This article argues that a pervasive but confused theory of free will is driving unwarranted resistance to behavioral genetic research and undermining the concept of personal responsibility enshrined in our moral and legal conventions. We call this the theory of ‘free-will-by-subtraction’. A particularly explicit version of this theory has been propounded by the psychologist Eric Turkheimer, who has proposed that human agency can be scientifically quantified as the behavioral variation that remains unexplained after known genetic and environmental causes have been accounted for. This theory motivates resistance to research that suggests genetic differences substantially account for differences in human behavior because that is seen to reduce the scope of human freedom. In academic philosophy, free-will-by-subtraction theory corresponds to a position called ‘libertarian incompatibilism’, which holds that human beings are not responsible for behavior that has antecedent causes yet maintains that free will nonetheless exists because some fraction of human behavioral variation is self-caused. However, this position is rejected by most professional philosophers. We argue that libertarian incompatibilism is inconsistent with a secular materialist outlook in which all human behavior is understood to have antecedent causes whether those causes are known to science or not — an outlook Turkheimer shares. We show that Turkheimer sustains this contradiction by adopting an untenable position we call ‘epistemic libertarianism’, which holds that antecedent causes of our behavior only infringe on our freedom if we know about them. By contrast, the overwhelming majority of secular materialist philosophers support a position called ‘compatibilism’, which maintains that free will is compatible with the comprehensive causation of human behavior. We show that compatibilism neutralizes the threat that genetic explanation poses to human agency and rescues a generous conception of personal responsibility that aligns with our moral intuitions.

The objective was to identify the predictive markers and develop a diagnostic model with predictive markers for Parkinson’s disease (PD) and investigate the roles of immune cells in the disease pathology. Microarray datasets of PD and control samples were obtained from the Gene Expression Omnibus (GEO) database. We then performed a comprehensive analysis of differentially expressed genes (DEGs), functional enrichment, and protein-protein interactions to pinpoint a set of promising candidate genes. To establish a diagnosis model for PD, we utilized machine learning algorithms and evaluated the corresponding diagnostic performance using the receiver operating characteristic (ROC) curve and the area under the ROC curve (AUC). Additionally, the differential abundance of immune cell subsets between PD and control samples was evaluated using the single-sample Gene Set Enrichment Analysis (ssGSEA) method. A total of 264 DEGs were identified in GSE72267. The PPI network ultimately identified 30 hub genes for model construction. Seven genes, namely CD79B, CD40, CCR9, ADRA2A, SIGLEC1, FLT3LG, and THBD, were identified as diagnostic markers for PD, with an AUC of 0.870. This seven-gene signature model was subsequently validated in an independent cohort (GSE22491), demonstrating an AUC of 0.825. Ultimately, the infiltration of 28 immune cells showed that activated B cells, natural killer T cells, and regulatory T cells may contribute to the occurrence and progression of PD. We also found complex associations between these genes and immune cells. CD79B, CD40, CCR9, ADRA2A, SIGLEC1, FLT3LG, and THBD were identified as diagnostic markers for PD, and the infiltration of immune cells may contribute to the pathogenesis of the disease.

Leveraging a unique dataset (the English Longitudinal Study of Aging) containing polygenic scores (PGSs) — estimated using meta-analytically-derived single nucleotide polymorphisms (SNPs) for the Big Five (BF) — the General Factor of Personality’s (GFP) existence as a veritable psychometric entity was investigated. Exploratory tests involving a subsample of 200 participants revealed that while the BF PGSs were adequate for factor analysis, parallel analysis suggested the presence of zero factors, indicating no “genetic GFP” among these PGSs, but did indicate the presence of a robust latent GFP among the phenotypic BF. Confirmatory factor analysis involving an independent sample of 4,533 participants was used to compete three models: full mediation by the GFP of PGS effects on the BF (common pathway or reflective); full mediation by the BF of PGS effects on the GFP (independent pathways or formative); and a mixed model. All models exhibited good fit, with the reflective model having the greatest parsimony. Statistically significant covariances were also observed among the PGSs, potentially consistent with pleiotropy. Even though the reflective model fit best, the common paths were extremely weak (and could be set to zero in most cases), with only the (negatively signed) path from the extraversion PGS to the GFP reaching significance. This finding is (weakly) consistent with the hypothesis that the GFP is a valid entity.

This study explores whether DNA methylation (DNAm) mediates the association between lean body mass (LBM) and cognition, as well as whether LBM mediates the association between DNAm and cognition. Based on the data of 59 monozygotic twin pairs, mediation analyses were performed using causal inference test method and mediation analyses. Average causal mediation effect (ACME), average direct effect (ADE), and total effect (TE) were calculated. Among the CpGs associated with LBM, five located within PDGFRB and RP11 genes (ACME: −0.0972−0.0463, |ACME/ADE|: 10.44%−18.30%) negatively mediated the association between LBM and cognition, while one in the PAX2 gene (ACME: 0.3510, |ACME/TE|: 11.84%) positively mediated the association. Besides, the methylation risk score (MRS) of RP11 gene (ACME: −0.0517, |ACME/ADE|: 10.64%) and MRS of all CpGs (ACME: −0.0511, |ACME/ADE|: 10.53%) negatively mediated the association of LBM with cognition. For another, LBM negatively mediated the association between the DNAm level of one CpG within UBXN6 and cognition (ACME: −0.0732, |ACME/TE|: 20.78%), while positively mediated the association between the DNAm level of four CpGs within FOXI2 and cognition (ACME: 0.2812−0.4496, |ACME/TE|: 18.15%−27.29%). It was found the DNAm in PDGFRB, RP11 and PAX2 partially mediates the association between LBM and cognition, and the association between DNAm in UBXN6 and FOXI2 with cognition is also partially mediated by LBM.

Patients with familial adenomatous polyposis (FAP) have increased risk of hepatoblastoma (HB). We report monozygotic twins with HB in a FAP family. To explore genetic alterations in the HBs of the twins, we carried out whole exome sequencing (WES), RNA-seq, and immunohistochemical analyses of the tumors. Additional multiregional digital PCR was performed to profile clonality of each tumor. To determine a pathogenic germline variant in APC, Sanger sequencing was applied for the twins, the father, and the siblings of the father. A pathogenic variant of the APC gene was identified in the father as well as the twins. The WES of the HBs in the twins identified somatic mutations, including an NRAS mutation in the tumor of the first infant (C1), and an ACVR2A mutation in the tumor of the second infant (C2). No somatic mutations were identified in the genes associated with the Wnt signaling pathway. However, accumulation of β-catenin was found in the C1 and C2 tumors by immunohistochemical staining, suggesting activation of the Wnt signaling pathway. Digital PCR analysis revealed that the NRAS mutation was found in multiregional specimens of C1 and those of C2. The ACVR2A mutation was found in multiregional specimens of C2, whereas the mutation was also identified in those of C1. The existence of a shared somatic mutation may suggest that microchimerism took place in the development of HBs through the utero-placental circulatory system. Importantly, the initiation of tumorigenesis is thought to occur during the fetal period after organ development of the liver.

Twin children are more likely to die than singletons. This is an additional burden in sub-Saharan African (SSA) countries, as child mortality levels are already higher than anywhere else. This article provides estimates of under-5 mortality rates (U5MRs) for twins and singletons in SSA from 1986 to 2016. It describes the geographical variations and changes over time. It also describes the variation of twins’ excess mortality according to age from 0 to 5 years. Additionally, it analyzes the factors associated with twins’ excess mortality. We used data from 156 national surveys from 42 countries. We estimated U5MRs for twins and single children and built a Cox model to analyze factors associated with excess mortality among twins. Although child mortality has declined on the continent, twins’ excess mortality remains very high. U5MRs are, on average, 3 times higher among twins than singletons. The Cox model shows that all other things being equal, the adjusted hazard ratio of under-5 mortality (U5M) is 3.2 (2.9−3.3; p < .001) times higher among twins than singletons. The main factors associated with excess mortality risks among twins are biomedical and nutritional features, such as low birth weight, non-use of cesarean section delivery, and lack of breastfeeding. Health policy makers in SSA should be aware of the vulnerability of twins, and interventions to prevent their early deaths should be considered.

Max Nicholls had an almost unique experience as a medical practitioner, researcher and teacher of medical genetics. An earlier paper described his contribution to the etiology of neurofibromatosis. This was followed by Nicholls’ own experience as lecturer in the Faculty of Medicine, University of New South Wales, Australia. This note draws attention to his research in immunology. For example, he was instrumental in the study of the buffy coat leuko-agglutination (BCLA) test, a sensitive assay for cell-mediated immunity that he introduced to detect conditions (including cancer) in preclinical stages.

Twin highlights from the 2025 summer meeting of the International Society for Human Ethology are reviewed. The value of observing twins in naturalistic and semi-naturalistic settings is revealed. Research reports involving twins with Feingold syndrome, twins with language delays, breastfeeding of twins, and twins with Olmsted syndrome are reviewed. The final section of this article covers timely and informative news of twins in the media. Topics include the loss of young Texas twins in the devasting July 4th flood, a sensational — and singular — musical twin performer, conjoined twin deliveries in Myanmar and India, and two pairs of twins headed to major league baseball teams.