scholarly journals The Infertility Trap: The Fertility Costs of Group-Living in Mammalian Social Evolution

2021 ◽  
Vol 9 ◽  
Author(s):  
Robin I. M. Dunbar ◽  
Susanne Shultz
Keyword(s):  
Group Size ◽  
Social Evolution ◽  
Low Cost ◽  
Social Groups ◽  
Group Living ◽  
The Other ◽  
Risk Averse ◽  
Limit Group ◽  
Grouping Patterns ◽  
Environmental Demands

Mammal social groups vary considerably in size from single individuals to very large herds. In some taxa, these groups are extremely stable, with at least some individuals being members of the same group throughout their lives; in other taxa, groups are unstable, with membership changing by the day. We argue that this variability in grouping patterns reflects a tradeoff between group size as a solution to environmental demands and the costs created by stress-induced infertility (creating an infertility trap). These costs are so steep that, all else equal, they will limit group size in mammals to ∼15 individuals. A species will only be able to live in larger groups if it evolves strategies that mitigate these costs. We suggest that mammals have opted for one of two solutions. One option (fission-fusion herding) is low cost but high risk; the other (bonded social groups) is risk-averse, but costly in terms of cognitive requirements.

scholarly journals Unique allometry of group size and collective brain mass in humans and primates relative to other mammals

2019 ◽  
Author(s):  
Marcus J. Hamilton ◽  
Robert S. Walker
Keyword(s):  
Social Networks ◽  
Body Size ◽  
Group Size ◽  
Brain Size ◽  
Social Groups ◽  
Group Living ◽  
Null Model ◽  
Mammalian Brain ◽  
Brain Mass ◽  
Trade Offs

AbstractGroup living is common in mammals, particularly in primates and humans. Across species, groups are social networks where co-residing members exchange information and balance trade-offs between competition and cooperation for space, resources, and reproductive opportunities. From a macroecological perspective, species-specific group sizes are ultimately constrained by body size, population density, and the environmental supply rate of home ranges. Here, we derive an allometric null model for group size in mammals based on individual energy demands and ecological constraints. Using Bayesian phylogenetic mixed models we show that primates exhibit unique allometries relative to other mammals. Moreover, as large-bodied primates, human hunter-gatherers have among the largest social groups of any mammal. We then explore the consequences of this unique social allometry by considering how mammalian brain size scales up in social groups that differ in size across mammals. We show similarly unique allometries in what we term the collective brain mass of social groups in primates relative to all other mammals. These results show that for a given body size primates have both larger brains and larger social networks than other mammals. Consequently, proportionally larger primate brains interact in proportionally larger social networks with important consequences for group cognition. We suggest that the size, scale, and complexity of human social networks in the 21st century have deep evolutionary roots in primate ecology and mammalian brain allometry.

Increased group size promotes task specialization in a normally solitary halictine bee

Behaviour ◽  
2013 ◽  
Vol 150 (12) ◽  
pp. 1449-1466 ◽  
Author(s):  
C. Tate Holbrook ◽  
Penelope F. Kukuk ◽  
Jennifer H. Fewell
Keyword(s):  
Group Size ◽  
Spatial Organization ◽  
Social Evolution ◽  
Fundamental Property ◽  
Group Living ◽  
Division Of Labour ◽  
Behavioral Variability ◽  
Organizational Models ◽  
Central Importance ◽  
Task Specialization

Division of labour is a fundamental property of animal groups; how it is generated and evolves is, therefore, of central importance to sociobiology. Self-organizational models suggest (1) that division of labour can emerge spontaneously at the origin of group living and (2) that increased group size further promotes task specialization. We examined the emergence and scaling of division of labour in an evolutionarily incipient social system: forced associations of the normally solitary halictine bee Lasioglossum (Ctenonomia) NDA-1. A division of labour between nest excavation and guarding arose in pairs and in groups of four bees, with individuals in larger groups exhibiting higher degrees of task specialization. Task differentiation may be facilitated by intrinsic behavioral variability and/or spatial organization. Our results support the hypotheses that division of labour can self-organize at early stages of social evolution and that greater individual specialization is an emergent consequence of increased group size.

Subjective Fear Dilutes as Group Size Increases

2020 ◽  
Author(s):  
dean mobbs ◽  
Ellen Tedeschi ◽  
Anastasia Buyalskaya ◽  
Brian Silston
Keyword(s):  
Group Size ◽  
Real World ◽  
Survival Benefit ◽  
Group Living ◽  
External Factors ◽  
Threat Perception ◽  
Perception Of Threat ◽  
Threat Level ◽  
Internal States ◽  
Risk Dilution

According to Hamilton’s Selfish Herd Theory, a crucial survival benefit of group living is that it provides a ‘risk dilution’ function against predation. Despite a large literature on group living benefits in animals, few studies have been conducted on how group size alters subjective fear or threat perception in humans, and on what factors drive preferences for being in groups when facing threats. We conducted seven experiments (N=3,838) to test (A) if the presence of others decreases perception of threat under a variety of conditions. In studies 1 to 3, we experimentally manipulated group size in hypothetical and real-world situations, to show that fear responses decreased as group size increased. In studies 4 to 7 we again used a combination of hypothetical, virtual and real-world decisions to test (B) how internal states (e.g. anxiety) and external factors (e.g. threat level, availability of help) affected participants’ preference for groups. Participants consistently chose larger groups when threat and anxiety were high. Overall, our findings show that group size provides a salient signal of protection and safety.

SAE 1039

Alloy Digest ◽  
1977 ◽  
Vol 26 (2) ◽  
Keyword(s):  
Fracture Toughness ◽  
Low Cost ◽  
Manganese Content ◽  
Heat Treating ◽  
General Purpose ◽  
Carbon Steels ◽  
The Other ◽  
Steel Mills ◽  
Medium Strength ◽  
Hot Rolled

Abstract SAF 1039 steel can be used in the hot-rolled, normalized, oil-quenched-and-tempered or water-quenched-and-tempered condition for general-purpose construction and engineering. Its manganese content is a little higher than some of the other standard carbon steels with comparable carbon levels; this gives it slightly higher hardenability and hardness. It provides medium strength and toughness at low cost. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as fracture toughness. It also includes information on corrosion resistance as well as forming, heat treating, machining, joining, and surface treatment. Filing Code: CS-66. Producer or source: Carbon steel mills.

Using Low Temperature, Cost-effective and Green Methods to Carbon Nanohorn Synthesis

2019 ◽  
Vol 9 (2) ◽  
pp. 157-160
Author(s):  
Ali Hasani
Keyword(s):  
Laser Ablation ◽  
Melting Point ◽  
Palm Olein ◽  
Arc Discharge ◽  
Low Cost ◽  
The Other ◽  
High Yield ◽  
Reaction Field ◽  
Carbon Nanohorns ◽  
Graphite Rod

Background: Laser ablation method has high-yield and pure SWCNHs. On the other hand, arc discharge methods have low-cost production of SWCNHs. However, these techniques have more desirable features, they need special expertness to use high power laser or high current discharge that either of them produces very high temperature. As for the researches, the temperatures of these techniques are higher than 4727°C to vaporize the graphite. So, to become aware of the advantages of SWCNHs, it is necessary to find a new way to synthesize SWCNHs at a lower temperature. In other words, reaction field can be expandable at a moderate temperature. This paper reports a new way to synthesize SWCNHs at an extremely reduced temperature. Methods: According to this study, the role of N2 is the protection of the copper holder supporting the graphite rod by increasing heat transfer from the holder. After the current of 70 A was supplied to the system, the temperature of graphite rod was raised to 1600°C. It is obvious that this temperature is somehow higher than the melting point of palladium, 1555°C, and much lower than graphite melting point, 3497°C. Results: Based on the results, there are transitional precursors simultaneous with the SWCNHs. This composition can be created by distortion of the primary SWCNTs at the higher temperature. Subsequently, each SWCNTs have a tendency to be broken into individual horns. With increasing the concentration of the free horns, bud-like SWCNHs can be produced. Moreover, there are individual horns almost separated from the mass of single wall carbon nanohorns. This structure is not common in SWCNHs synthesized by the usual method such as arc discharge or laser ablation. Through these regular techniques, SWCNHs are synthesized as cumulative particles with diameters about 30-150 nm. Conclusion: A simple heating is needed for SWCNTs transformation to SWCNHs with the presence of palladium as catalyst. The well-thought-out mechanism for this transformation is that SWCNTs were initially changed to highly curled shape, and after that were formed into small independent horns. The other rout to synthesize SWCNHs is the pyrolysis of palm olein at 950°C with the assistance of zinc nitrate and ferrocene. Palm olein was used as a promising, bio-renewable and inexpensive carbon source for the production of carbon nanohorns.

scholarly journals A Local Oscillator Phase Compensation Technique for Ultra-Wideband Stepped-Frequency Continuous Wave Radar Based on a Low-Cost Software-Defined Radio

Sensors ◽  
2021 ◽  
Vol 21 (3) ◽  
pp. 780
Author(s):  
Kazunori Takahashi ◽  
Takashi Miwa
Keyword(s):  
Software Defined Radio ◽  
Initial Phase ◽  
Continuous Wave ◽  
Low Cost ◽  
Local Oscillator ◽  
The Other ◽  
Ultra Wideband ◽  
Single Frequency ◽  
Wave Radar ◽  
Stepped Frequency

The paper discusses a way to configure a stepped-frequency continuous wave (SFCW) radar using a low-cost software-defined radio (SDR). The most of high-end SDRs offer multiple transmitter (TX) and receiver (RX) channels, one of which can be used as the reference channel for compensating the initial phases of TX and RX local oscillator (LO) signals. It is same as how commercial vector network analyzers (VNAs) compensate for the LO initial phase. These SDRs can thus acquire phase-coherent in-phase and quadrature (I/Q) data without additional components and an SFCW radar can be easily configured. On the other hand, low-cost SDRs typically have only one transmitter and receiver. Therefore, the LO initial phase has to be compensated and the phases of the received I/Q signals have to be retrieved, preferably without employing an additional receiver and components to retain the system low-cost and simple. The present paper illustrates that the difference between the phases of TX and RX LO signals varies when the LO frequency is changed because of the timing of the commencement of the mixing. The paper then proposes a technique to compensate for the LO initial phases using the internal RF loopback of the transceiver chip and to reconstruct a pulse, which requires two streaming: one for the device under test (DUT) channel and the other for the internal RF loopback channel. The effect of the LO initial phase and the proposed method for the compensation are demonstrated by experiments at a single frequency and sweeping frequency, respectively. The results show that the proposed method can compensate for the LO initial phases and ultra-wideband (UWB) pulses can be reconstructed correctly from the data sampled by a low-cost SDR.

Political Marriage Alliances at the Shi'i Court of Awadh

1983 ◽  
Vol 25 (4) ◽  
pp. 593-616 ◽  
Author(s):  
Michael H. Fisher
Keyword(s):  
Las Vegas ◽  
Mutual Recognition ◽  
Social Groups ◽  
The Other ◽  
Shared Identity ◽  
Wedding Ceremony ◽  
Eleanor Of Aquitaine ◽  
The Continuum

A marriage expresses a mutual recognition of some degree of shared identity. The wedding ceremony confirms these links and creates new ones, although to an extent variable with the culture and the specific case. The affinity can be between individuals acting for themselves, for families, or for larger social or national groups. At one extreme would be the temporary liason, stemming from personal whim or passion, between individuals who share little more than common acceptance of the culture which recognizes the form. A Las Vegas marriage followed by a quickie Mexican divorce, a Hindu Gāndharva marriage consummated without any ceremony, or a Shi'i mut 'ah (marriage of pleasure) of contractually stipulated length might typify this end of the continuum. At the other end would be the purely political marriage that links social groups, parties, or even nations together but which disregards the desires of the principals. Richard II's diplomatic marriage to Eleanor of Aquitaine, a Kulin Brahmin's ritual marriage with dozens of women, or Asaf al-Daula's apparently unconsummated marriage with Shams al-Nisā' Begum (discussed later) exemplifies this extreme. Between lie a diversity of forms within a variety of cultures.

Do Migrants Think Differently? Evidence from Eastern European and Post-Soviet States

2018 ◽  
Vol 53 (3) ◽  
pp. 831-868 ◽  
Author(s):  
Ruxanda Berlinschi ◽  
Ani Harutyunyan
Keyword(s):  
Risk Aversion ◽  
International Migration ◽  
The Other ◽  
Eastern European ◽  
Risk Averse ◽  
Economic Liberalism ◽  
Self Selection ◽  
Using Data ◽  
Politically Active ◽  
Beliefs And Attitudes

This research investigates migrant self-selection on values, beliefs, and attitudes using data from Eastern European and former Soviet countries. We find that individuals who intend to emigrate are more politically active, more critical of governance and institutions, more tolerant toward other cultures, less tolerant of cheating, more optimistic, and less risk averse. With the exception of risk aversion, all selection patterns are heterogeneous across regions of origin. On the other hand, no self-selection pattern is detected on education, willingness to pay for public goods, and economic liberalism. These findings provide new insights into the determinants of international migration and reveal some of its less known consequences, such as a possible reduction of domestic pressure for political improvements in post-Soviet states due to politically active citizens’ higher propensity to emigrate.

A comparative study of qualitative immunochemical screening assays for the combined measurement of T-2/HT-2 in cereals and cereal-based products

2011 ◽  
Vol 4 (4) ◽  
pp. 385-394 ◽  
Author(s):  
J. Meneely ◽  
F. Ricci ◽  
S. Vesco ◽  
M. Abouzied ◽  
M. Sulyok ◽  
...  
Keyword(s):  
Sample Preparation ◽  
Low Cost ◽  
Ease Of Use ◽  
The Other ◽  
Accuracy And Precision ◽  
Cost Implications ◽  
Electrochemical Array ◽  
The Cost ◽  
Preparation Techniques ◽  
Speed Of Analysis

Many different immunochemical platforms exist for the screening of naturally occurring contaminants in food from the low cost enzyme linked immunosorbent assays (ELISA) to the expensive instruments such as optical biosensors based on the phenomenon of surface plasmon resonance (SPR). The primary aim of this study was to evaluate and compare a number of these platforms to assess their accuracy and precision when applied to naturally contaminated samples containing HT-2/T-2 mycotoxins. Other important factors considered were the speed of analysis, ease of use (sample preparation techniques and use of the equipment) and ultimately the cost implications. The three screening procedures compared included an SPR biosensor assay, a commercially available ELISA and an enzymelinked immunomagnetic electrochemical array (ELIME array). The qualitative data for all methods demonstrated very good overall agreements with each other, however on comparison with mass spectrometry confirmatory results, the ELISA and SPR assay performed slightly better than the ELIME array, exhibiting an overall agreement of 95.8% compared to 91.7%. Currently, SPR is more costly than the other two platforms and can only be used in the laboratory whereas in theory both the ELISA and ELIME array are portable and can be used in the field, but ultimately this is dependent on the sample preparation techniques employed. Sample preparative techniques varied for all methods evaluated, the ELISA was the most simple to perform followed by that of the SPR method. The ELIME array involved an additional clean-up step thereby increasing both the time and cost of analysis. Therefore in the current format, field use would not be an option for the ELIME array. In relation to speed of analysis, the ELISA outperformed the other methods.

Sign in / Sign up

Export Citation Format

Share Document