Human kin detection

Natural selection has favored the evolution of behaviors that benefit not only one's genes, but also their copies in genetically related individuals. These behaviors include optimal outbreeding (choosing a mate that is neither too closely related, nor too distant), nepotism (helping kin), and spite (hurting non-kin at a personal cost), and all require some form of kin detection or kin recognition. Yet, kinship cannot be assessed directly; human kin detection relies on heuristic cues that take into account individuals' context (whether they were reared by our mother, or grew up in our home, or were given birth by our spouse), appearance (whether they smell or look like us), and ability to arouse certain feelings (whether we feel emotionally close to them). The uncertainties of kin detection, along with its dependence on social information, create ample opportunities for the evolution of deception and self-deception. For example, babies carry no unequivocal stamp of their biological father, but across cultures they are passionately claimed to resemble their mother's spouse; to the same effect, neutral' observers are greatly influenced by belief in relatedness when judging resemblance between strangers. Still, paternity uncertainty profoundly shapes human relationships, reducing not only the investment contributed by paternal versus maternal kin, but also prosocial behavior between individuals who are related through one or more males rather than females alone. Because of its relevance to racial discrimination and political preferences, the evolutionary pressure to prefer kin to non-kin has a manifold influence on society at large

Prevalence and side preference for tooth grinding in twins

The document attached has been archived with permission from the Australian Dental Association. An external link to the publisher’s copy is included.Background: Estimates of the prevalence of tooth grinding in children range considerably, reflecting different methods of recording. The main aims of this study were to determine the prevalence of tooth grinding in monozygotic (MZ) and dizygotic (DZ) twin pairs by assessing wear faceting on the primary canines, and to compare the faceting on the right and left to determine whether children have a side preference for grinding. Methods: The sample consisted of 116 MZ twin pairs and 124 dizygous DZ twin pairs, all participants in an ongoing study of dento-facial development at the dental schools in Adelaide and Melbourne. Evidence of wear faceting on primary maxillary and mandibular canine tips was recorded from dental casts, and the side with the larger wear facet recorded. Types of occlusal relationship, handedness, zygosity and gender were also recorded, and associations between variables analysed statistically. Results: Canine tip wear facets were found in 100 per cent of the sample, and grinding was lateralized in 59 per cent of children. MZ twin pairs showed a higher discordance for grinding side preference than DZ twin pairs (33.8 per cent compared with 16.8 per cent), providing evidence of a mirror-imaging effect for grinding side preference. There was no strong evidence that individuals had the same preference for grinding side and handedness, although right-handers (RH) showed a preference for a grinding side more often than non-righthanders (NRH) (63.6 per cent compared with 51.2 per cent), consistent with previous findings that RHs display more cerebral lateralization than NRHs. Conclusions: Tooth grinding appears to be a universal phenomenon in children and is commonly expressed more on one side than the other. The significantly higher discordance for grinding side preference in MZ twin pairs compared with DZ twin pairs may reflect a mirror-imaging effect in the former. However, at present we have no evidence to suggest that handedness and preferred tooth grinding side are associated.K V Dooland, G C Townsend, J A Kaidoni

Sex Ratio at Birth and Mortality Rates Are Negatively Related in Humans

Evolutionary theory posits that resource availability and parental investment ability could signal offspring sex selection, in order to maximize reproductive returns. Non-human studies have provided evidence for this phenomenon, and maternal condition around the time of conception has been identified as most important factor that influence offspring sex selection. However, studies on humans have reported inconsistent results, mostly due to use of disparate measures as indicators of maternal condition. In the present study, the cross-cultural differences in human natal sex ratio were analyzed with respect to indirect measures of condition namely, life expectancy and mortality rate. Multiple regression modeling suggested that mortality rates have distinct predictive power independent of cross-cultural differences in fertility, wealth and latitude that were earlier shown to predict sex ratio at birth. These findings suggest that sex ratio variation in humans may relate to differences in parental and environmental conditions

Fetal Programming of Adult Glucose Homeostasis in Mice

BACKGROUND: Emerging evidence suggests that dietary soy and phytoestrogens can have beneficial effects on lipid and glucose metabolism. We have previously shown that male mice fed from conception to adulthood with a high soy-containing diet had reduced body weight, adiposity and a decrease in glucose intolerance, an early marker of insulin resistance and diabetes. OBJECTIVES: The purpose of this study was to identify the precise periods of exposure during which phytoestrogens and dietary soy improve lipid and glucose metabolism. Since intrauterine position (IUP) has been shown to alter sensitivity to endocrine disruptors, we also investigated whether the combination of IUP and fetal exposure to dietary phytoestrogens could potentially affect adult metabolic parameters. METHODS: Male outbred mice (CD-1) were allowed ad libitum access to either a high soy-containing diet or a soy-free diet either during gestation, lactation or after weaning. Adiposity and bone mass density was assessed by dual x-ray absorptiometry. Glucose tolerance was assessed by a glucose tolerance test. Blood pressure was examined by the tail-cuff system. RESULTS: Here we show that metabolic improvements are dependent on precise windows of exposure during life. The beneficial effects of dietary soy and phytoestrogens on adiposity were apparent only in animals fed post-natally, while the improvements in glucose tolerance are restricted to animals with fetal exposure to soy. Interestingly, we observed that IUP influenced adult glucose tolerance, but not adiposity. Similar IUP trends were observed for other estrogen-related metabolic parameters such as blood pressure and bone mass density. CONCLUSION: Our results suggest that IUP and fetal exposure to estrogenic environmental disrupting compounds, such as dietary phytoestrogens, could alter metabolic and cardiovascular parameters in adult individuals independently of adipose gain

Thyroid Hormone Replacement in Women of Reproductive Age: Is Surgeon Knowledge Related to Operative Volume?

Background: It is not known if surgeons who place women of reproductive age on thyroid hormone replacement (levothyroxine, LT4) routinely inform them of the increased LT4 demands with future pregnancy. In addition, it is not clear whether reading the 2007 Endocrine Society's ?Guidelines on the Management of Thyroid Dysfunction during Pregnancy and Postpartum? influences the role of the surgeon in patient education. The objective of this study was to identify the role of the surgeon in patient education at the time of initiation of LT4 therapy. Methods: A two-sided one-page survey was distributed to the 260 surgeons attending the 2009 American Association of Endocrine Surgeons' meeting. Of those distributed, 109 (42%) surgeons returned the survey. Results: Although only 26/109 (23%) read the 2007 Endocrine Society's ?Guidelines on the Management of Thyroid Dysfunction during Pregnancy and Postpartum,? reading the guidelines was associated with a significantly greater likelihood of informing patients of higher LT4 requirements with pregnancy (p?<?0.0001). Eighty-five percent of those who read the guidelines ?often? or ?always? informed patients of higher LT4 requirements with future pregnancy, whereas only 44% of those who did not read the guidelines provided the same level of education. After controlling for surgeon sex, academic versus private practice, years in practice, and number of surgeries performed in 2008, the only independent predictor of patient education was reading the guidelines (p?=?0.006). On multivariable analysis, surgeon volume was associated with reading the guidelines (p?=?0.006). The mean number of thyroid surgeries performed by those who read the guidelines versus those who did not was 164.46?±?16.98 versus 115.01?±?8.27 (p?=?0.005). Conclusion: Surgeons who read the Endocrine Society's ?Guidelines on the Management of Thyroid Dysfunction during Pregnancy and Postpartum? were significantly more likely to inform patients of the need for higher LT4 doses with pregnancy. Thyroid surgery volume was associated with guideline awareness.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/85127/1/thy_2009_0320.pd

Culled males, infant mortality and reproductive success in a pre-industrial Finnish population

Theoretical and empirical literature asserts that the sex ratio (i.e. M/F) at birth gauges the strength of selection in utero and cohort quality of males that survive to birth. We report the first individual-level test in humans, using detailed life-history data, of the ‘culled cohort’ hypothesis that males born to low annual sex ratio cohorts show lower than expected infant mortality and greater than expected lifetime reproductive success. We applied time-series and structural equation methods to a unique multigenerational dataset of a natural fertility population in nineteenth century Finland. We find that, consistent with culled cohorts, a 1 s.d. decline in the annual cohort sex ratio precedes an 8% decrease in the risk of male infant mortality. Males born to lower cohort sex ratios also successfully raised 4% more offspring to reproductive age than did males born to higher cohort sex ratios. The offspring result, however, falls just outside conventional levels of statistical significance. In historical Finland, the cohort sex ratio gauges selection against males in utero and predicts male infant mortality. The reproductive success findings, however, provide weak support for an evolutionarily adaptive explanation of male culling in utero

The Role of Clinical Guidelines in Patient Care: Thyroid Hormone Replacement in Women of Reproductive Age

Background: Clinical guidelines have a role in medical education and in the standardization of patient care. However, it is not clear whether guidelines created by subspecialists reach relevant practicing physicians or influence patient care. In 2007 the Endocrine Society released ?Guidelines on the Management of Thyroid Dysfunction During Pregnancy and Postpartum.? The objective of this study was to characterize the role of these guidelines in provider education and in subsequent patient care decisions. Method: In 2009 three waves of mail surveys were distributed to 1601 Wisconsin health care providers with a history of providing obstetric care. Survey participants were members of the American College of Obstetricians and Gynecologists or the American Academy of Family Physicians. There were 881 returned surveys (55%) and 575 were eligible for the study (adjusted rate 52.5%). Results: Although only 11.5% of providers read the Endocrine Society's guidelines, reading the guidelines was associated with increased likelihood of prepregnancy counseling on levothyroxine management (p?<?0.0001), increased likelihood of screening for thyroid disease risk factors (p?=?0.0007), and increased likelihood of empiric levothyroxine dose increase in pregnant patients (p?=?0.0005). After controlling for provider sex, membership affiliation, practice setting, and number of years in practice, reading the guidelines was still an independent predictor of patient education prepregnancy (p?<?0.01). Conclusion: The Endocrine Society's ?Guidelines on the Management of Thyroid Dysfunction During Pregnancy and Postpartum? reached a minority of providers involved in obstetrics, but exposure to the guidelines did impact patient care. A multidisciplinary approach to guideline creation would improve the dissemination and practical application of guidelines.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/85109/1/thy_2009_0321.pd