If a meteorite had not fallen on the earth sixty-five million years ago, we would not be where we are now; or more exactly we would not be here at all. If icebergs had not covered a third of the globe's surface three hundred million years ago, this collision some two hundred and thirty-five million years later would have been of no benefit to us. If drought had not swept over the Eurasian continent some ten million years ago, we would (...) still be in the trees, and nothing would encourage us to come down from them. (shrink)

Many traditional attempts to show that nonhuman animals are deserving of moral consideration have taken the form of an argument by analogy. However, arguments of this kind have had notable weaknesses and, in particular, have not been able to convince two kinds of skeptics. One of the most important weaknesses of these arguments is that they fail to provide theoretical justifications for why particular physiological similarities should be considered relevant. This paper examines recent empirical research on pain and, in particular, (...) explores the implications of the dissociation between the sensory and the affective pain pathways. It is argued that these results show that the belief that nonhuman animals experience pain in a morally relevant way is reasonable, though not certain. It is further argued that the proposal to explore the relationship between consciousness and various forms of learning challenges the aforementioned skeptics to provide more physiological details for their claims that nonhuman mammals are probably not conscious. (shrink)

The present study combines dehumanization research with the concept of organizational trust to examine how employees perceive various types of maltreatment embedded within the organizational practices that form the ethical climate of an organization. With the help of grounded theory methodology, we analyzed 188 employment exit interview transcripts from an ICT subcontracting company. By examining perceived trustworthiness and perceived humanness, we found that dehumanizing employees can deteriorate trust within organizations. The violations found in the empirical material were divided into animalistic (...) and mechanistic forms of dehumanization and linked to perceived integrity and benevolence, respectively. Based on the results, a model describing the link between dehumanization and trust is presented and discussed in relation to the ways in which perceptions of humanness become rooted in practices and affect the basic assumptions underlying ethical organizational behavior. (shrink)

Fossil remains witness the relationship between the appearance of the middle ear and the expansion of the brain in early mammals. Nevertheless, the lack of detachment of ear ossicles in the mammaliaform Morganucodon, despite brain enlargement, points to other factors that triggered brain expansion in early mammals. Moreover, brain expansion in some early mammalian groups seems to have favored brain regions other than the cortex.

The Consequence Argument is the classic argument for the incompatibility of determinism and our ability to do otherwise. Daniel C. Dennett objects that the Consequence Argument suffers from the same error as a clearly unconvincing argument that there are no mammals. In this paper, I argue that these arguments do not suffer from the same error. The argument that there are no mammals is unconvincing as it takes the form of a sorites, whereas the Consequence Argument does not. Accordingly, Dennett's (...) objection misses its mark. (shrink)

Endogenous retrovirsuses (ERVs) have long been known to influence gene expression in plants in important ways, but what of their roles in mammals? Our relatively sparse knowledge in that area was recently increased with the finding that ERVs can influence the expression of mammalian resident genes by disrupting transcriptional termination. For many mammalian biologists, retrotransposition is considered unimportant except when it disrupts the reading frame of a gene, but this view continues to be challenged. It has been known for some (...) time that integration into an intron can create novel transcripts and integration upstream of a gene can alter the expression of the transcript, in many cases producing phenotypic consequences and disease. The new findings on transcriptional termination extend the opportunities for retrotransposons to play a role in human disease. (shrink)

Admixture, the genetic exchange between differentiated populations appears to be common in the history of species, but has not yet been comparatively studied across mammals. This limits the understanding of its mechanisms and potential role in mammalian evolution. The authors want to summarize the current knowledge on admixture in non‐human primates, and suggest that it is important to establish a comparative framework for this phenomenon in humans. Genetic observations in domesticated mammals and their wild counterparts are discussed, and a brief (...) global overview on other clades is presented. Based on this, some of the consequences of gene flow, including incompatibilities and their genomic footprint, as well as adaptive introgression are discussed, and suggestions for a functional genomics approach are made. It is proposed that the field is moving beyond descriptive observations in single species, to a comprehensive analysis of admixture and its impact. Admixture is becoming an integral part of mammalian evolution. (shrink)

Admixture, the genetic exchange between differentiated populations appears to be common in the history of species, but has not yet been comparatively studied across mammals. This limits the understanding of its mechanisms and potential role in mammalian evolution. The authors want to summarize the current knowledge on admixture in non‐human primates, and suggest that it is important to establish a comparative framework for this phenomenon in humans. Genetic observations in domesticated mammals and their wild counterparts are discussed, and a brief (...) global overview on other clades is presented. Based on this, some of the consequences of gene flow, including incompatibilities and their genomic footprint, as well as adaptive introgression are discussed, and suggestions for a functional genomics approach are made. It is proposed that the field is moving beyond descriptive observations in single species, to a comprehensive analysis of admixture and its impact. Admixture is becoming an integral part of mammalian evolution. (shrink)

The present article discusses different basic semiotic-scientific postulates regarding mammals’ sign activity. On the one hand, there are arguments denying animals sign activity, according to which mammals are not capable of semantic generalization on the basis of conventional linguistic values. According to another approach, mammals’ sign activity can be considered as means of ecological adaptation, that is, the features of animal behaviour based on the information, received by them through their habitat characteristics without direct visual contacts with their kind. Movement (...) elements, behavioural reactions of similar motivation and parameters of the sign field, which represents an animal’s sign-information environment, may have some numerical expression and can becalculated depending on the research tasks. Formalization of the animal activity implies simultaneous consideration of the following parameters: magnitude,intensity, anisotropy and the value of a given sign object. (shrink)

The standard behavioral index for human consciousness is the ability to report events with accuracy. While this method is routinely used for scientific and medical applications in humans, it is not easy to generalize to other species. Brain evidence may lend itself more easily to comparative testing. Human consciousness involves widespread, relatively fast low-amplitude interactions in the thalamocortical core of the brain, driven by current tasks and conditions. These features have also been found in other mammals, which suggests that consciousness (...) is a major biological adaptation in mammals. We suggest more than a dozen additional properties of human consciousness that may be used to test comparative predictions. Such homologies are necessarily more remote in non-mammals, which do not share the thalamocortical complex. However, as we learn more we may be able to make “deeper” predictions that apply to some birds, reptiles, large-brained invertebrates, and perhaps other species. (shrink)

The view that female mammals are more docile appears to arise in part from imposing human values on animal studies. Many reports of sexual dimorphism in physical aggression favouring the male in laboratory rodents appear to select circumstances where that expectation is supported. Other situations that favour the expression of conflict in females have been (until recently) relatively little studied. Although female rodents generally do not show the “ritualised” forms of conflict that characterise male sexual competition, they can use notably (...) damaging strategies (especially if they are of short duration). Such considerations might weigh in the selection of strategies by our own species. (shrink)

The use of anecdotes is not a viable research strategy to study animal culture. Social learning processes can often be documented with careful quantitative analyses of observational data. Unfortunately, suggestions that killer whales engage in teaching are entirely based on subjective interpretations of qualitative observations. Thus, of teaching in killer whales cannot be used to argue for the occurrence of culture in marine mammals.

Can mammalian mothers adaptively control the sex of their offspring? The influential Trivers-Willard hypothesis proposes that when maternal condition increases the fitness of sons more than that of daughters, the proportion of sons produced should increase with maternal condition. Studies of mammals, however, often fail to support this hypothesis. This article highlights recent advances, including studies on the assumptions of the TWH and physiological mechanisms for sex-ratio manipulation. Particular emphasis is placed on how factors such as paternal quality, maternal reproductive (...) costs and environmental conditions experienced by mothers early in life can mask/alter the expected relationship between maternal condition and offspring sex ratio or lead to apparent support for the TWH. While there is growing evidence that sex ratio around conception may be maternally and paternally manipulated, a challenge for future studies on sex allocation is to integrate how multiple and potentially opposite selective pressures affect offspring sex ratio. The relationship between offspring sex and maternal condition lies at the heart of one of the most controversial hypotheses in evolutionary biology. This review highlights recent findings on the Trivers-Willard hypothesis with particular emphasis on factors which may mask the relationship of interest or falsely demonstrate it. (shrink)

Transmissible cancers are elusive and understudied parasitic life forms caused by malignant clonal cells (nine lineages are known so far). They emerge by completing sequential steps that include breaking cell cooperation, evade anti‐cancer defences and shedding cells to infect new hosts. Transmissible cancers impair host fitness, and their importance as selective force is likely largely underestimated. It is, therefore, crucial to determine how common they might be in the wild. Here, we draw a parallel between the steps required for a (...) transmissible cancer to emerge and the steps required for an intelligent civilisation to emerge in the Milky Way using a modified Drake equation. Using numerical analyses, we estimate the potential number of extant marine and bivalve species in which transmissible cancers might exist. Our results suggest that transmissible cancers are more common than expected, and that new lineages can be found by screening a large number of species. (shrink)

Mammals have a very complex, tightly controlled, and developmentally regulated process of dosage compensation. One form of the process equalizes expression of the X‐linked genes, present as a single copy in males (XY) and as two copies in females (XX), by inactivation of one of the two X‐chromosomes in females. The second form of the process leads to balanced expression between the X‐linked and autosomal genes by transcriptional upregulation of the active X in males and females. However, not all X‐linked (...) genes are absolutely balanced. This review is focused on the recent advances in studying the dosage compensation phenomenon in mammals. (shrink)

Whilst the role of Maturation or M‐phase Promoting Factor (MPF) as a universal M‐phase regulator is well documented, much less attention has been paid to its role in nuclear transplantation experiments and especially to its influence upon remodelling of transplanted nuclei. There is currently wide acceptance that successful nuclear transplantation using differentiated nuclei is possible only in a cytoplasmic environment that is capable of inducing rapid nuclear de‐differentiation to a pronuclear‐like form. In this review our purpose is firstly, to outline (...) the conditions under which such remodelling can be induced, and secondly, to extend the debate to include a consideration of whether complete nuclear remodelling is an absolute necessity for clonal development. (shrink)

Regenerative medicine promises to greatly impact on human health by improving repair outcomes in a range of tissues and injury contexts. Successful therapies will rely on identifying both intrinsic and extrinsic biological circuits that control wound healing, proliferation, cell survival, and developmental cell fate. Animals such as the zebrafish and the salamander display powerful examples of near‐perfect regeneration and scar‐free healing in a range of injury contexts not attained in mammals. By studying regeneration in a range of highly regenerative species (...) that maintain regenerative potential throughout life, many instructive and permissive factors have been identified that could assist in the development of regenerative therapies. This review highlights some of the recent observations in immune regulation, epigenetic regulation, stem cell mobilization, and regenerative signatures that have improved our understanding of the regenerative process. Potential opportunities in harnessing this knowledge for future translation into the clinic are discussed. (shrink)

Comparative mapping and sequencing show that turnover of sex determining genes and chromosomes, and sex chromosome rearrangements, accompany speciation in many vertebrates. Here I review the evidence and propose that the evolution of therian mammals was precipitated by evolution of the male‐determining SRY gene, defining a novel XY sex chromosome pair, and interposing a reproductive barrier with the ancestral population of synapsid reptiles 190 million years ago (MYA). Divergence was reinforced by multiple translocations in monotreme sex chromosomes, the first of (...) which supplied a novel sex determining gene. A sex chromosome‐autosome fusion may have separated eutherians (placental mammals) from marsupials 160 MYA. Another burst of sex chromosome change and speciation is occurring in rodents, precipitated by the degradation of the Y. And although primates have a more stable Y chromosome, it may be just a matter of time before the same fate overtakes our own lineage. (shrink)

Although the developmental arguments in the Quartz & Sejnowski target article may have intrinsic merit, they do not warrant the authors' conclusion that innate modular architectures are absent or minimal, and that neocortical evolution is simply a progression toward more flexible representational structures. Modular architectures can develop and evolve in tandem with sub-cortical specialisation. I present comparative evidence for the co-evolution of specific thalamic and cortical visual pathways.

Important marine mammal areas (IMMAs)—‘discrete habitat areas, important for one or more marine mammal species, that have the potential to be delineated and managed for conservation’ (IUCN Marine Mammal Protected Areas Task Force 2018, p. 3)—were introduced in 2014 by the IUCN Marine Mammal Protected Areas Task Force to support marine mammal and wider ocean conservation. IMMAs provide decision-makers with a user-friendly, actionable tool to inform them of the whereabouts of habitat important for marine (...) class='Hi'>mammal survival. However, in view of their non-prescriptive, evidence-based and biocentric nature, the conservation effectiveness of IMMAs is strictly dependent on politicians’ willingness to make use of them. It has been the customary task of advocacy non-governmental organisations to lobby decision-makers to stimulate respect for environmental law, but the scientific community is increasingly joining this effort. Scientists can effectively strengthen a healthy relationship between scientific objectivity and political advocacy without damaging the credibility of conservation science. Thus, those undertaking the identification of IMMAs can be among those responsible for strongly advocating the implementation of IMMAs and other conservation initiatives. (shrink)

At fertilization in mammals the sperm activates the egg by triggering a series of oscillations in the intracellular free Ca2+ concentration. The precise sequence of events that occur between sperm‐egg contact and the increases in intracellular Ca2+ remains unknown. Here, we discuss recent evidence supporting the hypothesis that a cytosolic sperm protein enters the egg after gamete membrane fusion and triggers Ca2+ oscillations from within the egg cytoplasm. Biochemical studies suggest that there exists a novel sperm protein, named oscillin, that (...) specifically comigrates with Ca2+ oscillation‐inducing activity. Oscillin has been immunolocalised to the region of the sperm that first fuses with the egg. The concept of a specific protein that triggers Ca2+ oscillations may have wider physiological significance since sperm oscillin can induce Ca2+ oscillations in somatic cells, such as neurons and hepatocytes. Unravelling the novel signalling system involved in mammalian fertilization may help reveal some fundamental molecular mechanisms responsible for triggering cytoplasmic Ca2+ oscillations. (shrink)

Important marine mammal areas (IMMAs)—‘discrete habitat areas, important for one or more marine mammal species, that have the potential to be delineated and managed for conservation’ (IUCN Marine Mammal Protected Areas Task Force 2018, p. 3)—were introduced in 2014 by the IUCN Marine Mammal Protected Areas Task Force to support marine mammal and wider ocean conservation. IMMAs provide decision-makers with a user-friendly, actionable tool to inform them of the whereabouts of habitat important for marine (...) class='Hi'>mammal survival. However, in view of their non-prescriptive, evidence-based and biocentric nature, the conservation effectiveness of IMMAs is strictly dependent on politicians’ willingness to make use of them. It has been the customary task of advocacy non-governmental organisations to lobby decision-makers to stimulate respect for environmental law, but the scientific community is increasingly joining this effort. Scientists can effectively strengthen a healthy relationship between scientific objectivity and political advocacy without damaging the credibility of conservation science. Thus, those undertaking the identification of IMMAs can be among those responsible for strongly advocating the implementation of IMMAs and other conservation initiatives. (shrink)

The main objective of this essay is to validate some of the principal, currently competing, mammalian consciousness-brain theories by comparing these theories with data on both cognitive abilities and brain organization in birds. Our argument is that, given that multiple complex cognitive functions are correlated with presumed consciousness in mammals, this correlation holds for birds as well. Thus, the neuroanatomical features of the forebrain common to both birds and mammals may be those that are crucial to the generation of both (...) complex cognition and consciousness. The general conclusion is that most of the consciousness-brain theories appear to be valid for the avian brain. Even though some specific homologies are unresolved, most of the critical structures presumed necessary for consciousness in mammalian brains have clear homologues in avian brains. Furthermore, considering the fact that the reptile-bird brain transition shows more structural continuity than the stem amniote-mammalian transition, the line drawn at the origin of mammals for consciousness by several of the theorists seems questionable. An equally important point is that consciousness cannot be ruled out in the absence of complex cognition; it may in fact be the case that consciousness is a necessary prerequisite for complex cognition. (shrink)

Macphail’s comparative approach to intelligence focused on associative processes, an orientation inconsistent with more multifaceted lay and scientific understandings of the term. His ultimate emphasis on associative processes indicated few differences in intelligence among vertebrates. We explore options more attuned to common definitions by considering intelligence in terms of richness of representations of the world, the interconnectivity of those representations, the ability to flexibly change those connections, knowledge, and individual differences. We focus on marine mammals, represented by the amphibious pinnipeds (...) and the aquatic cetaceans and sirenians, as animals that transitioned from a terrestrial existence to an aquatic one, experiencing major changes in ecological pressures. They adapted with morphological transformations related to streamlining the body, physiological changes in respiration and thermoregulation, and sensory/perceptual changes, including echolocation capabilities and diminished olfaction in many cetaceans, both in-air and underwater visual focus, and enhanced senses of touch in pinnipeds and sirenians. Having a terrestrial foundation on which aquatic capacities were overlaid likely affected their cognitive abilities. Vocal and behavioral observational learning capabilities in the wild and in laboratory experiments suggest versatility in group coordination. Empirical reports on aspects of intelligent behavior like problem-solving, spatial learning, and concept learning by various species of cetaceans and pinnipeds, suggest rich cognitive abilities. The high energy demands of the brain suggest brain-intelligence relationships might be fruitful areas for the study when specific hypotheses are considered, e.g., brain mapping indicates hypertrophy of specific sensory areas in marine mammals. Modern neuroimaging techniques provide ways to study neural connectivity, and the patterns of connections between sensory, motor, and other cortical regions provide a biological framework for exploring how animals represent and flexibly use information in navigating and learning about their environment. At this stage of marine mammal research, it would still be prudent to follow Macphail’s caution that it is premature to make strong comparative statements without more empirical evidence, but an approach that includes learning more about how animals flexibly link information across multiple representations could be a productive way of comparing species by allowing them to use their specific strengths within comparative tasks. (shrink)

Self-medication behaviour is the use of natural materials or chemical substances to manipulate behaviour or alter the body’s response to parasites or pathogens. Self-medication can be preventive, performed before an individual becomes infected or diseased, and/or therapeutic, performed after an individual becomes infected or diseased. We summarized all available reports of self-medication in mammals and reconstructed its evolution. We found that reports of self-medication were restricted to eutherian mammals and evolved at least four times independently. Self-medication was most commonly reported (...) in primates. Detailed analyses of primates suggest that self-medication is a life-history trait associated with body size, absolute brain size and longevity, but we found no support for the hypothesis that self-medication evolved to reduce the costs of social living. Large, longer-lived species might thus benefit uniquely from self-medication. (shrink)

Burrowing mammals are ubiquitous on farms in South Africa and can hinder agricultural practices. This study explored farmer perspectives of these species, and specifically the factors that influence these perspectives. Forty-four farmers responded to a questionnaire that assessed their ecological knowledge of, tolerance towards and lethal management of burrowing mammals that occur on their farms. The results from generalised linear models showed that neither farmer age, nor level of education are accurate predictors of ecological knowledge, overall tolerance towards burrowers, or (...) their lethal management. Knowledge of burrowing mammals showed a significant relationship with tolerance, with more knowledgeable individuals displaying higher levels of tolerance. However, a farmer’s overall tolerance towards burrowing species did not affect the number of species managed. Our results also suggest that different values are attached to different species when it comes to lethal management. Thus, farmers commonly controlled the numbers of the problem rodent species, Highveld gerbil (Gerbilliscus brantsii) and Cape ground squirrel (Xerus inauris), but were less likely to manage black-backed jackal (Canis mesomelas) and warthog (Phacochoerus africanus), even when experiencing these as problematic. We suggest that the larger, more charismatic species possibly evoke more sympathy from farmers. Agro-ecosystems are likely to become increasingly important for conservation in the future, and we encourage continued studies on the environmental attitudes and approaches of agricultural practitioners as a means to understanding the current status and future trends in ecologically sustainable agriculture. (shrink)

The evolution and biodiversity of ageing have long fascinated scientists and the public alike. While mammals, including long‐lived species such as humans, show a marked ageing process, some species of reptiles and amphibians exhibit very slow and even the absence of ageing phenotypes. How can reptiles and other vertebrates age slower than mammals? Herein, I propose that evolving during the rule of the dinosaurs left a lasting legacy in mammals. For over 100 million years when dinosaurs were the dominant predators, (...) mammals were generally small, nocturnal, and short‐lived. My hypothesis is that such a long evolutionary pressure on early mammals for rapid reproduction led to the loss or inactivation of genes and pathways associated with long life. I call this the ‘longevity bottleneck hypothesis’, which is further supported by the absence in mammals of regenerative traits. Although mammals, such as humans, can evolve long lifespans, they do so under constraints dating to the dinosaur era. (shrink)

Paleontological and molecular data suggest quite different patterns for the early evolution of placental mammals. Paleontological evidence indicates a radiation, with most of the extant orders diverging at approximately the same time, close to the Cretaceous-Tertiary boundary, 65 Myr ago. Molecular evidence suggests a branching pattern of evolution that started much earlier. Resolving this discrepancy requires a consideration of the assumptions that underlie both approaches. It is argued here that the pattern indicated by the molecular approach is the most likely (...) to be correct. If it is correct then either: 1) A diversity of placental mammals remains to be sampled from the Cretaceous, or 2) The placental orders diverged phylogenetically long before they diversified morphologically, implying a decoupling of the evolutionary processes associated with speciation and adaptation. The adaptive diversification of placental mammals may have required the demise of the dinosaurs at the end of the Cretaceous, but it occurred in lineages that had a long prior history of independent existence. BioEssays 21: 1052–1058, 1999. © 1999 John Wiley & Sons, Inc. (shrink)

In summary, the creation and maintenance of the Wistar Rats as standardized animals can be attributed to the breeding work of Helen Dean King, coupled with the management and husbandry methods of Milton Greenman and Louise Duhring, and with supporting documentation provided by Henry Donaldson. The widespread use of the Wistar Rats, however, is a function of the ingenuity of Milton Greenman who saw in them a way for a small institution to provide service to science. Greenman's rhetoric, as captured (...) in his Director's Reports, prepared annually from 1905 until his death in 1937, shows that he was unusually sensitive to his times and to the economics of science and of society. In the era when biology was being defined, he recognized in the rat the potential to be a living analog to the pure chemicals that legitimated experimental science. From management literature he extracted the ideals of uniformity of product, standards of quality, and efficiency of production, applying them to scientific practice to generate an animal model that thrives as standard equipment in laboratories throughout the world today.I will close with a quote from Frederick W. Taylor that is a cogent statement of the contribution to science and scientific progress made by standardized tools and their creators. Equating the surgeon and the workman, Taylor wrote: [He is given] the finest implements, each one of which has been the subject of special study and development ... [and] the very best knowledge of his predecessors; and, provided with standard implements and methods which represent the best knowledge of the world up to date, he is able to use his own originality and ingenuity to make real additions to the world's knowledge, instead of reinventing things which are old.Standardized tools, whether surgeons' implements or laboratory-bred rats, are one of the vehicles for carrying scientific knowledge forward from generation to generation. In this sense, Greenman's Wistar Rats have done their job, in his words, of “providing service to science.”. (shrink)

Mammalian hibernation is characterized by profound reductions in metabolism, oxygen consumption and heart rate. As a result, the animal enters a state of suspended animation where core body temperatures can plummet as low as −2.9°C. Not only can hibernating mammals survive these physiological extremes, but they also return to a normothermic state of activity without reperfusion injury or other ill effects. This review examines recent findings on the genes, proteins and small molecules that control the induction and maintenance of hibernation (...) in mammals. The molecular events involved with remodeling metabolism, inducing hypothermia and maintaining organ function are discussed and considered with respect to analogous processes in non‐hibernating mammals such as mice and humans. The advent of sequenced genomes from three distantly related hibernators, a bat, hedgehog and ground squirrel, provides additional opportunities for molecular biologists to explore the mechanistic aspects of this biological adaptation in greater detail. BioEssays 29:431–440, 2007. © 2007 Wiley Periodicals, Inc. (shrink)

An unprecedented level of confidence has recently crystallized around a new hypothesis of how living placental mammals share a pattern of common descent. The major groups are afrotheres (e.g., aardvarks, elephants), xenarthrans (e.g., anteaters, sloths), laurasiatheres (e.g., horses, shrews), and euarchontoglires (e.g., humans, rodents). Compared with previous hypotheses this tree is remarkably stable; however, some uncertainty persists about the location of the placental root, and (for example) the position of bats within laurasiatheres, of sea cows and aardvarks within afrotheres, and (...) of dermopterans within euarchontoglires. A variety of names for sub‐clades within the new placental mammal tree have been proposed, not all of which follow conventions regarding priority and stability. More importantly, the new phylogenetic framework enables the formulation of new hypotheses and testing thereof, for example regarding the possible developmental dichotomy that seems to distinguish members of the newly identified southern and northern radiations of living placental mammals. (shrink)

Because network scaling costs tend to limit absolute brain size, Striedter suggests that large cetacean brains must have evolved some novel ways to cope with these costs. A new analysis of available data shows that the scaling pattern of interhemispheric connectivity in cetaceans is isometric and differs from that observed in terrestrial mammals.

(1941). A survey of the growth of knowledge about certain parts of the foetal cardio-vascular apparatus, and about the foetal circulation, in Man and some other mammals. Part I: Galen to Harvey. Annals of Science: Vol. 5, No. 1, pp. 57-89.

Australia is thought of as the home of marsupials, but South America has 60 or so species of these interesting mammals. The genome of one of these, the South American grey short-tailed opossum, Monodelphis domestica, has just been sequenced and published in June.1 The high quality 6× coverage is the first marsupial genome completed, pipping the 2× coverage of the Australian tammar wallaby at the post by half a year. The opossum genome has an unusual structure with fewer chromosomes than (...) the human genome (9 pairs versus 23 pairs) but a longer total length (3.4 billion versus 3 billion bases). The opossum autosomes, like those of all marsupials, are extremely large but, in contrast, the X chromosome is only 76 Mb long. The opossum genome has turned up several surprises and provided critical new information on the evolution of mammalian genomes2-6. BioEssays 29:1073–1076, 2007. © 2007 Wiley Periodicals, Inc. (shrink)

The circadian clock is a cell autonomous oscillator that controls many aspects of physiology through generating rhythmic gene expression in a time of day dependent manner. In addition, in endothermic mammals body temperature cycles contribute to rhythmic gene expression. These body temperature‐controlled rhythms are hard to distinguish from classic circadian rhythms if analyzed in vivo in endothermic organisms. However, they do not fulfill all criteria of being circadian if analyzed in cell culture or in conditions where body temperature of an (...) endothermic organism can be manipulated. Here we review and compare these characteristics, discuss the core clock independent mechanism of temperature‐controlled alternative splicing and highlight the requirement of double‐checking rhythms that appear circadian within an endothermic organism in a system that allows temperature manipulation. (shrink)

Observations on the morphological and functional similarity between embryonic or trophoblast tissues and tumors are very old. Over a period of time many investigators have created different hypotheses on the origin of cancerogenesis or tumor efficiency in relation to the host immune system. Some of these ideas have been rejected but many of them are still current. A presumption of the inefficiency of anti-tumor immunity in mammals due to the high similarity between trophoblast and embryonic cells to tumor cells is (...) very real. The mechanisms for the escape of tumors from the immune response are very similar to the mechanisms for the escape of a fetoplacental unit from the maternal immune response. The similarity between these two mechanisms is so great that any randomness must be banished. At the same time, an incidence of malignant tumors and the types of more frequent tumors in non-mammalian vertebrates is significantly different to that in mammals. Lastly, the mechanisms of anti-tumor immunity in mammals are substantially different from the mechanisms of anti-tumor immunity in other classes of vertebrates. These facts indicate that the immune system of mammals during anti-tumor immune response is tricked by the similarity between tumor cells and trophoblast or other placental cells. From this aspect, our conclusion is that anti-tumor immunity failure in mammals can be defined as an immunoreproductive phenomenon, which is developed under the evolutionary pressure of autoimmunity and reproductive effectiveness. (shrink)

Environmental factors routinely influence an organism's biology. The inheritance or transmission of such influences to descendant generations would be an efficient mode of information transfer across generations. The developmental stage at which a specific environment is encountered by the ancestral generation, and the number of generations over which information about that environment is registered, determines an inter‐ vs. trans‐generational effect of ancestral influence. This commentary will outline the distinction between these influences. While seductive in principle, inter‐ and trans‐generational inheritance in (...) mammals is a hotly debated area of research inquiry. We present constructive criticism of such inheritance, and suggest potential experimental avenues for reconciliation. Finally, epigenetic mechanisms present an avenue for gene regulation that is dynamic. We briefly discuss how such malleability affords the potential for a reversal of any detrimental environmental influences that might have adversely impacted ancestral or descendant generations. (shrink)

The primitive streak establishes the antero‐posterior body axis in all amniote species. It is thought to be the conduit through which mesoderm and endoderm progenitors ingress and migrate to their ultimate destinations. Despite its importance, the streak remains poorly defined and one of the most enigmatic structures of the animal kingdom. In particular, the posterior end of the primitive streak has not been satisfactorily identified in any species. Unexpectedly, and contrary to prevailing notions, recent evidence suggests that the murine posterior (...) primitive streak extends beyond the embryo proper. In its extraembryonic site, the streak creates a node‐like cell reservoir from which the allantois, a universal caudal appendage of all amniotes and the future umbilical cord of placental mammals, emerges. This new insight into the fetal/umbilical relationship may explain the etiology of a large number of umbilical‐associated birth defects, many of which are correlated with abnormalities of the embryonic midline. (shrink)

The considerable variation in shape, size, structure and properties of the enamel cap covering mammalian teeth is a topic of great evolutionary interest. No existing theories explain how such variations might be fit for the purpose of breaking food particles down. Borrowing from engineering materials science, we use principles of fracture and deformation of solids to provide a quantitative account of how mammalian enamel may be adapted to diet. Particular attention is paid to mammals that feed on ‘hard objects’ such (...) as seeds and dry fruits, the outer casings of which appear to have evolved structures with properties similar to those of enamel. These foods are important in the diets of some primates, and have been heavily implicated as a key factor in the evolutionary history of the hominin clade. As a tissue with intrinsic weakness yet exceptional durability, enamel could be especially useful as a dietary indicator for extinct taxa. BioEssays 30:374–385, 2008. © 2008 Wiley Periodicals, Inc. (shrink)