Polygyny, food security, and child health
Household survey in polygynous Maasai village
Polygyny, a marriage system where men can have multiple wives, is often considered to be detrimental to the well-being of women and children. David Lawson et al. (pp. 13827–13832) compared polygynous and monogamous households in 56 villages in northern Tanzania, where polygyny is prevalent among certain ethnic groups. Consistent with prior research, the authors found that polygyny was associated with low food security and poor child health when aggregating data across all villages. However, this pattern could be entirely accounted for by the tendency of polygyny to be most common in marginalized and ecologically vulnerable villages and ethnic groups. When comparing households within individual villages, polygynous households, at least those headed by males, often had relatively higher food security and superior child health. Polygynous households also owned more cattle and farmed more land than monogamous households. The findings are consistent with models in which polygyny is thought to serve women’s strategic interests when women depend on men for resources. The authors highlight the importance of local context in studying the implications of cultural practices, and suggest that in places with large differences in wealth among men, prohibiting polygyny might restrict women’s marriage options. — B.D.
Incidence and impact of negative citations
Incidence of negative citations is high in years immediately after publication.
Citations are an important measure of a scientific paper’s impact and, indirectly, of the influence of researchers, institutions, and journals. Using a technique called natural-language processing (NLP) to determine the existence and characteristics of negative citations, Christian Catalini et al. (pp. 13823–13826) analyzed the full text of 15,731 scientific articles. The articles, published in the Journal of Immunology between 1998 and 2007, contained 762,355 citations. To identify negative citations, the authors coded 15,000 citations as negative or objective and created an algorithm with NLP. Negative citations contained phrases such as “the conclusion appeared inconsistent with” or “our findings differ from.” Overall, 2.4% of the total citations were negative. Of the 146,891 papers represented in the citations, 7.1% received at least one negative citation. Negative citations were high in the immediate years after publication and for prominent papers, likely due to increased attention and scrutiny in both instances. Further, negative citations originated from those close to the cited authors’ disciplines. According to the authors, the methodology for identifying negative citations should be expanded into different fields and historical periods to trace the evolution of knowledge and improve search algorithms in online repositories. — T.H.D.
Sequencing protocols in human microbiome studies
Over the past decade, next-generation sequencing of the human microbiome has yielded insights into a variety of diseases, but the results have often been conflicting or inconclusive. The misinterpretation of data in the field might arise from artifacts introduced by next-generation sequencing protocols such as library preparation, which converts nucleic acid material into standard libraries suitable for loading onto a sequencing instrument. To address this issue, Marcus Jones et al. (pp. 14024–14029) compared whole-genome sequencing data from complete microbial communities using four different library preparation protocols. Two of these methods required PCR, which amplifies nucleic acid fragments in the library prior to sequencing. The authors compared the methods using stool samples from a healthy volunteer treated with antibiotics, as well as a synthetic mock community composed of a mixture of 20 microbial genomic DNAs. The two methods that did not require PCR resulted in lower error rates and higher-quality reads for the mock community, compared with the PCR-based methods. Moreover, the four different libraries showed significant variation in the relative abundance of microbial members of the mock community and the stool samples. According to the authors, the findings highlight the need for consistency across next-generation sequencing protocols to improve the interpretation of microbiome data in studies of human health and disease. — J.W.
Mechanisms of phenotypic plasticity
(Left) Eusocial wasp (Polistes canadensis) and (Right) ant (Dinoponera quadriceps).
Plasticity between phenotypes in organisms, such as transitions between worker and queen phenotypes in eusocial insect societies, plays a large role in societal adaptation, but the genetic mechanisms driving such plasticity are unknown. Solenn Patalano et al. (pp. 13970–13975) sequenced genomes and generated profiles of microRNA expression, transcription, and DNA methylation from the brains of two species of wasps and ants that retain phenotypic plasticity into adulthood. The authors found little difference in general transcriptome activity among worker and queen phenotypes, and also little difference in microRNA expression or DNA methylation, suggesting that these mechanisms are not responsible for regulating phenotypic expression. Although the authors found few genes that were differentially expressed between phenotypes, the genes that differed were organized into consistent, nonrandom networks. The networks included genes that had also been found in other organisms as well as genes specific to the respective wasp and ant species. Wasps and ants displayed levels of DNA methylation similar to other social insects, but the authors found few coherent patterns in DNA methylation in the species. The authors suggest that such lack of patterning may facilitate adult phenotypic plasticity. According to the authors, subtle networks of coexpressed genes and weak DNA methylation patterning may regulate phenotype transitions in eusocial insects. — P.G.
Endocannabinoid signaling and social interactions
Marijuana use can enhance interpersonal communication and improve social interactions, although the mechanism of such effects is unknown. To investigate the role of anandamide, a marijuana-like neurotransmitter, in social contact, Don Wei et al. (pp. 14084–14089) measured anandamide levels in mice that had been either isolated or in social contact. The authors found that social contact increased production of anandamide in the nucleus accumbens brain structure, and activation of endocannabinoid receptors was necessary to produce rewarding effects of social interaction. Further, the authors found that oxytocin, which has been associated with interpersonal bonding, can stimulate anandamide production in the nucleus accumbens, and that blockade of oxytocin receptors inhibited this effect. The finding suggests that activation of oxytocin receptors may enhance anandamide production and oxytocin activity can mediate cannabinoid signaling in the brain. Additionally, interruption of anandamide degradation mechanisms restored social reward functions when oxytocin receptors were blocked. The results suggest that anandamide signaling may underlie the rewards of social contact, and deficiencies in this signaling process may contribute to disorders affecting social interaction, such as autism, according to the authors. — P.G.