysis of data for humans and lions suggests the kin-structured migration may have a substantial effect on genetic population structure in both species. Its effect seems to be small in a population of pine voles

Doubts about isonymy

Journal ArticleThe method of isonymy, developed by Crow and Mange for estimating inbreeding from surname frequencies, requires an assumption that has not been appreciated: It is necessary to assume that all males in some ancestral generation, the founding stock, had unique surnames. Because this assumption is seldom justified in real populations, the applicability of the isonymy method is extremely limited. Even worse, the estimates it provides refer to an unspecified founding stock, and this implies that these estimates are devoid of information

Population differences in quantitative characters as opposed to gene frequencies

Journal ArticleHypotheses about evolution can be tested by comparing genetics differences with those of quantitative characters. Such comparisons are one source of information concerning the forces that maintain variation among natural populations

Genetic relatedness to sisters children has been underestimated

pre-printMales of many species help in the care and provisioning of offspring, and these investments often correlate with genetic relatedness. For example, many human males invest in the children of sisters, and this is especially so where men are less likely to share genes with children of wives. Although this makes qualitative sense, it has been difficult to support quantitatively. The prevailing model predicts investment in children of sisters only when paternity confidence falls below 0:268. This value is often seen as too low to be credible; so investment in sisters' children represents an unsolved problem. I show here that the prevailing model rests on a series of restrictive assumptions that underestimate relatedness to sisters' children. For this reason, it understates the fitness payoff to men who invest in these children. This effect can be substantial, especially in societies with low confidence in paternity. But this effect cannot be estimated solely from confidence in paternity. One must also estimate the probability that two siblings share the same father

Group selection by selective emigration: the effects of migration and kin structure

Journal ArticleGroup selection may operate through selective emigration, as Sewall Wright envisioned, as well as through selective extinction. The discrete-generation model of selective emigration developed here yields the following conclusions. 1. The fitness benefit of altruism, "depends on the frequency of altruists". Consequently, selective emigration is more likely than kin selection or selective extinction to lead to polymorphic equilibria. 2. In contrast to selective extinction, selective emigration is facilitated (weakly) by high levels of mobility between groups. 3. Like selective extinction, selective emigration is facilitated (weakly) by kinstructured migration and by isolation by distance, particularly where the dimensionality of the migration pattern is low. 4. The only factor with any great effect on the strength of selective emigration is the size of the social group within which altruistic interactions occur. 5. Wright emphasized that selective emigration requires a delicate balance between the migration rate and population size, but this balance appears to be less delicate than Wright thought. For any conceivable migration pattern, migration rate, number of groups, and level of kin structure, an allele for altruism is favored only if its benefit-to-cost ratio exceeds a number of the same order as group size

Evolution of time preference by natural selection

Journal ArticleThis paper entertains the hypothesis that human time preferences are in evolutionary equilibrium (i.e. that no mutation changing time preferences could be favored by natural selection). This hypothesis implies that the marginal rate of substitution (MRS) holding Darwinian fitness constant must equal the MRS holding utility constant. Furthermore, in a market economy the latter must equal the MRS in exchange. Exploiting these principles, I find that the long-term real interest rate should equal ln(2) per generation (about 2 percent per year) and that young adults should discount the future more rapidly than their elders