Hum Nat (2008) 19:1–6 DOI 10.1007/s12110-008-9027-3
Inherited Dimensions of Human Populations in the Past Alan Bittles & Michael Murphy & David Reher
Published online: 21 February 2008 # Springer Science + Business Media, LLC 2008
Keywords Intergenerational effects . Family effects . Fertility . Marriage . Heights . Health . Mortality . Demographic transition . Microdata . Historical data bases The five papers in this special issue of Human Nature were selected from the proceedings of a multidisciplinary workshop on “Inherited Dimensions of Human Populations in the Past: Exploring Intergenerational Dimensions of Human Behaviour” held in Menorca, Spain, in May 2005.1 While considerable attention has been paid to intergenerational transmission when it comes to variables such as education and socioeconomic status, there has been comparatively little focus on the role of family factors, including fertility (d’Addio 2007:42), and even less on the mechanisms of transmission. However, the magnitude of the correlation between a woman’s fertility and that of her mother is similar to that of their educational levels, a very widely used covariate. Moreover, the strength of this association is increasing
1
The workshop was organized by Prof. David Reher on behalf of the Institut Menorqui d’Estudis and the Grupo de Estudios Población y Sociedad (GEPS) of the Universidad Complutense de Madrid, with financial support provided by the Fundación BilbaoVizcaya (Fundación BBVA) and participants from Australia, Belgium, Canada, Netherlands, Spain, Sweden, UK, and USA. A. Bittles Centre for Comparative Genomics, Murdoch University, Perth, Western Australia 6150, Australia e-mail: [email protected] M. Murphy Department of Social Policy, London School of Economics, Houghton Street, London WC2A 2AE, UK e-mail: [email protected] D. Reher (*) Grupo de Estudios Población y Sociedad [GEPS], Facultad de Ciencias Políticas y Sociología, Universidad Complutense de Madrid, 28223 Madrid, Spain e-mail: [email protected]
2
Hum Nat (2008) 19:1–6
over time and spans more than one generation (Murphy 1999; Murphy and Wang 2001). It also seems probable that the nature and magnitude of intergenerational transfers will influence population composition, since people born into large families are themselves more likely to make an above-average contribution to overall numbers in succeeding generations and to have larger kin networks. The existence of intergenerational continuities in contemporary societies, with their consequent impacts on economic performance and people’s life expectancy, is attracting increasing attention in both academic studies (for example, Bowles and Gintis 2001) and policy agendas (d’Addio 2007). Substantial similarities in lifetime experiences are evident between successive generations when different societies or particular groups within a society are compared. In some cases, succeeding generations live longer, have larger families, marry earlier, or divorce more frequently. The extent to which such continuities exist at the individual family level is, however, much less apparent. Information on microlevel continuities requires high-quality data from representative populations over extended time periods, including data on socioeconomic status to control for confounders. The importance of such controls was initially identified by Karl Pearson (Pearson et al. 1899; Beeton and Pearson 1901), who was in the vanguard of those investigating the intergenerational transmission of both fertility and mortality. Pearson and colleagues (1899:277) were careful to distinguish between intergenerational correlations that could arise because of the transmission of fertility from parents to children and “spurious” associations owing to the mixing of heterogeneous populations. In many cases this will require careful linkage of data that originally had been collected for very different purposes. Paucity of data has restricted the ability to generalize on the nature of intergenerational continuities. In the past, available multigenerational data sources, such as those from genealogies, were mainly representative only of small and privileged strata within society. They also frequently exhibit systematic biases by differentially excluding groups such as childless people and female children, which can seriously affect the interpretation of results (Gavrilova et al. 2004; Westendorp and Kirkwood 1998). The five papers in this collection help to fill gaps in our understanding of the nature of intergenerational continuities in demographic processes by variously examining fertility, mortality, marriage, and height, the latter a key indicator of health status, in conjunction with broader analyses of socioeconomic status. The main focus of the papers is the nineteenth century, with studies from both Europe and North America during the period of the “demographic transition”—in other words, the social transformation from a regime of relatively static and moderately high fertility and mortality to a more modern regime of low fertility and mortality. In “Marriage Timing over the Generations,” Frans van Poppel, Christiaan Monden, and Kees Mandemakers show that the earlier findings of a negligible association between the marriage ages of parents and children, reported, for example, by Levine (1982) for an English village in the early nineteenth century, did not hold true in nineteenth-century Netherlands. The large-scale Dutch historical reconstruction project used by the authors as their data source is of sufficient size to enable meaningful comparisons between different geographical areas with varying patterns of economy, religion, and culture. In addition, it permits the investigation of individual characteristics, such as socioeconomic status. The lack of such
Hum Nat (2008) 19:1–6
3
information in earlier studies left open the question of how far any of the observed correlations might have arisen in part from continuities in social status, which in turn automatically would have led to continuities in demographic behavior if persistent differences in behavior existed at the group level. Contrary to sociological theories of modernization, the conclusion reached by The Netherlands study was that the strength of family ties, as reflected by intergenerational continuities in age at marriage, were actually increasing rather than decreasing over time. This finding is consistent with the empirical conclusion of Murphy (1999) that the strength of the intergenerational fertility relationship has increased over the past few centuries. Since age at marriage is a key gatekeeper of achieved fertility (and reproductive fitness) in societies, the determinants of age at entry to marriage and hence childbearing are important factors in the differential transmission of fertility between generations (although for a fuller analysis of intergenerational transmission, it would also be necessary to assess the role of non-marriage—in other words, what was the relationship between the age of marriage of the parents and the propensity of their children to marry). The Netherlands study was also able to show that such changes cannot be accounted for by changing occupational or economic circumstances. In passing, it is appropriate to compare the position of current knowledge with that of two decades ago. Van Poppel and colleagues refer to a single study published before 1990 on intergenerational marriage patterns, that of Levine (1982), which was based on a data set one thousandth the size of their Dutch data set, confined to a single English village, and containing no controls for socioeconomic status. The main methods of analysis employed by Levine were those typical of the period— simple tabulation and product moment correlation coefficients. In contrast, van Poppel and colleagues utilized multilevel modeling (which was relatively uncommon around 1990 but is particularly appropriate for analyzing processes taking place within family units) with their rich and very large data source. This is not to say that the experience of nineteenth-century Netherlands was necessarily typical of all preindustrial Europe; indeed, van Poppel and colleagues clearly demonstrate considerable variability between the areas of Zeeland, Overrijssel, and Limburg within their relatively small country. Rather, it serves to demonstrate the rapid developments in recent decades in the ability to investigate historical processes. The study “Intergenerational Transmission of Reproductive Traits in Spain during the Demographic Transition” by David Reher, José Antonio Ortega, and Alberto Sanz-Gimeno covers a substantial period of the demographic transition, previously identified as important in studies such as Kohler et al. (1999) of Danish twins. Using data derived from Civil Registration for the town of Aranjuez, located some 50 km south of Madrid, Reher and colleagues were able to analyze the detailed dynamics of fertility change during this era, when fertility within marriage was in the process of coming under the control of conscious choice (Coale 1973). This was achieved by analyzing a range of indicators of the family-building process and intergenerational reproductive fitness, including the most relevant indicator, that of the number of surviving children. The study reinforced the common but by no means universal finding that the relationship between daughters and their parents is much stronger than that of sons and parents (it is difficult to separate the roles of mothers and fathers). The authors once again found that the strength of the relationship increased over the study period from 1871 to 1970, especially for the key variable of surviving
4
Hum Nat (2008) 19:1–6
children. By comparison with van Poppel and colleagues, there was little evidence of intergenerational continuities with respect to age at marriage, which was strong in The Netherlands and was itself a key determinant of future fertility levels in many European societies up to that time. However, they found that age at last birth, which has a strong volitional component, showed a particularly strong intergenerational relationship. The study by Reher and colleagues also served to supplement the sparser literature relating to the role of birth order effects (Sulloway 1996), where the evidence has been much less clear-cut than for overall fertility by showing that intergenerational effects were much stronger for first-born daughters. The other three papers in the collection are concerned with mortality and morbidity; in the case of morbidity, the extent to which achieved height is a proxy for health experiences in childhood that then extend into adulthood. As with many historical studies, the paper by George Alter and Michel Oris—“Effects of Inheritance and Environment on the Heights of Brothers in Nineteenth-Century Belgium”—uses an opportunistic data source based on military conscript records, with the heights of all males measured between the ages of 19 and 20 years. As was the case in the neighboring Netherlands, the availability of data from three different areas of the country—Verviers, Limbourg, and Sart, characterized by varying ecological and socioeconomic contexts—permitted the assessment of area-level as well as family-level factors. Although intergenerational associations are not discussed explicitly, the association is implicit insofar as correlations between brothers were expected to be associated with family-level variables. The paper does serve to emphasize the point that, in the nineteenth century, sections of Belgian society representative of rural and industrializing populations were subject to differing levels of vulnerability (under the assumption that smaller correlations between sibs reflected the existence of more substantial “environmental” insults). The final two papers investigate determinants of mortality using two of the bestknown data sets for such an analysis, the Utah Population Database (UPDB) and the BALSAC Population Register, both of which have been extensively employed to investigate intergenerational transmission mechanisms. The UPDB contains multigenerational information on more than 6 million individuals, including the genealogies of Utah founders and their descendants. For their study, “Are Girls Good and Boys Bad for Parental Longevity? The Effects of Sex Composition of Offspring on Parental Mortality Past Age 50,” Colette Harrell, Ken Smith, and Geraldine Mineau limit the analysis to data abstracted from the UPDB on mothers born between 1820 and 1900. Their findings add to the growing literature on the role of the sex composition of children on old-age survival, and in Utah some penalty was associated with sons, but with little variation across different sectors. For this reason a biological explanation for the findings was preferred—that there are greater pregnancy-related costs associated with male fetuses. But as noted by the authors, such effects are relatively small when, for example, compared with religious adherence. “Intergenerational and Genealogical Approaches for the Study of Longevity in the Saguenay-Lac-St-Jean Population” by Louis Houde, Marc Tremblay, and Hélène Vézina utilizes the considerable strengths of the Québec data base to identify very long-lived individuals and thus allow more effective concentration on a small segment of the population. The BALSAC database in Québec draws on the fact that
Hum Nat (2008) 19:1–6
5
the present French-speaking population of the province, which numbers approximately 6 million, is largely descended from some 10,000 people who emigrated from France between 1608 and 1760. As the subsequent rapid population growth was mostly due to natural increase, founder effect would be expected to play an important role in the composition of the present-day gene pool, with the amplification of rare genetic variants that either were present in the founders or arose through mutation in the following generations. For their study Houde and colleagues investigated individuals who had died at 90 years or older between 1950 and 1974 and matched them with controls who were born during the same time period (1850–1884) but died at 50–74 years. Mother’s mean age at death in particular was significantly higher in the cases than in the controls, and the positive effect of kinship was more pronounced in the oldest 10% of the subjects. However, this effect was explained by close kinship links rather than sharing of distant ancestors (>5 generations), which highlights the benefits of follow-up across extended time periods (Bittles and Egerbladh 2005). Collectively, these papers emphasize that possibilities now exist to examine intergenerational processes in detail using larger data sets which contain information on more than one generation. In addition to the sources included here, there are increasing numbers of data sources for a range of historical populations. Nonetheless, the existence of clear-cut positive relationships in a number of different historical populations is not in doubt.
References Beeton, M., & Pearson, K. (1901). On the inheritance of the duration of life, and on the intensity of natural selection in man. Biometrika, 1, 50–89. Bittles, A. H., & Egerbladh, I. (2005). The influence of past endogamy and consanguinity on genetic disorders in Northern Sweden. Annals of Human Genetics, 69, 549–558. Bowles, S., & Gintis, H. (2001). The inheritance of economic status: Education, class and genetics. In M. Feldman, & P. Baltes (Eds.) International encyclopedia of the social and behavioral sciences: Genetics, behavior and society (pp. 4132–4141). New York: Oxford University Press and Elsevier. Coale, A. (1973). The demographic transition. In International Population Conference, Liège 1973, vol. 1 (pp. 53–72). Liège: International Union for the Scientific Study of Population. d’Addio, A. C. (2007). Intergenerational transmission of disadvantage: Mobility or immobility across generations? OECD Social, Employment and Migration Working Papers No. 52. Paris: Organisation for Economic Co-operation and Development. Gavrilova, N. S., Gavrilov, L. A., Semyonova, V. G., & Evdokushkina, G. N. (2004). Does exceptional human longevity come with high cost of infertility? Testing the evolutionary theories of aging. Annals of the New York Academy of Sciences, 1019, 513–517. Kohler, H. P., Rodgers, J. L., & Christensen, K. (1999). Is fertility behavior in our genes? Findings from a Danish twin study. Population and Development Review, 25, 253–288. Levine, D. (1982). “For their own reasons”: Individual marriage decisions and family life. Journal of Family History, 17, 255–264. Murphy, M. (1999). Is the relationship between fertility of parents and children really weak? Social Biology, 46, 122–145. Murphy, M., & Wang, D. (2001). Family-level continuities in childbearing in low-fertility societies. European Journal of Population, 17, 75–96. Pearson, K., Lee, A., & Bramley-Moore, L. (1899). Mathematical contributions to the theory of evolution, VI. Genetic (reproductive) selection: Inheritance of fertility in man, and of fecundity in thoroughbred racehorses. Philosophical Transactions of the Royal Society of London, A192, 257–330.
6
Hum Nat (2008) 19:1–6
Sulloway, F. (1996). Born to rebel. London: Little Brown and Co. Westendorp, R. G. J., & Kirkwood, T. B. L. (1998). Human longevity at the cost of reproductive success. Nature, 396(6713), 743–746.
Alan Bittles is an adjunct professor of community genetics, Edith Cowan University, and adjunct professor in the Centre for Comparative Genomics, Murdoch University, both in Perth, Australia. Educated in Trinity College, University of Dublin, and Queen’s University, Belfast, he has held research fellowships in Cambridge; LaTrobe, Michigan; Peking; Stanford; Umeå; and Washington universities. He is a Fellow of the Institute of Biology, the Royal College of Pathologists, and the Royal Society of Medicine, and in 2007 was elected to Fellowship of the American Association for the Advancement of Science. His current research interests center on the genetic structure of human populations, in particular the impact of consanguineous marriage and endogamy on reproductive behavior and community health. He is a member of the Congenital Defects and Haemoglobinopathies expert groups of the Global Burden of Disease program, serves as Senior Editor of Annals of Human Genetics, and is a member of the Editorial Boards of the American Journal of Human Biology, Annals of Human Biology, Genomic Medicine, Journal of Biosocial Science, and Public Health Genomics.
Michael Murphy is a professor of demography at the London School of Economics and Political Science. He is a Fellow of the British Academy, Research Secretary of the Population Investigation Committee, and was President of the British Society for Population Studies until 2005. His main areas of research include family, kinship and household demography; aging; social and genetic mechanisms for the inheritance of behavior; mathematical and statistical demography; methods of making and evaluating population and household forecasts; the demography of developed and transitional societies. Recent publications include work on morality crises in Russia; models for mortality forecasting in elderly populations; kinship differentials; intergenerational transfers between parents and children; and modeling the longterm effects of assortative mating, feedback mechanisms, and kinship correlations on population size and structure.
David Reher is a professor in the Department of Sociology II (Human Ecology and Population) at the School of Political Science and Sociology of the Universidad Complutense de Madrid. A native of California, has degrees from Santa Clara University (1972), California State University, Northridge (1973), and the University of Madrid (Licenciatura [1978] and PhD [1983]). Professor Reher has held positions in Spanish and international scientific organizations, most notably chair of the Historical Demography Committee of the International Union for the Scientific Study of Population (IUSSP). He has been on the Editorial Board of the journals Continuity and Change (UK), Revista de Historia Economica (Spain), Statistica (Italy) and Historical Methods (USA). He heads a network of researchers from various institutions dedicated to the study of population issues (Grupo de Estudios Población y Sociedad—GEPS). He is author of numerous studies in the fields of population history, social and economic history, urban history and family history, reproductive health, as well as family sociology, and has published on Spanish, European and Latin American topics.
Inherited Dimensions of Human Populations in the Past Alan Bittles & Michael Murphy & David Reher
Published online: 21 February 2008 # Springer Science + Business Media, LLC 2008
Keywords Intergenerational effects . Family effects . Fertility . Marriage . Heights . Health . Mortality . Demographic transition . Microdata . Historical data bases The five papers in this special issue of Human Nature were selected from the proceedings of a multidisciplinary workshop on “Inherited Dimensions of Human Populations in the Past: Exploring Intergenerational Dimensions of Human Behaviour” held in Menorca, Spain, in May 2005.1 While considerable attention has been paid to intergenerational transmission when it comes to variables such as education and socioeconomic status, there has been comparatively little focus on the role of family factors, including fertility (d’Addio 2007:42), and even less on the mechanisms of transmission. However, the magnitude of the correlation between a woman’s fertility and that of her mother is similar to that of their educational levels, a very widely used covariate. Moreover, the strength of this association is increasing
1
The workshop was organized by Prof. David Reher on behalf of the Institut Menorqui d’Estudis and the Grupo de Estudios Población y Sociedad (GEPS) of the Universidad Complutense de Madrid, with financial support provided by the Fundación BilbaoVizcaya (Fundación BBVA) and participants from Australia, Belgium, Canada, Netherlands, Spain, Sweden, UK, and USA. A. Bittles Centre for Comparative Genomics, Murdoch University, Perth, Western Australia 6150, Australia e-mail: [email protected] M. Murphy Department of Social Policy, London School of Economics, Houghton Street, London WC2A 2AE, UK e-mail: [email protected] D. Reher (*) Grupo de Estudios Población y Sociedad [GEPS], Facultad de Ciencias Políticas y Sociología, Universidad Complutense de Madrid, 28223 Madrid, Spain e-mail: [email protected]
2
Hum Nat (2008) 19:1–6
over time and spans more than one generation (Murphy 1999; Murphy and Wang 2001). It also seems probable that the nature and magnitude of intergenerational transfers will influence population composition, since people born into large families are themselves more likely to make an above-average contribution to overall numbers in succeeding generations and to have larger kin networks. The existence of intergenerational continuities in contemporary societies, with their consequent impacts on economic performance and people’s life expectancy, is attracting increasing attention in both academic studies (for example, Bowles and Gintis 2001) and policy agendas (d’Addio 2007). Substantial similarities in lifetime experiences are evident between successive generations when different societies or particular groups within a society are compared. In some cases, succeeding generations live longer, have larger families, marry earlier, or divorce more frequently. The extent to which such continuities exist at the individual family level is, however, much less apparent. Information on microlevel continuities requires high-quality data from representative populations over extended time periods, including data on socioeconomic status to control for confounders. The importance of such controls was initially identified by Karl Pearson (Pearson et al. 1899; Beeton and Pearson 1901), who was in the vanguard of those investigating the intergenerational transmission of both fertility and mortality. Pearson and colleagues (1899:277) were careful to distinguish between intergenerational correlations that could arise because of the transmission of fertility from parents to children and “spurious” associations owing to the mixing of heterogeneous populations. In many cases this will require careful linkage of data that originally had been collected for very different purposes. Paucity of data has restricted the ability to generalize on the nature of intergenerational continuities. In the past, available multigenerational data sources, such as those from genealogies, were mainly representative only of small and privileged strata within society. They also frequently exhibit systematic biases by differentially excluding groups such as childless people and female children, which can seriously affect the interpretation of results (Gavrilova et al. 2004; Westendorp and Kirkwood 1998). The five papers in this collection help to fill gaps in our understanding of the nature of intergenerational continuities in demographic processes by variously examining fertility, mortality, marriage, and height, the latter a key indicator of health status, in conjunction with broader analyses of socioeconomic status. The main focus of the papers is the nineteenth century, with studies from both Europe and North America during the period of the “demographic transition”—in other words, the social transformation from a regime of relatively static and moderately high fertility and mortality to a more modern regime of low fertility and mortality. In “Marriage Timing over the Generations,” Frans van Poppel, Christiaan Monden, and Kees Mandemakers show that the earlier findings of a negligible association between the marriage ages of parents and children, reported, for example, by Levine (1982) for an English village in the early nineteenth century, did not hold true in nineteenth-century Netherlands. The large-scale Dutch historical reconstruction project used by the authors as their data source is of sufficient size to enable meaningful comparisons between different geographical areas with varying patterns of economy, religion, and culture. In addition, it permits the investigation of individual characteristics, such as socioeconomic status. The lack of such
Hum Nat (2008) 19:1–6
3
information in earlier studies left open the question of how far any of the observed correlations might have arisen in part from continuities in social status, which in turn automatically would have led to continuities in demographic behavior if persistent differences in behavior existed at the group level. Contrary to sociological theories of modernization, the conclusion reached by The Netherlands study was that the strength of family ties, as reflected by intergenerational continuities in age at marriage, were actually increasing rather than decreasing over time. This finding is consistent with the empirical conclusion of Murphy (1999) that the strength of the intergenerational fertility relationship has increased over the past few centuries. Since age at marriage is a key gatekeeper of achieved fertility (and reproductive fitness) in societies, the determinants of age at entry to marriage and hence childbearing are important factors in the differential transmission of fertility between generations (although for a fuller analysis of intergenerational transmission, it would also be necessary to assess the role of non-marriage—in other words, what was the relationship between the age of marriage of the parents and the propensity of their children to marry). The Netherlands study was also able to show that such changes cannot be accounted for by changing occupational or economic circumstances. In passing, it is appropriate to compare the position of current knowledge with that of two decades ago. Van Poppel and colleagues refer to a single study published before 1990 on intergenerational marriage patterns, that of Levine (1982), which was based on a data set one thousandth the size of their Dutch data set, confined to a single English village, and containing no controls for socioeconomic status. The main methods of analysis employed by Levine were those typical of the period— simple tabulation and product moment correlation coefficients. In contrast, van Poppel and colleagues utilized multilevel modeling (which was relatively uncommon around 1990 but is particularly appropriate for analyzing processes taking place within family units) with their rich and very large data source. This is not to say that the experience of nineteenth-century Netherlands was necessarily typical of all preindustrial Europe; indeed, van Poppel and colleagues clearly demonstrate considerable variability between the areas of Zeeland, Overrijssel, and Limburg within their relatively small country. Rather, it serves to demonstrate the rapid developments in recent decades in the ability to investigate historical processes. The study “Intergenerational Transmission of Reproductive Traits in Spain during the Demographic Transition” by David Reher, José Antonio Ortega, and Alberto Sanz-Gimeno covers a substantial period of the demographic transition, previously identified as important in studies such as Kohler et al. (1999) of Danish twins. Using data derived from Civil Registration for the town of Aranjuez, located some 50 km south of Madrid, Reher and colleagues were able to analyze the detailed dynamics of fertility change during this era, when fertility within marriage was in the process of coming under the control of conscious choice (Coale 1973). This was achieved by analyzing a range of indicators of the family-building process and intergenerational reproductive fitness, including the most relevant indicator, that of the number of surviving children. The study reinforced the common but by no means universal finding that the relationship between daughters and their parents is much stronger than that of sons and parents (it is difficult to separate the roles of mothers and fathers). The authors once again found that the strength of the relationship increased over the study period from 1871 to 1970, especially for the key variable of surviving
4
Hum Nat (2008) 19:1–6
children. By comparison with van Poppel and colleagues, there was little evidence of intergenerational continuities with respect to age at marriage, which was strong in The Netherlands and was itself a key determinant of future fertility levels in many European societies up to that time. However, they found that age at last birth, which has a strong volitional component, showed a particularly strong intergenerational relationship. The study by Reher and colleagues also served to supplement the sparser literature relating to the role of birth order effects (Sulloway 1996), where the evidence has been much less clear-cut than for overall fertility by showing that intergenerational effects were much stronger for first-born daughters. The other three papers in the collection are concerned with mortality and morbidity; in the case of morbidity, the extent to which achieved height is a proxy for health experiences in childhood that then extend into adulthood. As with many historical studies, the paper by George Alter and Michel Oris—“Effects of Inheritance and Environment on the Heights of Brothers in Nineteenth-Century Belgium”—uses an opportunistic data source based on military conscript records, with the heights of all males measured between the ages of 19 and 20 years. As was the case in the neighboring Netherlands, the availability of data from three different areas of the country—Verviers, Limbourg, and Sart, characterized by varying ecological and socioeconomic contexts—permitted the assessment of area-level as well as family-level factors. Although intergenerational associations are not discussed explicitly, the association is implicit insofar as correlations between brothers were expected to be associated with family-level variables. The paper does serve to emphasize the point that, in the nineteenth century, sections of Belgian society representative of rural and industrializing populations were subject to differing levels of vulnerability (under the assumption that smaller correlations between sibs reflected the existence of more substantial “environmental” insults). The final two papers investigate determinants of mortality using two of the bestknown data sets for such an analysis, the Utah Population Database (UPDB) and the BALSAC Population Register, both of which have been extensively employed to investigate intergenerational transmission mechanisms. The UPDB contains multigenerational information on more than 6 million individuals, including the genealogies of Utah founders and their descendants. For their study, “Are Girls Good and Boys Bad for Parental Longevity? The Effects of Sex Composition of Offspring on Parental Mortality Past Age 50,” Colette Harrell, Ken Smith, and Geraldine Mineau limit the analysis to data abstracted from the UPDB on mothers born between 1820 and 1900. Their findings add to the growing literature on the role of the sex composition of children on old-age survival, and in Utah some penalty was associated with sons, but with little variation across different sectors. For this reason a biological explanation for the findings was preferred—that there are greater pregnancy-related costs associated with male fetuses. But as noted by the authors, such effects are relatively small when, for example, compared with religious adherence. “Intergenerational and Genealogical Approaches for the Study of Longevity in the Saguenay-Lac-St-Jean Population” by Louis Houde, Marc Tremblay, and Hélène Vézina utilizes the considerable strengths of the Québec data base to identify very long-lived individuals and thus allow more effective concentration on a small segment of the population. The BALSAC database in Québec draws on the fact that
Hum Nat (2008) 19:1–6
5
the present French-speaking population of the province, which numbers approximately 6 million, is largely descended from some 10,000 people who emigrated from France between 1608 and 1760. As the subsequent rapid population growth was mostly due to natural increase, founder effect would be expected to play an important role in the composition of the present-day gene pool, with the amplification of rare genetic variants that either were present in the founders or arose through mutation in the following generations. For their study Houde and colleagues investigated individuals who had died at 90 years or older between 1950 and 1974 and matched them with controls who were born during the same time period (1850–1884) but died at 50–74 years. Mother’s mean age at death in particular was significantly higher in the cases than in the controls, and the positive effect of kinship was more pronounced in the oldest 10% of the subjects. However, this effect was explained by close kinship links rather than sharing of distant ancestors (>5 generations), which highlights the benefits of follow-up across extended time periods (Bittles and Egerbladh 2005). Collectively, these papers emphasize that possibilities now exist to examine intergenerational processes in detail using larger data sets which contain information on more than one generation. In addition to the sources included here, there are increasing numbers of data sources for a range of historical populations. Nonetheless, the existence of clear-cut positive relationships in a number of different historical populations is not in doubt.
References Beeton, M., & Pearson, K. (1901). On the inheritance of the duration of life, and on the intensity of natural selection in man. Biometrika, 1, 50–89. Bittles, A. H., & Egerbladh, I. (2005). The influence of past endogamy and consanguinity on genetic disorders in Northern Sweden. Annals of Human Genetics, 69, 549–558. Bowles, S., & Gintis, H. (2001). The inheritance of economic status: Education, class and genetics. In M. Feldman, & P. Baltes (Eds.) International encyclopedia of the social and behavioral sciences: Genetics, behavior and society (pp. 4132–4141). New York: Oxford University Press and Elsevier. Coale, A. (1973). The demographic transition. In International Population Conference, Liège 1973, vol. 1 (pp. 53–72). Liège: International Union for the Scientific Study of Population. d’Addio, A. C. (2007). Intergenerational transmission of disadvantage: Mobility or immobility across generations? OECD Social, Employment and Migration Working Papers No. 52. Paris: Organisation for Economic Co-operation and Development. Gavrilova, N. S., Gavrilov, L. A., Semyonova, V. G., & Evdokushkina, G. N. (2004). Does exceptional human longevity come with high cost of infertility? Testing the evolutionary theories of aging. Annals of the New York Academy of Sciences, 1019, 513–517. Kohler, H. P., Rodgers, J. L., & Christensen, K. (1999). Is fertility behavior in our genes? Findings from a Danish twin study. Population and Development Review, 25, 253–288. Levine, D. (1982). “For their own reasons”: Individual marriage decisions and family life. Journal of Family History, 17, 255–264. Murphy, M. (1999). Is the relationship between fertility of parents and children really weak? Social Biology, 46, 122–145. Murphy, M., & Wang, D. (2001). Family-level continuities in childbearing in low-fertility societies. European Journal of Population, 17, 75–96. Pearson, K., Lee, A., & Bramley-Moore, L. (1899). Mathematical contributions to the theory of evolution, VI. Genetic (reproductive) selection: Inheritance of fertility in man, and of fecundity in thoroughbred racehorses. Philosophical Transactions of the Royal Society of London, A192, 257–330.
6
Hum Nat (2008) 19:1–6
Sulloway, F. (1996). Born to rebel. London: Little Brown and Co. Westendorp, R. G. J., & Kirkwood, T. B. L. (1998). Human longevity at the cost of reproductive success. Nature, 396(6713), 743–746.
Alan Bittles is an adjunct professor of community genetics, Edith Cowan University, and adjunct professor in the Centre for Comparative Genomics, Murdoch University, both in Perth, Australia. Educated in Trinity College, University of Dublin, and Queen’s University, Belfast, he has held research fellowships in Cambridge; LaTrobe, Michigan; Peking; Stanford; Umeå; and Washington universities. He is a Fellow of the Institute of Biology, the Royal College of Pathologists, and the Royal Society of Medicine, and in 2007 was elected to Fellowship of the American Association for the Advancement of Science. His current research interests center on the genetic structure of human populations, in particular the impact of consanguineous marriage and endogamy on reproductive behavior and community health. He is a member of the Congenital Defects and Haemoglobinopathies expert groups of the Global Burden of Disease program, serves as Senior Editor of Annals of Human Genetics, and is a member of the Editorial Boards of the American Journal of Human Biology, Annals of Human Biology, Genomic Medicine, Journal of Biosocial Science, and Public Health Genomics.
Michael Murphy is a professor of demography at the London School of Economics and Political Science. He is a Fellow of the British Academy, Research Secretary of the Population Investigation Committee, and was President of the British Society for Population Studies until 2005. His main areas of research include family, kinship and household demography; aging; social and genetic mechanisms for the inheritance of behavior; mathematical and statistical demography; methods of making and evaluating population and household forecasts; the demography of developed and transitional societies. Recent publications include work on morality crises in Russia; models for mortality forecasting in elderly populations; kinship differentials; intergenerational transfers between parents and children; and modeling the longterm effects of assortative mating, feedback mechanisms, and kinship correlations on population size and structure.
David Reher is a professor in the Department of Sociology II (Human Ecology and Population) at the School of Political Science and Sociology of the Universidad Complutense de Madrid. A native of California, has degrees from Santa Clara University (1972), California State University, Northridge (1973), and the University of Madrid (Licenciatura [1978] and PhD [1983]). Professor Reher has held positions in Spanish and international scientific organizations, most notably chair of the Historical Demography Committee of the International Union for the Scientific Study of Population (IUSSP). He has been on the Editorial Board of the journals Continuity and Change (UK), Revista de Historia Economica (Spain), Statistica (Italy) and Historical Methods (USA). He heads a network of researchers from various institutions dedicated to the study of population issues (Grupo de Estudios Población y Sociedad—GEPS). He is author of numerous studies in the fields of population history, social and economic history, urban history and family history, reproductive health, as well as family sociology, and has published on Spanish, European and Latin American topics.
