The evolution of male-female dimorphism: Older than sex?

This contribution considers the evolution of a dimorphism with respect to cell fusion characteristics in a population of primitive cells. These cells reproduce exclusively asexually. The evolution towards asymmetric fusion behaviour of cells is driven by selection promoting horizontal transfer of an endosymbiontic replicator. It is concluded that evolution of asymmetric cell fusion in this scenario is more likely than evolution of sexual differentiation in a sexually reproducing population. Pre-existing dimorphism with respect to cell fusion may thus have been the basis for the establishment of sexual differentiation at the level of gamete fusion, and this in turn is fundamental to the evolution of two different sexes, male and female.     

What limits the evolutionary emergence of pathogens?

The ability of a pathogen to cause an epidemic when introduced in a new host population often relies on its ability to adapt to this new environment. Here, we give a brief overview of recent theoretical and empirical studies of such evolutionary emergence of pathogens. We discuss the effects of several ecological and genetic factors that may affect the likelihood of emergence: migration, life history of the infectious agent, host heterogeneity, and the rate and effects of mutations. We contrast different modelling approaches and indicate how details in the way we model each step of a life cycle can have important consequences on the predicted probability of evolutionary emergence. These different theoretical perspectives yield important insights into optimal surveillance and intervention strategies, which should aim for a reduction in the emergence (and re-emergence) of infectious diseases.     

Quo vadis G protein-coupled receptor ligands? A tool for analysis of the emergence of new groups of compounds over time

Exponential growth in the number of compounds with experimentally verified activity towards particular target has led to the emergence of various databases gathering data on biological activity. In this study, the ligands of family A of the G Protein-Coupled Receptors that are collected in the ChEMBL database were examined, and special attention was given to serotonin receptors. Sets of compounds were examined in terms of their appearance over time, they were mapped to the chemical space of drugs deposited in DrugBank, and the emergence of structurally new clusters of compounds was indicated. In addition, a tool for detailed analysis of the obtained visualizations was prepared and made available online at http://chem.gmum.net/vischem, which enables the investigation of chemical structures while referring to particular data points depicted in the figures and changes in compounds datasets over time.     

Clinical aspects for the use of DNA image cytometry in detection of bladder cancer: a valuable tool?

The employment of DNA flow or image cytometry for oncological diagnostic procedures is favored because of its high correlation to tumor biological behavior. Prognostic statements and therapeutic strategies therefore are based on the high validity of DNA cytometric measurements. Using 151 bladder washings from patients suspected of bladder cancer for this study, we examined the clinical value of various common methods of DNA single cell (SCI) and stemline interpretations (SLI). Comparing the specificity and sensitivity of DNA image cytometry in detection of bladder tumors, we found 81 and 52%, respectively, for SCI of Boecking, 84 and 45% for SLI of Boecking, 61 and 58% for SLI of Fu, and 82 and 40% for conventional stemline interpretation. To improve diagnostic and prognostic validity of DNA image cytometry, we designed our own method of interpretation. In consequence, we identified six single DNA parameters out of all recorded measurements that correlated most to histopathological grading (G1-G3). Creating reference values at random and rating by points, we used a cytometric grading system for ranking. In detection of bladder cancer specificity and sensitivity ultimately arrived at almost 70% in application of our method. Thus, by this study, we were able to show that sensitivity of DNA examination can be increased by combining various DNA parameters. Apart from our own scheme, the discrepancy in interpretation of DNA image cytometry does not allow us to recommend this procedure as the only diagnostic in detection of bladder cancer. However, in regard to prognostic statements, particularly tumor biological behavior, DNA image cytometry appears to be useful.     

What's so special about human tool use?

Evidence suggests homologies in parietofrontal circuits involved in object prehension among humans and monkeys. Likewise, tool use is known to induce functional reorganization of their visuotactile limb representations. Yet, humans are the only species for whom tool use is a defining and universal characteristic. Why? Comparative studies of chimpanzee tool use indicate that critical differences are likely to be found in mechanisms involved in causal reasoning rather than those implementing sensorimotor transformations. Available evidence implicates higher-level perceptual areas in these processes.     

Where are inion and endinion? Variations of the exo- and endocranial morphology of the occipital bone during hominin evolution

The occipital bone is frequently investigated in paleoanthropological studies because it has several features that help to differentiate various fossil hominin species. Among these features is the separation between inion and endinion, which has been proposed to be an autapomorphic trait in (Asian) Homo erectus. Methodologies are developed here to quantify for the first time the location of these anatomical points, and to interpret their variation due to the complex interactions between exocranial and endocranial size and shape of the occipital and nuchal planes, as well as the occipital lobes and cerebellum. On the basis of our analysis, neither ‘the separation between inion and endinion’ nor ‘endinion below inion’ can be considered as an autapomorphic trait in H. erectus, since this feature is a condition shared by extant African great apes and fossil hominins. Moreover, our results show that the exo- and endocranial anatomy of the occipital bone differs between hominins (except Paranthropus boisei specimens and KNM-ER 1805) and great apes. For example, chimpanzees and bonobos are characterized by a very high position of inion and their occipital bone shows an antero-posterior compression. However, these features are partly correlated with their small size when compared with hominins. Asian H. erectus specimens have a thick occipital torus, but do not differ from other robust specimens, neither in this feature nor in the analysed exo- and endocranial proportions of the occipital bone. Finally, the apparent brain size reduction during the Late Pleistocene and variation between the sexes in anatomically modern humans (AMH) reflect that specimens with smaller brains have a relatively larger posterior height of the cerebellum. However, this trend is not the sole explanation for the ‘vertical shift’ of endinion above inion that appears occasionally and exclusively in AMH.     

Are the different hypotheses on the emergence of life as different as they seem?

This paper calls attention to a philosophical presupposition, coined here the continuity thesis which underlies and unites the different, often conflicting, hypotheses in the origin of life field. This presupposition, a necessary condition for any scientific investigation of the origin of life problem, has two components. First, it contends that there is no unbridgeable gap between inorganic matter and life. Second, it regards the emergence of life as a highly probable process. Examining several current origin-of-life theories. I indicate the implicit or explicit role played by the continuity thesis in each of them. In addition, I identify the rivals of the thesis within the scientific community — the almost miracle camp. Though adopting the anti-vitalistic aspect of the continuity thesis, this camp regards the emergence of life as involving highly improbable events. Since it seems that the chemistry of the prebiotic stages and of molecular self-organization processes rules out the possibility that life is the result of a happy accident, I claim that the almost miracle view implies in fact, a creationist position.     

Evolution,revolution or saltation scenario for the emergence of modern cultures?

Crucial questions in the debate on the origin of quintessential human behaviours are whether modern cognition and associated innovations are unique to our species and whether they emerged abruptly, gradually or as the result of a discontinuous process. Three scenarios have been proposed to account for the origin of cultural modernity. The first argues that modern cognition is unique to our species and the consequence of a genetic mutation that took place approximately 50 ka in Africa among already evolved anatomically modern humans. The second posits that cultural modernity emerged gradually in Africa starting at least 200 ka in concert with the origin of our species on that continent. The third states that innovations indicative of modern cognition are not restricted to our species and appear and disappear in Africa and Eurasia between 200 and 40 ka before becoming fully consolidated. We evaluate these scenarios in the light of new evidence from Africa, Asia and Europe and explore the mechanisms that may have led to modern cultures. Such reflections will demonstrate the need for further inquiry into the relationship between climate and demographic/cultural change in order to better understand the mechanisms of cultural transmission at work in Neanderthals and early Homo sapiens populations.     

Is 'hand preference' coded in the hominin skeleton? An in-vivo study of bilateral morphological variation

The presumed link between bilateral asymmetry and lateralized habitual activity in extinct hominins is the basis upon which inferences of ‘hand preference’ often derive. While this presumption is reasonable, in-vivo comparisons of skeletal asymmetries and self-reported handedness are rare, and as a result the accuracy of these inferences is questionable. To assess this relationship in living humans, reported ‘handedness’ was compared against peripheral quantitative computed tomography (pQCT) derived bilateral measurements of humeral, ulnar, and tibial midshaft cortical area (CA) and torsional rigidity (J). Significant bilateral differences were found in the humerus for all groups, and in the ulna for the cricketer and field hockey sub-samples. Additionally, cricketers’ non-dominant tibiae were more robust than their dominant tibiae. An assessment of ‘Dominance Asymmetry’ revealed that measures of CA and J were higher in the dominant humeri in ∼90% of participants; in the ulna this was true in ∼75% of cases, and in the tibia CA and J were higher in the dominant limb less than 50% of the time. Comparisons of (self)‘Reported’ hand preference against ‘Predicted’ hand preference (based on the calculation of % Directional Asymmetry) revealed a low level of error for predictions based on both humeral (∼4-5% error) and ulnar (6-11% error) asymmetry. Error was decreased with the exclusion of individuals displaying less than 2.5-5% asymmetry. Contrarily, predictions based on tibial analyses had a much higher level of ‘error’ (∼45%). Overall, the results support currently accepted approaches for inferring ‘hand preference’ from measures of upper limb geometric asymmetry in the hominin skeleton.     

Was monogamy a key step on the hominin road? reevaluating the monogamy hypothesis in the evolution of cooperative breeding

Because human mothers routinely rely on others to help raise their young, humans have been characterized as cooperative breeders.^1–9 Several large‐scale phylogenetic analyses have presented compelling evidence that monogamy preceded the evolution of cooperative breeding in a wide variety of nonhuman animals.^10–14 These studies have suggested that monogamy provides a general rule (the monogamy hypothesis) for explaining evolutionary transitions to cooperative breeding.¹⁵ Given the prevalence of cooperative breeding in contemporary human societies, we evaluate whether this suggests a monogamous hominin past.     

Why is the Pathology of Falciparum Worse than that of Vivax Malaria?

Here, Ian Clark and Bill Cowden summarize new evidence suggesting that nitric oxide (NO) generated by inducible NO synthase (iNOS) provides a functional link between the previously competing approaches to malarial disease pathogenesis: ischaemic hypoxia and NO. When combined with the newly recognized roles of iNOS in renal and pulmonary function and glucose metabolism, synergy between inflammatory cytokines and hypoxia in iNOS induction provides a framework to help explain, at a molecular level, the differences in the pathology seen in falciparum and vivax malaria. Thus sequestration, through localized hypoxia, might contribute to pathology by enhancing cytokine-induced iNOS. Generalized hypoxia might have the same effect.     

Captive breeding—a useful tool in the preservation of biodiversity?

Within the next decades species extinction may eliminate between 20 and 50% of the Earth's species. Captive breeding has often been claimed to be a useful tool in preservation of biodiversity. The role of zoos in conservation work and the value of captive breeding are discussed; the latter exemplified by the Peregrine Falcon (Falco peregrinus) Programme and the Arabian oryx (Oryx leucoryx) Programme. Captive breeding programmes are very resource demanding and can only be afforded for a very small number of species, which limits their value significantly. Zoos deal mainly with vertebrates, but these comprise less than 3% of the described species, and although the 878 zoos considered hold more than 20 000 specimens of 140 threatened mammal species, they probably only contribute to the conservation of 20 full species. The situation for birds, reptiles and amphibians is even worse. Zoos face serious problems with minimum viable population sizes and hybridization. However, zoos can make a major contribution to preservation of biodiversity through educating and informing the public. Today, where the crisis of extinction of species has reached such daunting dimensions, captive breeding and otherex situ conservation tools should be the last resort for preserving biodiversity, and captive breeding must not become an excuse to avoid dealing with preservation of habitats.     

Is virtual reality a useful tool in the teaching of physiology?

This opinion statement points out some of the considerations and pitfalls in using virtual reality computer programs in the teaching of life sciences. Emphasis is placed on the possibility of such programs leading to reductionist thinking including how reductionist thinking could foster the formation of misconceptions. Negative feedback is used as the classic example of reductionist thinking in physiological regulation, including how classic negative feedback is inconsistent with evidence of complexity in living systems. This statement concludes that virtual reality can be a useful tool in the teaching of physiology so long as the complexity of living systems is taken into account.