How do biological and social kinship play out within families in the U.S.? An evolutionary perspective on perceived parental care and closeness in adolescents

"Abgeleitet aus der Theorie der Verwandtenselektion sagen Evolutionsbiologen vorher, dass Individuen gegenüber ihren biologischen Kindern mehr Fürsorge zeigen sollten als gegenüber Kindern, zu denen eine soziale Elternschaft besteht. Entsprechend wird erwartet, dass biologische Kinder die Beziehungen zu ihren Eltern besser einschätzen als Stiefkinder. Zur Überprüfung dieser Hypothese ziehen wir die Daten der U.S. National Longitudinal Study of Adolescent Health (Add Health) heran. Diese Studie erlaubt es, im Gegensatz zu vielen anderen Datenquellen, die Konsequenzen der innerfamilialen Dynamik sozialer und biologischer Eltern-Kind-Beziehungen zu untersuchen. Um diesen Vergleich innerhalb der Familien zu ermöglichen, untersuchen wir Geschwisterdyaden und führen eine fixed-effects-Regression durch. Die Resultate der deskriptiven und der multivariaten Analysen bestätigen, dass der Status biologischer Elternschaft auch dann die Beziehungseinschätzungen der Jugendlichen (wahrgenommene elterliche Fürsorge und emotionale Nähe) vorhersagt, wenn für andere relevante Einflussfaktoren kontrolliert wird - sowohl in Bezug auf die väterliche als auch auf die mütterliche Beziehung. In der Diskussion kommentieren wir das Ergebnis im Hinblick auf eine mögliche Integration evolutionsbiologischer und soziologischer Forschungsperspektiven und schließen mit einigen Empfehlungen für die zukünftige empirische Datenerhebung ab. Eine Umsetzung dieser Empfehlungen könnte es interessierten Forscherinnen und Forschern in Zukunft ermöglichen, die relative Bedeutung biologischer und sozialer Einflüsse auf die Eltern detaillierter zu untersuchen." (Autorenreferat)"Consistent with inclusive fitness theory, evolutionary biologists predict that individuals care more for their biological than their social children and hence that biological children assess the relationships to their parents better than stepchildren. To test this assumption, we use data from the U.S. National Longitudinal Study of Adolescent Health (Add Health). Unlike many other studies that have been conducted so far, this survey allows us to analyze the consequences of the dynamic between social and biological parent-child relationships within the same families. We use comparisons of sibling pairs and fixed-effects regression to achieve the within-family comparison. Both the descriptive and multivariate regression results confirm that - even after controlling for other relevant influences - biological parenthood matters with regard to children's relationship assessments (perceived parental care and closeness of the parent-child relationship) and in both the relationships to resident fathers and mothers. In the discussion, we comment on the possible integration of the evolutionary and sociological perspectives and close with some recommendations for future data collection that could allow researchers to analyze the relative impact of biological and social influences on parent-child relationships on a more fine-grained level." (author's abstract

Mythos "Kleine Welt"? Eine konstruktive Kritik an der Konzeption und Methodologie der Small World-Forschung

"Die 'Small World' (SW)-Forschung ist den meisten unter dem Begriff 'six degress of separation' bekannt. Sie beschäftigt sich mit Netzwerken, die sowohl eine hohe Clusterung der Akteure als auch relativ kurze Verbindungspfade zwischen zwei beliebigen Akteuren im Netzwerk aufweisen. Sie kann grob in zwei Phasen eingeteilt werden: experimentelle Studien vornehmlich aus den 1970er und 1980er Jahren und Versuche, SW-Netzwerke mathematisch zu modellieren seit den späten 1990er Jahren. Der experimentelle Forschungszweig wurde ursprünglich als sozialwissenschaftliches Projekt gestartet (Milgram 1967, 1969). Die jüngere SW-Forschung präsentiert sich jedoch explizit als interdisziplinäres Projekt (Watts 2004). Während die Anwendung in den Naturwissenschaften meist leicht greifbar ist (z.B. Verbreitung von Viren), ist die SW-Forschung im Hinblick auf sozialwissenschaftliche Fragestellungen, in denen SW-Prozesse häufig durch Brief- oder ähnliche Kommunikationsketten operationalisiert werden, durch konzeptionelle Unklarheiten sowie methodische Probleme gekennzeichnet. In konzeptioneller Hinsicht ist zu beachten, dass folgende Aspekte nur unzureichend thematisiert bzw. empirisch untersucht worden sind: 1. die den Netzwerkverbindungen zugrundeliegenden Inhalte/ Mechanismen, 2. die Faktoren, die dazu beitragen, dass Ketten unterbrochen werden, 3. die Rolle von Anreizen für Netzwerkmitglieder, Information oder Ressourcen weiterzureichen, 4. der Unterschied zwischen Diffusion und gezielten Suchprozessen. Die SW-Forschung knüpft nur teilweise an bereits bekannte Konzepte der übrigen Netzwerkforschung an. Eine Integration mit bestehenden Konzepten könnte einige der konzeptionellen Unklarheiten beseitigen. Zu den Methoden ist anzumerken, dass alle Experimentalstudien mindestens einen der folgenden Schwachpunkte aufweisen: 1. kleine Stichproben, 2. Stichprobenbias oder 3. einen sehr geringen Anteil an Ketten, in denen die Zielperson erreicht wurde. Unter Berücksichtigung abgebrochener Ketten hat White (1970) mit einem Modell außerdem gezeigt, dass die in der Population vermuteten Kommunikationsketten länger sein dürften, als bis dahin angenommen. Im Vortrag wird der Verfasser die Ergebnisse einer Survivalanalyse als Metaanalyse vorstellen, mit der er die Medianlängen der Ketten bestimmt hat und Schätzungen zur Zuverlässigkeit der Daten abgeben kann. Angesichts der konzeptionellen und methodischen Kritik ist das Vorherrschen sozialer SW-Netzwerke und ihre Relevanz für soziale Akteure fragwürdig. Der heute weiterverbreitete und durch die frühe SW-Forschung inspirierte Glaube an die 'six degrees of separation' basiert auf einem Mythos. Die sechs Grade sind kein allgemeines Kennzeichen der Sozialstruktur. In dem Vortrag schlägt er vor, in welche Bereiche sich die SW-Forschung sinnvoll weiterentwickeln kann. Für die empirische Forschung ergeben sich Ideen zur Elitenforschung sowie zur Erforschung organisationeller Effizienz, der Sozialstruktur im Allgemeinen und der Strategien einzelner Akteure. Für die analytischen Studien wird auf bisher ausgelassene Parameter verwiesen, deren Implementation in mathematischen Modellen die Relevanz für sozialwissenschaftliche Anwendungen steigern könnte." (Autorenreferat

Human cellular restriction factors that target HIV-1 replication

Recent findings have highlighted roles played by innate cellular factors in restricting intracellular viral replication. In this review, we discuss in brief the activities of apolipoprotein B mRNA-editing enzyme 3G (APOBEC3G), bone marrow stromal cell antigen 2 (BST-2), cyclophilin A, tripartite motif protein 5 alpha (Trim5α), and cellular microRNAs as examples of host restriction factors that target HIV-1. We point to countermeasures encoded by HIV-1 for moderating the potency of these cellular restriction functions

Omecamtiv mecarbil in chronic heart failure with reduced ejection fraction, GALACTIC‐HF: baseline characteristics and comparison with contemporary clinical trials

Aims: The safety and efficacy of the novel selective cardiac myosin activator, omecamtiv mecarbil, in patients with heart failure with reduced ejection fraction (HFrEF) is tested in the Global Approach to Lowering Adverse Cardiac outcomes Through Improving Contractility in Heart Failure (GALACTIC‐HF) trial. Here we describe the baseline characteristics of participants in GALACTIC‐HF and how these compare with other contemporary trials. Methods and Results: Adults with established HFrEF, New York Heart Association functional class (NYHA) ≥ II, EF ≤35%, elevated natriuretic peptides and either current hospitalization for HF or history of hospitalization/ emergency department visit for HF within a year were randomized to either placebo or omecamtiv mecarbil (pharmacokinetic‐guided dosing: 25, 37.5 or 50 mg bid). 8256 patients [male (79%), non‐white (22%), mean age 65 years] were enrolled with a mean EF 27%, ischemic etiology in 54%, NYHA II 53% and III/IV 47%, and median NT‐proBNP 1971 pg/mL. HF therapies at baseline were among the most effectively employed in contemporary HF trials. GALACTIC‐HF randomized patients representative of recent HF registries and trials with substantial numbers of patients also having characteristics understudied in previous trials including more from North America (n = 1386), enrolled as inpatients (n = 2084), systolic blood pressure < 100 mmHg (n = 1127), estimated glomerular filtration rate < 30 mL/min/1.73 m2 (n = 528), and treated with sacubitril‐valsartan at baseline (n = 1594). Conclusions: GALACTIC‐HF enrolled a well‐treated, high‐risk population from both inpatient and outpatient settings, which will provide a definitive evaluation of the efficacy and safety of this novel therapy, as well as informing its potential future implementation

Revisiting a sample of U.S. billionaires : How sample selection and timing of maternal condition influence findings on the Trivers-Willard effect

Based on evolutionary theory, Trivers & Willard (TW) predicted the existence of mechanisms that lead parents with high levels of resources to bias offspring sex composition to favor sons and parents with low levels of resources to favor daughters. This hypothesis has been tested in samples of wealthy individuals but with mixed results. Here, I argue that both sample selection due to a high number of missing cases and a lacking specification of the timing of wealth accumulation contribute to this equivocal pattern. This study improves on both issues: First, analyses are based on a data set of U.S. billionaires with near-complete information on the sex of offspring. Second, subgroups of billionaires are distinguished according to the timing when they acquired their wealth. Informed by recent insights on the timing of a potential TW effect in animal studies, I state two hypotheses. First, billionaires have a higher share of male offspring than the general population. Second, this effect is larger for heirs and heiresses who are wealthy at the time of conception of all of their children than for self-made billionaires who acquired their wealth during their adult lives, that is, after some or all of their children have already been conceived. Results do not support the first hypothesis for all subgroups of billionaires. But for males, results are weakly consistent with the second hypothesis: Heirs but not self-made billionaires have a higher share of male offspring than the U.S. population. Heiresses, on the other hand, have a much lower share of male offspring than the U.S. average. This hints to a possible interplay of at least two mechanisms affecting sex composition. Implications for future research that would allow disentangling the distinct mechanisms are discussed

Nature plus nurture equals love? A test of the Trivers -Willard hypothesis of differential parental investment on the basis of sociological and biological explanations

In this dissertation, I test the Trivers-Willard hypothesis of differential parental investment using the genetic sample of the U.S. National Longitudinal Study of Adolescent Health. Based on general propositions of evolutionary theory, Trivers and Willard predicted that parents of higher socioeconomic status bias their parental investment to favor sons and that parents of lower socioeconomic status bias their investment to favor daughters. Empirical support for this hypothesis has been mixed. I aim to improve previous research in three ways: First, I draw on both biological and sociological explanations for differences in parental investment and reflect these explanations in the analyses. Second, I model parental investment both between and within families, whereas most empirical studies on the Trivers Willard hypothesis have examined parental investment differences only between families. Third, by using data on twins, full siblings, half siblings, and unrelated siblings I compare how biological parenthood and twin status play out in the assumed dynamic between parental status and child gender. The results are mixed and indicate partial support consistent with the TW hypothesis: Support is evident for breastfeeding initiation within families, but not with regard to breastfeeding continuation. Furthermore, I find support for children's perceptions of how much their parents care for them, but only within families and once previous perceptions and parental support are accounted for. There is no support for the Trivers-Willard hypothesis for parental engagement in activities with their children. In the last chapter I conclude with a discussion of reasons why the Trivers-Willard effect may be expressed only for certain types of parental investment and under specific circumstances. Furthermore, I suggest routes for future research that integrates biological and sociological concepts on a more detailed level and that can shed new light on the specific mechanisms that produce the interaction effect between parental status and child gender in parental investment

Economic stress or random variation? : Revisiting german reunification as a natural experiment to investigate the effect of economic contraction on sex ratios at birth

The economic stress hypothesis (ESH) suggests that economic decline leads to a decrease in the proportion of males born in a population. A multitude of additional influences on sex ratios that often cannot be accounted for empirically make assessing the validity of the ESH difficult. Thus, as a historical quasi-experiment, German reunification constitutes an interesting test case. The economy in East Germany, but not in West Germany, underwent a rapid decline in 1991. In the same year, the sex ratio decreased in East Germany, but not in West Germany. Catalano (2003) interpreted these developments as evidence in support of the ESH. Using more recent and detailed data, we re-examine this case to test an alternative explanation, the random variation hypothesis (RVH). Using aggregate data on sex ratios between 1946-2010 and individual-level data on over 13 million births from the German Birth Registry between 1991-2009, we find evidence supporting the RVH but not the ESH. First, the sex ratio in East Germany shows stronger deviations from the time trend in several years, and is seemingly unrelated to economic developments. The degree of variation is associated with the smaller and decreasing number of births in East Germany during the fertility decline following reunification. The individual-level analysis confirms that the 1991 decrease in the East German sex ratio could also be the result of random variation. A specificity of the East German transformation is the buffering of the consequences of economic decline through integration into the West German welfare state. Therefore, the ESH may be applicable in other transformation cases

Economic stress or random variation? : Revisiting German reunification as a natural experiment to investigate the effect of economic contraction on sex ratios at birth

BackgroundThe economic stress hypothesis (ESH) predicts decreases in the sex ratio at birth (SRB) following economic decline. However, as many factors influence the SRB, this hypothesis is difficult to test empirically. Thus, researchers make use of quasi-experiments such as German reunification: The economy in East, but not in West Germany, underwent a rapid decline in 1991. A co-occurrence of a decline in the East German SRB in 1991 has been interpreted by some as support for the ESH. However, another explanation might be that the low SRB in 1991 stems from increased random variation in the East German SRB due to a drastically reduced number of births during the crisis. We look into this alternative random variation hypothesis (RVH) by re-examining the German case with more detailed data.MethodsOur analysis has two parts. First, using aggregate-level birth register data for all births in the period between 1946 and 2011, we plot the quantum and variance of the SRB and the number of births and unemployment rates, separately for East and West Germany, and conduct a time series analysis on the East German SRB over time. Second, we model the odds for a male birth at the individual level in a multiple logistic regression (1991–2010, ~13.9 million births). Explanatory variables are related to the level of the individual birth, the mother of the child born, and the regional economic context.ResultsThe aggregate-level analysis reveals a higher degree of variation of the SRB in East Germany. Deviations from the time trend occur in several years, seemingly unrelated to economic development, and the deviation in 1991 is not statistically significant. The individual-level analysis confirms that the 1991-drop in the East German SRB cannot directly be attributed to economic development and that there is no statistically significant effect of economic development on sex determination in East or West Germany.ConclusionOutcomes support the RVH but not the ESH. Furthermore, our results speak against a statistically significant effect of the reunification event itself on the East German SRB. We discuss the relative importance of behavioral and physiological responses to macro-level stressors, a distinction that may help integrate previously mixed findings.publishe