Birth spacing patterns in humans and apes

Comparative studies of birth interval dynamics in wild primates suffer from several problems of analysis and interpretation: (1) the data are always right-censored, (2) sample sizes are usually small, (3) the distribution of birth intervals is expected to be non-normal, (4) early offspring mortality is a confounding variable, and (5) differences in life history (e.g., presence or absence of menopause) can complicate interpretation of the results. A survival analysis designed to minimize these problems is applied to published data on wild chimpanzees and gorillas from Gombe and Virunga Parks, respectively, and to new data on wild orangutans from Tanjung Puting National Park and on a human population, the Gainj of highland Papua New Guinea. According to this analysis, the estimated median birth interval (when the offspring whose birth opens the interval does not die within the interval) is 43.3 +/- 1.0 months for the Gainj, 45.5 +/- 1.2 months for gorillas, 66.6 +/- 1.3 months for chimpanzees, and 92.6 +/- 2.4 months for orangutans.     

Birth spacing and infant mortality in Brazil

The effects of birth spacing on neonatal and post-neonatal mortality in Brazil were found to be very consistent with models based on data from other South American countries. The model for neonatal mortality simplified to three significant variables, whereas the model for post-neonatal mortality included four significant interactions.     

Birth spacing in langur monkeys (Presbytis entellus)

This paper presents 10 years of reproductive data on birth interval length and 5 years of data on reproductive behavior postpartum from a captive colony of gray langur monkeys (Presbytis entellus)housed in Berkeley, California. Birth intervals of females following different pregnancy and nursing schedules are compared. Females whose infants survive to the age of 9 months have a median birth interval of 15.4 months. The experimental separation of mothers from infants for a period of 2 weeks, 6 to 9 months postpartum, had no significant effect on the median birth interval length. Females experiencing a pregnancy failure or the loss of a neonate had median birth intervals of 9.6 and 10.7 months, respectively. These intervals were significantly shorter than the birth intervals of females whose infants survived to 9 months, showing that the presence of a nursing infant delays the female’s time to next conception by approximately 5 to 6 months. Females experienced a median of three estrous periods (two estrous cycles) before conceiving postpartum, regardless of pregnancy outcome or length of infant survival, and females rarely conceived during their first estrous period postpartum. Weaning did not occur until after the mother’s next conception. These data indicate that, in populations of langurs characterized by average birth intervals of 15 to 16 months, the loss of an infant after the age of 5 to 6 months will not accelerate a female’s ability to conceive or shorten the birth interval length. The available data on birth spacing from populations of free-ranging langurs are reviewed. It could not be demonstrated that non-Himalayan populations are characterized by birth intervals which are as long as 20 to 24 months. Rather, it is suggested that female langurs inhabiting seasonally arid sites, such as Jodhpur, Abu, and Dharwar, may be capable of producing infants on the average of every 15 to 16 months. Flexibility in the timing of births and the lack of well-defined birth seasons at these sites may be explained by this species’ dietary and digestive adaptations. Additionally, data on birth spacing and the age of missing infants from the above field sites, where it has been suggested that infanticide following changes in male leadership occurs habitually, do not lend support to the sexual selection hypothesis of infanticide as proposed by S. Hrdy (1974, 1977).     

Birth spacing and child mortality in a Caribbean population.

Ten independent variables were used to predict death before the first birthday for 4411 births that took place from 1878 to 1976 to 978 women of native ancestry on the island of St. Barthélemy. Significant predictors of death include the death of the mother within a year, the birth year, multiple birth, whether the preceding child also died before 1 year of age, and whether the next child was conceived before the index child was 1 year old. Unlike most prior studies, birth-spacing variables were only weakly related to death in the first year. The relative absence of contraceptive techniques to control birth spacing in the study population and the use of vital records rather than survey data distinguish this project from others and may account at least partly for the unusual findings.     

Birth spacing and infant mortality: evidence for eighteenth and nineteenth century German villages

Data from an historical population in which fertility control was minimal and modern health services were mostly unavailable are used to show that there appears to have been a strong association between previous birth interval length and infant mortality, especially when the previous child survived. Although only imperfect proxies for breast-feeding practices and other potentially confounding factors are available for this population, the results suggest that the association between previous interval length and infant mortality in this population is not solely, or primarily, a function of differences in breast-feeding behaviour or socioeconomic status. Other factors, e.g. maternal depletion or sibling competition, are more likely to explain the observed association.     

Birth spacing,breastfeeding, and early child mortality in a traditional Indian society: A hazards model analysis

Abstract

There are few studies of the interrelationships among breastfeeding, child spacing, and child mortality in traditional societies that incorporate extensive controls for social and demographic characteristics of the mother and child. In this paper, we investigate the impact of breastfeeding and the length of the preceding birth interval on early child mortality (defined as a death in the first two years of life) using data from a traditional society of India. Multivariate hazards models are used to analyze the data. Most prior analyses related the impact of breastfeeding duration to the duration of child survivability by taking breastfeeding as a fixed covariate. The present study has a methodological focus in the sense that breastfeeding information from retrospective survey data is treated as a time‐dependent covariate both as a status variate as well as a duration—with empirical findings compared across the two specifications. The effects of postpartum amenorrhoea and various other demographic and socioeconomic characteristics of mother and child are also studied. The results suggest that breastfeeding duration has a strong impact in reducing the relative risk of early child mortality; but it does not explain the effect of the length of the preceding birth interval on early child mortality.     

The Role of Quality Health Services and Discussion about Birth Spacing in Postpartum Contraceptive Use in Sindh,Pakistan: A Multilevel Analysis

IntroductionRapid population growth, stagnant contraceptive prevalence, and high unmet need for family planning present significant challenges for meeting Pakistan’s national and international development goals. Although health behaviors are shaped by multiple social and environmental factors, research on contraceptive uptake in Pakistan has focused on individual and household determinants, and little attention has been given to community characteristics that may affect access to services and reproductive behavior.MethodsIndividual and community determinants of contraceptive use were identified using multivariable multilevel logistic regression to analyze data from a 2014 cross-sectional survey of 6,200 mothers in 503 communities in Sindh, Pakistan.ResultsOnly 27% of women who had given birth in the two years before the study reported using contraceptives. After adjusting for individual and community characteristics, there was no difference in the odds of contraceptive use between urban and rural women. Women who had delivered at a health facility had 1.4 times higher odds of contraceptive use than women who delivered at home. Those who received information about birth spacing from a doctor or relatives/friends had 1.81 and 1.38 times higher odds of contraceptive use, respectively, than those who did not. Living in a community where a higher proportion of women received quality antenatal care and where discussion of birth spacing was more common was significantly associated with contraceptive use. Community-wide poverty lowered contraceptive use.ConclusionsQuality of care at the community level has strong effects on contraceptive use, independent of the characteristics of individual households or women. These findings suggest that powerful gains in contraceptive use may be realized by improving the quality of antenatal care in Pakistan. Community health workers should focus on generating discussion of birth spacing in the community. Outreach efforts should target communities where the demand for contraception appears to be depressed due to high levels of poverty.     

New Protocetid Whale from the Middle Eocene of Pakistan: Birth on Land,Precocial Development,and Sexual Dimorphism

Background

Protocetidae are middle Eocene (49–37 Ma) archaeocete predators ancestral to later whales. They are found in marine sedimentary rocks, but retain four legs and were not yet fully aquatic. Protocetids have been interpreted as amphibious, feeding in the sea but returning to land to rest.

Methodology/Principal Findings

Two adult skeletons of a new 2.6 meter long protocetid, Maiacetus inuus, are described from the early middle Eocene Habib Rahi Formation of Pakistan. M. inuus differs from contemporary archaic whales in having a fused mandibular symphysis, distinctive astragalus bones in the ankle, and a less hind-limb dominated postcranial skeleton. One adult skeleton is female and bears the skull and partial skeleton of a single large near-term fetus. The fetal skeleton is positioned for head-first delivery, which typifies land mammals but not extant whales, evidence that birth took place on land. The fetal skeleton has permanent first molars well mineralized, which indicates precocial development at birth. Precocial development, with attendant size and mobility, were as critical for survival of a neonate at the land-sea interface in the Eocene as they are today. The second adult skeleton is the most complete known for a protocetid. The vertebral column, preserved in articulation, has 7 cervicals, 13 thoracics, 6 lumbars, 4 sacrals, and 21 caudals. All four limbs are preserved with hands and feet. This adult is 12% larger in linear dimensions than the female skeleton, on average, has canine teeth that are 20% larger, and is interpreted as male. Moderate sexual dimorphism indicates limited male-male competition during breeding, which in turn suggests little aggregation of food or shelter in the environment inhabited by protocetids.

Conclusions/Significance

Discovery of a near-term fetus positioned for head-first delivery provides important evidence that early protocetid whales gave birth on land. This is consistent with skeletal morphology enabling Maiacetus to support its weight on land and corroborates previous ideas that protocetids were amphibious. Specimens this complete are virtual ‘Rosetta stones’ providing insight into functional capabilities and life history of extinct animals that cannot be gained any other way.     

Birth in marsupials

Birth is an event that allows the relatively immature marsupial to move from the internal environment of the uterus to the external environment of the pouch. The newborn marsupial passes down from the uterus to the urogenital sinus and then makes its way to the pouch and attaches to the teat at a very early stage of development. From the studies available, there appear to be three methods used by the newborn to move from the uterus to the pouch. In marsupials with a forward pouch such as the red kangaroo, tammar wallaby and the brushtail possum, the mother positions her urogenital sinus below the pouch and the newborn climb upward towards the pouch. The young climb with a swimming motion, moving the head from side-to-side and use the forearms in alternate strokes. In the bandicoot with a backward facing pouch, the mother positions the urogenital sinus above the pouch and the young slither down into the pouch. The young do not have a definite crawl, as seen with the macropodids and possum. The third method of birth has been observed in the marsupials without a definite pouch that have a mammary region that develops as the young grow in size. This type of pouch is observed in the dasyurids. The mother was noted to stand on four legs with her hips raised so that the urogenital sinus was above the pouch and the newborn young crawled downwards from the sinus to the pouch. In all species, birth was completed in 2–4 min.     

Long spacing collagen in dermal disorders

Electron microscopic studies of biopsy material from the vulva of six patients with lichen sclerosus et atrophicus and two patients with condyloma latum, and from the skin of the back and shoulder of one patient with scleromyxoedema and the forearm of one patient with macular amyloidosis revealed the presence of long spacing collagen (LSC) of one patient with macular amyloidosis revealed the presence of long spacing collagen (LSC) intermingled with an increased amount of ground substance and extracellular microfibrils. The presence of LSC in condyloma latum is believed not to have been reported previously. The LSC displayed an axial periodicity varying from 1000 to 2000 A. Our studies support the contention that the appearance of LSC is not specific of any disorder, and the formation of LSC is associated with the presence of increased amounts of glycosaminoglycan-rich ground substance and the abundance of microfilaments in the extracellular space.     

Pakistan santonica

This anthelmintic drug, consisting of dried unexpanded flower heads of several species of Artemisia native to widely separated areas in both the Old and New Worlds, has heretofore been commercially obtained principally from A. Cina of Turkestan. Today A. maritima of West Pakistan has supplanted the Russian source as the principal supplier.     

Y-chromosomal DNA variation in Pakistan

Eighteen binary polymorphisms and 16 multiallelic, short-tandem-repeat (STR) loci from the nonrecombining portion of the human Y chromosome were typed in 718 male subjects belonging to 12 ethnic groups of Pakistan. These identified 11 stable haplogroups and 503 combination binary marker/STR haplotypes. Haplogroup frequencies were generally similar to those in neighboring geographical areas, and the Pakistani populations speaking a language isolate (the Burushos), a Dravidian language (the Brahui), or a Sino-Tibetan language (the Balti) resembled the Indo-European-speaking majority. Nevertheless, median-joining networks of haplotypes revealed considerable substructuring of Y variation within Pakistan, with many populations showing distinct clusters of haplotypes. These patterns can be accounted for by a common pool of Y lineages, with substantial isolation between populations and drift in the smaller ones. Few comparative genetic or historical data are available for most populations, but the results can be compared with oral traditions about origins. The Y data support the well-established origin of the Parsis in Iran, the suggested descent of the Hazaras from Genghis Khan's army, and the origin of the Negroid Makrani in Africa, but do not support traditions of Tibetan, Syrian, Greek, or Jewish origins for other populations.     

The optimum finger spacing in human swimming

Competitive swimmers spread fingers during the propulsive stroke. Due to the inherent inefficiency of human swimming, the question is: does this strategy enhance performance or is it just a more comfortable hand posture? Here we show, through computational fluid dynamics (CFD) of a 3D model of the hand, that an optimal finger spacing (12°, roughly corresponding to the resting hand posture) increases the drag coefficient (+8.8%), which is ‘functionally equivalent’ to a greater hand palm area, thus a lower stroke frequency can produce the same thrust, with benefits to muscle, hydraulic and propulsive efficiencies. CFD, through flow visualization, provides an explanation for the increased drag associated with the optimum finger spacing.