Barbara Fischer

• PhD
• Group Leader at Konrad Lorenz Institute for Evolution and Cognition Research

Significance Because of the tight fit of the large human neonate through the narrow maternal birth canal, childbirth is remarkably difficult. In this study we show that the dimensions of head, stature, and pelvis in a human body are linked in a complex way that was not recognized before and that contributes to ameliorate this tight fit. We show tha...

Significance Compared with other primates, human childbirth is difficult because the fetus is large relative to the maternal pelvic canal. It is a long-standing evolutionary puzzle why the pelvis has not evolved to be wider, thus reducing the risk of obstructed labor. We present a mathematical model that explains the high rates of fetopelvic dispro...

Sexual dimorphism in the human pelvis has evolved in response to several jointly acting selection regimes that result from the pelvis? multiple roles in locomotion and childbirth, among others. Because human males are, on average, taller than females, some aspects of sexual dimorphism in pelvis shape might result from allometry, the association bet...

It is commonly assumed that the strong sexual dimorphism of the human pelvis evolved for delivering the relatively large human foetuses. Here we compare pelvic sex differences across modern humans and chimpanzees using a comprehensive geometric morphometric approach. Even though the magnitude of sex differences in pelvis shape was two times larger...

Human fetuses at term are large relative to the dimensions of the maternal birth canal, implying that their birth can be associated with difficulties. The tight passage through the human birth canal can lead to devastating outcomes if birth becomes obstructed, including maternal and fetal death. Although macaques have to accommodate similarly large...

Here is the permanent link to our preprint on Authorea: https://doi.org/10.22541/au.173130506.65606430/v1

Compared to other primates, modern humans face high rates of maternal and neonatal morbidity and mortality during childbirth. Since the early 20th century, this "difficulty" of human parturition has prompted numerous evolutionary explanations, typically assuming antagonistic selective forces acting on maternal and fetal traits, which has been terme...

Artificial-intelligence (AI) allows large-scale analyses of long-leg-radiographs (LLRs). We used this technology to derive an update for the classical regression formulae by Trotter and Gleser, which are frequently used to infer stature based on long-bone measurements. We analyzed calibrated, standing LLRs from 4200 participants taken between 2015...

Introduction To determine whether a pelvis is wide enough for spontaneous delivery has long been the subject of obstetric research. A number of variables have been proposed as predictors, all with limited accuracy. In this study, we use a novel three‐dimensional (3D) method to measure the female pelvis and assess which pelvic features influence bir...

Artificial-intelligence (AI) allows large scale analyses of long-leg-radiographs (LLRs). We use this technology to derive an update for the classical regression formulae by Trotter and Gleser and Bass, which are frequently used to infer stature based on long-bone measurements. We analyzed calibrated, standing LLRs from 4,200 participants taken betw...

Introduction and hypothesis In women, the risk of pelvic floor prolapse is known to be associated with age and parity. Different studies suggested that it is also related to pelvic dimensions, e.g. biomechanical modelling showed that a larger pelvic canal results in higher values of displacement, stress and strain in the pelvic floor muscles, which...

Plant-based repellents represent a safe, economic, and viable alternative to managing invasive insects that threaten native fauna. Observations of self-medication in animals can provide important cues to the medicinal properties of plants. A recent study in the Galapagos Islands found that Darwin’s finches apply the leaves of Psidium galapageium (H...

Background The human foetus typically needs to rotate when passing through the tight birth canal because of the complex shape of the pelvis. In most women, the upper part, or inlet, of the birth canal has a round or mediolaterally oval shape, which is considered ideal for parturition, but it is unknown why the lower part of the birth canal has a pr...

Age-at-death estimation from skeletal remains typically utilizes the roughness of pubic symphysis articular surfaces. This study presents a new quantitative method adapting a tool from geometric morphometrics, bandpass filtering of partial warp bending energy to extract only age-related changes of the surfaces. The study sample consisted of 440 sur...

The bony symphyseal surface is an important trait for age-at-death estimation from human skeletal remains. In this paper, we demonstrate for the first time that the outline of the human symphyseal surface is sexually dimorphic and that it changes with age. We present a geometric morphometric analysis based on a sample of 323 symphyseal pubic bones...

The human foetus needs to rotate when passing through the tight birth canal because of the complex shape of the pelvis. In most women the upper part, or inlet, of the birth canal has a round or mediolaterally oval shape, which is considered ideal for parturition, but it is unknown why the lower part, or outlet, of the birth canal has a pronounced a...

Pelvic dimensions differ, on average, among modern human populations. Some recent studies reported that population differences in pelvic form evolved mainly by neutral processes, without considerable natural selection. This is a surprising claim given the many important functions of the human pelvis. Here, we reevaluate this claim by reviewing the...

Birds host a wide range of ectoparasites and have developed behavioural strategies to combat them, such as preening, dust bathing and water bathing. In addition, a wide range of avian taxa anoint their feathers with insects or plants that have pharmaceutical properties, though most observations on anointing are anecdotal. Darwin's finches preen wit...

In 2019, the American Association of Physical Anthropologists issued a statement on biological aspects of race, concluding that “pure races, in the sense of genetically homogenous populations, do not exist in the human species today, nor is there any evidence that they have ever existed in the past.” The statement continues: “… The only living spec...

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Photographs of articulated bony pelves of representatives of all major mammalian (marsupial and placental) groups. Sexual dimorphism (or the lack thereof) can also be observed by comparing male and female specimens.

Objectives The narrow human birth canal evolved in response to multiple opposing selective forces on the pelvis. These factors cannot be sufficiently disentangled in humans because of the limited range of relevant variation. Here, we outline a comparative strategy to study the evolution of human childbirth and to test existing hypotheses in primate...

Appendix S1: Supporting information Figures

Table S2 Supporting information Table S2. The number of species by higher‐order taxon used to produce each Figure in the main text, including the data source.

Table S1 Supporting information Table S1. Data on neonatal and female body mass for 284 mammalian species. Data for 266 species were taken from Tague (2016), and data for an additional twelve species (highlighted in yellow) were collated from the indicated sources. When no reference is given, data are from Tague (2016).

The narrow human birth canal evolved in response to multiple opposing selective forces on the pelvis. These factors cannot be sufficiently disentangled in humans because of the limited range of relevant variation. We outline a comparative strategy to study the evolution of human childbirth and to test existing hypotheses in primates and other mamma...

In their interesting article, Huseynov et al. (1) propose the “developmental obstetric dilemma (DOD) hypothesis,” which posits that human pelvic morphology reflects the changing obstetric needs during a female’s lifetime. In particular, the authors state that the female pelvis reaches its “obstetrically most adequate morphology” during peak fertili...

In the threespine stickleback Gasterosteus aculeatus model system, phenotypes are often classified into three morphs according to lateral plate number. Morph identity has been shown to be largely genetically determined, but substantial within-morph variation in plate number exists. In this study, we test whether plate number has a plastic component...

In our paper (1) we report on a previously unknown association between human pelvis shape, head size, and stature that appears to ameliorate—but in no way resolve—the obstetric dilemma. In an interesting response to this article, Underdown and Oppenheimer (2) emphasize that “one must explicitly consider whether the suggested relationship is an evol...

Phenotypic plasticity is a major factor contributing to variation of organisms in nature, yet its evolutionary significance is insufficiently understood. One example system where plasticity might have played an important role in an adaptive radiation is the threespine stickleback (Gasterosteus aculeatus), a fish that has diversified after invading...

Abstract When organisms encounter environments that are heterogeneous in time, phenotypic plasticity is often favored by selection. The degree of such plasticity can vary during an organism's lifetime, but the factors promoting differential plastic responses at different ages or life stages remain poorly understood. Here we develop and analyze an e...

Compared to other primates, childbirth is remarkably difficult in humans, primarily because the head and shoulders of the human fetus are large in comparison to the birth-relevant dimensions of the human pelvis. Modern human pelvic morphology must serve more than one purpose: It is thought to have evolved as a compromise between being shaped for up...

The presence of fat stores in fish is widely used as a correlate of fish health and fitness. Techniques to measure fat content with some accuracy are available for medium-sized and large fish, but apart from morphometric indices, a noninvasive method to determine fat content in small fish has hitherto been lacking. In this study, we introduce a nov...

Maternal effects on offspring size can have a strong effect on fitness, as larger offspring often survive better under harsh environmental conditions. Selection should hence favour mothers that find an optimal solution to the offspring size versus number tradeoff. If environmental conditions are variable, there will not be a single optimal offsprin...

The ability to store energy enables organisms to deal with temporarily harsh and uncertain conditions. Empirical studies have demonstrated that organisms adapted to fluctuating energy availability plastically adjust their storage strategies. So far, however, theoretical studies have investigated general storage strategies only in constant or determ...

When environmental conditions vary stochastically, individuals accrue fitness benefits by exhibiting phenotypic plasticity. Here we analyze a general dynamic-programming model describing an individual's optimal energy allocation in a stochastic environment. After maturation, individuals repeatedly decide how to allocate incoming energy between repr...