Leptin Is Inversely Related to Age at Menarche in Human Females, Velimir Matkovic, Jasminka Z. Ilich, Mario Skugor, Nancy E. Badenhop, Prem Goel, Albert Clairmont, Dino Klisovic, Ramzi W. Nahhas and John D. Landoll
Over the last century there has been a trend toward an earlier onset of menarche attributed to better nutrition and body fatness. With the discovery of the obesity gene and its product, leptin, we reexamined this hypothesis from a new perspective. As delayed menarche and leanness are considered risk factors for osteoporosis, we also evaluated the relation between leptin and bone mass......
A critical blood leptin level is necessary to trigger reproductive ability in women, suggesting a threshold effect. Leptin is a mediator between adipose tissue and the gonads. Leptin may also mediate the effect of obesity on bone mass by influencing the periosteal envelope. This may have implications for the development of osteoporosis and osteoarthritis.
THE AGE AT which women develop menarche is an important factor in determining population size, breast cancer, and osteoporosis, all of which are of enormous present-day concern (1, 2, 3). Therefore, understanding all potential factors responsible for early menarche is of considerable interest. Over the last century there has been a trend toward earlier onset of puberty and menarche in affluent societies, attributed primarily to the improvement in nutritional status and general health of younger generations of women (4, 5). The onset of menarche was closely related with the achievement of a certain body weight (6) or percent body fat (7, 8). The only explanation given for this association was the influence of an unknown mediator on the hypothalamic-pituitary-gonadal axis.
With the recent discovery of the obesity gene (ob) and its product, leptin (11), it is possible to reexamine the relationship between body fatness and the timing of menarche from a new perspective. In support of this are recent discoveries in ob/ob mice treated with leptin showing signs of early onset of ovarian maturation and reproductive function (12, 13, 14). Similar data for humans do not exist.
According to our knowledge this is the first study to examine longitudinally the influence of body fatness and serum leptin on the timing of menarche in human females. In addition, this is the first study to evaluate, either cross-sectionally or longitudinally, the relationship between leptin and body fat in children. Serum leptin is strongly associated with body fat and indexes of body fatness (percent body fat and BMI) as well as with the change in body fat over time. As leptin is encoded by the ob gene and produced only in the fat cells, its serum concentration indirectly reflects body fat stores (11, 20). The above data are in agreement with the results obtained in a small group of teenage females who participated in a diurnal variation study of leptin (21) and also with the data obtained in adults (22)
It is anticipated, therefore, that leptin deficiency is a primary reason for delayed puberty and menarche in individuals and in populations accustomed to absolute or relative dietary energy deficiency. In menstruating women, a negative energy balance caused by either fasting and/or exercise could cause secondary amenorrhea (24, 25, 26), presumably due to low levels of circulating leptin. Low serum leptin levels were found in young amenorrheic athletes (27) and in women suffering from anorexia nervosa (28). A decrease in the serum leptin concentration was documented in older women in response to exercise.
Tuesday, May 30, 2006
Prenatal undernutrition, postnatal environments
Prenatal undernutrition, postnatal environments, and antibody response to vaccination in adolescence, Thomas W McDade, Melinda A Beck, Christopher Kuzawa, and Linda S Adair
ABSTRACT
Background: Recently, researchers have considered the fetal and infant origins of several adult cardiovascular and metabolic diseases, but the implications of early events for immune function and infectious disease are unclear.
Objective: We investigated the association between prenatal undernutrition and immunocompetence in adolescence and hypothesized that intrauterine growth retardation is associated with a lower likelihood of mounting an adequate antibody response later in life.
Design: A subsample of one hundred three 14–15-y-olds was recruited from an ongoing longitudinal study in which data collection began while participants were in utero. A typhoid vaccine was given, and anti-typhoid antibodies were measured 2 wk and 3 mo later as a functional marker of immunocompetence. The likelihood of mounting an adequate antibody response was compared for adolescents who were small for gestational age or appropriate for gestational age at birth while controlling for a
range of postnatal exposures.
Results: The predicted probability of mounting a positive antibody response for adolescents who were prenatally and currently undernourished was 0.32, compared with probabilities of 0.49–0.70 for adequately nourished adolescents (P = 0.023). Diarrhea in the first year of life (P = 0.009) and fast weight gain during the first 6 mo (P = 0.003) were also associated with a higher probability of response.
Conclusions: These findings extend the concept of fetal and early infant programming of adult diseases to the immune system and suggest that early environments may have long-term implications for immunocompetence and infectious disease risk, particularly in developing countries. Am J Clin Nutr 2001;74:543–8.
ABSTRACT
Background: Recently, researchers have considered the fetal and infant origins of several adult cardiovascular and metabolic diseases, but the implications of early events for immune function and infectious disease are unclear.
Objective: We investigated the association between prenatal undernutrition and immunocompetence in adolescence and hypothesized that intrauterine growth retardation is associated with a lower likelihood of mounting an adequate antibody response later in life.
Design: A subsample of one hundred three 14–15-y-olds was recruited from an ongoing longitudinal study in which data collection began while participants were in utero. A typhoid vaccine was given, and anti-typhoid antibodies were measured 2 wk and 3 mo later as a functional marker of immunocompetence. The likelihood of mounting an adequate antibody response was compared for adolescents who were small for gestational age or appropriate for gestational age at birth while controlling for a
range of postnatal exposures.
Results: The predicted probability of mounting a positive antibody response for adolescents who were prenatally and currently undernourished was 0.32, compared with probabilities of 0.49–0.70 for adequately nourished adolescents (P = 0.023). Diarrhea in the first year of life (P = 0.009) and fast weight gain during the first 6 mo (P = 0.003) were also associated with a higher probability of response.
Conclusions: These findings extend the concept of fetal and early infant programming of adult diseases to the immune system and suggest that early environments may have long-term implications for immunocompetence and infectious disease risk, particularly in developing countries. Am J Clin Nutr 2001;74:543–8.
Early Origins of Immune Function
Life History, Maintenance, and the Early Origins of Immune Function, THOMAS W. MCDADE
ABSTRACT There is compelling evidence to suggest that early environments are important determinants of immune function over the life course. While current research focuses on proximate mechanisms and clinical implications, an adaptationist perspective may contribute a theoretical basis for explaining, rather than merely describing, the long-term impact of early environments. Life history theory in particular, with its emphasis on the life cycle and investment in maintenance effort—of which immune function is a central component—provides a predictive framework for identifying prenatal and early postnatal factors that are likely to shape immunity. Key life history issues at these stages include avoiding death from infectious disease, investing in immune defenses that are appropriate for the local disease ecology, and optimizing competing demands for investment in immune function and growth. A series of hypotheses derived from these issues are proposed and evaluated with data from ongoing research in the Philippines and Bolivia. Ecologically-informed research on immunity is in its earliest stages, and life history theory has the potential to make important contributions to our understanding of the development and function of this critical physiological system.
ABSTRACT There is compelling evidence to suggest that early environments are important determinants of immune function over the life course. While current research focuses on proximate mechanisms and clinical implications, an adaptationist perspective may contribute a theoretical basis for explaining, rather than merely describing, the long-term impact of early environments. Life history theory in particular, with its emphasis on the life cycle and investment in maintenance effort—of which immune function is a central component—provides a predictive framework for identifying prenatal and early postnatal factors that are likely to shape immunity. Key life history issues at these stages include avoiding death from infectious disease, investing in immune defenses that are appropriate for the local disease ecology, and optimizing competing demands for investment in immune function and growth. A series of hypotheses derived from these issues are proposed and evaluated with data from ongoing research in the Philippines and Bolivia. Ecologically-informed research on immunity is in its earliest stages, and life history theory has the potential to make important contributions to our understanding of the development and function of this critical physiological system.
Predictors of C-Reactive Protein
Predictors of C-Reactive Protein in Tsimane’ 2 to 15 Year-Olds in Lowland Bolivia
ABSTRACT Infectious disease is a major global determinant of child morbidity and mortality, and energetic investment in immune defenses (even in the absence of overt disease) is an important life-history variable, with implications for human growth and development.
This study uses a biomarker of immune activation (C-reactive protein) to investigate an important aspect of child health among the Tsimane’, a relatively isolated
Amerindian population in lowland Bolivia. Our objectives are twofold: 1) to describe the distribution of CRP by age and gender in a cross-sectional sample of 536
2–15-year-olds; and 2) to explore multiple measures of pathogen exposure, economic resources, and acculturation as predictors of increased CRP. The median bloodspot
CRP concentration was 0.73 mg/l, with 12.9% of the sample having concentrations greater than 5 mg/L, indicating a relatively high degree of immune activation in
this population. Age was the strongest predictor of CRP, with the highest concentrations found among younger individuals. Increased CRP was also associated with higher pathogen exposure, lower household economic resources, and increased maternal education and literacy.
The measurement of CRP offers a direct, objective indicator of immune activation, and provides insights into a potentially important pathway through which environmental quality may shape child growth and health. Am J Phys Anthropol 127:000–000, 2005.
ABSTRACT Infectious disease is a major global determinant of child morbidity and mortality, and energetic investment in immune defenses (even in the absence of overt disease) is an important life-history variable, with implications for human growth and development.
This study uses a biomarker of immune activation (C-reactive protein) to investigate an important aspect of child health among the Tsimane’, a relatively isolated
Amerindian population in lowland Bolivia. Our objectives are twofold: 1) to describe the distribution of CRP by age and gender in a cross-sectional sample of 536
2–15-year-olds; and 2) to explore multiple measures of pathogen exposure, economic resources, and acculturation as predictors of increased CRP. The median bloodspot
CRP concentration was 0.73 mg/l, with 12.9% of the sample having concentrations greater than 5 mg/L, indicating a relatively high degree of immune activation in
this population. Age was the strongest predictor of CRP, with the highest concentrations found among younger individuals. Increased CRP was also associated with higher pathogen exposure, lower household economic resources, and increased maternal education and literacy.
The measurement of CRP offers a direct, objective indicator of immune activation, and provides insights into a potentially important pathway through which environmental quality may shape child growth and health. Am J Phys Anthropol 127:000–000, 2005.
The Ecologies of Human Immune Function
The Ecologies of Human Immune Function Thomas W. McDade
Abstract
Immune function is notoriously complex, and current biomedical research elaborates this complexity by focusing on the cellular and molecular mechanisms that characterize immune defenses. However, the human immune system is a product of natural selection that develops and functions in whole organisms that are integral parts of their surrounding environments. A population-level, cross-cultural, adaptationist perspective is therefore a necessary complement to the micro levels of analysis currently favored by biomedical immunology.
Prior field-based research on human immunity is reviewed to demonstrate the relevance of cultural ecological factors, with an emphasis on the ecologies of nutrition, infectious disease, reproduction, and psychosocial stress. Common themes and anthropological contributions are identified in an attempt to promote future research in human ecological immunology that integrates theory and method for a more contextualized understanding of this important physiological system.
Abstract
Immune function is notoriously complex, and current biomedical research elaborates this complexity by focusing on the cellular and molecular mechanisms that characterize immune defenses. However, the human immune system is a product of natural selection that develops and functions in whole organisms that are integral parts of their surrounding environments. A population-level, cross-cultural, adaptationist perspective is therefore a necessary complement to the micro levels of analysis currently favored by biomedical immunology.
Prior field-based research on human immunity is reviewed to demonstrate the relevance of cultural ecological factors, with an emphasis on the ecologies of nutrition, infectious disease, reproduction, and psychosocial stress. Common themes and anthropological contributions are identified in an attempt to promote future research in human ecological immunology that integrates theory and method for a more contextualized understanding of this important physiological system.
Life History Theory and the Immune System
Ok, after a short, unavoidable, absence I am now back at work. Kaplan argues that the two most energy intense components of the human body are the brain and the immune system. This paper addresses some of the implications of immune system demands in the presence of nutritional constraints:
Life History Theory and the Immune System: Steps Toward a Human Ecological Immunology
Thomas W. MCDade
ABSTRACT Within anthropology and human biology, there is growing interest in immune function and its importance to the ecology of human health and development. Biomedical research currently dominates our understanding of immunology, and this paper seeks to highlight the potential contribution of a population-based, ecological
approach to the study of human immune function. Concepts from life-history theory are applied to highlight the major challenges and demands that are likely to shape
immune function in a range of ecological contexts. Immune function is a major component of maintenance effort, and since resources are limited, trade-offs are expected between investment in maintenance and other critical life-history functions involving growth and reproduction.
An adaptationist, life-history perspective helps make sense of the unusual developmental trajectory of immune tissues, and emphasizes that this complex system is designed to incorporate information from the surrounding ecology to guide its development. As a result, there is substantial population variation in immune development and function that is not considered by current biomedical approaches. In an attempt to construct a framework for understanding this variation, immune development is considered in relation to the competing life-history demands
that define gestation, infancy, childhood, adolescence, and adulthood. Each life stage poses a unique set of adaptive challenges, and a series of hypotheses is proposed
regarding their implications for immune development and function. Research in human ecological immunology is in its earliest stages, but this is a promising area
of exploration, and one in which anthropology is wellpositioned to make important contributions. Yrbk Phys Anthropol 46:100–125, 2003. © 2003 Wiley-Liss, Inc.
Life History Theory and the Immune System: Steps Toward a Human Ecological Immunology
Thomas W. MCDade
ABSTRACT Within anthropology and human biology, there is growing interest in immune function and its importance to the ecology of human health and development. Biomedical research currently dominates our understanding of immunology, and this paper seeks to highlight the potential contribution of a population-based, ecological
approach to the study of human immune function. Concepts from life-history theory are applied to highlight the major challenges and demands that are likely to shape
immune function in a range of ecological contexts. Immune function is a major component of maintenance effort, and since resources are limited, trade-offs are expected between investment in maintenance and other critical life-history functions involving growth and reproduction.
An adaptationist, life-history perspective helps make sense of the unusual developmental trajectory of immune tissues, and emphasizes that this complex system is designed to incorporate information from the surrounding ecology to guide its development. As a result, there is substantial population variation in immune development and function that is not considered by current biomedical approaches. In an attempt to construct a framework for understanding this variation, immune development is considered in relation to the competing life-history demands
that define gestation, infancy, childhood, adolescence, and adulthood. Each life stage poses a unique set of adaptive challenges, and a series of hypotheses is proposed
regarding their implications for immune development and function. Research in human ecological immunology is in its earliest stages, but this is a promising area
of exploration, and one in which anthropology is wellpositioned to make important contributions. Yrbk Phys Anthropol 46:100–125, 2003. © 2003 Wiley-Liss, Inc.
Monday, May 15, 2006
'Natural' Fertility
Between natural fertility and intentional control: evidence from the African Demographic and Health Surveys, Jennifer Johnson-Hanks
This article examines patterns of marital fertility in age and time (AFMFR and AIBI by parity) from 18 African Demographic and Health Surveys, and compares them to the patterns found in North America and Europe in the seventeenth through nineteenth centuries. On the basis of such birth spacing and timing data, demographers have long made inferences about reproductive intentions and reproductive behavior (e.g. Coale 1973, 1986; Knodel 1977, 1987). In the DHS data, however, we have information about both intentions and reproductive practice on the one hand, and birth spacing and timing on the other. Thus, it is possible to compare inferences about intentional states from population rates to selfreported intentional states themselves. The article demonstrates that the shape of age-specific marital fertility rates and the patterns of interbirth intervals among women in 18 African countries who assert that they have no intention to limit fertility and have never used contraception differ quite substantially from that of 19th century Europe and North America. On the basis of this and related data, the article argues against the widely assumed indexical relationship between specific population-level reproductive patterns and individual intentions. As the social organization of reproduction in contemporary Africa differs fundamentally from that of historical Europe, the quantitative methods
developed in that context are inapplicable to Africa.
This article examines patterns of marital fertility in age and time (AFMFR and AIBI by parity) from 18 African Demographic and Health Surveys, and compares them to the patterns found in North America and Europe in the seventeenth through nineteenth centuries. On the basis of such birth spacing and timing data, demographers have long made inferences about reproductive intentions and reproductive behavior (e.g. Coale 1973, 1986; Knodel 1977, 1987). In the DHS data, however, we have information about both intentions and reproductive practice on the one hand, and birth spacing and timing on the other. Thus, it is possible to compare inferences about intentional states from population rates to selfreported intentional states themselves. The article demonstrates that the shape of age-specific marital fertility rates and the patterns of interbirth intervals among women in 18 African countries who assert that they have no intention to limit fertility and have never used contraception differ quite substantially from that of 19th century Europe and North America. On the basis of this and related data, the article argues against the widely assumed indexical relationship between specific population-level reproductive patterns and individual intentions. As the social organization of reproduction in contemporary Africa differs fundamentally from that of historical Europe, the quantitative methods
developed in that context are inapplicable to Africa.
Department of Wow
I have obviously been reading too much evolutionary biology lately. Reading through this very interesting paper by John Hobcraft I came across this intriguing paragraph:
Our emotions play an important part in any long-term relationship. A ‘good’ partnership can successfully meet many of our basic needs for sex, for nurture, and for intimacy (Panksepp, 1998). On the other hand intimate partnerships are too often associated with emotions of fear, disgust, or anger (Fiske 2004). Demographers need to engage with neuroscience and gain a better understanding of the role of emotions in relationships (see also Massey 2002). Moreover, we need to pay attention to some emergent suggestions that pair-bonding and love generate lasting changes in brain structure (Young 2003). In other words, the key importance of feedback loops in relationship formation and breakdown need to be included in our consideration.
"emergent suggestions that pair-bonding and love generate lasting changes in brain structure" hmmm, I thought. So I dug out the reference and went looking for Young:
Young, L.J. 2003. The neural basis of pair bonding in a monogamous species: a model for understanding the biological basis of human behavior, in K.W. Wachter and R.A. Bulatao (eds.) Offspring: Human Fertility Behavior in Biodemographic Perspective. Washington D.C.: National Academy Press.
where I found:
Studies of voles have produced an exciting hypothesis that suggests pair bond formation is regulated by the same brain regions involved in the actions of drugs of abuse. These so-called reward circuits are regions of the brain that regulate feelings of pleasure and reward. These regions are activated by a neurotransmitter called dopamine, which is increased in the brain after taking cocaine and amphetamines. Those experiencing love of-ten report feelings of euphoria when intimate with their partners, and these feelings are often reported as being similar to being “high.” There is some scientific evidence that these reward circuits may in fact be involved in the psychobiology of love. One study examined brain activation in people while viewing photographs of someone to whom the subject reported being deeply in love. Brain activity was also determined while these same subjects viewed photographs of other familiar individuals. The authors reported that viewing photographs of their lovers elicited brain activation that was remarkably similar to that seen in other studies after drug consumption (Bartels and Zeki, 2000). This suggests that perhaps similar neural circuits are used to facilitate pair bonding in voles and humans. Perhaps the saying “love is an addiction” has biological support.
The biological basis of the pair bond in humans may change with time. In the early years of a relationship, love is experienced as an incredibly intense sensation that often drives the behavior of the individual. People experience a euphoria that may be similar to that experienced by drugs of addiction, and this experience undoubtedly has a specific neurochemistry underlying it. The individuals in these relationships are consumed by thoughts of being with their partner, often at the expense of other relationships. However, often in later years of a marriage, the nature of this bond changes and becomes less visceral and more a relationship of codependence. Perhaps for our primitive ancestors, the transition between these two types of love, which would occur after the offspring of the relationship are less dependent on the mother, would mark the dissolution of the relationship.
Hmmm, hmmmm
Our emotions play an important part in any long-term relationship. A ‘good’ partnership can successfully meet many of our basic needs for sex, for nurture, and for intimacy (Panksepp, 1998). On the other hand intimate partnerships are too often associated with emotions of fear, disgust, or anger (Fiske 2004). Demographers need to engage with neuroscience and gain a better understanding of the role of emotions in relationships (see also Massey 2002). Moreover, we need to pay attention to some emergent suggestions that pair-bonding and love generate lasting changes in brain structure (Young 2003). In other words, the key importance of feedback loops in relationship formation and breakdown need to be included in our consideration.
"emergent suggestions that pair-bonding and love generate lasting changes in brain structure" hmmm, I thought. So I dug out the reference and went looking for Young:
Young, L.J. 2003. The neural basis of pair bonding in a monogamous species: a model for understanding the biological basis of human behavior, in K.W. Wachter and R.A. Bulatao (eds.) Offspring: Human Fertility Behavior in Biodemographic Perspective. Washington D.C.: National Academy Press.
where I found:
Studies of voles have produced an exciting hypothesis that suggests pair bond formation is regulated by the same brain regions involved in the actions of drugs of abuse. These so-called reward circuits are regions of the brain that regulate feelings of pleasure and reward. These regions are activated by a neurotransmitter called dopamine, which is increased in the brain after taking cocaine and amphetamines. Those experiencing love of-ten report feelings of euphoria when intimate with their partners, and these feelings are often reported as being similar to being “high.” There is some scientific evidence that these reward circuits may in fact be involved in the psychobiology of love. One study examined brain activation in people while viewing photographs of someone to whom the subject reported being deeply in love. Brain activity was also determined while these same subjects viewed photographs of other familiar individuals. The authors reported that viewing photographs of their lovers elicited brain activation that was remarkably similar to that seen in other studies after drug consumption (Bartels and Zeki, 2000). This suggests that perhaps similar neural circuits are used to facilitate pair bonding in voles and humans. Perhaps the saying “love is an addiction” has biological support.
The biological basis of the pair bond in humans may change with time. In the early years of a relationship, love is experienced as an incredibly intense sensation that often drives the behavior of the individual. People experience a euphoria that may be similar to that experienced by drugs of addiction, and this experience undoubtedly has a specific neurochemistry underlying it. The individuals in these relationships are consumed by thoughts of being with their partner, often at the expense of other relationships. However, often in later years of a marriage, the nature of this bond changes and becomes less visceral and more a relationship of codependence. Perhaps for our primitive ancestors, the transition between these two types of love, which would occur after the offspring of the relationship are less dependent on the mother, would mark the dissolution of the relationship.
Hmmm, hmmmm
Sunday, May 14, 2006
Russian Mortality
Autopsy on an Empire: Understanding Mortality in Russia and the Former Soviet Union, Elizabeth Brainerd, David M. Cutler
"Male life expectancy at birth fell by over six years in Russia between 1989 and 1994. Many other countries of the former Soviet Union saw similar declines, and female life
expectancy fell as well. Using cross-country and Russian household survey data, we assess six possible explanations for this upsurge in mortality. Most find little support in the data: the deterioration of the health care system, changes in diet and obesity, and material deprivation fail to explain the increase in mortality rates. The two factors that do appear to be important are alcohol consumption, especially as it relates to external causes of death (homicide, suicide, and accidents) and stress associated with a poor outlook for the future. However, a large residual remains to be explained."
"Male life expectancy at birth fell by over six years in Russia between 1989 and 1994. Many other countries of the former Soviet Union saw similar declines, and female life
expectancy fell as well. Using cross-country and Russian household survey data, we assess six possible explanations for this upsurge in mortality. Most find little support in the data: the deterioration of the health care system, changes in diet and obesity, and material deprivation fail to explain the increase in mortality rates. The two factors that do appear to be important are alcohol consumption, especially as it relates to external causes of death (homicide, suicide, and accidents) and stress associated with a poor outlook for the future. However, a large residual remains to be explained."
Modernisation and the Demographic Transition
Economic Development, Formation of Human Capital and the Demographic Transition: Southern Sweden 1750 – 1900. Tommy Bengtsson & Patrick Svensson.
Modernisation caused a demographic transition from high mortality to low mortality and, later from high fertility, to low fertility. Short-term variations in mortality and fertility meanwhile diminished. The delay in the fertility decline was due to the fact that the social norms influencing fertility only change slowly. This is the way the theory of the demographic transition was formulated in the 1950s by Davis and Notestein. For some time, it was considered as a cornerstone of social science but was later questioned both from theoretical and empirical points of view. Still the concept ‘demographic transition’ is widely used to describe the change from high to low rates of mortality and fertility.
Bengtsson and Ohlsson (1994), in their reformation of the theory, argue that while the causal mechanisms are correct, the dating of the theory is wrong. They argue that the start of the mortality decline did not mark the beginning of the demographic transition. The initial decline, which shows great similarity throughout Europe despite various stages of economic development, was instead spontaneous (Fridlizius 1984, Perrenoud 1984, Schofield 1984) and similar changes have taken place many times in the past. But instead of a rebound to high mortality, which had been the pattern of the past, mortality continued to decline. This marks the start of the demographic transition and this was the result of modernisation. In this way redefining the time for the onset of the demographic transition, to the mid-nineteenth century or shortly before, the lag between modernisation and the fertility decline is also narrowed down to a couple of decades and supersedes the assumption of slowly changing social norms in regulating family size.
Modernisation caused a demographic transition from high mortality to low mortality and, later from high fertility, to low fertility. Short-term variations in mortality and fertility meanwhile diminished. The delay in the fertility decline was due to the fact that the social norms influencing fertility only change slowly. This is the way the theory of the demographic transition was formulated in the 1950s by Davis and Notestein. For some time, it was considered as a cornerstone of social science but was later questioned both from theoretical and empirical points of view. Still the concept ‘demographic transition’ is widely used to describe the change from high to low rates of mortality and fertility.
Bengtsson and Ohlsson (1994), in their reformation of the theory, argue that while the causal mechanisms are correct, the dating of the theory is wrong. They argue that the start of the mortality decline did not mark the beginning of the demographic transition. The initial decline, which shows great similarity throughout Europe despite various stages of economic development, was instead spontaneous (Fridlizius 1984, Perrenoud 1984, Schofield 1984) and similar changes have taken place many times in the past. But instead of a rebound to high mortality, which had been the pattern of the past, mortality continued to decline. This marks the start of the demographic transition and this was the result of modernisation. In this way redefining the time for the onset of the demographic transition, to the mid-nineteenth century or shortly before, the lag between modernisation and the fertility decline is also narrowed down to a couple of decades and supersedes the assumption of slowly changing social norms in regulating family size.
Saturday, May 13, 2006
Monique Borgerhoff Mulder
I'd forgotten about Monique. You can find a lot of very useful material on her website, here.
Maimonides For The Hard of Hearing
Controversies in the evolutionary social sciences: a guide for the perplexed. Eric A. Smith, Monique Borgerhoff Mulder and Kim Hill.
It is 25 years since modern evolutionary ideas were first applied extensively to human behavior, jump-starting a field of study once known as ‘sociobiology’. Over the years, distinct styles of evolutionary analysis have emerged within the social sciences. Although there is considerable complementarity between approaches that emphasize the study of psychological mechanisms and those that focus on adaptive fit to environments, there are also substantial theoretical and methodological differences. These differences have generated a recurrent debate that is now exacerbated by growing popular media attention to evolutionary human behavioral studies. Here,we provide a guide to current controversies surrounding evolutionary studies of human social behavior, emphasizing theoretical and methodological issues.We conclude that a greater use of formal models, measures of current fitness costs and benefits, and attention to adaptive tradeoffs, will enhance the power and reliability of evolutionary analyses of human social behavior.
It is 25 years since modern evolutionary ideas were first applied extensively to human behavior, jump-starting a field of study once known as ‘sociobiology’. Over the years, distinct styles of evolutionary analysis have emerged within the social sciences. Although there is considerable complementarity between approaches that emphasize the study of psychological mechanisms and those that focus on adaptive fit to environments, there are also substantial theoretical and methodological differences. These differences have generated a recurrent debate that is now exacerbated by growing popular media attention to evolutionary human behavioral studies. Here,we provide a guide to current controversies surrounding evolutionary studies of human social behavior, emphasizing theoretical and methodological issues.We conclude that a greater use of formal models, measures of current fitness costs and benefits, and attention to adaptive tradeoffs, will enhance the power and reliability of evolutionary analyses of human social behavior.
Friday, May 12, 2006
A Short Story
Is short height really a risk factor for coronary heart disease and stroke mortality? A review, Thomas T. Samaras, Harold Elrick, Lowell H. Storms, Med Sci Monit, 2004; 10(4): RA63-76.
For the past 30 years, Thomas T. Samaras and his associates Dr. Elrick and Dr. Storms have published 16 papers in scientific and medical journals on the positive aspects of shorter height and smaller body size. Mr. Samaras is the Director and Senior Researcher at Reventropy Associates in San Diego, California. These have included papers in the Bulletin of the World Health Organization, Journal of the National Medical Association, Life Sciences, Western Journal of Medicine, Journal of the Washington Academy of Sciences, Acta Pediatrica and Ageing Research Reviews. This page presents a summary of their findings.
For the past 30 years, Thomas T. Samaras and his associates Dr. Elrick and Dr. Storms have published 16 papers in scientific and medical journals on the positive aspects of shorter height and smaller body size. Mr. Samaras is the Director and Senior Researcher at Reventropy Associates in San Diego, California. These have included papers in the Bulletin of the World Health Organization, Journal of the National Medical Association, Life Sciences, Western Journal of Medicine, Journal of the Washington Academy of Sciences, Acta Pediatrica and Ageing Research Reviews. This page presents a summary of their findings.
Thursday, May 04, 2006
Histology
FUNCTION
The primary function of the female reproductive system is reproduction, which includes
* the production of ova
* the transportation of ova from the ovary to the site of fertilization
* transportation of spermatozoa from the point of deposition in the female tract to the site of fertilization
* nourishment of the developing embryo and fetus
* parturition and nourishment of the infant.
continue reading
The primary function of the female reproductive system is reproduction, which includes
* the production of ova
* the transportation of ova from the ovary to the site of fertilization
* transportation of spermatozoa from the point of deposition in the female tract to the site of fertilization
* nourishment of the developing embryo and fetus
* parturition and nourishment of the infant.
continue reading
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