Son preference in Bangladesh: an emerging barrier to fertility regulation

This study investigates the effect of son preference on contraceptive use and desire for additional children using national level survey data from Bangladesh for the years 1969 and 1979. National probability samples of ever married women between the ages of 10 and 50 were selected and stratified by urban-rural residence. Specifically, the study focuses on contraceptive use and desire for additional children and separates the effect of sex preference from that of high parity on fertility control. Son preference has a negative effect on contraceptive use and a positive effect on the desire for additional children regardless of socioeconomic and demographic characteristics. This advese effect of son preference on fertility regulation seemed to have persisted over the years. Relevent socioeconomic conditions in Bangladesh are described. In 1979, the effect of sex composition on contraceptive use or desire for additional children varied by parity. The negative effect of fewer living sons on contraceptive use and its positive effect on desire for additional children was higher in parities between 2 and 4 than in other parities. The effect of sex composition was stronger on desire for additional children than on contraceptive usage. In 1969, however, there was no consistent positive relationship between sex composition and contraceptive use. The relationship between sex composition and desire for more children was positive. Among women of parities 2 to 4, an excess of daughters continued to have a major positive effect on desire for additional children, and a negative effect on contraceptive use, after controlling for other sociodemographic variables. For parities 1 and 5 or above, the effect was either weak or inconsistent.     

Son preference and fertility in China

This paper examines the effect of son preference on the hazards of having a second and a third birth. With data from the Two-per-thousand National Sample Survey on Fertility and Contraception conducted in 1988 by the State Family Planning Commission of China, the hazard of having a second birth among 62+ thousand married women who have had a first birth, and the hazard of having a third birth among 43+ thousand married women who have had two births was examined. These two hazards (i.e. the hazard of moving from the first to the second birth, and the hazard of moving from the second to the third birth) were analysed by estimating Cox proportional hazard models. The major covariate in the first analysis is whether or not the first-born was a daughter. In the second analysis the main covariate is whether both of the first two children were girls. In both models seven covariates known to have independent effects on the transition to a second (or third) birth are controlled for, namely, whether the woman is a Han, whether she is a farmer, her age at the birth of the first (or second) child, whether she had her first (or second) birth prior to the initiation in 1979 of the one-child policy, and three dummy variables reflecting her level of education. The results show the important influence of son preference on the hazard of having another birth.     

A test of the child replacement hypothesis: nineteenth century Massachusetts

Child mortality experiences may affect subsequent fertility of couples by exerting a physiological effect, influencing length of birth, interval, or a replacement effect, in which couples continue to procreate in an attempt to reach a desired number of surviving offspring. Where biological constraints are potentially important, however, it may be difficult to distinguish between purely physiological and purely behavioral components of the process regulating production. Natural spacing of births and onset of sterility may be affected by health and diet and prior childbearing and breastfeeding practices. Biological pressures can, in turn, be infuenced behaviorally both by social custom and individual choice. Studies of 126 families in 19th century Massachusetts show that reduction in infant mortality is not a prerequisite for onset of family limitation. Results for the study population did not exhibit a relationship between parity progression ratios and the experience of child mortality, consisten with the child replacement hypothesis. 1 factor involved may be the parent's expectations of more than the desired number of children because of imperfect contraceptive technology at the time. Preference for the sex of children also may weaken overall replacement effect, since the death of a child of "undesired" sex will not be replaced. The cohort age-specific fertility patterns indicate that a reduction in overall fertility level in the communities studied was parity-dependent and directed at stopping childbearing at some given range of family size. At any rate, parents are not passive participants in a natural regime of births and deaths. While child replacement may be present in some societies, it is relatively inefficient and perhaps infrequent.     

Son preference and the sex ratio at birth in China: A provincial level analysis

Abstract

Data from a Samoan menstruation study suggest that lactation, even intensive on‐demand lactation, does not inhibit menstruation or conception. This paper explores the applied and theoretical implications of continuing to accept lactation as a universally effective fertility control mechanism. Such thinking can have disastrous implications for family planning programs, and it keeps us from challenging long‐held assumptions about lactation's role in population growth in early populations.     

A critical look at the embodied cognition hypothesis and a new proposal for grounding conceptual content.

Many studies have demonstrated that the sensory and motor systems are activated during conceptual processing. Such results have been interpreted as indicating that concepts, and important aspects of cognition more broadly, are embodied. That conclusion does not follow from the empirical evidence. The reason why is that the empirical evidence can equally be accommodated by a 'disembodied' view of conceptual representation that makes explicit assumptions about spreading activation between the conceptual and sensory and motor systems. At the same time, the strong form of the embodied cognition hypothesis is at variance with currently available neuropsychological evidence. We suggest a middle ground between the embodied and disembodied cognition hypotheses--grounding by interaction. This hypothesis combines the view that concepts are, at some level, 'abstract' and 'symbolic', with the idea that sensory and motor information may 'instantiate' online conceptual processing.     

A second look at the second messenger hypothesis

Several hundred hormones, neurotransmitters, growth factors and other "first messengers" bind to specific cell membrane receptors and induce a myriad of effects: short term, transport, metabolic, mitotic and regulation of thousands of specific genes. Yet, less than a dozen "second messengers" have been clearly established to date. Even allowing for the discovery of a large number of additional second messengers, there remains a paradox in terms of information-transfer within the cell: how can so many specific signals produce so many effects through so few relatively nonspecific intermediates? We consider several possible solutions to this paradox, including the hypothesis that signal specificity is encoded in part in the primary structure of the receptor.     

Effect of child survival on contraceptive use in Bangladesh.

A study in Bangladesh showed that couples who lost a child often stopped practising contraception in order to have another child. Logistic regression analysis revealed that contraceptive continuation was related to maternal age, parity, husband's education and the sex of the last child.     

Fireflies at one hundred plus: a new look at flash control

The mysterious process by which fireflies can control theirflashing has inspired over a century of careful observationbut has remained elusive. Many studies have implicated oxygenas the controlling element in the photochemical reaction, andthe discovery of nitric oxide synthetase (NOS) in the lanternhas suggested that nitric oxide (NO) may control oxygen accessto the light-emitting photocytes, thereby triggering the flash.However, there are several drawbacks to oxygen as a controllingagent, and in view of the prominence of peroxisomes in lanternmorphology and biochemistry, we suggest that it is hydrogenperoxide that triggers the flash, and we present a model bywhich this may take place.     

Pods and Nods: a new look at symbiotic nitrogen fixing bacteria

How can growing a crop plant make a field more fertile? With legumes, this is precisely what happens. Working in partnership with symbiotic bacteria that can create root nodules on their chosen host, legumes can fix atmospheric nitrogen and enhance the nitrogen status of soils. How does this symbiosis develop? And how did it evolve? Bacterial and plant genomics are beginning to provide the answers.     

Cladoendesis and a new look at the evolution of insect metamorphosis

Cladoendesis is a method of phylogeny analysis opposed to various matrix methods. In contrast to matrix methods, in cladoendesis phylogenetic trees are not built each time as new ones, but are reconstructed based on the previous results. Each character of each taxon is compared with its ancestral condition in the ground-plan of the higher taxon. The revealed part of the phylogeny is represented in a form of hierarchical classification. In addition to the principles of natural classification elaborated by C. Linnaeus, P.-A. Latreille, and others, evolutionary theory elaborated by Ch. Darwin and others, and principles of phylogenetic systematics elaborated by W. Hennig and others, cladoendesis includes rank-free dual nomenclature system (DualNom) and advanced method of text layout elaborated by the author. Important components of cladoendesis are the use of the term “plesiomorphon” and taking into account such important evolutionary events as conservation and deconservation of characters. Cladoendesis allowed the author to make comprehensive revision of the phylogeny of Ephemeroptera, find homology in the structure of the maxillae of adult Aphaniptera, larval maxillae of Neuropteroidea-Birostrata, larval legs of Nannomecoptera, and genital parts of some insect taxa. It also allows understanding the nature and evolution of insect metamorphosis. It is generally believed that initially insect ontogenesis proceeds the shortest way, while such phenomena as substitutions of organs by means of their atrophy and subsequent restoring are secondary. In contrast to this, the flagellum of the antenna of Amyocerata initially grows by addition of proximal segments and simultaneous loss of distal ones; in many taxa, including Metabola (insects with complete metamorphosis), distal segments are not aborted. Some authors tried to explain the origin of complete metamorphosis by various reasons: ecological, morphogenetic, or others. This approach is wrong because all insects with complete metamorphosis constitute the holophyletic taxon Metabola Burmeister 1832, i.e., originate from a single ancestral species which acquired this kind of metamorphosis. If complete metamorphosis could appear in response to some factor, it would appear many times in different species, in which case the taxon Metabola, characterized by complete metamorphosis, would be polyphyletic. The holophyly of Metabola is well proven by cladoendesis but cannot be revealed by any matrix method. Based on understanding of these facts, the author was able to discover the specific features which appeared in the common ancestor of Metabola and then became conserved and were inherited by all its descendants. These features include loss of the scape in the larval antenna (leading to a peculiar transformation of antennae in metamorphosis) and a peculiar mode of leg transformation during molt from larva to pupa. During the larval/pupal molt, the leg loses musculature and gets an immobile knee bend, so that the pupa is unable to use its legs. This conserved feature determines the inactive mode of life of the pupae of most insects. It is usually believed that male coccids (Gallinsecta De Geer 1776) have metamorphosis similar to the complete metamorphosis of Metabola. But the phylogenetic position of Gallinsecta and Metabola, as revealed by cladoendesis, does not allow one to assume common modifications in their metamorphoses. Now, when concrete autapomorphies of Metabola have been found, it becomes possible to compare metamorphoses of Metabola and Gallinsecta. Examination of Orthezia urticae and some other coccids shows that metamorphosis of their males shares no modifications with the true complete metamorphosis. The inactive mode of life of their nymphs is not connected with any anatomical reason, but purely with the fact that in the course of transformation from the feeding wingless larva to the non-feeding winged adult, the nymph has already lost its mouth apparatus and has not yet got functional wings, so it does not need to move. At the same time, actively feeding stages of Gallinsecta, both males and females, have an unusual mode of molt transformation of the legs and antennae; this is a unique autapomorphy of Gallinsecta not found in any other insect taxon.     

Early hominid brain evolution: a new look at old endocasts

Early hominid brain morphology is reassessed from endocasts of Australopithecus africanus and three species of Paranthropus, and new endocast reconstructions and cranial capacities are reported for four key specimens from the Paranthropus clade. The brain morphology of Australopithecus africanus appears more human like than that of Paranthropus in terms of overall frontal and temporal lobe shape. These new data do not support the proposal that increased encephalization is a shared feature between Paranthropus and early Homo. Our findings are consistent with the hypothesis that Australopithecus africanus could have been ancestral to Homo, and have implications for assessing the tempo and mode of early hominid neurological and cognitive evolution.