Gestational Potential Space Hypothesis: Evolutionary Explanation of Human Females Body Fat Redistribution

Homo sapiens, as well as other primates, developed the evolutionary advantage of storing excess energy as body fat, primarily in the readily accessible visceral fat compartment when food is plentiful for use during scarcity. However, uniquely to female humans, a second transient dimorphic phenotypic change begins at menarche and is reversed by menopause. It is the diversion of visceral fat stores from the abdominal cavity to the gluteofemoral region. The evolutionary purpose for this remains unclear. The author proposes the gestational potential space (GPS) hypothesis: that such fat diversion is for the reproductive purpose of increasing the potential abdominal space available for gestation and reducing the intraabdominal pressure. This hypothesis is supported by the basic laws of physics and increased rates of maternal and fetal complications experienced by those with visceral adiposity. It is important that the GPS hypothesis and alternative hypotheses are tested by comparing the health (particularly reproductive) outcomes of women with varying fat distributions and their offspring. Lay summary The author proposes that fat shifting from the abdominal cavity to the hips and thighs in women, during the childbearing period, is for beneficial for reducing the intraabdominal contents consequently increasing pregnancy potential space. Secondarily, it prevents intraabdominal pressure elevation and reduces maternal and fetal complications associated with visceral fat in pregnancy.

Women who breastfeed exhibit cognitive benefits after age 50

Background and objectives Women who breastfeed may experience long-term benefits for their health in addition to the more widely-appreciated effects on the breastfed child. Breastfeeding may induce long-term effects on biopsychosocial systems implicated in brain health. Also, due to diminished breastfeeding in the post-industrial era, it is important to understand the lifespan implications of breastfeeding for surmising maternal phenotypes in our species’ collective past. Here, we assess how women’s breastfeeding history relates to post-menopausal cognitive performance. Methodology A convenience sample of Southern California women age 50+ was recruited via two clinical trials, completed a comprehensive neuropsychological test battery and answered a questionnaire about reproductive life-history. General linear models examined whether cognitive domain scores were associated with breastfeeding in depressed and non-depressed women, controlling for age, education, and ethnicity. Results Women who breastfed exhibited superior performance in the domains of Learning, Delayed Recall, Executive Functioning and Processing Speed compared to women who did not breastfeed (p-values 0.0003-0.015). These four domains remained significant in analyses limited to non-depressed and parous subsets of the cohort. Among those depressed, only Executive Functioning and Processing Speed were positively associated with breastfeeding. Conclusions and implications We add to the growing list of lifespan health correlates of breastfeeding for women’s health, such as lower risk of type-2 diabetes, cardiovascular disease, and breast cancer. We surmise that women’s post-menopausal cognitive competence may have been greater in past environments in which breastfeeding was more prevalent, bolstering the possibility that post-menopausal longevity may have been adaptive across human evolutionary history. Lay Summary Breastfeeding may affect women’s cognitive performance. Breastfeeding’s biological effects and psychosocial effects, such as improved stress regulation, could exert long-term benefits for the mother’s brain. We found that women who breastfed performed better on a series of cognitive tests in later life compared to women who did not breastfeed.

Variation among human populations in endometriosis and PCOS: a test of the inverse comorbidity model

ABSTRACT Evidence linking endometriosis to low prenatal testosterone, and evidence that risk of polycystic ovary syndrome (PCOS) is associated with high prenatal testosterone, has motivated the hypothesis that endometriosis and PCOS exhibit inverse comorbidity. The inverse comorbidity hypothesis predicts that populations exhibiting higher prevalence of one disorder should show lower prevalence of the other. To test this prediction, data were compiled from the literature on the prevalence of endometriosis and PCOS, levels of serum testosterone in women during pregnancy, and digit ratios as indicators of prenatal testosterone, in relation to variation in inferred or observed population ancestries. Published studies indicate that rates of endometriosis are highest in women from Asian populations, intermediate in women from European populations, and lowest in women from African populations (i.e., with inferred or observed African ancestry); by contrast, rates of PCOS show evidence of being lowest in Asian women, intermediate in Europeans, and highest in individuals from African populations. Women from African populations also show higher serum testosterone during pregnancy (which may increase PCOS risk, and decrease endometriosis risk, in daughters), and higher prenatal testosterone (as indicated by digit ratios), than European women. These results are subject to caveats involving ascertainment biases, socioeconomic, cultural and historical effects on diagnoses, data quality, uncertainties regarding the genetic and environmental bases of population differences, and population variation in the causes and symptoms of PCOS and endometriosis. Despite such reservations, the findings provide convergent, preliminary support for the inverse comorbidity model, and they should motivate further tests of its predictions.

Prevalence and factors related to psychological distress among ethnic minority adults in a semi-modern village in rural vietnam: an evolutionary mismatch framework

ABSTRACT Background and objectives Psychological distress is one of the greatest health threats facing humanity and has been hypothesized to represent an evolutionary mismatch. This hypothesis can be tested in semi-traditional societies that are undergoing transitions to modern lifestyles. This study used an evolutionary medicine framework to examine the predictors of psychological distress symptomology in a semi-modern ethnic minority village in rural Vietnam that is transitioning into a developing economy. Methodology A cross-sectional survey was conducted in Chieng Sai Village among White Thai ethnic minority adults aged 18-75. The DASS-21 scale was used to measure the prevalence of psychological distress symptoms, and a closed format questionnaire was used to collect data on independent variables. Binary logistic regression analyses were used to determine associated factors of psychological distress symptomology. Results The prevalence of psychological distress symptoms was 22% (depression = 16.9%, stress = 16.3%). Common features of modernity, such as low levels of exercise, boredom, and low income, showed a positive association with psychological distress, while lifestyle features that were more similar to those expected in the evolutionary past and that fulfilled evolutionary adaptations, such as getting enough sleep, physical exertion, and earning sufficient income (access to resources), showed a negative association with psychological distress. Conclusions and Implications This study suggests that modern lifestyles might have generated evolutionary mismatches that are negatively impacting mental health in Chieng Sai Village. Future research should focus on determining the causal relationship between psychological distress and evolutionary mismatches. Evolutionary medicine approaches to understanding and treating psychological distress are potential forces of disease reduction to be considered in public health and educational policy. Lay Summary Approximately 22% of White Thai ethnic minority adults in the village of Cheing Sai reported psychological distress symptoms. I found that lifestyle factors unique to modern society had positive associations with psychological distress symptomology, while lifestyle factors that mimic aspects of human evolutionary past, such as exercise, had negative associations with psychological distress symptoms.

Daily rhythms of both host and parasite affect antimalarial drug efficacy

Background and objectives Circadian rhythms contribute to treatment efficacy in several non-communicable diseases. However, chronotherapy (administering drugs at a particular time-of-day) against infectious diseases has been overlooked. Yet, the daily rhythms of both hosts and disease-causing agents can impact the efficacy of drug treatment. We use the rodent malaria parasite Plasmodium chabaudi, to test if the daily rhythms of hosts, parasites, and their interactions, affect sensitivity to the key antimalarial, artemisinin. Methodology Asexual malaria parasites develop rhythmically in the host’s blood, in a manner timed to coordinate with host daily rhythms. Our experiments coupled or decoupled the timing of parasite and host rhythms, and we administered artemisinin at different times of day to coincide with when parasites were either at an early (ring) or later (trophozoite) developmental stage. We quantified the impacts of parasite developmental stage, and alignment of parasite and host rhythms, on drug sensitivity. Results We find that rings were less sensitive to artemisinin than trophozoites, and this difference was exacerbated when parasite and host rhythms were misaligned, with little direct contribution of host time-of-day on its own. Furthermore, the blood concentration of haem at the point of treatment correlated positively with artemisinin efficacy but only when parasite and host rhythms were aligned. Conclusions and implications Parasite rhythms influence drug sensitivity in vivo. The hitherto unknown modulation by alignment between parasite and host daily rhythms suggests that disrupting the timing of parasite development could be a novel chronotherapeutic approach. Lay Summary We reveal that chronotherapy (providing medicines at a particular time-of-day) could improve treatment for malaria infections. Specifically, parasites’ developmental stage at the time of treatment and the coordination of timing between parasite and host both affect how well antimalarial drug treatment works.

Between a hygiene rock and a hygienic hard place: Avoiding SARS-CoV-2 while needing environmental exposures for immunity

Suboptimal understanding of concepts related to hygiene by the general public, clinicians, and researchers is a persistent problem in health and medicine. Although hygiene is necessary to slow or prevent deadly pandemics of infectious disease such as COVID-19, hygiene can have unwanted effects. In particular, some aspects of hygiene cause a loss of biodiversity from the human body, characterized by the almost complete removal of intestinal worms (helminths) and protists. Research spanning more than half a century documents that this loss of biodiversity results in an increased propensity for autoimmune disease, allergic disorders, probably neuropsychiatric problems, and adverse reactions to infectious agents. The differences in immune function between communities with and communities without helminths have become so pronounced that the reduced lethality of SARS-CoV-2 in low-income countries compared to high-income countries was predicted early in the COVID-19 pandemic. This prediction, based on the maladaptive immune responses observed in many cases of COVID-19 in high-income countries, is now supported by emerging data from low-income countries. Herein, hygiene is subdivided into components involving personal choice versus components instituted by community wide systems such as sewage treatment facilities and water treatment plants. The different effects of personal hygiene and systems hygiene are described, and appropriate measures to alleviate the adverse effects of hygiene without losing the benefits of hygiene are discussed. Finally, text boxes summarizing this information are provided to function as stand-alone, public-domain handouts with the goal of informing the public about hygiene and suggesting solutions for biomedical researchers and policy makers.

Hymenolepis diminuta-based helminth therapy in C3(1)-TAg mice does not alter breast tumor onset or progression

Background and objectives An individual’s risk of breast cancer is profoundly affected by evolutionary mismatch. Mismatches in Western society known to increase the risk of breast cancer include a sedentary lifestyle and reproductive factors. Biota alteration, characterized by a loss of biodiversity from the ecosystem of the human body as a result of Western society, is a mismatch known to increase the risk of a variety of inflammation-related diseases, including colitis-associated colon cancer. However, the effect of biota alteration on breast cancer has not been evaluated. Methodology In this study, we utilized the C3(1)-TAg mouse model of breast cancer to evaluate the role of biota alteration in the development of breast cancer. This model has been used to recapitulate the role of exercise and pregnancy in reducing the risk of breast cancer. C3(1)-TAg mice were treated with Hymenolepis diminuta, a benign helminth that has been shown to reverse the effects of biota alteration in animal models. Results No effect of the helminth Hymenolepis diminuta was observed. Neither the latency nor tumor growth was affected by the therapy, and no significant effects on tumor transcriptome were observed based on RNAseq analysis. Conclusions and implications These findings suggest that biota alteration, although known to affect a variety of Western-associated diseases, might not be a significant factor in the high rate of breast cancer observed in Western societies. Lay Summary An almost complete loss of intestinal worms in high-income countries has led to increases in allergic disorders, autoimmune conditions, and perhaps colon cancer. However, in this study, results using laboratory mice suggest that loss of intestinal worms might not be associated with breast cancer.

Cytokine Storms, Evolution, and COVID-19

Since the identification of severe illness caused by the novel coronavirus SARS-CoV-2, the role of the host immune system in causing disease has attracted widespread attention, along with intense interest in medical interventions that target the host immune response. A wide variety of agents have been proposed to treat a cytokine storm in COVID-19, but so far, only one class of medications, corticosteroids, has proved useful. In recent decades, experimental therapies for cytokine storms have been tried and mostly failed to help patients with severe sepsis and other infections. We summarize this history in order to frame expectations for novel interventions in COVID-19 and to bring an evolutionary medicine perspective to the concept of cytokine storms and their treatment.

One Health Disparities and COVID-19

The global impact of the COVID-19 pandemic has disproportionately affected some communities and populations more than others. We propose that an interdisciplinary framework of “One Health Disparities” advances understanding of the social and systemic issues that drive COVID-19 in vulnerable populations. One Health Disparities integrates the social environment with One Health perspectives on the interconnectedness of human, animal, and environmental health. To apply this framework, we consider One Health Disparities that emerge in three key components of disease transmission: exposure, susceptibility, and disease expression. Exposure disparities arise through variation in contact with COVID-19’s causative agent, SARS-CoV-2. Disparities in susceptibility and disease expression also exist; these are driven by biological and social factors, such as diabetes and obesity, and through variation in access to healthcare. We close by considering how One Health Disparities informs understanding of spillback into new animal reservoirs, and what this might mean for further human health disparities. Lay Summary One Health focuses on interconnections between human, animal, and environmental health. We propose that social environments are also important to One Health and help illuminate disparities in the coronavirus pandemic, including its origins, transmission and susceptibility among humans, and spillback to other species. We call this framework One Health Disparities.