scholarly journals The importance of population growth and regulation in human life history evolution

2013 ◽  
Author(s):  
Ryan Baldini
Keyword(s):  
Life History ◽  
Population Growth ◽  
Life History Theory ◽  
Human Life ◽  
Life History Evolution ◽  
Structured Populations ◽  
Life History Strategies ◽  
Age Structured ◽  
Zero Population Growth ◽  
Strategy I

Explaining the evolution of human life history characteristics remains an outstanding problem to evolutionary anthropologists. Progress is hindered by common misunderstandings of how selection works in age-structured populations. I review two important results of life history theory related to demography. First, different life history strategies evolve under density-independent and density-dependent population growth. Second, and more poorly appreciated, different kinds of density-dependence also select for different life history strategies; assuming zero population growth alone is insufficient to determine the optimal strategy. I show that these facts are more than methodological niceties by reanalyzing the model by Kaplan et al. (2000) and showing that the results depend strongly on the form of population regulation assumed. This analysis suggests that progress in human life history theory requires better understanding of the demography of our ancestors. I close with a discussion of empirical implications.

scholarly journals Estimating the evolution of human life history traits in age-structured populations

2014 ◽  
Author(s):  
Ryan Baldini
Keyword(s):  
Life History ◽  
Human Life ◽  
Life History Evolution ◽  
Selection Response ◽  
Structured Populations ◽  
Life History Trait ◽  
Vital Rates ◽  
Structured Population ◽  
Age Structured ◽  
Genetic Contributions

I propose a method that estimates the selection response of all vital rates in an age-structured population. I assume that vital rates are determined by the additive genetic contributions of many loci. The method uses all relatedness information in the sample to inform its estimates of genetic parameters, via an MCMC Bayesian framework. One can use the results to estimate the selection response of any life history trait that is a function of the vital rates, including the age at first reproduction, total lifetime fertility, survival to adulthood, and others. This method closely ties the empirical analysis of life history evolution to dynamically complete models of natural selection, and therefore enjoys some theoretical advantages over other methods. I demonstrate the method on a simulated model of evolution with two age classes. Finally I discuss how the method can be extended to more complicated cases.

Life History Strategies

2018 ◽  
pp. 95-126
Author(s):  
Marco Del Giudice
Keyword(s):  
Life History ◽  
Individual Differences ◽  
Life History Theory ◽  
Human Life ◽  
Life History Strategy ◽  
Current Theory ◽  
Life History Strategies ◽  
Extended Model ◽  
Life History Variation ◽  
Basic Model

The chapter introduces the basics of life history theory, the concept of life history strategy, and the fast–slow continuum of variation. After reviewing applications to animal behavior and physiology, the chapter reviews current theory and evidence on individual differences in humans as manifestations of alternative life history strategies. The chapter first presents a “basic model” of human life history–related traits, then advances an “extended model” that identifies multiple cognitive-behavioral profiles within fast and slow strategies. Specifically, it is proposed that slow strategies comprise prosocial/caregiving and skilled/provisioning profiles, whereas fast strategies comprise antisocial/exploitative and seductive/creative profiles. The chapter also reviews potential neurobiological markers of life history variation and considers key methodological issues in this area.

scholarly journals AEGIS: An In Silico Tool to model Genome Evolution in Age-Structured Populations

2019 ◽  
Author(s):  
William J. Bradshaw ◽  
Arian Šajina ◽  
Dario Riccardo Valenzano
Keyword(s):  
Life History ◽  
In Silico ◽  
Evolutionary Biology ◽  
Life History Evolution ◽  
Structured Populations ◽  
Time Simulation ◽  
Sexual And Asexual Reproduction ◽  
Wide Range ◽  
Survival And Reproduction ◽  
Age Structured

AbstractAEGIS (Ageing of Evolving Genomes In Silico) is a versatile population-genetics numerical-simulation tool that enables the evolution of life history trajectories under sexual and asexual reproduction and a wide variety of evolutionary constraints. By encoding age-specific survival and reproduction probabilities as discrete genomic elements, AEGIS allows these probabilities to evolve freely and independently over time. Simulation of population evolution with AEGIS demonstrates that ageing-like phenotypes evolve in stable environments under a wide range of conditions, that life history trajectories depend heavily on mutation rates, and that sexual populations are better able to accumulate high levels of beneficial mutations affecting early-life survival and reproduction. AEGIS is free and open-source, and aims to become a standard reference tool in the study of life-history evolution and the evolutionary biology of ageing.

scholarly journals Cyclical environments drive variation in life history strategies: a general theory of cyclical phenology

2018 ◽  
Author(s):  
John S. Park
Keyword(s):  
Life History ◽  
Life History Theory ◽  
Natural Populations ◽  
Life History Evolution ◽  
Life Cycles ◽  
Life History Strategies ◽  
Life History Variation ◽  
Trade Offs ◽  
Overwhelming Evidence ◽  
Phenological Shifts

ABSTRACTCycles, such as seasons or tides, characterize many systems in nature. Overwhelming evidence shows that climate change-driven alterations to environmental cycles—such as longer seasons— are associated with phenological shifts around the world, suggesting a deep link between environmental cycles and life cycles. However, general mechanisms of life history evolution in cyclical environments are still not well understood. Here I build a demographic framework and ask how life history strategies optimize fitness when the environment perturbs a structured population cyclically, and how strategies should change as cyclicality changes. I show that cycle periodicity alters optimality predictions of classic life history theory because repeated cycles have rippling selective consequences over time and generations. Notably, fitness landscapes that relate environmental cyclicality and life history optimality vary dramatically depending on which trade-offs govern a given species. The model tuned with known life history trade-offs in a marine intertidal copepod T. californicus successfully predicted the shape of life history variation across natural populations spanning a gradient of tidal periodicities. This framework shows how environmental cycles can drive life history variation—without complex assumptions of individual responses to cues such as temperature—thus expanding the range of life history diversity explained by theory and providing a basis for adaptive phenology.

scholarly journals Cyclical environments drive variation in life-history strategies: a general theory of cyclical phenology

2019 ◽  
Vol 286 (1898) ◽  
pp. 20190214 ◽  
Author(s):  
John S. Park
Keyword(s):  
Life History ◽  
Life History Theory ◽  
Natural Populations ◽  
Life History Evolution ◽  
Life Cycles ◽  
Life History Strategies ◽  
Life History Variation ◽  
Trade Offs ◽  
Overwhelming Evidence ◽  
Phenological Shifts

Cycles, such as seasons or tides, characterize many systems in nature. Overwhelming evidence shows that climate change-driven alterations to environmental cycles—such as longer seasons—are associated with phenological shifts around the world, suggesting a deep link between environmental cycles and life cycles. However, general mechanisms of life-history evolution in cyclical environments are still not well understood. Here, I build a demographic framework and ask how life-history strategies optimize fitness when the environment perturbs a structured population cyclically and how strategies should change as cyclicality changes. I show that cycle periodicity alters optimality predictions of classic life-history theory because repeated cycles have rippling selective consequences over time and generations. Notably, fitness landscapes that relate environmental cyclicality and life-history optimality vary dramatically depending on which trade-offs govern a given species. The model tuned with known life-history trade-offs in a marine intertidal copepod Tigriopus californicus successfully predicted the shape of life-history variation across natural populations spanning a gradient of tidal periodicities. This framework shows how environmental cycles can drive life-history variation—without complex assumptions of individual responses to cues such as temperature—thus expanding the range of life-history diversity explained by theory and providing a basis for adaptive phenology.

scholarly journals Harsh environments and "fast" human life histories: What does the theory say?

2015 ◽  
Author(s):  
Ryan Baldini
Keyword(s):  
Life History ◽  
Life Histories ◽  
Life History Theory ◽  
Environmental Changes ◽  
Human Life ◽  
Life History Evolution ◽  
Harsh Environments ◽  
Harsh Environment ◽  
Common Belief ◽  
Vital Rates

A common belief among human life history researchers is that "harsher" environments - i.e., those with higher mortality rates and resource stress - select for "fast" life histories, i.e. earlier reproduction and faster senescence. I show that these "harsh environments, fast life histories" - or HEFLH - hypotheses are poorly supported by evolutionary theory. First, I use a simple model to show that effects of environmental harshness on life history evolution are incredibly diverse. In particular, small changes in basic but poorly understood variables - e.g., whether and how population density affects vital rates - can cause selection to favor very different life histories. Furthermore, I show that almost all life history theory used to justify HEFLH hypotheses is misapplied in the first place. The reason is that HEFLH hypotheses usually treat plastic responses to heterogeneous environmental conditions within a population, whereas the theory used to justify such hypotheses treat genetic responses to environmental changes across an entire population. Counter-intuitively, the predictions of the former do not generally apply to the latter: the optimal response to a harsh environment within a large heterogeneous environment is not necessarily the optimal strategy of a population uniformly inhabiting the same harsh environment. I discuss these theoretical results in light of the current state of empirical research.

scholarly journals Co-occurrence of contrasting life-history strategies in a metapopulation inhabiting temporally variable and stable breeding sites

2018 ◽  
Author(s):  
Hugo Cayuela ◽  
Sam Cruickshank ◽  
Hannelore Brandt ◽  
Arpat Ozgul ◽  
Benedikt Schmidt
Keyword(s):  
Resource Allocation ◽  
Life History ◽  
Life History Theory ◽  
Life History Evolution ◽  
Environmental Stochasticity ◽  
Life History Strategies ◽  
Slowing Down ◽  
Trade Offs ◽  
Temporal Variance ◽  
History Evolution

Life-history theory states that, during the lifetime of an individual, resources are allocated to either somatic maintenance or reproduction. Resource allocation trade-offs determine the evolution and ecology of life-history strategies and determine an organism position along the fast-slow continuum. Theory predicts that environmental stochasticity is an important driver of resource allocation and therefore life-history evolution. Highly stochastic environments are expected to increase uncertainty in reproductive success and select for iteroparity and a slowing down of the life history. To date, most empirical studies have used comparisons among species to examine these theoretical predictions. By contrast, few have investigated how environmental stochasticity affects life-history strategies at the intraspecific level. In this study, we examined how variation in breeding site stochasticity (among-year variability in pond volume and hydroperiod) promotes the co-occurrence of different life-history strategies in a spatially structured population, and determines life-history position along the fast-slow continuum in the yellow-bellied toad (Bombina variegata). We collected mark-recapture data from a metapopulation and used multievent capture-recapture models to estimate survival, recruitment and breeding probabilities. We found higher survival and longer lifespans in populations inhabiting variable sites compared to those breeding in stable ones. In addition, probabilities of recruitment and skipping a breeding event were higher in variable sites. The temporal variance of survival and recruitment probabilities as well as the probability to skip breeding was higher in variable sites. Taken together, these findings indicate that populations breeding in variable sites experienced a slowing down of the life-history. Our study thus revealed similarities in the macroevolutionary and microevolutionary processes shaping life-history evolution.

Demography of Xenosaurus platyceps (Squamata: Xenosauridae): a comparison between tropical and temperate populations

2008 ◽  
Vol 29 (2) ◽  
pp. 245-256 ◽  
Author(s):  
Carissa Jones ◽  
Isaac Rojas-González ◽  
Julio Lemos-Espinal ◽  
Jaime Zúñiga-Vega
Keyword(s):  
Life History ◽  
Population Growth ◽  
Adult Mortality ◽  
Life History Strategies ◽  
Relative Importance ◽  
Theoretical Frameworks ◽  
Population Growth Rates ◽  
Relative Contribution ◽  
Two Populations ◽  
Average Fitness

Abstract There appears to be variation in life-history strategies even between populations of the same species. For ectothermic organisms such as lizards, it has been predicted that demographic and life-history traits should differ consistently between temperate and tropical populations. This study compares the demographic strategies of a temperate and a tropical population of the lizard Xenosaurus platyceps. Population growth rates in both types of environments indicated populations in numerical equilibrium. Of the two populations, we found that the temperate population experiences lower adult mortality. The relative importance (estimated as the relative contribution to population growth rate) of permanence and of the adult/reproductive size classes is higher in the temperate population. In contrast, the relative importance for average fitness of fecundity and growth is higher in the tropical population. These results are consistent with the theoretical frameworks about life-historical differences among tropical and temperate lizard populations.

Sexual size dimorphism and life history traits in an island-mainland system: an overview of the lizard genus Microlophus

2021 ◽  
pp. 1-7
Author(s):  
Ken S. Toyama ◽  
Christopher K. Boccia
Keyword(s):  
Life History ◽  
South America ◽  
Life History Theory ◽  
Life History Traits ◽  
Sexual Size Dimorphism ◽  
Life History Strategies ◽  
Galápagos Islands ◽  
Size Dimorphism ◽  
Rensch's Rule ◽  
Comprehensive Compilation

Abstract Opposing life history strategies are a common result of the different ecological settings experienced by insular and continental species. Here we present a comprehensive compilation of data on sexual size dimorphism (SSD) and life history traits of Microlophus, a genus of lizards distributed in western South America and the Galápagos Islands, and test for differences between insular and continental species under life history theory expectations. Contrary to our predictions, we found no differences in SSD between localities or evidence that Microlophus follows Rensch’s rule. However, as expected, head dimensions and maturity sizes were significantly larger in insular species while continental species had larger clutches. Our results show that Microlophus exhibits some of the patterns expected from an island-mainland system, but unexplained patterns will only be resolved through future ecological, morphological and behavioural studies integrating both faunas.

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