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.

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 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 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.

The evolution of childhood as a by-product?

2006 ◽  
Vol 29 (3) ◽  
pp. 288-289
Author(s):  
Peter Kappeler
Keyword(s):  
Life History ◽  
Life Histories ◽  
Nonhuman Primates ◽  
Homo Sapiens ◽  
Human Life ◽  
Life History Evolution ◽  
History Evolution ◽  
Linguistic Skills

The proposition that selective advantages of linguistic skills have contributed to shifts in ontogenetic landmarks of human life histories in early Homo sapiens is weakened by neglecting alternative mechanisms of life history evolution. Moreover, arguments about biological continuity through sweeping comparisons with nonhuman primates do not support various assumptions of this scenario.

Endocrinology

2019 ◽  
pp. 612-672
Author(s):  
Richard G. Bribiescas
Keyword(s):  
Life History ◽  
Social Dynamics ◽  
Human Life ◽  
Life History Evolution ◽  
Sexually Dimorphic ◽  
Human Variation ◽  
Men And Women ◽  
Metabolic Hormones ◽  
Gene Environment ◽  
Key Aspects

This chapter on endocrinology aims to shed light on the biology of hormones within the context of human life history evolution. An evolutionary perspective contributes to not only our understanding of human evolution, but also to the contemporary and emerging health challenges across the spectrum of ecologies and environments. Evolutionary endocrinology extends our understanding of human biology and health through the engagement of gene–environment interactions, social dynamics, human variation, and how hormones regulate life history traits such as growth, immune function, metabolism, and ageing. This chapter describes key aspects of endocrinology that are specific to men and women, while also being mindful of the importance of human variation. For example, men and women exhibit reproductive states that deploy specific functions. In women, these are menstruation, gestation, and lactation. These processes are governed largely by the hypothalamic–pituitary–ovarian axis and how it responds to environmental challenges such as nutritional demands, activity, and social stresses. Men also exhibit reproductive states, although they are mostly in the form of investment in sexually dimorphic tissue and behavioural variation. These states are governed by hormones which allocate resources between tissues that are indicative of different forms of reproductive effort. These include sexually dimorphic muscle tissue and adiposity. Spermatogenesis is obviously key but has differential effects on fertility compared to gametogenesis in women. Additional aspects of human evolutionary endocrinology include stress homoeostasis and metabolism, which involve the hypothalamic–pituitary–adrenal axis as well as the thyroid and other metabolic hormones.

scholarly journals From stochastic environments to life histories and back

2009 ◽  
Vol 364 (1523) ◽  
pp. 1499-1509 ◽  
Author(s):  
Shripad Tuljapurkar ◽  
Jean-Michel Gaillard ◽  
Tim Coulson
Keyword(s):  
Life History ◽  
Growth Rates ◽  
Life Histories ◽  
Life History Evolution ◽  
Environmental Stochasticity ◽  
Vital Rates ◽  
Stochastic Growth ◽  
Individual Fitness ◽  
History Evolution ◽  
Average Individual

Environmental stochasticity is known to play an important role in life-history evolution, but most general theory assumes a constant environment. In this paper, we examine life-history evolution in a variable environment, by decomposing average individual fitness (measured by the long-run stochastic growth rate) into contributions from average vital rates and their temporal variation. We examine how generation time, demographic dispersion (measured by the dispersion of reproductive events across the lifespan), demographic resilience (measured by damping time), within-year variances in vital rates, within-year correlations between vital rates and between-year correlations in vital rates combine to determine average individual fitness of stylized life histories. In a fluctuating environment, we show that there is often a range of cohort generation times at which the fitness is at a maximum. Thus, we expect ‘optimal’ phenotypes in fluctuating environments to differ from optimal phenotypes in constant environments. We show that stochastic growth rates are strongly affected by demographic dispersion, even when deterministic growth rates are not, and that demographic dispersion also determines the response of life-history-specific average fitness to within- and between-year correlations. Serial correlations can have a strong effect on fitness, and, depending on the structure of the life history, may act to increase or decrease fitness. The approach we outline takes a useful first step in developing general life-history theory for non-constant environments.

scholarly journals Inclusive fitness and differential productivity across the life course determine intergenerational transfers in a small-scale human society

2015 ◽  
Vol 282 (1803) ◽  
pp. 20142808 ◽  
Author(s):  
Paul L. Hooper ◽  
Michael Gurven ◽  
Jeffrey Winking ◽  
Hillard S. Kaplan
Keyword(s):  
Life History ◽  
Inclusive Fitness ◽  
Human Life ◽  
Intergenerational Transfers ◽  
Essential Element ◽  
Life History Evolution ◽  
Small Scale ◽  
Human Society ◽  
Extended Lifespan ◽  
The Life Course

Transfers of resources between generations are an essential element in current models of human life-history evolution accounting for prolonged development, extended lifespan and menopause. Integrating these models with Hamilton's theory of inclusive fitness, we predict that the interaction of biological kinship with the age-schedule of resource production should be a key driver of intergenerational transfers. In the empirical case of Tsimane’ forager–horticulturalists in Bolivian Amazonia, we provide a detailed characterization of net transfers of food according to age, sex, kinship and the net need of donors and recipients. We show that parents, grandparents and siblings provide significant net downward transfers of food across generations. We demonstrate that the extent of provisioning responds facultatively to variation in the productivity and demographic composition of families, as predicted by the theory. We hypothesize that the motivation to provide these critical transfers is a fundamental force that binds together human nuclear and extended families. The ubiquity of three-generational families in human societies may thus be a direct reflection of fundamental evolutionary constraints on an organism's life-history and social organization.

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