Family Resolutions
Projections of human kinship for all countries
Diego Alburez-Gutierrez, Iván Williams & Hal Caswell
Proceedings of the National Academy of Sciences, 26 December 2023
Abstract:
Demographers have long attempted to project future changes in the size and composition of populations, but have ignored what these processes will mean for the size, composition, and age distribution of family networks. Kinship structures matter because family solidarity -- a crucial source of informal care for millions of people around the world -- is conditional on kin being alive. Here, we present innovative projections of biological kin for the 1950 to 2100 period and discuss what they imply for the availability of informal care. Overall, we project that the number of living kin for individuals will decline dramatically worldwide. While a 65-yo woman in 1950 could expect to have 41 living kin, a 65-yo woman in 2095 is projected to have just 25 [18.8 to 34.7] relatives (lower and upper 80% projection intervals). This represents a 38% [15 to 54] global decline. The composition of family networks is also expected to change, with the numbers of living grandparents and great-grandparents markedly increasing, and the numbers of cousins, nieces and nephews, and grandchildren declining. Family networks will age considerably, as we project a widening age gap between individuals and their kin due to lower and later fertility and longer lifespans. In Italy, for example, the average age of a grandmother of a 35-yo woman is expected to increase from 77.9 y in 1950 to 87.7 y [87.1 to 88.5] in 2095. The projected changes in kin supply will put pressure on the already stretched institutional systems of social support, as more individuals age with smaller and older family networks.
Evolutionary Influences on Assistance to Kin: Evidence from the Panel Study of Income Dynamics
Andrew Cherlin
Sociological Science, December 2023
Abstract:
Amid the changes that have diversified family life, studies have shown the continuing importance of attachment to kin through established patterns such as ties among full siblings and newer patterns such as efforts by donor-conceived individuals to find their donor siblings. Sociologists have good explanations for the diversity of family forms but not for the persistence of kinship ties. This article argues that evolutionary processes focused on genetic relatedness can provide a partial explanation for both the persistence and expansion of kinship ties. It proposes that the easing of social constraints on family-related behaviors and the resulting expansion of choices may have increased the importance of genetic relatedness in producing the current patterns. To illustrate this perspective, this article examines the consistency between patterns of financial assistance to kin and Hamilton’s rule, derived from the evolutionary theory of inclusive fitness, using the 1985 to 2019 waves of the Panel Study of Income Dynamics (PSID).
Neighborhood selection by parent personality, depression, and coparent support: A two-study replication
Chia-Feng Chen, Jennifer Weaver & Thomas Schofield
Journal of Family Psychology, forthcoming
Abstract:
This study addresses the degree to which three selection factors (parent personality, depression, and coparent support) drive movement into neighborhoods and predict changes in youth externalizing behavior. Two studies followed children from birth to age 15 (N = 1,364 for Study 1; N = 4,898 for Study 2). Neighborhood socioeconomic disadvantage, family income, and youth externalizing behavior were consistently and significantly correlated cross sectionally and longitudinally. Selection factors predicted changes in youth externalizing behavior. Higher family income, mother agreeableness, and perceived support from a coparent predicted movement over time into less disadvantaged neighborhoods. Lower levels of mother impulsivity, neuroticism, and depression also predicted movement over time into less disadvantaged neighborhoods. Neighborhood disadvantage did not predict change in youth externalizing behavior when any of the above selection factors were included in the model.
Everyday language input and production in 1,001 children from six continents
Elika Bergelson et al.
Proceedings of the National Academy of Sciences, 26 December 2023
Abstract:
Language is a universal human ability, acquired readily by young children, who otherwise struggle with many basics of survival. And yet, language ability is variable across individuals. Naturalistic and experimental observations suggest that children’s linguistic skills vary with factors like socioeconomic status and children’s gender. But which factors really influence children’s day-to-day language use? Here, we leverage speech technology in a big-data approach to report on a unique cross-cultural and diverse data set: >2,500 d-long, child-centered audio-recordings of 1,001 2- to 48-mo-olds from 12 countries spanning six continents across urban, farmer-forager, and subsistence-farming contexts. As expected, age and language-relevant clinical risks and diagnoses predicted how much speech (and speech-like vocalization) children produced. Critically, so too did adult talk in children’s environments: Children who heard more talk from adults produced more speech. In contrast to previous conclusions based on more limited sampling methods and a different set of language proxies, socioeconomic status (operationalized as maternal education) was not significantly associated with children’s productions over the first 4 y of life, and neither were gender or multilingualism. These findings from large-scale naturalistic data advance our understanding of which factors are robust predictors of variability in the speech behaviors of young learners in a wide range of everyday contexts.
Infants’ looking preferences for social versus non-social objects reflect genetic variation
Ana Maria Portugal et al.
Nature Human Behaviour, forthcoming
Abstract:
To what extent do individual differences in infants’ early preference for faces versus non-facial objects reflect genetic and environmental factors? Here in a sample of 536 5-month-old same-sex twins, we assessed attention to faces using eye tracking in two ways: initial orienting to faces at the start of the trial (thought to reflect subcortical processing) and sustained face preference throughout the trial (thought to reflect emerging attention control). Twin model fitting suggested an influence of genetic and unique environmental effects, but there was no evidence for an effect of shared environment. The heritability of face orienting and preference were 0.19 (95% confidence interval (CI) 0.04 to 0.33) and 0.46 (95% CI 0.33 to 0.57), respectively. Face preference was associated positively with later parent-reported verbal competence (β = 0.14, 95% CI 0.03 to 0.25, P = 0.014, R2 = 0.018, N = 420). This study suggests that individual differences in young infants’ selection of perceptual input -- social versus non-social -- are heritable, providing a developmental perspective on gene–environment interplay occurring at the level of eye movements.
The Trivers-Willard Effect for Educational Investment: Evidence from an African Sample
Matthias Borgstede & Annette Scheunpflug
Evolutionary Psychological Science, December 2023, Pages 419–427
Abstract:
The Trivers-Willard hypothesis (TWH) states that individuals in good condition favor offspring of the sex that has a higher variance in reproductive value. Empirical studies with historical human populations suggest that the TWH might explain biased birth-ratios as well as biased parental investment in male or female offspring. However, empirical tests of the TWH in modern human populations are less conclusive. In this study, we investigate whether parental investment in education might be skewed according to the TWH in an African sample (N = 314) that includes students from 8 different countries. The data show that male students who rate their family’s wealth high tend to report more parental involvement in their own education, whereas the opposite is true for female students. This pattern is in accordance with the TWH for parental investment. The results support the validity of evolutionary explanations of behavioral bias in the context of parental investment in offspring education.
Evidence for the role of selection for reproductively advantageous alleles in human aging
Erping Long & Jianzhi Zhang
Science Advances, December 2023
Abstract:
The antagonistic pleiotropy hypothesis posits that natural selection for pleiotropic mutations that confer earlier or more reproduction but impair the post-reproductive life causes aging. This hypothesis of the evolutionary origin of aging is supported by case studies but lacks unambiguous genomic evidence. Here, we genomically test this hypothesis using the genotypes, reproductive phenotypes, and death registry of 276,406 U.K. Biobank participants. We observe a strong, negative genetic correlation between reproductive traits and life span. Individuals with higher polygenetic scores for reproduction (PGSR) have lower survivorships to age 76 (SV76), and PGSR increased over birth cohorts from 1940 to 1969. Similar trends are seen from individual genetic variants examined. The antagonistically pleiotropic variants are often associated with cis-regulatory effects across multiple tissues or on multiple target genes. These and other findings support the antagonistic pleiotropy hypothesis of aging in humans and point to potential molecular mechanisms of the reproduction–life-span antagonistic pleiotropy.