Yong Cai and William Lavely
- Published in print:
- 2007
- Published Online:
- May 2007
- ISBN:
- 9780199299294
- eISBN:
- 9780191715082
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199299294.003.0007
- Subject:
- Economics and Finance, South and East Asia
This chapter examines regional patterns of sex ratios for children aged 0 to 4 using county-level data collected by the 2000 census. Great regional disparities in sex ratios were observed among young ...
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This chapter examines regional patterns of sex ratios for children aged 0 to 4 using county-level data collected by the 2000 census. Great regional disparities in sex ratios were observed among young children. Nearly half of China's population now lives in areas where the sex ratio of children aged 0 to 4 is above 120 boys per 100 girls. Rising sex ratios has already become a serious social problem. Some explanations are offered for regional variations in the sex ratios of young children.Less
This chapter examines regional patterns of sex ratios for children aged 0 to 4 using county-level data collected by the 2000 census. Great regional disparities in sex ratios were observed among young children. Nearly half of China's population now lives in areas where the sex ratio of children aged 0 to 4 is above 120 boys per 100 girls. Rising sex ratios has already become a serious social problem. Some explanations are offered for regional variations in the sex ratios of young children.
Mukesh Eswaran
- Published in print:
- 2006
- Published Online:
- September 2006
- ISBN:
- 9780195305197
- eISBN:
- 9780199783519
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/0195305191.003.0010
- Subject:
- Economics and Finance, Development, Growth, and Environmental
This essay discusses why fertility is high in many developing countries; why it declines with economic development; why the institution of child labor facilitates high fertility; and why high ...
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This essay discusses why fertility is high in many developing countries; why it declines with economic development; why the institution of child labor facilitates high fertility; and why high fertility is intimately tied to the extent of female autonomy in decision making. It then discusses the reasons for the biased sex ratio at birth alluded to above. It concludes with suggestions for policy measures that will address the problems identified.Less
This essay discusses why fertility is high in many developing countries; why it declines with economic development; why the institution of child labor facilitates high fertility; and why high fertility is intimately tied to the extent of female autonomy in decision making. It then discusses the reasons for the biased sex ratio at birth alluded to above. It concludes with suggestions for policy measures that will address the problems identified.
Mark Regnerus and Jeremy Uecker
- Published in print:
- 2010
- Published Online:
- January 2011
- ISBN:
- 9780199743285
- eISBN:
- 9780199894741
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199743285.003.0004
- Subject:
- Religion, Religion and Society
This chapter considers the sex lives of college students, beginning with an extended discussion of the hookup. In-person interviews describe what hooking up means and what it’s ...
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This chapter considers the sex lives of college students, beginning with an extended discussion of the hookup. In-person interviews describe what hooking up means and what it’s looked like in their own lives. According to recent estimates, hookup sex remains a minority practice because many students never do it, many that have do so irregularly, and plenty of hookups stop well short of intercourse. The chapter also explores the ramifications of gender ratio imbalances for how women perceive men on campus, and how they go about pursuing romantic relationships with them. The chapter also documents the sexualization of campus life, which contrasts with the average sexual lives of many collegians, especially when compared with young Americans who are not enrolled in college at all — these remain the most sexually prolific group in the country. The chapter ends by discussing how social networking and texting have altered the sexual landscape on campus.Less
This chapter considers the sex lives of college students, beginning with an extended discussion of the hookup. In-person interviews describe what hooking up means and what it’s looked like in their own lives. According to recent estimates, hookup sex remains a minority practice because many students never do it, many that have do so irregularly, and plenty of hookups stop well short of intercourse. The chapter also explores the ramifications of gender ratio imbalances for how women perceive men on campus, and how they go about pursuing romantic relationships with them. The chapter also documents the sexualization of campus life, which contrasts with the average sexual lives of many collegians, especially when compared with young Americans who are not enrolled in college at all — these remain the most sexually prolific group in the country. The chapter ends by discussing how social networking and texting have altered the sexual landscape on campus.
Stephen Wilkinson
- Published in print:
- 2010
- Published Online:
- May 2010
- ISBN:
- 9780199273966
- eISBN:
- 9780191706585
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199273966.003.0008
- Subject:
- Philosophy, Moral Philosophy, Political Philosophy
This chapter addresses the issue of ‘social’ sex selection (sex selection for reasons other than the avoidance of sex-linked disorders). After outlining the legal and regulatory context in the UK, it ...
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This chapter addresses the issue of ‘social’ sex selection (sex selection for reasons other than the avoidance of sex-linked disorders). After outlining the legal and regulatory context in the UK, it examines the view that ‘family balancing’ sex selection is morally preferable to other (‘social’) forms and should enjoy a relatively privileged (moral and/or legal) status. It concludes that ‘family balancing’ is not (or need not be) any better than other forms of sex selection. The remaining part of the chapter considers the more fundamental question of whether any form of sex selection is permissible and reviews several further arguments against it. The conclusion ultimately arrived at is complex. It is argued that while sex selection is not intrinsically or necessarily wrong, many actual instances of it are, either because of their negative effects (for example, on population sex ratios) or because they are based on sexist beliefs and attitudes.Less
This chapter addresses the issue of ‘social’ sex selection (sex selection for reasons other than the avoidance of sex-linked disorders). After outlining the legal and regulatory context in the UK, it examines the view that ‘family balancing’ sex selection is morally preferable to other (‘social’) forms and should enjoy a relatively privileged (moral and/or legal) status. It concludes that ‘family balancing’ is not (or need not be) any better than other forms of sex selection. The remaining part of the chapter considers the more fundamental question of whether any form of sex selection is permissible and reviews several further arguments against it. The conclusion ultimately arrived at is complex. It is argued that while sex selection is not intrinsically or necessarily wrong, many actual instances of it are, either because of their negative effects (for example, on population sex ratios) or because they are based on sexist beliefs and attitudes.
Bradley R. Anholt
- Published in print:
- 2008
- Published Online:
- September 2008
- ISBN:
- 9780199230693
- eISBN:
- 9780191710889
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199230693.003.0013
- Subject:
- Biology, Ecology, Animal Biology
Acquiring the resources for reproduction comes at the risk of death. After emergence, females of most odonate species gain more mass than males and concomitantly suffer higher mortality rates. ...
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Acquiring the resources for reproduction comes at the risk of death. After emergence, females of most odonate species gain more mass than males and concomitantly suffer higher mortality rates. Differences in adult mortality rates affect the operational sex ratio. The expected number of future matings for males affects whether males should defend territories or contact guard mates. Where females gain much more mass than males and suffer higher mortality as a result, a male with a mate has a very low expectation of additional matings and should contact guard a mate to maximize reproductive success. When the operational sex ratio is less male-biased, a male with a mate may have additional opportunities to mate and can maximize his reproductive success by territorial behaviour.Less
Acquiring the resources for reproduction comes at the risk of death. After emergence, females of most odonate species gain more mass than males and concomitantly suffer higher mortality rates. Differences in adult mortality rates affect the operational sex ratio. The expected number of future matings for males affects whether males should defend territories or contact guard mates. Where females gain much more mass than males and suffer higher mortality as a result, a male with a mate has a very low expectation of additional matings and should contact guard a mate to maximize reproductive success. When the operational sex ratio is less male-biased, a male with a mate may have additional opportunities to mate and can maximize his reproductive success by territorial behaviour.
Peter Biller
- Published in print:
- 2003
- Published Online:
- October 2011
- ISBN:
- 9780199265596
- eISBN:
- 9780191699085
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199265596.003.0004
- Subject:
- History, European Medieval History, History of Ideas
Historians have examined chronicler Giovanni Villani's figures in order to reconstruct past demographic reality, but not to ask what the practice, figures, and phrases used by Villani represented in ...
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Historians have examined chronicler Giovanni Villani's figures in order to reconstruct past demographic reality, but not to ask what the practice, figures, and phrases used by Villani represented in his and other people's minds: a notion of ‘sex-ratio’. If we go backwards in time from Villani — say, into the 12th century — do we find anything in this area? Did people ‘think’ the thought ‘sex-ratio’? This chapter considers when and how the notion emerged.Less
Historians have examined chronicler Giovanni Villani's figures in order to reconstruct past demographic reality, but not to ask what the practice, figures, and phrases used by Villani represented in his and other people's minds: a notion of ‘sex-ratio’. If we go backwards in time from Villani — say, into the 12th century — do we find anything in this area? Did people ‘think’ the thought ‘sex-ratio’? This chapter considers when and how the notion emerged.
Anne E. Magurran
- Published in print:
- 2005
- Published Online:
- September 2007
- ISBN:
- 9780198527855
- eISBN:
- 9780191713576
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198527855.003.0002
- Subject:
- Biology, Evolutionary Biology / Genetics
This chapter reveals that there are significant complexities in the Trinidadian guppy system that make the investigation of the evolutionary ecology of the guppy both more challenging than it ...
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This chapter reveals that there are significant complexities in the Trinidadian guppy system that make the investigation of the evolutionary ecology of the guppy both more challenging than it initially appears. The particular configuration of the river systems in Trinidad and distribution of fish species, including guppies, amongst them has resulted in marked, rapid, and interpretable population differentiation in a range of adaptive traits. Key differences between populations are summarized, Trinidadian freshwater habitats are introduced, and the importance of predators in driving population differentiation is highlighted. Complexities in predator-guppy interactions are discussed and their implications assessed. The covariance in predation regime and productivity levels as well as the direct and indirect consequences of this covariance for guppy evolution are reviewed. Other factors that shape the evolutionary ecology of the guppy include history, water quality, water temperature, and human intervention. The chapter concludes by drawing attention to the extensive background data on Trinidad, which makes it one of the better-known tropical systems. The level of documentation is such that it is possible to visit Trinidad for the first time and complete a publishable study within a few weeks.Less
This chapter reveals that there are significant complexities in the Trinidadian guppy system that make the investigation of the evolutionary ecology of the guppy both more challenging than it initially appears. The particular configuration of the river systems in Trinidad and distribution of fish species, including guppies, amongst them has resulted in marked, rapid, and interpretable population differentiation in a range of adaptive traits. Key differences between populations are summarized, Trinidadian freshwater habitats are introduced, and the importance of predators in driving population differentiation is highlighted. Complexities in predator-guppy interactions are discussed and their implications assessed. The covariance in predation regime and productivity levels as well as the direct and indirect consequences of this covariance for guppy evolution are reviewed. Other factors that shape the evolutionary ecology of the guppy include history, water quality, water temperature, and human intervention. The chapter concludes by drawing attention to the extensive background data on Trinidad, which makes it one of the better-known tropical systems. The level of documentation is such that it is possible to visit Trinidad for the first time and complete a publishable study within a few weeks.
Jan Komdeur
- Published in print:
- 2012
- Published Online:
- December 2013
- ISBN:
- 9780199692576
- eISBN:
- 9780191774737
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199692576.003.0010
- Subject:
- Biology, Evolutionary Biology / Genetics
This chapter reviews various social and ecological circumstances linked to parental care that could drive variation in adaptive sex allocation in of vertebrates. The most extreme and precise sex ...
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This chapter reviews various social and ecological circumstances linked to parental care that could drive variation in adaptive sex allocation in of vertebrates. The most extreme and precise sex ratio adjustments in relation to such social and environmental factors were found in species where the fitness benefits of facultative sex ratio adjustment are high and the apparent costs low. Furthermore, some studies report evidence for sex ratio bias, either at birth or at the end of the parental care period, while other studies do not, despite conditions predicted to favour adaptive sex ratio adjustments being satisfied. This discrepancy between studies conducted on different species, or even the same species, emphasizes the need for more robust predictions based on accurate estimates of potential fitness pay-offs. To this end, there is a need for better information on the long-term consequences of sex allocation on individual fitness. A major task for future work is to obtain more detailed information on the fitness functions of both parents and male and female offspring. Finally, theoretical models need to be developed that can predict the observed variation in the amount and precision of sex-ratio manipulation in response to the various factors that influence the selection pressure.Less
This chapter reviews various social and ecological circumstances linked to parental care that could drive variation in adaptive sex allocation in of vertebrates. The most extreme and precise sex ratio adjustments in relation to such social and environmental factors were found in species where the fitness benefits of facultative sex ratio adjustment are high and the apparent costs low. Furthermore, some studies report evidence for sex ratio bias, either at birth or at the end of the parental care period, while other studies do not, despite conditions predicted to favour adaptive sex ratio adjustments being satisfied. This discrepancy between studies conducted on different species, or even the same species, emphasizes the need for more robust predictions based on accurate estimates of potential fitness pay-offs. To this end, there is a need for better information on the long-term consequences of sex allocation on individual fitness. A major task for future work is to obtain more detailed information on the fitness functions of both parents and male and female offspring. Finally, theoretical models need to be developed that can predict the observed variation in the amount and precision of sex-ratio manipulation in response to the various factors that influence the selection pressure.
Wei Chen
- Published in print:
- 2007
- Published Online:
- May 2007
- ISBN:
- 9780199299294
- eISBN:
- 9780191715082
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199299294.003.0006
- Subject:
- Economics and Finance, South and East Asia
This chapter investigates changes in induced abortion and their relationship with the implementation of the family planning policies, the decline in fertility, and the rise of sex ratios at birth. It ...
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This chapter investigates changes in induced abortion and their relationship with the implementation of the family planning policies, the decline in fertility, and the rise of sex ratios at birth. It identifies a number of factors that have markedly influenced patterns of abortion. It shows that while the contribution of abortion to fertility decline is relatively small, it has a considerable impact on sex ratio at birth in many regions.Less
This chapter investigates changes in induced abortion and their relationship with the implementation of the family planning policies, the decline in fertility, and the rise of sex ratios at birth. It identifies a number of factors that have markedly influenced patterns of abortion. It shows that while the contribution of abortion to fertility decline is relatively small, it has a considerable impact on sex ratio at birth in many regions.
Jukka Suhonen, Markus J. Rantala, and Johanna Honkavaara
- Published in print:
- 2008
- Published Online:
- September 2008
- ISBN:
- 9780199230693
- eISBN:
- 9780191710889
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199230693.003.0016
- Subject:
- Biology, Ecology, Animal Biology
This chapter discusses causes and consequences of territorial behaviour in odonates. In territorial species, males may use two mating tactics or strategies that may be environmentally or genetically ...
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This chapter discusses causes and consequences of territorial behaviour in odonates. In territorial species, males may use two mating tactics or strategies that may be environmentally or genetically determined: territoriality and non-territoriality. The tactic a male exhibits in each particular case is determined by the cost-benefit ratio of territorial and non-territorial behaviours. The main benefit of territoriality is increased access to females, and the costs may accumulate due to e.g., predation, injuries, and/or energy loss due to territorial contests. Moreover, density of both males and females as well as sex-ratio at breeding sites both contribute to the costs and benefits of each tactic. Interspecific aggression by heterospecific males may also influence the profitability of these tactics.Less
This chapter discusses causes and consequences of territorial behaviour in odonates. In territorial species, males may use two mating tactics or strategies that may be environmentally or genetically determined: territoriality and non-territoriality. The tactic a male exhibits in each particular case is determined by the cost-benefit ratio of territorial and non-territorial behaviours. The main benefit of territoriality is increased access to females, and the costs may accumulate due to e.g., predation, injuries, and/or energy loss due to territorial contests. Moreover, density of both males and females as well as sex-ratio at breeding sites both contribute to the costs and benefits of each tactic. Interspecific aggression by heterospecific males may also influence the profitability of these tactics.
Leo W. Beukeboom and Nicolas Perrin
- Published in print:
- 2014
- Published Online:
- August 2014
- ISBN:
- 9780199657148
- eISBN:
- 9780191748103
- Item type:
- book
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199657148.001.0001
- Subject:
- Biology, Evolutionary Biology / Genetics
Sexual reproduction is a fundamental aspect of life. It is defined by the occurrence of meiosis and the fusion of two gametes of different sexes or mating types. Genetic mechanisms for the ...
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Sexual reproduction is a fundamental aspect of life. It is defined by the occurrence of meiosis and the fusion of two gametes of different sexes or mating types. Genetic mechanisms for the determination and differentiation of the two sexes are diverse and evolutionary labile. This book synthesizes the contemporary literature on patterns and processes of sex determination evolution. The first chapter introduces definitions and concepts of sexual reproduction. Chapter 2 provides a comprehensive classification of sex-determination systems and describes the diversity of sexual cycles across eukaryote lineages, from excavates to mammals. Subsequent chapters detail the molecular mechanisms and quantitative genetics of sex determination (Chapters 3 and 4), examine the processes of sex-chromosome evolution (Chapter 5), and discuss life-history consequences of sex-determination systems (Chapter 6). The final chapter addresses the evolutionary processes responsible for the diversity and turnover in sex determination (Chapter 7). The book provides an overview of different sex-determination systems and details of its molecular regulation in fungi, plants, and animals, many of which are covered in separate text boxes and figures. It is argued that sex determination and primary sex differentiation cannot be regarded as separate processes and that the traditional dichotomous view of genotypic (GSD) and environmental (ESD) sex determination is no longer accurate. Ample documentation is provided about how sex determination affects, and is affected by, various forms of sexual conflict, sexual selection, and speciation. The book makes clear that sex-determination evolution will remain a highly dynamic field of research in the future.Less
Sexual reproduction is a fundamental aspect of life. It is defined by the occurrence of meiosis and the fusion of two gametes of different sexes or mating types. Genetic mechanisms for the determination and differentiation of the two sexes are diverse and evolutionary labile. This book synthesizes the contemporary literature on patterns and processes of sex determination evolution. The first chapter introduces definitions and concepts of sexual reproduction. Chapter 2 provides a comprehensive classification of sex-determination systems and describes the diversity of sexual cycles across eukaryote lineages, from excavates to mammals. Subsequent chapters detail the molecular mechanisms and quantitative genetics of sex determination (Chapters 3 and 4), examine the processes of sex-chromosome evolution (Chapter 5), and discuss life-history consequences of sex-determination systems (Chapter 6). The final chapter addresses the evolutionary processes responsible for the diversity and turnover in sex determination (Chapter 7). The book provides an overview of different sex-determination systems and details of its molecular regulation in fungi, plants, and animals, many of which are covered in separate text boxes and figures. It is argued that sex determination and primary sex differentiation cannot be regarded as separate processes and that the traditional dichotomous view of genotypic (GSD) and environmental (ESD) sex determination is no longer accurate. Ample documentation is provided about how sex determination affects, and is affected by, various forms of sexual conflict, sexual selection, and speciation. The book makes clear that sex-determination evolution will remain a highly dynamic field of research in the future.
Graham Bell
- Published in print:
- 2007
- Published Online:
- May 2008
- ISBN:
- 9780198569725
- eISBN:
- 9780191717741
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198569725.003.0009
- Subject:
- Biology, Evolutionary Biology / Genetics
Genetic elements that spread by parasitizing the replicative machinery of a host cell are common inhabitants of the genome, especially in multicellular sexual organisms. They show how genetic ...
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Genetic elements that spread by parasitizing the replicative machinery of a host cell are common inhabitants of the genome, especially in multicellular sexual organisms. They show how genetic elements can evolve despite reducing the fitness of individuals. The first section in this chapter is all about infection and explains the following: bacterial plasmids; 2-micron plasmid of yeast; transposable elements; transposons as regulatory elements; transposons as mutator elements; transposons as hitch-hiking elements; transposons as selfish genetic elements; the spread of transposable elements; parasites of transposons'; selfish mitochondria; and finally population genetic engineering. The second section is about interference and describes the Poison-Antidote system; Gamete Killers; meiotic drive on sex-chromosomes; and phoenix elements. The final section in this chapter, called Gonotaxis, describes B-chromosome; and infectious agents that control sexual development.Less
Genetic elements that spread by parasitizing the replicative machinery of a host cell are common inhabitants of the genome, especially in multicellular sexual organisms. They show how genetic elements can evolve despite reducing the fitness of individuals. The first section in this chapter is all about infection and explains the following: bacterial plasmids; 2-micron plasmid of yeast; transposable elements; transposons as regulatory elements; transposons as mutator elements; transposons as hitch-hiking elements; transposons as selfish genetic elements; the spread of transposable elements; parasites of transposons'; selfish mitochondria; and finally population genetic engineering. The second section is about interference and describes the Poison-Antidote system; Gamete Killers; meiotic drive on sex-chromosomes; and phoenix elements. The final section in this chapter, called Gonotaxis, describes B-chromosome; and infectious agents that control sexual development.
P. J. P. Goldberg
- Published in print:
- 1992
- Published Online:
- October 2011
- ISBN:
- 9780198201540
- eISBN:
- 9780191674938
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198201540.003.0004
- Subject:
- History, British and Irish Medieval History, Economic History
This chapter deals with servants and servanthood in life-cycle terms. Any relationship between the master or mistress and employee can be technically seen as one of service. The employee was the ...
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This chapter deals with servants and servanthood in life-cycle terms. Any relationship between the master or mistress and employee can be technically seen as one of service. The employee was the master's servant. As an element in the labour force, servants had an economic function also. Changes in the economy are reflected in the changes in the demand for, and conditions of service of servants in both town, where servants appear to have been especially numerous, and country, where servants are less documented and less numerous.Less
This chapter deals with servants and servanthood in life-cycle terms. Any relationship between the master or mistress and employee can be technically seen as one of service. The employee was the master's servant. As an element in the labour force, servants had an economic function also. Changes in the economy are reflected in the changes in the demand for, and conditions of service of servants in both town, where servants appear to have been especially numerous, and country, where servants are less documented and less numerous.
James H. Hunt
- Published in print:
- 2007
- Published Online:
- April 2010
- ISBN:
- 9780195307979
- eISBN:
- 9780199894192
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780195307979.003.0010
- Subject:
- Biology, Animal Biology
This chapter examines inclusive fitness, which is the conceptual paradigm that has dominated the field for the past three decades. This paradigm is shown to be wanting as a framework to understand ...
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This chapter examines inclusive fitness, which is the conceptual paradigm that has dominated the field for the past three decades. This paradigm is shown to be wanting as a framework to understand how social wasps evolved.Less
This chapter examines inclusive fitness, which is the conceptual paradigm that has dominated the field for the past three decades. This paradigm is shown to be wanting as a framework to understand how social wasps evolved.
Barbara Maas and David W. Macdonald
- Published in print:
- 2004
- Published Online:
- September 2007
- ISBN:
- 9780198515562
- eISBN:
- 9780191705632
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198515562.003.0014
- Subject:
- Biology, Biodiversity / Conservation Biology
This chapter presents a case study of bat-eared foxes in the Serengeti in order to shed light on the questions: how does their behaviour differ from that of other canids, and why? Topics discussed ...
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This chapter presents a case study of bat-eared foxes in the Serengeti in order to shed light on the questions: how does their behaviour differ from that of other canids, and why? Topics discussed include group composition, dispersal, and philopatry; litter size, sex ratio, and reproductive success; energetics of female reproduction; rabies and mortality; and resources and sociality.Less
This chapter presents a case study of bat-eared foxes in the Serengeti in order to shed light on the questions: how does their behaviour differ from that of other canids, and why? Topics discussed include group composition, dispersal, and philopatry; litter size, sex ratio, and reproductive success; energetics of female reproduction; rabies and mortality; and resources and sociality.
Elliott Sober
- Published in print:
- 2007
- Published Online:
- March 2013
- ISBN:
- 9780226720807
- eISBN:
- 9780226720838
- Item type:
- chapter
- Publisher:
- University of Chicago Press
- DOI:
- 10.7208/chicago/9780226720838.003.0008
- Subject:
- History, History of Science, Technology, and Medicine
This chapter demonstrates how Charles Darwin's theory inaugurated a steady progression toward an ever-sharper distinction between living creatures and artificial devices, and describes how natural ...
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This chapter demonstrates how Charles Darwin's theory inaugurated a steady progression toward an ever-sharper distinction between living creatures and artificial devices, and describes how natural life became nonartificial. Artificial life contrasts with life found in nature. Sex ratio provides an interesting case study of the problem of whether one should regard living things as artifacts or as the result of mindless natural processes. John Arbuthnot believes that a benevolent deity would seek to insure an even sex ratio at the age of marriage. Nicolas Bernoulli concludes that Arbuthnot's data provide no argument at all for Divine Providence. The problem with Arbuthnot's argument is that he does not keep the tasks of proximate and ultimate explanation separate. Modern sex ratio theory makes testable predictions about the sex ratios observed. The Even foundress has been more successful in producing grandoffspring.Less
This chapter demonstrates how Charles Darwin's theory inaugurated a steady progression toward an ever-sharper distinction between living creatures and artificial devices, and describes how natural life became nonartificial. Artificial life contrasts with life found in nature. Sex ratio provides an interesting case study of the problem of whether one should regard living things as artifacts or as the result of mindless natural processes. John Arbuthnot believes that a benevolent deity would seek to insure an even sex ratio at the age of marriage. Nicolas Bernoulli concludes that Arbuthnot's data provide no argument at all for Divine Providence. The problem with Arbuthnot's argument is that he does not keep the tasks of proximate and ultimate explanation separate. Modern sex ratio theory makes testable predictions about the sex ratios observed. The Even foundress has been more successful in producing grandoffspring.
Walter D. Koenig
- Published in print:
- 2008
- Published Online:
- September 2008
- ISBN:
- 9780199230693
- eISBN:
- 9780191710889
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199230693.003.0012
- Subject:
- Biology, Ecology, Animal Biology
This chapter summarizes studies of lifetime reproductive success (LRS) conducted on odonates. Such studies have focused on many characters, but have typically concluded that survivorship — the main ...
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This chapter summarizes studies of lifetime reproductive success (LRS) conducted on odonates. Such studies have focused on many characters, but have typically concluded that survivorship — the main component of natural selection, is more important than mating efficiency — a primary component of sexual selection, in determining LRS. They have also frequently found that environmental factors are important and that selection and the opportunity for selection vary considerably depending on density, sex ratio, and community composition. LRS studies have been most successful when focused on specific traits and when complemented by experimental manipulations. Progress in understanding the current actions of natural and sexual selection is thus most likely to involve long-term LRS work combined with experimental or comparative approaches. Particularly desirable are studies that incorporate the larval stage in fitness calculations, perform parentage analyses to determine realized fitness, and consider the role of non-breeding behaviours such as foraging efficiency.Less
This chapter summarizes studies of lifetime reproductive success (LRS) conducted on odonates. Such studies have focused on many characters, but have typically concluded that survivorship — the main component of natural selection, is more important than mating efficiency — a primary component of sexual selection, in determining LRS. They have also frequently found that environmental factors are important and that selection and the opportunity for selection vary considerably depending on density, sex ratio, and community composition. LRS studies have been most successful when focused on specific traits and when complemented by experimental manipulations. Progress in understanding the current actions of natural and sexual selection is thus most likely to involve long-term LRS work combined with experimental or comparative approaches. Particularly desirable are studies that incorporate the larval stage in fitness calculations, perform parentage analyses to determine realized fitness, and consider the role of non-breeding behaviours such as foraging efficiency.
Steven Hecht Orzack
- Published in print:
- 2001
- Published Online:
- November 2020
- ISBN:
- 9780195131543
- eISBN:
- 9780197561461
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/oso/9780195131543.003.0018
- Subject:
- Environmental Science, Applied Ecology
Understanding the allocation of energy is the goal of the evolutionary analysis of sex allocation. Whether one is concerned with the relative sizes of male and female flower parts in plants like ...
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Understanding the allocation of energy is the goal of the evolutionary analysis of sex allocation. Whether one is concerned with the relative sizes of male and female flower parts in plants like those discussed by Campbell (1998), the ratio of males and females in insects like those discussed by Orzack et al. (1991), or the relative sizes of male and female reproductive organs in hermaphroditic fish like those discussed by Leonard (1993), one is concerned with how energy allocated toward reproduction is apportioned into one sex as opposed to the other (or more in the case of some kinds of organisms). Here, the sexes are entities that at regular or irregular intervals produce gametes, some of which come together to produce zygotes. The abstract nature of this description underscores the degree to which there are common evolutionary aspects to all of these problems, despite the fact that the biological details involved are so diverse. One of the most influential and important agendas for evolutionary studies of sex allocation was laid out by Charnov (1982). He described the underlying evolutionary similarities between phenomena as diverse as sex change in shrimp and sex ratio in vertebrates like us. Even more important, he promoted sex allocation as a central evolutionary problem by describing how seemingly unrelated allocation problems could all be analyzed with a kind of mathematical approach elaborated by Shaw and Mohler (1953). I consider in turn four important examples of this approach. Shaw and Mohler’s goal was to understand the evolution of the proportions of males and females. This problem of the sex ratio was most famously addressed by Darwin in his 1871 book, The Descent of Man, and Selection in Relation to Sex, as well as by others in the subsequent decades. The most influential analysis is that of Fisher (1930); however, Carl Düsing, who worked in the 1880s, can rightly be regarded as the progenitor of modern sex ratio theory (see Edwards 1998).
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Understanding the allocation of energy is the goal of the evolutionary analysis of sex allocation. Whether one is concerned with the relative sizes of male and female flower parts in plants like those discussed by Campbell (1998), the ratio of males and females in insects like those discussed by Orzack et al. (1991), or the relative sizes of male and female reproductive organs in hermaphroditic fish like those discussed by Leonard (1993), one is concerned with how energy allocated toward reproduction is apportioned into one sex as opposed to the other (or more in the case of some kinds of organisms). Here, the sexes are entities that at regular or irregular intervals produce gametes, some of which come together to produce zygotes. The abstract nature of this description underscores the degree to which there are common evolutionary aspects to all of these problems, despite the fact that the biological details involved are so diverse. One of the most influential and important agendas for evolutionary studies of sex allocation was laid out by Charnov (1982). He described the underlying evolutionary similarities between phenomena as diverse as sex change in shrimp and sex ratio in vertebrates like us. Even more important, he promoted sex allocation as a central evolutionary problem by describing how seemingly unrelated allocation problems could all be analyzed with a kind of mathematical approach elaborated by Shaw and Mohler (1953). I consider in turn four important examples of this approach. Shaw and Mohler’s goal was to understand the evolution of the proportions of males and females. This problem of the sex ratio was most famously addressed by Darwin in his 1871 book, The Descent of Man, and Selection in Relation to Sex, as well as by others in the subsequent decades. The most influential analysis is that of Fisher (1930); however, Carl Düsing, who worked in the 1880s, can rightly be regarded as the progenitor of modern sex ratio theory (see Edwards 1998).
Leo W. Beukeboom and Nicolas Perrin
- Published in print:
- 2014
- Published Online:
- August 2014
- ISBN:
- 9780199657148
- eISBN:
- 9780191748103
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199657148.003.0007
- Subject:
- Biology, Evolutionary Biology / Genetics
Transitions among sex-determination systems and mechanisms are manifold and surprisingly frequent. The ultimate causes for such transitions are classified in three main categories: i) neutral ...
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Transitions among sex-determination systems and mechanisms are manifold and surprisingly frequent. The ultimate causes for such transitions are classified in three main categories: i) neutral processes, ii) fitness differences between sex phenotypes (stemming e.g. from sexually antagonistic mutations or accumulating mutational load), and iii) sex-ratio selection, arguably the most important evolutionary force triggering transitions. Sex-ratio selection may result from changes in population structure or environmental conditions, or from conflicts between genetic elements. Intergenomic conflicts may arise from differences between parents and offspring over optimal sex allocation, and intragenomic conflicts from differences in inheritance modes. The latter may have led to the control of sex determination by endosymbiotic microbes, and ensuing evolution towards haplodiploidy. Open questions in this area include why turnover rates differ between lineages, whether particular sex-determination systems are more labile and some transitions more likely to occur, and whether particular chromosome pairs are more likely to evolve into sex chromosomes. It is argued that experimental evolution approaches offer a promising way forward.Less
Transitions among sex-determination systems and mechanisms are manifold and surprisingly frequent. The ultimate causes for such transitions are classified in three main categories: i) neutral processes, ii) fitness differences between sex phenotypes (stemming e.g. from sexually antagonistic mutations or accumulating mutational load), and iii) sex-ratio selection, arguably the most important evolutionary force triggering transitions. Sex-ratio selection may result from changes in population structure or environmental conditions, or from conflicts between genetic elements. Intergenomic conflicts may arise from differences between parents and offspring over optimal sex allocation, and intragenomic conflicts from differences in inheritance modes. The latter may have led to the control of sex determination by endosymbiotic microbes, and ensuing evolution towards haplodiploidy. Open questions in this area include why turnover rates differ between lineages, whether particular sex-determination systems are more labile and some transitions more likely to occur, and whether particular chromosome pairs are more likely to evolve into sex chromosomes. It is argued that experimental evolution approaches offer a promising way forward.
Germaine M. Buck Louis
- Published in print:
- 2011
- Published Online:
- May 2011
- ISBN:
- 9780195387902
- eISBN:
- 9780199895328
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780195387902.003.0019
- Subject:
- Public Health and Epidemiology, Epidemiology
Human fecundity and fertility comprise the research domains of reproductive epidemiology and each has a spectrum of outcomes suitable for epidemiologic study. Fecundity outcomes in either or both ...
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Human fecundity and fertility comprise the research domains of reproductive epidemiology and each has a spectrum of outcomes suitable for epidemiologic study. Fecundity outcomes in either or both partners of a couple as reviewed in this chapter include hormonal profiles, pubertal onset and progression, sexual function, semen quality, time to pregnancy, and reproductive senescence or andropause and menopause. Fertility outcomes include fertility rates, primary and secondary sex ratios, and twinning or higher order births. The chapter summarizes available evidence regarding the determinants of male and female fecundity. In addition, a comparison of available study designs suitable for assessing fecundity or fertility outcomes is presented and includes discussion of the strengths and limitations of prospective cohort, retrospective, current duration, historic cohort, and the case cohort designs.Less
Human fecundity and fertility comprise the research domains of reproductive epidemiology and each has a spectrum of outcomes suitable for epidemiologic study. Fecundity outcomes in either or both partners of a couple as reviewed in this chapter include hormonal profiles, pubertal onset and progression, sexual function, semen quality, time to pregnancy, and reproductive senescence or andropause and menopause. Fertility outcomes include fertility rates, primary and secondary sex ratios, and twinning or higher order births. The chapter summarizes available evidence regarding the determinants of male and female fecundity. In addition, a comparison of available study designs suitable for assessing fecundity or fertility outcomes is presented and includes discussion of the strengths and limitations of prospective cohort, retrospective, current duration, historic cohort, and the case cohort designs.
