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The peculiar and characteristic structure of the human ethmoid is probably the result of 1) encephalisation and 2) insufficient adaptation to rapid evolution. In simiae only one ethmoturbinate is found, in man four or five. Due to posterior displacement of the lamina lateralis the turbinates compress each other, with overlapping, fusion, deformation and displacement, in highly constricted interorbital spaces.
The pH has an influence on the molecular dissociation of the Oniscoidea hemocyanins. The dissociation electrophoretic patterns are characteristic for the species investigated. This method allows to confirm the systematic evolution and the adaptative possibilities of terrestrial Isopods. The hemocyanins of Oniscoidea are similar to those of Decapoda having a structure of comparable molecular weight protomers.
As the genes encoding the glucuronidating enzymes are discovered, it is evident that glucuronidation is a magnificent example of how in evolution, man became adapted to his "intoxicating" environment. A superfamily of genes is necessary to dispose of the toxins and carcinogens that are encountered by inhalation and ingestion. The enzymes that glucuronidate endogenous compounds are members of this large family. For the clinician, it is important to remember that jaundice may sometimes be the result of interactions at the level of bilirubin glucuronidation. When jaundice results from inactivation of members of the UGT1 family, conjugation of certain phenols, such as the anesthetic propofol, or synthetic estrogens, such as ethinylestradiol, can also be impaired. In the case of severe bilirubin glucuronidation deficiencies, such as the Crigler Najjar syndrome type I, there are exciting prospects for a possible cure by gene therapy.
Present status of the problem of origin of extra-chromosomal inheritance elements is reviewed in the light of literary data and some results obtained by the author. The role of plasmids in the ecology of bacteria, in their adaptive variability and evolution is discussed. Extra-chromosomal inheritance is regarded as a particular case of biological inheritance.
While it has been of general interest for a long time, the issue of a Medical Kit for Commercial Airlines is now close to the top of the priority list because of recent activities in Europe within the Joint Aviation Authorities (JAA) and in the United States at the Congressional Level. The Aerospace Medical Association (AsMA) requested its Air Transport Medicine Committee to review the situation and make recommendations for a basic medical kit for international airlines. After reviewing the contents of existing kits, and the limited amount of available data, a proposal was submitted to and accepted by the AsMA Council. This is just a beginning. The Air Transport Medicine Committee will continue to follow the evolution and periodically adapt the kit accordingly.
Taxonomic diversification commonly occurs through adaptive radiation, the rapid evolution of a single lineage into a range of genotypes or species each adapted to a different ecological niche. Radiation size (measured as the number of new types) varies widely between phylogenetically distinct taxa and between replicate radiations within a single taxon where the ecological opportunities available seem to be identical. Here we show how variation in energy input (productivity) and environmental disturbance combine to determine the extent of diversification in a single radiating lineage of Pseudomonas fluorescens adapting to laboratory conditions. Diversity peaked at intermediate rates of both productivity and disturbance and declined towards the extremes in a manner reminiscent of well-known ecological patterns. The mechanism responsible for the decrease in diversity arises from pleiotropic fitness costs associated with niche specialization, the effects of which are modulated by gradients of productivity and disturbance. Our results indicate that ecological gradients may constrain the size of adaptive radiations, even in the presence of the strong diversifying selection associated with ecological opportunity, by decoupling evolutionary diversification from ecological coexistence.
The appearance of Oldowan sites ca. 2.6 million years ago (Ma) may reflect one of the most important adaptive shifts in human evolution. Stone artifact manufacture, large mammal butchery, and novel transport and discard behaviors led to the accumulation of the first recognized archaeological debris. The appearance of the Oldowan sites coincides with generally cooler, drier, and more variable climatic conditions across Africa, probably resulting in a net decrease in woodland foods and an increase in large mammal biomass compared to the early and middle Pliocene. Shifts in plant food resource availability may have provided the stimulus for incorporating new foods into the diet, including meat from scavenged carcasses butchered with stone tools. Oldowan artifact form varies with clast size, shape, raw material physical properties, and flaking intensity. Oldowan hominins preferred hard raw materials with good fracture characteristics. Habitual stone transport is evident from technological analysis, and raw material sourcing to date suggests that stone was rarely moved more than 2-3 km from source. Oldowan debris accumulation was spatially redundant, reflecting recurrent visitation of attractive points on the landscape. Thin archaeological horizons from Bed I Olduvai Gorge, Tanzania, were probably formed and buried in less than 10 years and document hominin processing of multiple carcasses per year. Transport beyond simple refuging behavior is suggested by faunal density at some site levels. By 2.0 Ma, hominin rank within the predatory guild may have been moderately high, as they probably accessed meaty carcasses through hunting and confrontational scavenging, and hominin-carnivore competition appears minimal at some sites. It is likely that both Homo habilis sensu stricto and early African H. erectus made Oldowan tools. H. habilis sensu stricto was more encephalized than Australopithecus and may foreshadow H. erectus in lower limb elongation and some thermoregulatory adaptations to hot, dry climatic conditions. H. erectus was large and wide-ranging, had a high total energy expenditure, and required a high-quality diet. Reconstruction of H. erectus reproductive energetics and socioeconomic organization suggests that reproductively active females received assistance from other group members. This inference, combined with archaeological evidence for acquisition of meaty carcasses, suggests that meat would have been a shared food. This is indirectly confirmed by nutritional analysis suggesting that the combination of meat and nutritionally dense plant foods was the likely diet fueling body size increase and encephelization in Homo. Most discussion of Oldowan hominin behavior and ecology, including that presented here, is based on materials from a few sites. There is a critical need to analyze additional large, primary-context lithic and faunal assemblages to better assess temporal, geographic, and environmental variability in Oldowan behavior.
A fundamental focus of ecological and evolutionary biology is determining how natural populations adapt to environmental changes. Rapid parallel phenotypic evolution can be leveraged to uncover the genetics of adaptation. Using population genomic approaches, we investigated the genetic architecture underlying rapid parallel freshwater adaptation of Neosalanx brevirostris by comparing four freshwater-resident populations with their common ancestral anadromous population. We demonstrated that the rapid parallel adaptation to freshwater followed a complex polygenic architecture and was characterized by genomic-level parallelism, which proceeded predominantly through repeated selection on the preexisting standing genetic variations. Frequencies of the genome-wide adaptive standing variations were moderate in the ancestral anadromous population, which had pre-adapted to fluctuating salinities. Relatively large allele frequency shifts were observed at some adaptive single-nucleotide polymorphisms (SNPs) during parallel adaptation to freshwater environments, with a large fraction of freshwater-favored alleles being fixed or nearly fixed. These adaptive SNPs were involved in multiple biological functions associated with osmoregulation, immunoregulation, locomotion, metabolism, etc., which were highly consistent with the polygenic architecture of adaptive divergence between the two ecotypes involving multiple complex physiological and behavioral traits. This work provides insight into the mechanisms by which natural populations rapidly evolve to changes in the environment and highlights the importance of standing genetic variation for the evolutionary potential of populations facing global environmental changes.
This paper describes the evolution of a model of adaptative coping, as well as an example of the converse, a maladaptive coping pattern, type C. It was hypothesized that the more closely a coping process resembles the inverted U-shaped function that characterizes homeostasis for most biological systems, the more likely it is to be adaptive, and to be associated with more positive health outcomes. Maladaptive learned coping patterns, such as type C coping, represent deviations from homeostasis in that they fail to recognize, respond appropriately to, and/or resolve stressors, thus keeping the physiological stress response chronically engaged, with subsequent long-term damage to implicated biological systems. This interpretation of how maladaptive coping patterns such as type C can influence health outcomes is consistent with findings from the author's 20-year program of research on the type C pattern, its assessment, and its association with poorer health indicators and outcomes in cancer (malignant melanoma) and HIV/AIDS.
Adaptation to local environments may be an important determinant of species' geographic range. However, little is known about which traits contribute to adaptation or whether their further evolution would facilitate range expansion. In this study, we assessed the adaptive value of stress avoidance traits in the common annual Cocklebur (Xanthium strumarium) by performing a reciprocal transplant across a broad latitudinal gradient extending to the species' northern border. Populations were locally adapted and stress avoidance traits accounted for most fitness differences between populations. At the northern border where growing seasons are cooler and shorter, native populations had evolved to reproduce earlier than native populations in the lower latitude gardens. This clinal pattern in reproductive timing corresponded to a shift in selection from favouring later to earlier reproduction. Thus, earlier reproduction is an important adaptation to northern latitudes and constraint on the further evolution of this trait in marginal populations could potentially limit distribution.
Long-distance dispersal in microbial eukaryotes has been shown to result in the establishment of populations on continental and global scales. Such "ubiquitous dispersal" has been claimed to be a general feature of microbial eukaryotes, homogenising populations over large scales. However, the unprecedented sampling of opportunistic infectious pathogens created by the global AIDS pandemic has revealed that a number of important species exhibit geographic endemicity despite long-distance migration via aerially dispersed spores. One mechanism that might tend to drive such endemicity in the face of aerial dispersal is the evolution of niche-adapted genotypes when sexual reproduction is rare. Dispersal of such asexual physiological "species" will be restricted when natural habitats are heterogeneous, as a consequence of reduced adaptive variation. Using the HIV-associated endemic fungus Penicillium marneffei as our model, we measured the distribution of genetic variation over a variety of spatial scales in two host species, humans and bamboo rats. Our results show that, despite widespread aerial dispersal, isolates of P. marneffei show extensive spatial genetic structure in both host species at local and country-wide scales. We show that the evolution of the P. marneffei genome is overwhelmingly clonal, and that this is perhaps the most asexual fungus yet found. We show that clusters of genotypes are specific to discrete ecological zones and argue that asexuality has led to the evolution of niche-adapted genotypes, and is driving endemicity, by reducing this pathogen's potential to diversify in nature.
Genetic differentiation among nine populations of the endemic lizard Lacerta dugesii Milne-Edwards 1829 (Lacertidae) from four groups of islands constituting the Archipelago of Madeira, was investigated by protein electrophoresis at 23 enzyme loci. Among twenty polymorphic loci, the total genetic diversity was due primarily to intra-population variation. The allele and genotypic frequencies among populations showed some heterogeneity, allowing the species to present a structuring pattern compatible with their geographical clustering. Some evidence suggests that selection acting on some loci in different ecological conditions may be responsible for the clustering of the populations studied. There was no apparent isolation effect expected under an "island" model of population divergence, and no correlation was found between genetic and geographic distances among populations. Morphological variation of the proposed three L. dugesii subspecies is not congruent with the allozyme analysis. This most probably suggests a rapid colonization of the islands followed by a strong effect of selection operating over the morphological characters used to define the subspecies.
Pancreatic ductal adenocarcinoma (PDAC) remains a highly lethal malignancy, largely because of its profound and evolving therapeutic resistance. Resistance is not determined by a single molecular alteration but arises from interconnected mechanisms, including intrinsic resistance, treatment-induced adaptive resistance, acquired resistance, genomic evolution, clonal selection, cancer stemness, phenotypic plasticity, metabolic adaptation, and tumor microenvironment-mediated effects. Emerging therapeutic approaches targeting KRAS/RAS signaling, stromal and immune components, metabolic dependencies, and DNA damage repair pathways offer opportunities to address these mechanisms, although durable efficacy remains limited by biological heterogeneity and adaptive responses. In this review, we examine therapeutic resistance as an evolutionary and multidimensional process and summarize emerging strategies for overcoming resistance. We further propose a Dynamic Precision Oncology (DPO) framework that extends conventional precision oncology beyond baseline molecular profiling by integrating longitudinal assessment of tumor genomics, circulating tumor DNA, CA19-9, imaging, radiomics, and clinical characteristics. This framework emphasizes iterative detection and characterization of emerging resistance, mechanism-informed treatment adaptation, and subsequent reassessment rather than automatic treatment modification based on a single biomarker. DPO may provide a conceptual framework for integrating evolving tumor biology into treatment decision-making, while prospective studies are needed to validate biomarkers, define actionable thresholds, and determine whether longitudinal resistance-guided strategies improve clinical outcomes in PDAC.
Some hypotheses for the evolution of sex focus on adaptation to changing or heterogeneous environments, but these hypotheses have rarely been tested. We tested for advantages of sex and of increased mutation rates in yeast strains in two contrasting environments: a standard and relatively homogeneous laboratory environment of minimal medium in test tubes, and the variable environment of a mouse brain experienced by pathogenic strains. Evolving populations were founded as equal mixtures of sexual and obligately asexual genotypes. In the sexuals, cycles of sporulation, meiosis, and mating were induced approximately every 50 mitotic generations, with the asexuals undergoing sporulation but not ploidy cycles or recombination. In both environments, replicate negative control populations established with the same pair of strains were propagated with neither mating nor meiosis. In test tubes with no sex induced, sexuals were fixed in all five replicates within 250 mitotic generations, whereas in mice with no sex induced, asexuals were fixed in all four replicates by 170 generations. Inducing sex altered these outcomes in opposite directions in test tubes and mice, decreasing the fixation frequencies of sexuals in test tubes but increasing them in mice. These contrasts with asexual controls suggest an advantage for sex in mice but not in test tubes, although there was no difference between test tubes and mice in the numbers of populations fixed-for sexuals. In analogous experiments testing for an advantage of increased mutation rates, wild-type genotypes became fixed at the expense of mutators in every replicate of both test tube and mouse populations, indicating a disadvantage for mutators in both environments. Increased rates of point mutation do not appear to accelerate adaptation.
Thyroid hormones (THs, T(3)/T(4)) are essential central regulators that link many biological tasks, including embryonic and post-natal growth, reproductive function, and the behavioral and physiological responses to stress. Recently I proposed a novel theory to explain the role of THs in vertebrate evolution. Here I review the concept and discuss its ability to explain changes over time in hominid morphology, behavior and life history. THs are produced in a distinctly pulsatile manner and appear to generate species-specific TH rhythms with distinct ontogenic shifts. Individual variations in genetically controlled TH rhythms (TR phenotypes) must generate coordinated individual variation in morphology, reproduction and behavior within populations. Selection for any manifestation of a particular TR phenotype in an ancestral population selects all traits under thyroid control, resulting in rapid and well-coordinated changes in descendants. The concept provides the first really plausible explanation for a number of phenomena, including the convergent evolution of bipedalism in early hominids, species-specific sexual dimorphism, coordinated changes in morphology, brain function and gut length over time in hominids, cold adaptation in Homo neanderthalensis, the possible independent evolution of H. sapiens in Asia, and regional adaptation of hominid populations. This new paradigm provides a unique theoretical framework for explaining human origins that has important implications for human health.
One of the challenges of comparative genomics is to identify specific genetic changes associated with the evolution of a novel adaptation or trait. We need to be able to disassociate the genes involved with a particular character from all the other genetic changes that take place as lineages diverge. Here we show that by comparing the transcriptional profile of segregating families with that of parent species differing in a novel trait, it is possible to narrow down substantially the list of potential target genes. In addition, by assuming synteny with a related model organism for which the complete genome sequence is available, it is possible to use the cosegregation of markers differing in transcription level to identify regions of the genome which probably contain quantitative trait loci (QTLs) for the character. This novel combination of genomics and classical genetics provides a very powerful tool to identify candidate genes. We use this methodology to investigate zinc hyperaccumulation in Arabidopsis halleri, the sister species to the model plant, Arabidopsis thaliana. We compare the transcriptional profile of A. halleri with that of its sister nonaccumulator species, Arabidopsis petraea, and between accumulator and nonaccumulator F(3)s derived from the cross between the two species. We identify eight genes which consistently show greater expression in accumulator phenotypes in both roots and shoots, including two metal transporter genes (NRAMP3 and ZIP6), and cytoplasmic aconitase, a gene involved in iron homeostasis in mammals. We also show that there appear to be two QTLs for zinc accumulation, on chromosomes 3 and 7.
Rattus norvegicus is an important experimental organism and interesting to evolutionary biologists. The recently published draft rat genome sequence provides us with insights into both the rat's evolution and its physiology. We learn more about genome evolution and, in particular, the adaptive significance of gene family expansions and the evolution of rodent genomes, which appears to have decelerated since the divergence of mouse and rat. An important observation is that some regions of genomes, many in noncoding regions, show very high sequence conservation, while others show unexpectedly fast evolution. Both of these may be pointers to functional significance.
Previous explanations of why bacterial genes for certain "optional" traits tend to occur on plasmids rather than chromosomes are based on an outdated misunderstanding of natural selection. They also fail to explain why certain characters that are ubiquitous in some bacterial species tend to occur on plasmids. This paper shows that all major classes of traits usually associated with plasmids rather than chromosomes confer adaptations to locally restricted conditions. A new "local adaptation" model of plasmid evolution, based on simultaneous application of modern selection theory at the levels of gene, plasmid, cell, and clone reproduction, shows that genes coding local adaptations will reproduce more successfully when on plasmids than when on chromosomes, due to plasmids' greater horizontal mobility.