Jenni E. Pettay
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View article: Reproductive inequality in humans and other mammals
Reproductive inequality in humans and other mammals Open
To address claims of human exceptionalism, we determine where humans fit within the greater mammalian distribution of reproductive inequality. We show that humans exhibit lower reproductive skew (i.e., inequality in the number of surviving…
View article: The role of mating effort and co-residence history in step-grandparental investment
The role of mating effort and co-residence history in step-grandparental investment Open
The prevalence of divorce in both parental and grandparental generations has led to a rise in the number of children who now have families that include both biological and step-grandparents. Despite the thorough examination of biological g…
View article: Step-Gap in Upward Support: The Role of Biological Relatedness and Childhood Co-residence Duration
Step-Gap in Upward Support: The Role of Biological Relatedness and Childhood Co-residence Duration Open
Objectives Although prior research has detected a step-gap in intergenerational relationships in various aspects, there is a lack of studies examining adult children’s support toward their biological parents and stepparents. We investigate…
View article: Step-grandparental investment: role of childhood co-residence with grandchild’s parent
Step-grandparental investment: role of childhood co-residence with grandchild’s parent Open
The prevalence of divorce in both parental and grandparental generations has led to a rise in the number of children who now have families that include both biological and step-grandparents. Despite the thorough examination of biological g…
View article: Parental Investment by Birth Fathers and Stepfathers
Parental Investment by Birth Fathers and Stepfathers Open
This study investigates the determinants of paternal investment by birth fathers and stepfathers. Inclusive fitness theory predicts higher parental investment in birth children than stepchildren, and this has consistently been found in pre…
View article: Reproductive inequality in humans and other mammals
Reproductive inequality in humans and other mammals Open
To address claims of human exceptionalism, we determine where humans fit within the greater mammalian distribution of reproductive inequality. We show that humans exhibit lower reproductive skew (i.e., inequality in the number of surviving…
View article: Step-gap in Upward Support Regarding Biological Relatedness and Childhood Co-residence Duration
Step-gap in Upward Support Regarding Biological Relatedness and Childhood Co-residence Duration Open
ObjectivesThis study investigated the differences between the biological and stepfamily members (step-gap) regarding upward support from adult children to their biological parents and stepparents. We examined (i) whether adult children pro…
View article: Grandparental co-residence and grandchild survival: the role of resource competition in a pre-industrial population
Grandparental co-residence and grandchild survival: the role of resource competition in a pre-industrial population Open
Although grandparents are and have been important alloparents to their grandchildren, they are not necessarily only beneficial but can also compete with grandchildren over limited resources. Competition over parental care or other resource…
View article: Sex, age, and family structure influence dispersal behaviour after a forced migration
Sex, age, and family structure influence dispersal behaviour after a forced migration Open
Dispersal does not only mean moving from one environment to another, but can also refer to shifting from one social group to another. Individual characteristics such as sex, age and family structure might influence an individual's propensi…
View article: Lack of anti-predator recognition in a marine isopod under the threat of an invasive predatory crab
Lack of anti-predator recognition in a marine isopod under the threat of an invasive predatory crab Open
The prey naïveté hypothesis suggests that the failure of prey to recognize novel predators as a threat is caused by a lack of anti-predator adaptations. We tested this hypothesis in a unique natural setting, where the isopod Idotea balthic…
View article: Correction to: Female-biased sex ratios in urban centers create a “fertility trap” in 
post-war Finland
Correction to: Female-biased sex ratios in urban centers create a “fertility trap” in 
post-war Finland Open
[This corrects the article DOI: 10.1093/beheco/arab007.].
View article: Lack of Anti-Predator Recognition in a Marine Isopod Under the Threat of an Invasive Predatory Crab
Lack of Anti-Predator Recognition in a Marine Isopod Under the Threat of an Invasive Predatory Crab Open
The prey naïveté hypothesis suggests that the failure of prey to recognize novel predators as a threat is caused by a lack of anti-predator adaptations. We tested this hypothesis in a unique natural setting, where the isopod Idotea balthic…
View article: Socio-cultural similarity with host population rather than ecological similarity predicts success and failure of human migrations
Socio-cultural similarity with host population rather than ecological similarity predicts success and failure of human migrations Open
Demographers argue that human migration patterns are shaped by people moving to better environments. More recently, however, evolutionary theorists have argued that people move to similar environments to which they are culturally adapted. …
View article: The seasonality of three childhood infections in a pre-industrial society without schools
The seasonality of three childhood infections in a pre-industrial society without schools Open
Background The burden of many infectious diseases varies seasonally and a better understanding of the drivers of infectious disease seasonality would help to improve public health interventions. For directly transmitted highly-immunizing c…
View article: Female-biased sex ratios in urban centers create a “fertility trap” in post-war Finland
Female-biased sex ratios in urban centers create a “fertility trap” in post-war Finland Open
Because sex ratios are a key factor regulating mating success and subsequent fitness both across and within species, there is widespread interest in how population-wide sex ratio imbalances affect marriage markets and the formation of fami…
View article: The Resettlement and Subsequent Assimilation of Evacuees from Finnish Karelia during and after the Second World War
The Resettlement and Subsequent Assimilation of Evacuees from Finnish Karelia during and after the Second World War Open
This chapter investigates sociodemographic and environmental factors associated with the relocation and settlement of Karelian evacuees during and after the Second World War. During the war over 400,000 people were forcibly displaced from …
View article: Grandmotherhood across the demographic transition
Grandmotherhood across the demographic transition Open
Grandmothers provide key care to their grandchildren in both contemporary and historic human populations. The length of the grandmother-grandchild relationship provides a basis for such interactions, but its variation and determinants have…
View article: Limited support for the X-linked grandmother hypothesis in pre-industrial Finland
Limited support for the X-linked grandmother hypothesis in pre-industrial Finland Open
The level of kin help often depends on the degree of relatedness between a helper and the helped. In humans, grandmother help is known to increase the survival of grandchildren, though this benefit can differ between maternal grandmothers …
View article: Changes in Length of Grandparenthood in Finland 1790-1959
Changes in Length of Grandparenthood in Finland 1790-1959 Open
The importance of grandparents for their grandchildren is well-studied in several disciplines, and studies are now also addressing the potential effects of grandchildren on grandparental wellbeing. Any such effects are limited by the time …
View article: Newly Digitized Database Reveals the Lives and Families of Forced Migrants from Finnish Karelia
Newly Digitized Database Reveals the Lives and Families of Forced Migrants from Finnish Karelia Open
Studies on displaced persons often suffer from a lack of data on the long-term effects of forced migration. A register created during 1960s and published as a book series ‘Siirtokarjalaisten tie’ in 1970 documented the lives of individuals…
View article: Effects of female reproductive competition on birth rate and reproductive scheduling in a historical human population
Effects of female reproductive competition on birth rate and reproductive scheduling in a historical human population Open
Personality affects response to alarm calls. This study reveals that boldness explains how vigilant chipmunks behave in response to alarm calls, and that vigilance diminishes in response to shyer callers. Chipmunks thus evaluate the person…
View article: What have humans done for evolutionary biology? Contributions from genes to populations
What have humans done for evolutionary biology? Contributions from genes to populations Open
Many fundamental concepts in evolutionary biology were discovered using non-human study systems. Humans are poorly suited to key study designs used to advance this field, and are subject to cultural, technological, and medical influences o…
View article: Supplementary material from "Limited support for the X-linked grandmother hypothesis in pre-industrial Finland"
Supplementary material from "Limited support for the X-linked grandmother hypothesis in pre-industrial Finland" Open
The level of kin help in a species often depends on the degree of relatedness between a helper and the helped. In humans, grandmother help is known to increase the survival of grandchildren, though this benefit can differ between maternal …