scholarly journals Periodic catastrophes over human evolutionary history are necessary to explain the forager population paradox

2019 ◽  
Vol 116 (26) ◽  
pp. 12758-12766 ◽  
Author(s):  
Michael D. Gurven ◽  
Raziel J. Davison
Keyword(s):  
Evolutionary History ◽  
Homo Sapiens ◽  
Vital Rate ◽  
Small Scale ◽  
Human Populations ◽  
Wild Chimpanzee ◽  
Population Fluctuations ◽  
Vital Rates ◽  
Zero Population Growth ◽  
Major Adjustment

The rapid growth of contemporary human foragers and steady decline of chimpanzees represent puzzling population paradoxes, as any species must exhibit near-stationary growth over much of their evolutionary history. We evaluate the conditions favoring zero population growth (ZPG) among 10 small-scale subsistence human populations and five wild chimpanzee groups according to four demographic scenarios: altered mean vital rates (i.e., fertility and mortality), vital rate stochasticity, vital rate covariance, and periodic catastrophes. Among most human populations, changing mean fertility or survivorship alone requires unprecedented alterations. Stochastic variance and covariance would similarly require major adjustment to achieve ZPG in most populations. Crashes could maintain ZPG in slow-growing populations but must be frequent and severe in fast-growing populations—more extreme than observed in the ethnographic record. A combination of vital rate alteration with catastrophes is the most realistic solution to the forager population paradox. ZPG in declining chimpanzees is more readily obtainable through reducing mortality and altering covariance. While some human populations may have hovered near ZPG under harsher conditions (e.g., violence or food shortage), modernHomo sapienswere equipped with the potential to rapidly colonize new habitats and likely experienced population fluctuations and local extinctions over evolutionary history.

scholarly journals Human uniqueness? Life history diversity among small-scale societies and chimpanzees

PLoS ONE ◽  
2021 ◽  
Vol 16 (2) ◽  
pp. e0239170
Author(s):  
Raziel J. Davison ◽  
Michael D. Gurven
Keyword(s):  
Life History ◽  
Population Growth ◽  
Child Mortality ◽  
Adult Mortality ◽  
Vital Rate ◽  
Small Scale ◽  
Human Populations ◽  
Infant Survival ◽  
Selection Pressures ◽  
Human Subsistence

Background Humans life histories have been described as “slow”, patterned by slow growth, delayed maturity, and long life span. While it is known that human life history diverged from that of a recent common chimpanzee-human ancestor some ~4–8 mya, it is unclear how selection pressures led to these distinct traits. To provide insight, we compare wild chimpanzees and human subsistence societies in order to identify the age-specific vital rates that best explain fitness variation, selection pressures and species divergence. Methods We employ Life Table Response Experiments to quantify vital rate contributions to population growth rate differences. Although widespread in ecology, these methods have not been applied to human populations or to inform differences between humans and chimpanzees. We also estimate correlations between vital rate elasticities and life history traits to investigate differences in selection pressures and test several predictions based on life history theory. Results Chimpanzees’ earlier maturity and higher adult mortality drive species differences in population growth, whereas infant mortality and fertility variation explain differences between human populations. Human fitness is decoupled from longevity by postreproductive survival, while chimpanzees forfeit higher potential lifetime fertility due to adult mortality attrition. Infant survival is often lower among humans, but lost fitness is recouped via short birth spacing and high peak fertility, thereby reducing selection on infant survival. Lastly, longevity and delayed maturity reduce selection on child survival, but among humans, recruitment selection is unexpectedly highest in longer-lived populations, which are also faster-growing due to high fertility. Conclusion Humans differ from chimpanzees more because of delayed maturity and lower adult mortality than from differences in juvenile mortality or fertility. In both species, high child mortality reflects bet-hedging costs of quality/quantity tradeoffs borne by offspring, with high and variable child mortality likely regulating human population growth over evolutionary history. Positive correlations between survival and fertility among human subsistence populations leads to selection pressures in human subsistence societies that differ from those in modern populations undergoing demographic transition.

scholarly journals Data on the frequency of non-reproductive adults in a cross-cultural sample of small-scale human societies

2015 ◽  
Author(s):  
Cody Ross ◽  
Paul Hooper ◽  
Monique Borgerhoff Mulder
Keyword(s):  
Cooperative Breeding ◽  
Homo Sapiens ◽  
Cross Cultural ◽  
Small Scale ◽  
Ethnographic Research ◽  
Human Populations ◽  
Patterns Of Behavior ◽  
Definition Of ◽  
Cultural Data

A number of recent accounts have described Homo sapiens as a species that practices cooperative breeding [e.g., Hill and Hurtado (2009); Hrdy (2009); Kramer (2010); Mace and Sear (2005); van Schaik and Burkart (2010)]. These claims raise two important questions: first, do humans in general, or humans under a specific set of conditions, exhibit behaviors conforming to the technical definition of cooperative breeding? And second, to what extent are patterns of behavior and reproduction in humans similar to, or distinct from those found in non-human animals that are classified as cooperative breeders? The goal of this brief communication is to report cross-cultural data with relevance to researchers studying cooperative breeding in humans in the context of other non-human mammals. The data are derived from ethnographic research in 4 small-scale human populations.

scholarly journals Beyond demographic buffering: Context dependence in demographic strategies across animals

2021 ◽  
Author(s):  
Omar Lenzi ◽  
Arpat Ozgul ◽  
Roberto Salguero-Gomez ◽  
Maria Paniw
Keyword(s):  
Growth Rate ◽  
Population Growth ◽  
Temporal Variation ◽  
Population Growth Rate ◽  
Natural Populations ◽  
Environmental Context ◽  
Context Dependence ◽  
Vital Rate ◽  
Rate Variation ◽  
Vital Rates

Temporal variation in vital rates (e.g., survival, reproduction) can decrease the long-term mean performance of a population. Species are therefore expected to evolve demographic strategies that counteract the negative effects of vital rate variation on the population growth rate. One key strategy, demographic buffering, is reflected in a low temporal variation in vital rates critical to population dynamics. However, comparative studies in plants have found little evidence for demographic buffering, and little is known about the prevalence of buffering in animal populations. Here, we used vital rate estimates from 31 natural populations of 29 animal species to assess the prevalence of demographic buffering. We modeled the degree of demographic buffering using a standard measure of correlation between the standard deviation of vital rates and the sensitivity of the population growth rate to changes in such vital rates across populations. We also accounted for the effects of life-history traits, i.e., age at first reproduction and spread of reproduction across the life cycle, on these correlation measures. We found no strong or consistent evidence of demographic buffering across the study populations. Instead, key vital rates could vary substantially depending on the specific environmental context populations experience. We suggest that it is time to look beyond concepts of demographic buffering when studying natural populations towards a stronger focus on the environmental context-dependence of vital-rate variation.

scholarly journals Codiversification of gut microbiota with humans

2021 ◽  
Author(s):  
Taichi A. Suzuki ◽  
Liam Fitzstevens ◽  
Victor T. Schmidt ◽  
Hagay Enav ◽  
Kelsey Huus ◽  
...  
Keyword(s):  
Gut Microbiota ◽  
Vertical Transmission ◽  
Evolutionary History ◽  
Human Populations ◽  
African Origin ◽  
Strain Transfer ◽  
Close Proximity ◽  
Different Populations ◽  
Specific Health

Some gut microbes have cospeciated with hominids, but whether they further codiversified with human populations is unclear. Here, we identify predominant gut microbial species sharing a parallel evolutionary history with human populations. Patterns of strain transfer between populations are generally consistent with an African origin, and suggest long-term vertical transmission over thousands of generations. We show the same strains also faithfully transmit between mothers and their children. Consistent with the development of intimate symbiosis, species with strongest patterns of codiversification have the smallest genomes. This study reveals long-term fidelity of gut microbiota with human populations through transmission among individuals living in close proximity. Dominance of specific strains in different populations is based in part on vertical transmission and they may provide population-specific health benefits.

scholarly journals Evolutionary history of regulatory variation in human populations

2010 ◽  
Vol 19 (R2) ◽  
pp. R197-R203 ◽  
Author(s):  
T. Lappalainen ◽  
E. T. Dermitzakis
Keyword(s):  
Evolutionary History ◽  
Human Populations ◽  
Regulatory Variation ◽  
History Of

scholarly journals Spondylolysis and spinal adaptations for bipedalism

2020 ◽  
Vol 2020 (1) ◽  
pp. 35-44
Author(s):  
Kimberly A Plomp ◽  
Keith Dobney ◽  
Mark Collard
Keyword(s):  
Fatigue Fracture ◽  
Evolutionary History ◽  
Homo Sapiens ◽  
Lumbar Vertebrae ◽  
Great Ape ◽  
Shape Variation ◽  
3D Data ◽  
Schmorl’S Nodes ◽  
Vertebral Shape ◽  
Range Of Variation

Abstract Background and objectives The study reported here focused on the aetiology of spondylolysis, a vertebral pathology usually caused by a fatigue fracture. The goal was to test the Overshoot Hypothesis, which proposes that people develop spondylolysis because their vertebral shape is at the highly derived end of the range of variation within Homo sapiens. Methodology We recorded 3D data on the final lumbar vertebrae of H. sapiens and three great ape species, and performed three analyses. First, we compared H. sapiens vertebrae with and without spondylolysis. Second, we compared H. sapiens vertebrae with and without spondylolysis to great ape vertebrae. Lastly, we compared H. sapiens vertebrae with and without spondylolysis to great ape vertebrae and to vertebrae of H. sapiens with Schmorl’s nodes, which previous studies have shown tend to be located at the ancestral end of the range of H. sapiens shape variation. Results We found that H. sapiens vertebrae with spondylolysis are significantly different in shape from healthy H. sapiens vertebrae. We also found that H. sapiens vertebrae with spondylolysis are more distant from great ape vertebrae than are healthy H. sapiens vertebrae. Lastly, we found that H. sapiens vertebrae with spondylolysis are at the opposite end of the range of shape variation than vertebrae with Schmorl’s nodes. Conclusions Our findings indicate that H. sapiens vertebrae with spondylolysis tend to exhibit highly derived traits and therefore support the Overshoot Hypothesis. Spondylolysis, it appears, is linked to our lineage’s evolutionary history, especially its shift from quadrupedalism to bipedalism. Lay summary: Spondylolysis is a relatively common vertebral pathology usually caused by a fatigue fracture. There is reason to think that it might be connected with our lineage’s evolutionary shift from walking on all fours to walking on two legs. We tested this idea by comparing human vertebrae with and without spondylolysis to the vertebrae of great apes. Our results support the hypothesis. They suggest that people who experience spondylolysis have vertebrae with what are effectively exaggerated adaptations for bipedalism.

scholarly journals ‘Disperse abroad in the land’: the role of wildlife in the dissemination of antimicrobial resistance

2016 ◽  
Vol 12 (8) ◽  
pp. 20160137 ◽  
Author(s):  
Kathryn E. Arnold ◽  
Nicola J. Williams ◽  
Malcolm Bennett
Keyword(s):  
Antimicrobial Resistance ◽  
Natural Environment ◽  
High Throughput Sequencing ◽  
Small Scale ◽  
Human Populations ◽  
Long Distance ◽  
Antimicrobial Drugs ◽  
Clinical Resistance ◽  
Wildlife Populations ◽  
The Impact

Antimicrobial resistance (AMR) has been detected in the microbiota of many wildlife species, including long-distance migrants. Inadequately treated wastes from humans and livestock dosed with antimicrobial drugs are often assumed to be the main sources of AMR to wildlife. While wildlife populations closely associated with human populations are more likely to harbour clinically important AMR related to that found in local humans and livestock, AMR is still common in remote wildlife populations with little direct human influence. Most reports of AMR in wildlife are survey based and/or small scale, so researchers can only speculate on possible sources and sinks of AMR or the impact of wildlife AMR on clinical resistance. This lack of quantitative data on the flow of AMR genes and AMR bacteria across the natural environment could reflect the numerous AMR sources and amplifiers in the populated world. Ecosystems with relatively simple and well-characterized potential inputs of AMR can provide tractable, but realistic, systems for studying AMR in the natural environment. New tools, such as animal tracking technologies and high-throughput sequencing of resistance genes and mobilomes, should be integrated with existing methodologies to understand how wildlife maintains and disperses AMR.

Hunter-gatherers on the best-seller list: Steven Pinker and the “Bellicose School's” treatment of forager violence

2014 ◽  
Vol 6 (4) ◽  
pp. 216-228 ◽  
Author(s):  
Richard B. Lee
Keyword(s):  
Homo Sapiens ◽  
Human Populations ◽  
Hunter Gatherers ◽  
Content Type ◽  
Lethal Violence ◽  
Use Of Data ◽  
Hunting And Gathering ◽  
History Of ◽  
Early Farmers ◽  
Philosophical Debates

Purpose – The question of violence in hunter-gatherer society has animated philosophical debates since at least the seventeenth century. Steven Pinker has sought to affirm that civilization, is superior to the state of humanity during its long history of hunting and gathering. The purpose of this paper is to draw upon a series of recent studies that assert a baseline of primordial violence by hunters and gatherers. In challenging this position the author draws on four decades of ethnographic and historical research on hunting and gathering peoples. Design/methodology/approach – At the empirical heart of this question is the evidence pro- and con- for high rates of violent death in pre-farming human populations. The author evaluates the ethnographic and historical evidence for warfare in recorded hunting and gathering societies, and the archaeological evidence for warfare in pre-history prior to the advent of agriculture. Findings – The view of Steven Pinker and others of high rates of lethal violence in hunters and gatherers is not sustained. In contrast to early farmers, their foraging precursors lived more lightly on the land and had other ways of resolving conflict. With little or no fixed property they could easily disperse to diffuse conflict. The evidence points to markedly lower levels of violence for foragers compared to post-Neolithic societies. Research limitations/implications – This conclusion raises serious caveats about the grand evolutionary theory asserted by Steven Pinker, Richard Wrangham and others. Instead of being “killer apes” in the Pleistocene and Holocene, the evidence indicates that early humans lived as relatively peaceful hunter-gathers for some 7,000 generations, from the emergence of Homo sapiens up until the invention of agriculture. Therefore there is a major gap between the purported violence of the chimp-like ancestors and the documented violence of post-Neolithic humanity. Originality/value – This is a critical analysis of published claims by authors who contend that ancient and recent hunter-gatherers typically committed high levels of violent acts. It reveals a number of serious flaws in their arguments and use of data.

Mammals: A Very Short Introduction

2017 ◽  
Author(s):  
T. S. Kemp
Keyword(s):  
Fossil Record ◽  
Evolutionary History ◽  
Homo Sapiens ◽  
Short Introduction ◽  
Large Brain ◽  
Modes Of Life ◽  
Huge Variety

Mammals: A Very Short Introduction explores the nature, evolutionary history, and modern diversity of mammals. From a little shrew-like, nocturnal, insect-eating ancestor living 200 million years ago (mya), mammals have evolved into a huge variety of different kinds of animals. This VSI explains how it is endothermy—‘warm-bloodedness’—enabling high levels of activity and the relatively large brain associated with complex, adaptable behaviour that epitomizes mammals. It describes their remarkable fossil record, revealing how and when the mammals gained their characteristics, and the tortuous course of their evolution. It reveals the adaptations mammals evolved to suit their varied modes of life, including those of mainly arboreal primates culminating in Homo sapiens.

Human Evolution

1984 ◽  
Vol 8 ◽  
pp. 182-198
Author(s):  
Catherine Badgley
Keyword(s):  
Human Evolution ◽  
Evolutionary History ◽  
Pan Paniscus ◽  
Homo Sapiens ◽  
Great Apes ◽  
Sister Group ◽  
The Family ◽  
History Of ◽  
Living Species ◽  
Single Living

The evolutionary history of humans is well understood in outline, compared to that of many other groups of mammals. But human evolution remains enigmatic in its details, and these are compelling both scientifically and personally because they relate to the biological uniqueness of humans. Humans are placed in the primate family Hominidae, which, in traditional classifications, contains a single living species, Homo sapiens. The closest living relatives of humans are great apes: the chimpanzees Pan paniscus and Pan troglodytes, the gorilla Gorilla gorilla, and the orangutan Pongo pygmaeus. These apes have traditionally been placed in the family Pongidae as the sister group of Hominidae. Living Hominidae and Pongidae, together with Hylobatidae (gibbons) comprise the modern representatives of the primate suborder Hominoidea.

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