Stabilization of cultural innovations depends on population density: Testing an epidemiological model of cultural evolution against a global dataset of rock art sites and climate-based estimates of ancient population densities

Demographic models of human cultural evolution have high explanatory potential but weak empirical support. Here we use a global dataset of rock art sites and climate and genetics-based estimates of ancient population densities to test a new model based on epidemiological principles. The model focuses on the process whereby a cultural innovation becomes endemic in a population, predicting that this cannot occur unless population density exceeds a critical threshold. Analysis of the data, using a Bayesian statistical framework, shows that the model has stronger empirical support than a proportional model, where detection is directly proportional to population density, or a null model, where rock art detection ratios and population density are independent. Results for different geographical areas and periods are compatible with the predictions of the model and confirm its superiority with respect to the null model. Re-analysis of the rock art data, using a second set of independent population estimates, again supports the superiority of the model. Although the available data is sparse and the analysis cannot exclude all possible sources of bias, this is evidence that population density above a critical threshold may be a necessary condition for the maintenance of rock art as a stable part of a population’s cultural repertoire. Methods similar to those described can be used to test the model for other classes of archaeological artifact and to compare it against other models.

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Stabilization of cultural innovations depends on population density: testing an epidemiological model of cultural evolution against a global dataset of rock art sites and climate-based estimates of ancient population densities

10.1101/705137 ◽

2019 ◽

Author(s):

Richard Walker ◽

Anders Eriksson ◽

Camille Ruiz ◽

Taylor Howard Newton ◽

Francesco Casalegno

Keyword(s):

Population Density ◽

Cultural Evolution ◽

Rock Art ◽

Empirical Support ◽

Necessary Condition ◽

Critical Threshold ◽

Population Densities ◽

Value Analysis ◽

Ancient Population ◽

Independent Population

AbstractDemographic models of human cultural evolution have high explanatory potential but weak empirical support. Here we use a global dataset of rock art sites and climate and genetics-based estimates of ancient population densities to test a new model based on epidemiological principles. The model focuses on the process whereby a cultural innovation becomes endemic in a population. It predicts that this cannot occur unless population density exceeds a critical value. Analysis of the data, using a Bayesian statistical framework, shows that the model has stronger empirical support than a null model, where rock art detection rates and population density are independent, or a proportional model where detection is directly proportional to population density. Comparisons between results for different geographical areas and periods yield qualitatively similar results, supporting the robustness of the model. Re-analysis of the rock art data, using a second set of independent population estimates, yields similar results. We conclude that population density above a critical threshold is a necessary condition for the maintenance of rock art as a stable part of a population’s cultural repertoire. Methods similar to those described can be used to test the model for other classes of archaeological artifact and to compare it against other models.

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Effects of crop sequence and rainfall on population dynamics of Fusarium solani f.sp. phaseoli in soil

Canadian Journal of Botany ◽

10.1139/b92-249 ◽

1992 ◽

Vol 70 (10) ◽

pp. 2005-2008 ◽

Cited By ~ 17

Author(s):

Robert Hall ◽

Lana Gay Phillips

Keyword(s):

Population Dynamics ◽

Phaseolus Vulgaris ◽

Population Density ◽

Fusarium Solani ◽

Population Densities ◽

Total Rainfall ◽

Colony Forming Units ◽

Bean Crop ◽

Previous Summer ◽

Crop Sequence

Evidence is presented that population dynamics of Fusarium solani f.sp. phaseoli in soil depend on the effects of crop sequence and rainfall on parasitic activities of the pathogen. In a rotation trial started in 1978 and conducted over 14 years, population densities (colony-forming units/g) of the fungus in soil remained below 50 in treatments (fallow, repeated corn, repeated soybean) where the preferred host plant (common bean, Phaseolus vulgaris) was not grown. Where bean was grown every 3rd year or every year, population densities reached 475 and 660, respectively, by 1984. Thereafter, population densities of the fungus fluctuated widely from year to year in both rotation and repeated bean treatments. In the rotation treatment, peaks in population density of the pathogen coincided with the years of bean production. In repeated bean plots between 1985 and 1991, population density of the fungus in June was significantly correlated (r = 0.77, p = 0.04) with total rainfall received during the previous summer (June–August). It is postulated that higher rainfall during the growing season of the bean crop stimulated root growth and root infection, leading to the accumulation of higher levels of potential inoculum in infected tissue and the release of higher levels of inoculum into the soil by the following June. Key words: Fusarium solani f.sp. phaseoli, bean, Phaseolus vulgaris, rainfall, crop rotation.

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Population Densities Allowed Around Dutch SEVESO Establishments

10.1115/imece2000-1033 ◽

2000 ◽

Author(s):

G. M. H. Laheij ◽

B. J. M. Ale ◽

J. G. Post

Keyword(s):

Population Density ◽

The Netherlands ◽

Individual Risk ◽

Population Densities ◽

Planning Policy ◽

Relative Contribution ◽

Societal Risk ◽

Dangerous Substances ◽

The Individual ◽

Uniform Population

Abstract In the Netherlands, the individual risk and societal risk are used in efforts to reduce the number of people exposed to the effect of an accident at an establishment with dangerous substances. To facilitate the societal risk planning policy an investigation was carried out for the Dutch SEVESO establishments to investigate the possibility of determining a generic uniform population density for the zone between the individual risk contours of 10−5 and 10−6 per year. The indicative limit for the societal risk at this density was not to be exceeded. Also there was to be enough space left for a significantly higher population density outside the individual risk contour of 10−6 per year. The RORISC methodology and the actual data for the 124 Dutch SEVESO establishments were used to determine the generic uniform population density. Based on the data available it can be concluded that the maximum allowed uniform population density in the zone between the individual risk contours of 10−5 and 10−6 per year is lower than one person per hectare. At this density there is no space left for a higher population density outside the individual risk contour of 10−6 per year. For uniform population densities the relative contribution to the societal risk has been found significant up to the individual risk contour of 10−7 per year.

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Effects of population density on cauliflower crop (Brassica oleracea L. var. botrytis)

Anais da Escola Superior de Agricultura Luiz de Queiroz ◽

10.1590/s0071-12761981000100003 ◽

1981 ◽

Vol 38 (1) ◽

pp. 1-10

Author(s):

Keigo Minami ◽

Ricardo Victoria Fº

Keyword(s):

Population Density ◽

Brassica Oleracea ◽

Plant Population ◽

Population Densities ◽

Plant Population Density ◽

Brassica Oleracea L ◽

Quality Weight

An experiment was carried out to study the effects of the following population densities cauliflowers (plants per ha): 20,833 (0.60 m x 0.80 m), 25,641 (0.60 m x 0.65 m), ....37.037 (0.60 m x 0.45 m) , 55.555 (.0.60 m x 0.30 m), and 111,111 (0,60 m x 0,15 m) ; variety Snow ball. It was concluded that the effects of plant population density are greater on curd quality (weight and size) than on production per ha. The best plant population density to produce cauliflowers curd for Brazil market is from 20,000 to 25,000 plants/ha while for mini-curd is above 55,000 plants/ha.

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Population dynamics and production of a brine shrimp, Parartemia zietziana Sayce (Crustacea : Anostraca), in two salt lakes in westren Victoria, Australia

Marine and Freshwater Research ◽

10.1071/mf9770417 ◽

1977 ◽

Vol 28 (4) ◽

pp. 417 ◽

Cited By ~ 19

Author(s):

R Marchant ◽

WD Williams

Keyword(s):

Population Dynamics ◽

Population Density ◽

Temperature Stress ◽

Brine Shrimp ◽

Dry Weight ◽

Salt Lakes ◽

Confidence Limits ◽

Length Frequency ◽

Population Densities ◽

The Mean

Quantitative samples of P. zietziana were taken monthly for two years from Pink Lake and Lake Cundare. Shrimps were usually contagiously distributed. To reduce error, samples were stratified resulting in confidence limits of 40-50% for the mean population density. Despite this variability, stable trends emerged, and variation was not so great as to mask significant differences. Length-frequency analyses distinguished cohorts; a regression was established between length and dry weight, enabling growth to be estimated from samples. By combining growth with population densities in Allen curves, production was computed. In Pink Lake and Lake Cundare mean pro- duction was 11.3 and 1.0 g dry weight m-2 year-1 respectively. Generally there were two or three generations per year, but time and extent of recruitment were not predictable. Each generation suffered continuous mortality, the death of young shrimps accounting for most of the production. This mortality remains unexplained; there are no significant predators and salinity and temperature stress would occur only during summer.

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Grain Yield Gains and Associated Traits in Tropical X Temperate Maize Germplasm Under High and Low Plant Density

10.21203/rs.3.rs-401021/v1 ◽

2021 ◽

Author(s):

Vince Ndou ◽

Edmore Gasura ◽

Pauline Chivenge ◽

John Derera

Keyword(s):

Population Density ◽

Grain Yield ◽

Plant Density ◽

Plant Population ◽

Population Densities ◽

Genetic Gains ◽

Maize Germplasm ◽

High Plant Density ◽

Number Of Leaves ◽

Plant Population Density

Abstract Development of ideal breeding and crop management strategies that can improve maize grain yield under tropical environments is crucial. In the temperate regions, such yield improvements were achieved through use of genotypes that adapt high plant population density stress. However, tropical germplasm has poor tolerance to high plant population density stress, and thus it should be improved by temperate maize. The aim of this study was to estimate the genetic gains and identify traits associated with such gains in stable and high yielding temperate x tropical hybrids under low and high plant population densities. A total of 200 hybrids derived from a line x tester mating design of tropical x temperate germplasm were developed. These hybrids were evaluated for grain yield and allied traits under varied plant population densities. High yielding and stable hybrids, such as 15XH214, 15XH215 and 15XH121 were resistant to lodging and had higher number of leaves above the cob. The high genetic gains of 26% and desirable stress tolerance indices of these hybrids made them better performers over check hybrids under high plant population density. At high plant population density yield was correlated to stem lodging and number of leaves above the cob. Future gains in grain yield of these hybrids derived from temperate x tropical maize germplasm can be achieved by exploiting indirect selection for resistance to stem lodging and increased number of leaves above the cob under high plant density conditions.

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Testing biodiversity theory using species richness of reef-building corals across a depth gradient

Biology Letters ◽

10.1098/rsbl.2019.0493 ◽

2019 ◽

Vol 15 (10) ◽

pp. 20190493 ◽

Cited By ~ 2

Author(s):

T. Edward Roberts ◽

Sally A. Keith ◽

Carsten Rahbek ◽

Tom C. L. Bridge ◽

M. Julian Caley ◽

...

Keyword(s):

Species Richness ◽

Large Scale ◽

Coral Species ◽

Environmental Gradients ◽

Abiotic Factors ◽

Empirical Support ◽

Null Model ◽

Local Scale ◽

Small Scale ◽

Energy Availability

Natural environmental gradients encompass systematic variation in abiotic factors that can be exploited to test competing explanations of biodiversity patterns. The species–energy (SE) hypothesis attempts to explain species richness gradients as a function of energy availability. However, limited empirical support for SE is often attributed to idiosyncratic, local-scale processes distorting the underlying SE relationship. Meanwhile, studies are also often confounded by factors such as sampling biases, dispersal boundaries and unclear definitions of energy availability. Here, we used spatially structured observations of 8460 colonies of photo-symbiotic reef-building corals and a null-model to test whether energy can explain observed coral species richness over depth. Species richness was left-skewed, hump-shaped and unrelated to energy availability. While local-scale processes were evident, their influence on species richness was insufficient to reconcile observations with model predictions. Therefore, energy availability, either in isolation or in combination with local deterministic processes, was unable to explain coral species richness across depth. Our results demonstrate that local-scale processes do not necessarily explain deviations in species richness from theoretical models, and that the use of idiosyncratic small-scale factors to explain large-scale ecological patterns requires the utmost caution.

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Studies on the Ecology of the New Zealand Long-finned Eel, Anguilla dieffenbachii Gray

Marine and Freshwater Research ◽

10.1071/mf9520032 ◽

1952 ◽

Vol 3 (1) ◽

pp. 32 ◽

Cited By ~ 39

Author(s):

AMR Burnet

Keyword(s):

New Zealand ◽

Population Density ◽

Mathematical Analysis ◽

Feeding Habits ◽

Stomach Contents ◽

Limiting Factor ◽

Population Densities ◽

Baited Traps ◽

Anguilla Dieffenbachii

Experimental trapping of eels, using carrion-baited traps, was carried out on a number of rivers of various types throughout New Zealand. Where possible, a mathematical analysis has been applied to the trapping results and an estimate of the efficiency obtained. Total trappable population densities of between 30 and 1,368 lb./ac. Were found. An attempt has been made to correlate type of river with the population density. The amount of cover present is apparently the limiting factor. The baited trap takes very few eels of less than 24 in. long and is thus not a very efficient means of keeping a stream free from eels. The feeding habits of the eel are generalized and readily adaptable to most faunas. In most rivers trout occurred only infrequently in the stomach contents.

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Changes in Human Population Density and Protected Areas in Terrestrial Global Biodiversity Hotspots, 1995–2015

Land ◽

10.3390/land7040136 ◽

2018 ◽

Vol 7 (4) ◽

pp. 136 ◽

Cited By ~ 8

Author(s):

Caitlin Cunningham ◽

Karen Beazley

Keyword(s):

Population Density ◽

Protected Areas ◽

Protected Area ◽

Human Population ◽

Area Coverage ◽

Biodiversity Hotspots ◽

Population Densities ◽

Human Population Density ◽

Global Average ◽

Global Biodiversity

Biodiversity hotspots are rich in endemic species and threatened by anthropogenic influences and, thus, considered priorities for conservation. In this study, conservation achievements in 36 global biodiversity hotspots (25 identified in 1988, 10 added in 2011, and one in 2016) were evaluated in relation to changes in human population density and protected area coverage between 1995 and 2015. Population densities were compared against 1995 global averages, and percentages of protected area coverage were compared against area-based targets outlined in Aichi target 11 of the Convention on Biological Diversity (17% by 2020) and calls for half Earth (50%). The two factors (average population density and percent protected area coverage) for each hotspot were then plotted to evaluate relative levels of threat to biodiversity conservation. Average population densities in biodiversity hotspots increased by 36% over the 20-year period, and were double the global average. The protected area target of 17% is achieved in 19 of the 36 hotspots; the 17 hotspots where this target has not been met are economically disadvantaged areas as defined by Gross Domestic Product. In 2015, there are seven fewer hotspots (22 in 1995; 15 in 2015) in the highest threat category (i.e., population density exceeding global average, and protected area coverage less than 17%). In the lowest threat category (i.e., population density below the global average, and a protected area coverage of 17% or more), there are two additional hotspots in 2015 as compared to 1995, attributable to gains in protected area. Only two hotspots achieve a target of 50% protection. Although conservation progress has been made in most global biodiversity hotspots, additional efforts are needed to slow and/or reduce population density and achieve protected area targets. Such conservation efforts are likely to require more coordinated and collaborative initiatives, attention to biodiversity objectives beyond protected areas, and support from the global community.

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Effect of soybean population density on soybean yield, nitrogen accumulation and residual nitrogen

Australian Journal of Experimental Agriculture ◽

10.1071/ea9880099 ◽

1988 ◽

Vol 28 (1) ◽

pp. 99 ◽

Cited By ~ 11

Author(s):

MJ Blumenthal ◽

VP Quach ◽

PGE Searle

Keyword(s):

Population Density ◽

Grain Yield ◽

Dry Matter ◽

Nitrogen Accumulation ◽

Soil N ◽

Population Densities ◽

N Accumulation ◽

Soybean Yield ◽

Residual Nitrogen ◽

Residual N

The effect of soybean population density on soybean yield, nitrogen accumulation and residual nitrogen was examined at Camden, N.S.W. (34�S.). In the first experiment, treatments were soybeans (cv. Ransom) at 50, 100, 200 and 400 x 103 plants ha-1; maize (cv. XL66); and a weed-free fallow. Total dry matter yields of tops and grain yields were highest at 200x 103 plants ha-1 (6214 and 3720 kg ha-1, respectively). The yield component most affected by population density was number of branches per plant, with values decreasing with increasing population density. The proportion of unfilled pods was highest at the highest population density. Total nitrogen (N) accumulation in the tops and in the grain was also at a maximum at 200x 103 plants ha-1. The rate of dry matter accumulation declined during pod filling at all population densities. N accumulation continued at high rates throughout the growing season except in the 400x 103 plants ha-1 population. There was a trend for residual dry matter and N in residues to increase with increasing population density. After grain and forage harvest of the first experiment, a crop of wheat (cv. Kite) was sown over the whole area to determine residual N available at anthesis and at maturity (experiment 2). The values of N accumulation in the wheat at maturity were 24 kg N ha-l for the maize treatment, 40-60 kg N ha-l for the soybean treatments and 69 kg N ha-1 for the fallow treatment. Grain yield and grain N followed the pattern of dry matter production and N accumulation at final harvest. The data suggest that soybean depletes soil N to a lesser extent than does maize. For the soybean treatments, there was a trend of increasing residual N at the 3 highest population densities (40-60 kg N ha-1). This was probably a result of an increase in N in leaf fall and in decaying tops and roots at the highest population density. The high value (57 kg N ha-l) at the lowest population density may be due to soybean plants at this density not using as much soil N as the other soybean treatments. No benefit in residual N was gained from planting soybeans at a density beyond the optimum for grain yield when residues were removed by forage harvesting.

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