Martin Fieder

Hibernation effects on memory in European ground squirrels (Spermophilus citellus).

Effects of hibernation on memory were tested in European ground squirrels (Spermophilus citellus). The animals were trained in summer to successfully accomplish two tasks: a spatial memory task in a maze and an operant task on a feeding machine. One group hibernated normally, and the other was prevented from hibernation by maintaining ambient temperature at 22 °C. In spring, the same tasks were repeated for both groups and their individual performances compared to the initial training phase. The experimental groups differed significantly in both tasks. The nonhibernating animals had higher levels of retention and needed significantly fewer trials to relearn the tasks than the group that had hibernated. In addition to testing the retention of conditioned tasks, social memory was also studied. The ground squirrels were given a social recognition test in spring with one familiar and one unfamiliar conspecific. In contrast to the conditioned tasks, social memory did not seem to be affected by hibernation. The results indicate negative effects of hibernation on the retention of conditioned tasks, which could produce important constraints on animals. A potential explanation for this memory loss might be changes in neuronal activity, which occur during hibernation.

Socioeconomic status, education, and reproduction in modern women: An evolutionary perspective

Although associations between status or resources and reproduction are positive in premodern societies and also in men in modern societies, in modern women the associations are typically negative. We investigated how the association between socioeconomic status and reproductive output varies with the source of status and resources, the womans education, and her age at reproductive onset (proxied by age at marriage). By using a large sample of US women, we examined the association between a womans reproductive output and her own and her husbands income and education. Education, income, and age at marriage are negatively associated with a womans number of children and increase her chances of childlessness. Among the most highly educated two‐thirds of the sample of women, husbands income predicts the number of children. The association between a womans number of children and her husbands income turns from positive to negative when her education and age at marriage is low (even though her mean offspring number rises at the same time). The association between a womans own income and her number of children is negative, regardless of education. Rather than maximizing the offspring number, these modern women seem to adjust investment in children based on their family size and resource availability. Striving for resources seems to be part of a modern female reproductive strategy—but, owing to costs of resource acquisition, especially higher education, it may lead to lower birthrates: a possible evolutionary explanation of the demographic transition, and a complement to the human capital theory of net reproductive output. Am. J. Hum. Biol. 22:578–587, 2010.

The Communication Paradox and Possible Solutions

In the history of both animal and human ethology the direct observation of unstaged interactions in a natural habitat plays a critical role for methodological and theoretical considerations. Even when ethologists think that they already know much about adaptations and the ways in which they interact with the environment, the principles which have been involved in the evolution of increasingly complex human behaviour are still not very well understood.

Too much noise in the Times Higher Education rankings.

Several individual indicators from the Times Higher Education Survey (THES) data base—the overall score, the reported staff-to-student ratio, and the peer ratings—demonstrate unacceptably high fluctuation from year to year. The inappropriateness of the summary tabulations for assessing the majority of the “top 200” universities would be apparent purely for reason of this obvious statistical instability regardless of other grounds of criticism. There are far too many anomalies in the change scores of the various indices for them to be of use in the course of university management.

Socioeconomic status, marital status and childlessness in men and women: an analysis of census data from six countries.

This study compares the effects of two distinct forms of human capital - income and education - on marital status and childlessness separately by sex in six different countries. Nearly 10 million individual records on individuals aged 16 to 50 were used from censuses from Brazil, Mexico, Panama, South Africa, USA and Venezuela dating from 2000 or later, to analyse the relationship between education, income and marital status and childlessness in men and women. Regarding income, the findings for both outcome variables are strongly consistent across all six countries. Highest-income males and lower-income females have the highest proportion of ever-married and the lowest proportion of childlessness (using a proxy for childlessness: own children in the household or not). There is no corresponding consistency of findings as regards education either between the sexes or among the countries. To conclude, a lower percentage of low-income men are selected by females, because for women male status and resources provided by men are important criteria in mate selection. Therefore a higher proportion of low-income men remain unmarried and childless. Thus selection seems to play a role in modern societies.

Strong association between birth month and reproductive performance of Vietnamese women

Epidemiological studies on premodern and modern Western societies indicate that birth season may influence female reproduction. Nothing is known, however, about this effect in developing economies. Many of the latter are characterised by tropical climates with a rainy season associated with lower food availability and a greater prevalence of infectious diseases. We therefore predict that an association between birth month and reproductive output, if it exists, should be related to the rainy season. To test this prediction, we analysed census data of Vietnam obtained from IPUMS‐International (Vietnam 1999 Population and Housing Census). Based on 493,853 women born between 1950 and 1977 and thus aged 22 to 49 years, we found that the time series of mean offspring count per month of birth has a highly significant period of 12 months (power = 46.871, P < 0.00001). Our results further indicate that the 12‐month periodic signal has a maximum in July and a minimum in January. Accordingly, the peak corresponds to birth during the rainy season, the low if the third pregnancy month concurs with the rainy season. The month of birth is therefore clearly associated with the later reproductive performance of Vietnamese women, strongly supporting the assumption that environmental and maternal conditions during early development exert long‐term effects on reproductive functioning. Provided the rainy season adversely affects developmental processes due to inadequate food and/or high infection risk, the association reported here points to a critical period of reproductive development during early pregnancy. Am. J. Hum. Biol., 2009.

An Evolutionary Account of Status, Power, and Career in Modern Societies

We hypothesize that in modern societies the striving for high positions in the hierarchy of organizations is equivalent to the striving for status and power in historical and traditional societies. Analyzing a sample of 4,491 US men and 5,326 US women, we find that holding a supervisory position or being in charge of hiring and firing is positively associated with offspring count in men but not in women. The positive effect in men is attributable mainly to the higher proportion of childlessness among men in non-supervisory positions and those without the power to hire and fire. This effect is in accordance with the positive relationship between other status indicators and reproductive success found in men from traditional, historical, and modern societies. In women, we further find a curvilinear relationship between income percentile and offspring number by analyzing US census data, indicating that women may strive for resources associated with advancement rather than for status per se.

Educational Homogamy Lowers the Odds of Reproductive Failure

Assortative mating based on education is a common phenomenon. We investigated whether it affected parameters of reproductive performance such as childlessness, offspring number and age at first marriage. On the basis of the US census from 1980 (n = 670,631 married US couples), we find that the proportion of childless individuals is usually minimal in women married to a husband of the same educational level. This holds particularly true in the highest and the lowest educated women. Educational homogamy is also associated with a lower average age at first marriage. No obvious effect of educational homogamy on a womans average offspring number is found, where mean offspring number generally increases both with decreasing womans and decreasing husbands educational attainment. We conclude that educational homogamy reduces the likelihood of reproductive failure.

Geometric morphometric footprint analysis of young women

BackgroundMost published attempts to quantify footprint shape are based on a small number of measurements. We applied geometric morphometric methods to study shape variation of the complete footprint outline in a sample of 83 adult women.MethodsThe outline of the footprint, including the toes, was represented by a comprehensive set of 85 landmarks and semilandmarks. Shape coordinates were computed by Generalized Procrustes Analysis.ResultsThe first four principal components represented the major axes of variation in foot morphology: low-arched versus high-arched feet, long and narrow versus short and wide feet, the relative length of the hallux, and the relative length of the forefoot. These shape features varied across the measured individuals without any distinct clusters or discrete types of footprint shape. A high body mass index (BMI) was associated with wide and flat feet, and a high frequency of wearing high-heeled shoes was associated with a larger forefoot area of the footprint and a relatively long hallux. Larger feet had an increased length-to-width ratio of the footprint, a lower-arched foot, and longer toes relative to the remaining foot. Footprint shape differed on average between left and right feet, and the variability of footprint asymmetry increased with BMI.ConclusionsFoot shape is affected by lifestyle factors even in a sample of young women (median age 23 years). Geometric morphometrics proved to be a powerful tool for the detailed analysis of footprint shape that is applicable in various scientific disciplines, including forensics, orthopedics, and footwear design.

Month of birth and offspring count of women: data from the Southern hemisphere

BACKGROUND Several studies indicate that the month of birth affects later reproductive output of women in the Northern hemisphere. METHODS To investigate whether a comparable but time-shifted effect is also present in the Southern hemisphere where the seasonal variation of the environment is reversed, we analysed the association between birth month and offspring count in post-reproductive New Zealand women. We further examined whether this association differed with the hemisphere of birth as well as the socio-economic background. RESULTS We find that the association between birth month and offspring count of New Zealand women born in the Southern, albeit not Northern, hemisphere is a mirror image of the pattern reported from Austrian women: on average, women born during the Southern hemisphere summer months have fewer children than women born in winter. This association is highly significant within the lowest family income category but insignificant within higher family income categories. CONCLUSIONS This study provides evidence for a causal link between the seasonality of the environment during the pre- and perinatal period and offspring count of women. It further indicates that the main contribution of the birth month effect found in the present study comes from the lowest family income category.