Nothing in medicine makes sense, except in the light of evolution

Medicinal plants meet modern biodiversity science

Plants have been an essential source of human medicine for millennia. In this review, we argue that a holistic, interdisciplinary approach to the study of medicinal plants that combines methods and insights from three key disciplines - evolutionary ecology, molecular biology/biochemistry, and ethnopharmacology - is poised to facilitate new breakthroughs in science, including pharmacological discoveries and rapid advancements in human health and well-being. Such interdisciplinary research leverages data and methods spanning space, time, and species associated with medicinal plant species evolution, ecology, genomics, and metabolomic trait diversity, all of which build heavily on traditional Indigenous knowledge. Such an interdisciplinary approach contrasts sharply with most well-funded and successful medicinal plant research during the last half-century, which, despite notable advancements, has greatly oversimplified the dynamic relationships between plants and humans, kept hidden the larger human narratives about these relationships, and overlooked potentially important research and discoveries into life-saving medicines. We suggest that medicinal plants and people should be viewed as partners whose relationship involves a complicated and poorly explored set of (socio-)ecological interactions including not only domestication but also commensalisms and mutualisms. In short, medicinal plant species are not just chemical factories for extraction and exploitation. Rather, they may be symbiotic partners that have shaped modern societies, improved human health, and extended human lifespans.

Developmental Programming, Evolution, and Animal Welfare: A Case for Evolutionary Veterinary Science

The conditions animals experience during the early developmental stages of their lives can have critical ongoing effects on their future health, welfare, and proper development. In this paper we draw on evolutionary theory to improve our understanding of the processes of developmental programming, particularly Predictive Adaptive Responses (PAR) that serve to match offspring phenotype with predicted future environmental conditions. When these predictions fail, a mismatch occurs between offspring phenotype and the environment, which can have long-lasting health and welfare effects. Examples include metabolic diseases resulting from maternal nutrition and behavioral changes from maternal stress. An understanding of these processes and their evolutionary origins will help in identifying and providing appropriate developmental conditions to optimize offspring welfare. This serves as an example of the benefits of using evolutionary thinking within veterinary science and we suggest that in the same way that evolutionary medicine has helped our understanding of human health, the implementation of evolutionary veterinary science (EvoVetSci) could be a useful way forward for research in animal health and welfare.

Explanatory integration and integrated explanations in Darwinian medicine and evolutionary medicine

Recently, two research traditions that bring together evolutionary biology and medicine, that is to say, Darwinian medicine and evolutionary medicine, have been identified. In this paper, I analyse these two research traditions with respect to explanatory and interdisciplinary integration. My analysis shows that Darwinian medicine does not integrate medicine and evolutionary biology in any strong sense but does incorporate evolutionary concepts into medicine. I also show that backward-looking explanations in Darwinian medicine are not integrated proximate-and-ultimate explanations but functional explanations that include reference to evolutionary concepts. Nevertheless, explanations in Darwinian medicine have heuristic roles as they potentially contribute to conceptual change and tie pieces of knowledge from different fields of medical research together. I argue that Darwinian medicine is an "interfield" that fosters cross-disciplinary exchange between evolutionary biologists and medical researchers and practitioners based on division of labour and separation, rather than unity. Research in evolutionary medicine, on the other hand, happens at the intersection of evolutionary biology and medicine where the two disciplines are already integrated and is designed to produce entangled proximate-evolutionary explanations. My analysis thus adds another important aspect to the philosophical discussion on the distinction between Darwinian medicine and evolutionary medicine.

First principles of terrestrial life: exemplars for potential extra-terrestrial biology

The search for life elsewhere in the universe represents not only a potential expansion of our knowledge regarding life, but also a clarification of the first principles applicable to terrestrial life, which thus restrict the very search for extra-terrestrial life. Although there are no exact figures for how many species have existed throughout Earth's total history, we can still make inferences about how the distribution of this life has proceeded through a bell curve. This graph shows the totality of life, from its origin to its end. The system enclosing life contains a number of first principles designated the walls of minimal complexity and adaptive possibility, the fence of adaptation, and right-skewed extension. In this discussion of life, a framework will be formulated that, based on the dynamic relationship between mesophiles and extremophiles, will be imposed on exoworlds in order to utilize the graph's predictive power to analyze how extra-terrestrial life could unfold. In this framework the evolutionary variation does not depend on the specific biochemistry involved. Once life is 'up and running,' the various biochemical systems that can constitute terrestrial and extra-terrestrial life will have secondary significance. The extremophilic tail represents a range expansion in which all habitat possibilities are tested and occupied. This tail moves to the right not because of the biochemistry constitutions of organisms, but because it can do nothing else. Thus, it can be predicted that graphs of terrestrial and extra-terrestrial life will be similar overall. A number of other predictions can be made; for example, for worlds in which the atmospheric disequilibrium is approaching equilibrium, it is predicted that life may still be present because the extremophilic range expansion is stretched increasingly farther to the right. Because life necessarily arises at a left wall of minimal complexity, it is predicted that any origin of cellular life will have a close structural resemblance to that of the first terrestrial life. Thus, in principle, life may have originated more than once on Earth, and still exist. It is also predicted that there may be an entire subset of life existing among other domains that we do not see because, in an abstract sense, we are inside the graph. If we view the graph in its entirety, this subset appears very much like a vast supra-domain of life.

An anthropogenic model of cardiovascular system adaptation to the Earth's gravity as the conceptual basis of pathological anthropology

Applying human biological evolution to solve topical problems of medicine and preventive cardiology was inspired by the realization of the need for clinical and experimental studies of biological (evolutionary) prerequisites in the occurrence of a pathology. Although it has been stated that there is a need to provide a full biological understanding of features, including those that increase an animal's vulnerability to diseases, unfortunately, in this regard, erectile and associated adaptations to the Earth's gravity in their physiological and pathological manifestations have not been considered. At the same time, it should be noted that humans, unlike other animal species, have the greatest vulnerability of the cardiovascular system (CVS). The latter is associated with fundamental differences in the functioning and regulation of the CVS by the influence of gravity on blood circulation in humans as upright creatures. Based on a review of comparative physiological, ontogenetic, and clinical studies from an evolutionary perspective, the idea of adaptation to the Earth's gravity when walking upright in humans is justified as an anthropogenic basis for the physiology and pathology of the cardiovascular system and hemodynamic support systems (physio-anthropology and pathological anthropology).

Evolution and medicine - The central role of anatomy

In medicine, there is an increasing number of publications that deal with or at least consider an evolutionary background. In zoology or comparative anatomy, work on evolutionary developments is taking on an ever-greater role in parallel. The pre-clinical (or pre-medical) phase in medical studies would be able to form a bridge between these related and yet so distant subjects but is currently completely evolution-free. This means that there is no consideration of the evolution of the healthy human being as a prerequisite for a systematic study of the evolutionary background in medicine. In this work the view is expressed that anatomy should be given a central, framework-giving and integrating role, which should urgently be actively pursued.

Antagonistic Interactions Between Fusaria Species and Their Host Plants Are Influenced by Host Taxonomic Distance: A Case Study From Mexico

Interactions between cultivated and wild plants with their fungal pathogens have strong ecological, evolutionary and economic implications. Antagonistic interactions, however, have been scantily studied in an applied context by using ecological networks, phylogeny and spatial ecology concurrently. In this study, we describe for the first time, the topological structure of plant-fungi networks involving species of the genus Fusarium and their native and introduced (exotic) cultivated host plants in Mexico. For this, we based our study on a recent database describing the attack on 75 native and introduced plant species, including 35 species of the genus Fusarium. Host plant species varied in their degree of phylogenetical relatedness (Monocots and Dicots) and spatial geographical distribution. Therefore, we also tested whether or not plant-Fusarium networks are phylogenetically structured and highlighted the spatial correlation between pathogens and their host plants across the country. In general, the pathogen-plant network is more specialized and compartmentalized in closely related taxa. Closely related hosts are more likely to share the same pathogenic Fusarium species. Host plants are present in different ecosystems and climates, with regions having more cultivated plant species presenting the highest number of fusaria pathogens. From an economic standpoint, different species of the same taxonomic family may be more susceptible to being attacked by the same species of Fusarium, whereas from an ecological standpoint the movement of pathogens may expose wild and cultivated plants to new diseases. Our study highlights the relevance of interaction intimacy in structuring trophic relationships between plants and fusaria species in native and introduced species. Furthermore, we show that the analytical tools regarding host distribution and phylogeny could permit a rapid assessment of which plant species in a region are most likely to be attacked by a given fusaria.

Evolutionary transcriptomics implicates HAND2 in the origins of implantation and regulation of gestation length

The developmental origins and evolutionary histories of cell types, tissues, and organs contribute to the ways in which their dysfunction produces disease. In mammals, the nature, development and evolution of maternal-fetal interactions likely influence diseases of pregnancy. Here we show genes that evolved expression at the maternal-fetal interface in Eutherian mammals play essential roles in the evolution of pregnancy and are associated with immunological disorders and preterm birth. Among these genes is HAND2, a transcription factor that suppresses estrogen signaling, a Eutherian innovation allowing blastocyst implantation. We found dynamic HAND2 expression in the decidua throughout the menstrual cycle and pregnancy, gradually decreasing to a low at term. HAND2 regulates a distinct set of genes in endometrial stromal fibroblasts including IL15, a cytokine also exhibiting dynamic expression throughout the menstrual cycle and gestation, promoting migration of natural killer cells and extravillous cytotrophoblasts. We demonstrate that HAND2 promoter loops to an enhancer containing SNPs implicated in birth weight and gestation length regulation. Collectively, these data connect HAND2 expression at the maternal-fetal interface with evolution of implantation and gestational regulation, and preterm birth.

Human and Nonhuman Primate Lineage-Specific Footprints in the Salivary Proteome

Proteins in saliva are needed for preprocessing food in the mouth, maintenance of tooth mineralization, and protection from microbial pathogens. Novel insights into human lineage-specific functions of salivary proteins and clues to their involvement in human disease can be gained through evolutionary studies, as recently shown for salivary amylase AMY1 and salivary agglutinin DMBT1/gp340. However, the entirety of proteins in saliva, the salivary proteome, has not yet been investigated from an evolutionary perspective. Here, we compared the proteomes of human saliva and the saliva of our closest extant evolutionary relatives, chimpanzees and gorillas, using macaques as an outgroup, with the aim to uncover features in saliva protein composition that are unique to each species. We found that humans produce a waterier saliva, containing less than half total protein than great apes and Old World monkeys. For all major salivary proteins in humans, we could identify counterparts in chimpanzee and gorilla saliva. However, we discovered unique protein profiles in saliva of humans that were distinct from those of nonhuman primates. These findings open up the possibility that dietary differences and pathogenic pressures may have shaped a distinct salivary proteome in the human lineage.

(Re-) Defining evolutionary medicine

The applicability of evolutionary biology principles to diseases has been largely questioned by the medical field. While Evolutionary Medicine (EM) developed in part to lessen this gap, EM is an independent field from both evolution and medicine, whose continued narrowing of topics as a consequence of its reductionist approach, in addition to its focus to introduce itself at a late stage in medical education, has led to its continued resistance toward implementation. In turn, this has had a profound and lasting impact on the awareness of evolution in medicine among physicians. For both the evolutionary and medical communities to reach a common perspective and obtain a greater frame-work of medical thought, a comprehensive view of the evolution of the healthy human being needs to be introduced as a starting point during the premedical curriculum. Here, we present our views on the ongoing challenges that have caused the continued division between the evolutionary fields and medicine, and provide solutions to help bridge the gap for an interdisciplinary field of evolution in medicine.

The Molecular Basis of Human Brain Evolution

Humans are a remarkable species, especially because of the remarkable properties of their brain. Since the split from the chimpanzee lineage, the human brain has increased three-fold in size and has acquired abilities for vocal learning, language and intense cooperation. To better understand the molecular basis of these changes is of great biological and biomedical interest. However, all the about 16 million fixed genetic changes that occurred during human evolution are fully correlated with all molecular, cellular, anatomical and behavioral changes that occurred during this time. Hence, as humans and chimpanzees cannot be crossed or genetically manipulated, no direct evidence for linking particular genetic and molecular changes to human brain evolution can be obtained. Here, I sketch a framework how indirect evidence can be obtained and review findings related to the molecular basis of human cognition, vocal learning and brain size. In particular, I discuss how a comprehensive comparative approach, leveraging cellular systems and genomic technologies, could inform the evolution of our brain in the future.

Evolution of the archaeal and mammalian information processing systems: towards an archaeal model for human disease

Current evolutionary models suggest that Eukaryotes originated from within Archaea instead of being a sister lineage. To test this model of ancient evolution, we review recent studies and compare the three major information processing subsystems of replication, transcription and translation in the Archaea and Eukaryotes. Our hypothesis is that if the Eukaryotes arose within the archaeal radiation, their information processing systems will appear to be one of kind and not wholly original. Within the Eukaryotes, the mammalian or human systems are emphasized because of their importance in understanding health. Biochemical as well as genetic studies provide strong evidence for the functional similarity of archaeal homologs to the mammalian information processing system and their dissimilarity to the bacterial systems. In many independent instances, a simple archaeal system is functionally equivalent to more elaborate eukaryotic homologs, suggesting that evolution of complexity is likely an central feature of the eukaryotic information processing system. Because fewer components are often involved, biochemical characterizations of the archaeal systems are often easier to interpret. Similarly, the archaeal cell provides a genetically and metabolically simpler background, enabling convenient studies on the complex information processing system. Therefore, Archaea could serve as a parsimonious and tractable host for studying human diseases that arise in the information processing systems.

On the apparent rarity of epithelial cancers in captive chimpanzees

Malignant neoplasms arising from epithelial cells are called carcinomas. Such cancers are diagnosed in about one in three humans in 'developed' countries, with the most common sites affected being lung, breast, prostate, colon, ovary and pancreas. By contrast, carcinomas are said to be rare in captive chimpanzees, which share more than 99% protein sequence homology with humans (and possibly in other related 'great apes'-bonobos, gorillas and orangutans). Simple ascertainment bias is an unlikely explanation, as these nonhuman hominids are recipients of excellent veterinary care in research facilities and zoos, and are typically subjected to necropsies when they die. In keeping with this notion, benign tumours and cancers that are less common in humans are well documented in this population. In this brief overview, we discuss other possible explanations for the reported rarity of carcinomas in our closest evolutionary cousins, including inadequacy of numbers surveyed, differences in life expectancy, diet, genetic susceptibility, immune responses or their microbiomes, and other potential environmental factors. We conclude that while relative carcinoma risk is a likely difference between humans and chimpanzees (and possibly other 'great apes'), a more systematic survey of available data is required for validation of this claim.

The status of evolutionary medicine education in North American medical schools

BACKGROUND

Medical and public health scientists are using evolution to devise new strategies to solve major health problems. But based on a 2003 survey, medical curricula may not adequately prepare physicians to evaluate and extend these advances. This study assessed the change in coverage of evolution in North American medical schools since 2003 and identified opportunities for enriching medical education.

METHODS

In 2013, curriculum deans for all North American medical schools were invited to rate curricular coverage and perceived importance of 12 core principles, the extent of anticipated controversy from adding evolution, and the usefulness of 13 teaching resources. Differences between schools were assessed by Pearson's chi-square test, Student's t-test, and Spearman's correlation. Open-ended questions sought insight into perceived barriers and benefits.

RESULTS

Despite repeated follow-up, 60 schools (39%) responded to the survey. There was no evidence of sample bias. The three evolutionary principles rated most important were antibiotic resistance, environmental mismatch, and somatic selection in cancer. While importance and coverage of principles were correlated (r = 0.76, P < 0.01), coverage (at least moderate) lagged behind importance (at least moderate) by an average of 21% (SD = 6%). Compared to 2003, a range of evolutionary principles were covered by 4 to 74% more schools. Nearly half (48%) of responders anticipated igniting controversy at their medical school if they added evolution to their curriculum. The teaching resources ranked most useful were model test questions and answers, case studies, and model curricula for existing courses/rotations. Limited resources (faculty expertise) were cited as the major barrier to adding more evolution, but benefits included a deeper understanding and improved patient care.

CONCLUSION

North American medical schools have increased the evolution content in their curricula over the past decade. However, coverage is not commensurate with importance. At a few medical schools, anticipated controversy impedes teaching more evolution. Efforts to improve evolution education in medical schools should be directed toward boosting faculty expertise and crafting resources that can be easily integrated into existing curricula.

The importance of evolution in the development and course of rheumatoid arthritis

Rheumatoid arthritis (RA) is a complex autoimmune disease of recent evolutionary origin. Genetic drift determines diverse polymorphisms implicated in the susceptibility to RA including the major histocompatibility complex (MHC) class II genes in the so-called shared epitope. These genes originated after the divergence between Homo and Pan from their common ancestry Ardipithecus ramidus about 5 million years ago. Natural selection determined the particular changes in the legs (bipedal position), hands, neck, brain and eusociality in humans which influence the clinical presentation of RA. In this article, we hypothesized that the origin and course of RA may be explainable in the light of evolution.

Evolutionary perspectives on the obesity epidemic: adaptive, maladaptive, and neutral viewpoints

The prevalence of obesity in modern societies has two major contributory factors-an environmental change that has happened in historical times and a genetic predisposition that has its origins in our evolutionary history. Understanding both aspects is complex. From an evolutionary perspective, three different types of explanation have been proposed. The first is that obesity was once adaptive and enabled us to survive (or sustain fecundity) through periods of famine. People carrying so-called thrifty genes that enabled the efficient storage of energy as fat between famines would be at a selective advantage. In the modern world, however, people who have inherited these genes deposit fat in preparation for a famine that never comes, and the result is widespread obesity. The key problem with this, and any other adaptive scenario, is to understand why, if obesity was historically so advantageous, many people did not inherit these thrifty genes and in modern society are able to remain slim, despite the environmental change favoring fat storage. The second type of explanation is that obesity is not adaptive and may never even have existed in our evolutionary past, but it is favored today as a maladaptive by-product of positive selection on some other trait. An example of this type of explanation is the suggestion that obesity results from variation in brown adipose tissue thermogenesis. Finally, a third class of explanation is that most mutations in the genes that predispose us to obesity are neutral and have been drifting over evolutionary time--so-called drifty genes, leading some individuals to be obesity prone and others obesity resistant. In this article, I review the current evidence for and against these three different scenarios and conclude that the thrifty gene hypothesis is untenable but the other two ideas may provide a cogent explanation of the modern obesity phenomenon.

Disease consequences of human adaptation

Adaptive evolution has provided us with a unique set of characteristics that define us as humans, including morphological, physiological and cellular changes. Yet, natural selection provides no assurances that adaptation is without human health consequences; advantageous mutations will increase in frequency so long as there is a net gain in fitness. As such, the current incidence of human disease can depend on previous adaptations. Here, I review genome-wide and gene-specific studies in which adaptive evolution has played a role in shaping human genetic disease. In addition to the disease consequences of adaptive phenotypes, such as bipedal locomotion and resistance to certain pathogens, I review evidence that adaptive mutations have influenced the frequency of linked disease alleles through genetic hitchhiking. Taken together, the links between human adaptation and disease highlight the importance of their combined influence on functional variation within the human genome and offer opportunities to discover and characterize such variation.

Evolutionary medicine: its scope, interest and potential

This review is aimed at readers seeking an introductory overview, teaching courses and interested in visionary ideas. It first describes the range of topics covered by evolutionary medicine, which include human genetic variation, mismatches to modernity, reproductive medicine, degenerative disease, host-pathogen interactions and insights from comparisons with other species. It then discusses priorities for translational research, basic research and health management. Its conclusions are that evolutionary thinking should not displace other approaches to medical science, such as molecular medicine and cell and developmental biology, but that evolutionary insights can combine with and complement established approaches to reduce suffering and save lives. Because we are on the cusp of so much new research and innovative insights, it is hard to estimate how much impact evolutionary thinking will have on medicine, but it is already clear that its potential is enormous.