Wednesday, June 15, 2022

Studying two highly divergent phyla of worms that contain numerous parasites that cause human and livestock diseases, new research sheds light on how sexual reproduction and subsequent great diversity of sex chromosomes might have evolved

Yifeng Wang, Robin B. Gasser, Deborah Charlesworth, Qi Zhou. Evolution of sexual systems, sex chromosomes and sex-linked gene transcription in flatworms and roundworms. Nature Communications, 2022; 13 (1). Jun 10 2022. DOI: 10.1038/s41467-022-30578-z

Abstract: Many species with separate male and female individuals (termed ‘gonochorism’ in animals) have sex-linked genome regions. Here, we investigate evolutionary changes when genome regions become completely sex-linked, by analyses of multiple species of flatworms (Platyhelminthes; among which schistosomes recently evolved gonochorism from ancestral hermaphroditism), and roundworms (Nematoda) which have undergone independent translocations of different autosomes. Although neither the evolution of gonochorism nor translocations fusing ancestrally autosomal regions to sex chromosomes causes inevitable loss of recombination, we document that formerly recombining regions show genomic signatures of recombination suppression in both taxa, and become strongly genetically degenerated, with a loss of most genes. Comparisons with hermaphroditic flatworm transcriptomes show masculinisation and some defeminisation in schistosome gonad gene expression. We also find evidence that evolution of sex-linkage in nematodes is accompanied by transcriptional changes and dosage compensation. Our analyses also identify sex-linked genes that could assist future research aimed at controlling some of these important parasites.

Popular version: Parasitic worms reveal new insights into the evolution of sex and sex chromosomes Two worm phyla give clues on how sex chromosomes might have evolved. Jun 15 2022.


The evolution of sex chromosomes in some taxa involves the primary transition from a hermaphroditic system or from environmental sex determination to a dioecious/gonochoristic species with genetic sex determination. Such transitions usually are accompanied by potential suppression of recombination in and around the sex-determining gene(s), and the recombination suppression sometimes even extends to other sex chromosome regions. In other species, turnover events may create new sex-determining regions, which may also evolve into non-recombining regions. In either case, autosomal regions that fused or translocated to sex chromosomes may sometimes also become completely sex-linked, either in species that lack recombination in the heterogametic sex26, or potentially in species with recombination in both sexes through subsequent recombination loss.

Schistosomes have evolved gonochorism from hermaphroditism and exhibit strong morphological sexual dimorphism (see above). As explained earlier, the first step in such a primary transition must either involve a mutation creating females (producing a gynodioecious population), or one creating males (producing an androdioecious population). A mutation in the highly conserved oogenesis-related or feminising gene mag-1 might have produced males in the ancestor of schistosomes. However, it seems unlikely that such a mutation could have greatly increased male fitness, compared with that of the ancestral hermaphrodite, as required for the establishment of androdioecy. Females could have arisen due to a dominant mutation in the reported W-linked candidate sex-determining gene U2AF2 (Fig. 5k)85,86. The involvement of these genes in the evolution of schistosome sex-determination needs to be tested in the future.

Our finding that the evolution of the present schistosome sex-linked regions was followed by transcriptional changes of many genes in gonads (Fig. 5d–g) is consistent with the hypothesis of sexual antagonism in the hermaphroditic ancestor, favouring re-allocation of resources after separate sexes evolved75. Assuming that higher transcription levels reflect advantageous changes, the results in schistosomes suggest that conflicts were resolved and a new optimum reached more frequently in males (masculinisation and overwhelming defeminisation) than in females (feminisation) in the gonads. In the transition to dioecy in Silene latifolia, with male, instead of female heterogamety, and an XY sex chromosome system, transcriptional changes occurred most frequently in females92. The results suggest transcriptional changes after the X or Z chromosome became hemizygous in one sex, resulting in masculinisation of the schistosome Z (as shown in Supplementary Fig. 16) and feminisation of the X chromosome in S. latifolia.

Following the origin of gonochorism, both schistosome and nematode ancestral sex chromosomes have undergone translocations of autosomes, like those in many other taxa26,56 (Figs. 3 and 5a). The translocated autosomes, or large parts of them, have become completely non-recombining in both phyla, and in nematodes they have become strongly degenerated like the ancestral sex chromosomes. How loss of recombination happened is an interesting question. Recombination between the autosomes involved in a fusion or translocation with sex chromosomes often maintain autosomes’ former recombination patterns. However, the study of fusions between the C. elegans X chromosome and chromosome IV62 suggested that crossovers may be re-positioned away from the fusion junction, creating a new chromosome with two arm regions (whereas the two participating chromosomes each contained two arm regions). In the fused chromosome, a potentially large former arm region close to the fusion point may thus have greatly reduced recombination, and if the fusion involves the X chromosome, this will occur specifically in males. Such events can therefore create new sex-linked regions without involving selection for suppressed recombination.

Translocations of autosomes to ancestral sex chromosomes may be common in nematodes because some, though not all, nematodes have holocentric chromosomes93. Such chromosomes may be more prone to fusions or fissions than monocentric ones, in which such rearrangements may lead to a loss or multiplication of centromeres94. However, a recent comparison of insects with different centromere types found no evidence supporting this hypothesis95.

Finally, we annotated many Y- or W-linked genes additional to those already known in the flatworm and roundworm species studied here (Figs. 4 and 5). We also found homologs of C. elegans sex-determination pathway genes that may have undergone duplications in different nematode species. These genes could be involved in the divergence of the sex-determination pathways, as has already been documented between C. elegans vs. C. briggsae96. Functional verification in other nematode species is needed in the future. The present study could not identify further changes that may have occurred after lineage-specific duplications of these genes, and possible changes also need to be studied further. For example, gld-1 was independently recruited into the sex-determination pathways of C. elegans and C. briggsae; in C. elegans it acts to promote spermatogenesis, but it promotes oogenesis in C. briggsae97. Its co-factor, fog-2, evolved by a duplication and acquisition of a new GLD-1-binding domain in C. elegans88,98. The newly annotated, candidate sex-determining genes could be a useful resource for future studies of parasite control through interfering with their sexual life cycles.

We cannot read the generosity of others from their facial features, but we are convinced that the good looking are more generous

You Cannot Judge a Book by Its Cover: Evidence from a Laboratory Experiment on Recognizing Generosity from Facial Information. Ninghua Du, Fei Song, C. Bram Cadsby. Journal of Behavioral and Experimental Economics, June 14 2022, 101909.

• People cannot glean information about other-regarding preferences from facial information

• People make systematic errors when they try to identify generosity from facial information

• Those who are rated as more attractive are perceived to be more generous

• There is no actual relationship between physical attractiveness and generosity

Abstract: People form first impressions of others and may make judgments about their social traits and character on the basis of facial perceptions. We implement a controlled laboratory experiment to investigate whether people can glean information about another person's other-regarding preferences from uncropped photographs of their face. To do so, we conduct a dictator game with an allocator and a recipient, and then present pairs of allocator photos to observers. Each pair portrays one relatively generous allocator and another who has demonstrated less generosity. The experimental results show that the observers cannot accurately recognize more generous allocators, but instead make systematic errors. In particular, the observers believe that allocators who are rated more attractive by others are more generous, despite there being no actual relationship between physical attractiveness and generosity.

Keywords: Face-based JudgmentExperimentDictator GameOther-regarding PreferencesGenerosityAppearance

Feeling younger than one's chronological age was associated with better mental and physical health, presence of meaning in life, successful aging, optimism, personal mastery, resilience, curiosity, hope, and social support

Subjective age and its relationships with physical, mental, and cognitive functioning: A cross-sectional study of 1,004 community-dwelling adults across the lifespan. Awais Aftab et al. Journal of Psychiatric Research, June 14 2022.

Abstract: Perceived younger age is associated with positive health outcomes in existing literature. Few studies have examined these associations using a wide range of variables in large sample of adults of all ages. The objective of present study was to characterize the discrepancy between chronological age (CA) and subjective age (SA) in a large sample of community-dwelling adults across the lifespan, investigate associations with mental, physical, and cognitive health, and examine how it is related to a broad array of psychosocial variables relevant to well-being. Cross-sectional data from 1,004 individuals aged 21–100+ years from the Successful AGing Evaluation (SAGE) study were used for this analysis. Data included self-report measures of physical health (SF-36 – Physical Component), mental health composite score (created using CES-D Happiness scale, Satisfaction with Life Scale, SF-36 Mental Component, Brief Symptom Inventory Anxiety Scale, Patient Health Questionnaire-9, and Perceived Stress Scale), Telephone Interview for Cognitive Status - modified (TICS-m), and validated measures of various positive psychological variables such as meaning in life and optimism. On average, SA was 11.5 years younger than CA (SD 11.3). The discrepancy increased with CA. A younger SA compared to CA was associated with better mental and physical health in all age groups and was positively associated with measures of presence of meaning in life, successful aging, optimism, personal mastery, resilience, curiosity, hope, and social support. The association between age discrepancy and cognitive functioning was not statistically significant. These findings indicate that SA is potentially valuable for the purposes of clinical assessment and intervention, and this possibility should be investigated in future research.

Keywords: Positive psychiatryMeaning in lifeSuccessful agingOptimismPersonal masteryResilience

High social status, good looks, and being well-off and influential did not belong to the traits found desirable in a friend, and women held higher expectations for friends than men

Friendship Preferences: Examining Desirable and Undesirable Traits in a Friend. Menelaos Apostolou & Panagiota Vetsa. Evolutionary Psychological Science, Jun 14 2022.

Abstract: Friendship constitutes a human universal, with people across different times and places forming friendly relationships. Yet, people are selective in whom they befriend. The current research aimed to identify friendship preferences, that is, the traits that people find desirable or undesirable in a friend. More specifically, Study 1 employed open-ended questionnaires and identified 50 traits that participants preferred their friends to have, and 43 traits that they preferred their friends not to have. Study 2 employed a sample of 706 Greek-speaking participants and classified desirable traits into 10 broader factors; the most important one was being honest, followed by being ethical, pleasant, and available. Study 3 employed a sample of 865 Greek-speaking participants and classified undesirable traits into three broader factors. The most undesirable one was being dishonest, followed by being competitive and being impatient. In both studies, women tended to give higher scores than men. In addition, significant age effects were found for most factors in both studies.

The biological basis of intelligence

The biological basis of intelligence: Benchmark findings. Kirsten Hilger et al. Intelligence, Volume 93, July–August 2022, 101665.


• Focused overview of research on the biological basis of intelligence.

• Benchmark findings from EEG, neuroimaging, and genetic research.

• Critical open questions and future directions.

Abstract: The scientific study of the biological basis of intelligence has been contributing to our understanding of individual differences in cognitive abilities for decades. In particular, the ongoing development of electrophysiological, neuroimaging, and genetic methods has created new opportunities to gain insights into pressing questions, allowing the field to come closer towards a comprehensive theory that explains how genotypes exert their influence on human intelligence through intermediate biological and cognitive endophenotypes. The aim of this article is to provide a focused overview of empirical benchmark findings on biological correlates of intelligence. Specifically, we summarize benchmark findings from electrophysiological, neuroimaging, and genetic research. Moreover, we discuss four open questions: (1) The robustness of research findings; (2) the relation between neural parameters and cognitive processes; (3) promising methodological developments; and (4) theory development. The aim of this paper is to assemble the most important and robust findings on the biological basis of intelligence to stimulate future research and to contribute to theory development.

Keywords: NeuroscienceElectroencephalographyMagnet resonance imaging (MRI)GeneticsIntelligenceCognitive abilities