How did the European Marriage Pattern persist? Social versus familial inheritance: England and Quebec, 1650-1850.

The European Marriage Pattern (EMP), in place in NW Europe for perhaps 500 years, substantially limited fertility. But how could such limitation persist when some individuals who deviated from the EMP norm had more children? If their children inherited their deviant behaviors, their descendants would quickly become the majority of later generations. This puzzle has two possible solutions. The first is that all those that deviated actually had lower net fertility over multiple generations. We show, however, no fertility penalty to future generations from higher initial fertility. Instead the EMP survived because even though the EMP persisted at the social level, children did not inherit their parents' individual fertility choices. In the paper we show evidence consistent with lateral, as opposed to vertical, transmission of EMP fertility behaviors.

Twins Support the Absence of Parity-Dependent Fertility Control in Pretransition Populations.

A conclusion of the European Fertility Project in 1986 was that pretransition populations mostly displayed natural fertility, where parity-dependent birth control was absent. This conclusion has recently been challenged for England by new empirical results and has also been widely rejected by theorists of long-run economic growth, where pre-industrial fertility control is integral to most models. In this study, we use the accident of twin births to show that for three Western European-derived pre-industrial populations-namely, England (1730-1879), France (1670-1788), and Québec (1621-1835)-we find no evidence for parity-dependent control of marital fertility. If a twin was born in any of these populations, family size increased by 1 compared with families with a singleton birth at the same parity and mother age, with no reduction of subsequent fertility. Numbers of children surviving to age 14 also increased. Twin births also show no differential effect on fertility when they occurred at high parities; this finding is in contrast to populations where fertility is known to have been controlled by at least some families, such as in England, 1900-1949, where a twin birth increased average births per family by significantly less than 1.

Randomness in the Bedroom: There Is No Evidence for Fertility Control in Pre-Industrial England.

Overturning a generation of research, Cinnirella et al. Demography, 54, 413-436 (2017) found strong parity-dependent fertility control in pre-Industrial England 1540-1850. We show that their result is an unfortunate artifact of their statistical method, relying on mother fixed effects, which contradicts basic biological possibilities for fecundity. These impossible parity effects also appear with simulated fertility data that by design have no parity control. We conclude that estimating parity control using mother fixed effects is in no way feasible. We also show, using the Cambridge Group data that Cinnirella et al. used, that there is no sign of parity-dependent fertility control in English marriages before 1850.

Surnames and social mobility in England, 1170-2012.

Using educational status in England from 1170 to 2012, we show that the rate of social mobility in any society can be estimated from knowledge of just two facts: the distribution over time of surnames in the society and the distribution of surnames among an elite or underclass. Such surname measures reveal that the typical estimate of parent-child correlations in socioeconomic measures in the range of 0.2-0.6 are misleading about rates of overall social mobility. Measuring education status through Oxbridge attendance suggests a generalized intergenerational correlation in status in the range of 0.70-0.90. Social status is more strongly inherited even than height. This correlation is unchanged over centuries. Social mobility in England in 2012 was little greater than in preindustrial times. Thus there are indications of an underlying social physics surprisingly immune to government intervention.

The effect of saddle design on stresses in the perineum during cycling.

PURPOSE: Repetitive internal stress in the perineum has been associated with soft-tissue trauma in bicyclists. Using an engineering approach, the purpose of this study was to quantify the amount of compression exerted in the perineum for a range of saddle widths and orientations. METHODS: Computer tomography was used to create a three-dimensional voxel-based finite element model of the right side of the male perineum-pelvis. For the creation of the saddle model, a commercially available saddle was digitized and the surface manipulated to represent a variety of saddle widths and orientations. The two models were merged, and a static downward load of 189 N was applied to the model at the region representing the sacroiliac joint. For validation purposes, external stresses along the perineum-saddle interface were compared with the results of pressure sensitive film. Good agreement was found for these external stresses. The saddles were then stretched and rotated, and the magnitude and location of maximum stresses within the perineum were both recorded. In all cases, the model of the pelvis-perineum was held in an upright position. RESULTS: Stresses within the perineum were reduced when the saddle was sufficiently wide to support both ischial tuberosities. This supporting mechanism was best achieved when the saddle was at least two times wider than the bi-ischial width of the cyclist. Stresses in the anterior of the perineum were reduced when the saddle was tilted downward, whereas stresses in the posterior were reduced when the saddle was tilted upward. CONCLUSIONS: Recommendations that saddles should be sufficiently wide to support the ischial tuberosities appear to be well founded. Recommendations that saddles be tilted downward (i.e., nose down) are supported by the model, but with caution, given the limitations of the model.

The effect of mouthguard design on stresses in the tooth-bone complex.

PURPOSE: Mouthguards protect the tooth-bone complex from impact loads that occur during sporting activity. The aim of this study is to investigate the effects of varying mouthguard thickness and stiffness on the magnitude of tensile stresses in the tooth-bone-complex. METHODS: A two-dimensional, plane stress, finite element representation of a central maxillary incisor (CMI) is created. For validation purposes, displacements of the incisal edge of the unprotected tooth model are compared with in vivo displacements under similar loads. A protective mouthguard is then superimposed over the model with varied labial thickness (1-6 mm) and stiffness (9-900MPa) representing a range of designs available. A large horizontal static load of 500N is then applied to the anterior surface of the mouthguard and the resulting stresses in the tooth-bone complex are presented. It is suggested that this loading condition most accurately represent the situation occurring when a guarded tooth collides with a soft object (e.g. boxing glove). RESULTS: It is generally found that mouthguard thickness and stiffness are both desirable in terms of reducing stresses. However, the protection offered by the low-stiffness guards, regardless of thickness, is minimal. Since this low-stiffness (9MPa) is representative of the most common choice of material in mouthguard fabrication, such findings may cast doubt on the ability of popular mouthguards to redistribute stress. CONCLUSION: While few would disagree that these low-stiffness guards absorb shock during hard-object collisions (e.g. baseballs), they may not protect the tooth-bone during soft-object collisions (e.g. boxing gloves). In order to optimize their protective capabilities for a range of loads, the range of materials used in mouthguard construction may have to be reconsidered.