A striking example of developmental bias in an evolutionary process: The “domestication syndrome”

The question of whether “developmental bias” can influence evolution is still controversial, despite much circumstantial evidence and a good theoretical argument. Here, I will argue that the domestication of mammalian species, which took place independently more than two dozen times, provides a particularly convincing example of developmental bias in evolution. The singular finding that underlies this claim is the repeated occurrence in domesticated mammals of a set of distinctive traits, none of which were deliberately selected. This phenomenon has been termed “the domestication syndrome”. In this article, I will: (a) describe the properties of the domestication syndrome; (b) show how it can be explained in terms of the operation of a specific genetic regulatory network, that which governs neural crest cell development; and (c) discuss Dmitry Belyaev's idea of “destabilizing selection,” which holds that selecting for a new behavior often entails neuroendocrine alterations that alter many aspects of development. Finally, I will argue for the potential general significance of such destabilizing selection, in combination with developmental bias, in animal evolution.     

Hormonal control of invertebrate behavior

Invertebrates show a wide variety of behaviors that are influenced by hormones. In insects the involvement of hormones at a particular life stage is directly correlated with the complexity of the behavioral repertoire at that stage. In larval stages, the steroid hormone, ecdysone, when present with juvenile hormone, apparently causes the behaviors observed during the periodic molts. At the end of larval life, ecdysone in the absence of juvenile hormone triggers the onset of premetamorphic behaviors such as wandering behavior and cocoon-spinning behavior. In insects having complete metamorphosis, the emergence (eclosion) of the adult from the pupal case is accomplished by a stereotyped program of movements that are triggered by a peptide hormone. In moths, injection of this “eclosion hormone” into competent recipients will cause the release of the eclosion program. Also this program can be elicited by the hormone from the isolated abdominal central nervous system (CNS). The onset of reproductive behavior in females of various species requires juvenile hormone. In addition, certain peptides are then involved in the transition from virgin to mated behaviors. Also, pupatitive peptide factors trigger specific stereotyped behaviors such as those involved in mate attraction and in oviposition. In males, the control is simpler. Juvenile hormone is required for the maturation of sexual behavior in only a few species. But in at least one insect group, the cockroaches, a neurosecretory hormone serves to release directly copulatory behavior. Social behavior and migratory behavior in certain insects are also under hormonal influence. Hormones play a prominent role in regulating the behavior of gastropod mollusks. The best studied examples involve the hormonal stimulation of egg-laying behavior by CNS peptides. Also, peptide hormones cause stereotyped changes in specific identified neurons in the CNS of various gastropods. In at least some cases, these latter changes are related to arousal from aestivation.With their simple nervous systems, invertebrates are especially suited for studies on the mode of action of hormones on the nervous system. In most cases the behavioral effects of these hormones appear to be due to their direct action on the CNS. Indeed, the isolated moth CNS will respond to the eclosion hormone by generating the motor program that gives rise to the emergence behavior, and various isolated molluscan preparations will respond to hormones with stereotyped neural responses. By the direct application of hormone to the surface of identified nerve cells in mollusks it has been possible to localize target cells for specific hormones. Little is known of the mode of action of ecdysone or juvenile hormone in altering behavior. Peptide hormones appear to have effects which long outlast the actual presence of the hormone. In at least two cases, cyclic AMP has been implicated as a mediator of the hormonal response.     

Wanting,liking and welfare: The role of affective states in proximate control of behaviour in vertebrates

Animals choose a course of action countless times each day. To do so, they need to prioritise their behaviour within a set of alternative actions and decide which of these actions to perform at any one time and for how long, that is, determine when the behaviour has reached its desired effect. This process has classically been called the proximate behavioural control mechanism. Several aspects contribute to this process: internal and external stimuli, the emotions that they elicit, motivation (wants), behavioural goals, valuation, decision‐making and its modulation by mood, and the assessment of behavioural outcomes (liking). I will address all these aspects in the form of an integrated conceptual model. In the process of behavioural control, options need to be valued, and I will refer to evidence showing that an affective hedonic process in respect to (future) reward and punishment heavily affects this value. Moreover, I view motivation, the force that finally drives a specific behavioural output, as being primarily influenced by affective states or even corresponding fully to them. Given the feedback in behavioural control by (dis‐)liking outcomes of behaviour, I reason that in respect to welfare it is more important for animals to reach proximate goals than to avoid negative stimuli. All behavioural choices are modulated, and I show how mood, a long‐term affective state, can cause such modulation. Proximate control of behaviour takes place in the brain, and I will briefly discuss how current and future brain research may elucidate how the brain computes these processes. Furthermore, the inclusion of affective states in the conceptual model raises the question of the subjective experience of animals, and I will address some of the important open questions in this area of research. I will conclude that neural studies cannot currently provide a detailed and general theory on the algorithms of proximate behavioural control. In parallel to further developing these approaches, I propose to strengthen a refined ethological approach with a focus on the states of “wanting” and “liking” in ecologically meaningful circumstances and with a strong ontogenetic (within species) and comparative (between species) component. I consider this ethological approach to be a highly promising step in understanding proximate behavioural control.     

Extending the quasi-neutral concept

In caricature, the equilibrium paradigm of community ecology states that plant communities are stable entities consisting of competing species - and that such species coexist because each has its “niche”. This paradigm, in its extreme, has been dead for some time. Nevertheless, it has yet to be replaced by a credible “non” — equilibrium paradigm. The quasi-neutral concept of plant communities, proposed by Kristjan Zobel,Folia Geobot. 36: 3–8, 2001, possesses some of the key ingredients of a nonequilibrium theory of diversity. It recognizes that there are inescapable relationships between diversity at different scales, that similarity can influence the rate of competitive exclusion, that successional change is typically associated with changes in life form, and that rarefaction (i.e. “sampling artifacts”) can have strong effects on fine-scale diversity. However, the current formulation of the quasi-neutral concept is incomplete in that it relies on an unrealistic definition of community, it assumes that random sampling means that species richness at one scale will be linearly related to richness at finer scales, it ignores the possibility of fine-scale processes producing broader-scale patterns, and it avoids the subject of fine-scale environmental heterogeneity. But the most serious limitation of the quasi-neutral concept is that similarity of species alone is not sufficient to allow indefinite coexistence. I present the results of a simple simulation to demonstrate that: (1) identical species will eventually be lost from communities due to stochastic “drift”, (2) slight variations in reproductive rates accelerate this loss, but (3) adding a miniscule “cost of commonness” to the model allows the indefinite coexistence of species. I conclude that the quasi-neutral model cannot work without some kind of trade-off.     

The cultural construction of gendered bodies: Biology and metaphors of production and destruction*

One way of conceiving of the anthropological task is that of countering the degradations and “dehumanizations” of the “other” to which the species is prone by promoting “transcendent humanization.” However efficiently and professionally anthropologists gather their materials and form them into their ethnographic and ethnologic analyses, may not this “ethical impulse” be postulated as the “final cause” of our efforts? But what could such a sonorous phrase mean ? And what is its relationship to the systematic study of the “differences that make or do not make a difference” in culture to which anthropology has long been devoted? I will argue that it involves a dynamic of categories and that this dynamic is itself an object of systematic study. Recently, for example, some anthropologists have been writing “against culture,” seeing the culture concept and associated theory more as barriers than as benefits to pan‐human understanding. I will argue that this is an instance of “transcendent humanization.” One cannot but be sympathetic to the thrust and merits of this argument. But at the same time one wants to ask what implications it holds for the systematic study and understanding of the other. This article, then, examines some elementary vectors in the “dynamic of the categorical” involved in these and related recent debates which also may be seen in terms of transcendence and humanization: the debate over relativism and the recently emergent debate over “enlightenment mythmaking” in anthropology.     

Structures of Arg‐ and Gln‐type bacterial cysteine dioxygenase homologs

In some bacteria, cysteine is converted to cysteine sulfinic acid by cysteine dioxygenases (CDO) that are only ～15–30% identical in sequence to mammalian CDOs. Among bacterial proteins having this range of sequence similarity to mammalian CDO are some that conserve an active site Arg residue (“Arg‐type” enzymes) and some having a Gln substituted for this Arg (“Gln‐type” enzymes). Here, we describe a structure from each of these enzyme types by analyzing structures originally solved by structural genomics groups but not published: a Bacillus subtilis “Arg‐type” enzyme that has cysteine dioxygenase activity (BsCDO), and a Ralstonia eutropha “Gln‐type” CDO homolog of uncharacterized activity (ReCDOhom). The BsCDO active site is well conserved with mammalian CDO, and a cysteine complex captured in the active site confirms that the cysteine binding mode is also similar. The ReCDOhom structure reveals a new active site Arg residue that is hydrogen bonding to an iron‐bound diatomic molecule we have interpreted as dioxygen. Notably, the Arg position is not compatible with the mode of Cys binding seen in both rat CDO and BsCDO. As sequence alignments show that this newly discovered active site Arg is well conserved among “Gln‐type” CDO enzymes, we conclude that the “Gln‐type” CDO homologs are not authentic CDOs but will have substrate specificity more similar to 3‐mercaptopropionate dioxygenases.     

Multiple roles for Hox genes in segment-specific shaping of CNS lineages

In this “Extra View” article we highlight some of the recently accumulating evidence showing that Hox genes are involved at different steps during the development of neural cell lineages to control segmental patterning of the CNS. In addition to their well-known early role in establishing segmental identities, Hox genes act on neural stem cells and their progeny at various stages during embryonic and postembryonic development to control proliferation, cell fate and/or apoptosis in a segment-specific manner. This leads to differential shaping of serially homologous lineages and thus to structural diversification of segmental CNS units (neuromeres) in adaptation to their specific functional tasks in processing sensory information and generation of motor patterns.     

Is Santa Claus an evening owl?

Case studies have a long tradition in biomedical research. Here, I will analyze an important person from a chronobiological aspect, Santa Claus. Although it might be dangerous for researchers to publish analyses about Santa Claus, because, given the possibility that he may be unsatisfied with my analysis, this could lead to an embargo of parcels for my whole family. Nevertheless, some intrepid researches already diagnosed Santa Claus, ending up in some important research results. A search in Web of Science revealed only N = 224 publications about Santa Claus, which is really low. The question, I am addressing here is, whether Santa Claus is an “evening owl” or a night chronotype. In this report, I summarize the facts known about Santa Claus on the one side and about evening chronotypes on the other and sum up these results in a “vote counting” manner as pros and cons. The results are summarized in Table 1. In total, there is 12 times support for the hypothesis, 2 times against and 1 equivocal (Table 1). This result is significant (binomial test, p = 0.013). Therefore, the conclusion is “Santa Claus is an evening type”.     

DNA Repair: A changing geography? (1964–2008)

This article aims to explain the current state of DNA Repair studies’ global geography by focusing on the genesis of the community. Bibliometric data is used to localize scientific activities related to DNA Repair at the city level. The keyword “DNA Repair” was introduced first by American scientists. It started to spread after 1964 that is to say, after P. Howard-Flanders (Yale University), P. Hanawalt (Stanford University) and R. Setlow (Oak Ridge Laboratories) found evidence for Excision Repair mechanisms. It was the first stage in the emergence of an autonomous scientific community. In this article, we will try to assess to what extent the geo-history of this scientific field is determinant in understanding its current geography. In order to do so, we will localize the places where the first “DNA Repair” publications were signed fifty years ago and the following spatial diffusion process, which led to the current geography of the field. Then, we will focus on the evolution of the research activity of “early entrants” in relation to the activity of “latecomers”. This article is an opportunity to share with DNA Repair scientists some research results of a dynamic field in Science studies: spatial scientometrics.     

Is there a special conservation biology?

Conservation biology is special to the extent that it fills useful roles in the scientific and conservation fields that are not being filled by practitioners of other disciplines. The emergence of the “new conservation biology” in the late 1970's and its blossoming in the 1980's and 1990's reflect, to a large degree, a failure of traditional academic ecology and the natural resource disciplines to address modern conservation problems adequately. Yet, to be successful conservation biology, as an interdisciplinary field, must build on the strengths of other disciplines both basic and applied. The new conservation biology grew out of concern over extinction of species, although the field has expanded to include issues about management of several levels of biological organization. I examine four controversial questions of importance to conservation biologists today: 1) are there any robust principles of conservation biology? 2) Is advocacy an appropriate activity of conservation biologists? 3) Are we educating conservation biologists properly? 4) Is conservation biology distinct from other biological and resource management disciplines? I answer three of these questions with a tentative “yes” and one (3) with a regretful “in most cases, no.” I see a need for broader Training for students of conservation biology, more emphasis on collecting basic field data, compelling applications of conservation biology to real problems, increased influence on policy, and expansion of the international scope of the discipline. If all these occur, conservation biology will by truly special.     

HYBRID ZONES WITH DOBZHANSKY-TYPE EPISTATIC SELECTION

Dobzhansky's model of epistatic selection assumes that viable genotypes form “clusters” in genotype space so that populations can evolve from one state to a reproductively isolated state following a “ridge” of well-fit genotypes without crossing any deep adaptive valleys. Recently, the importance of Dobzhansky-type models in evolutionary studies has been reemphasized by Gavrilets (1997a) and Gavrilets and Gravner (1997) who argue that the existence of “ridges” of well-fit genotypes connecting reproductively isolated genotypes is actually a general property of multidimensional adaptive landscapes. Using rigorous techniques and numerical simulations, I analyze clines in the frequencies of selected and neutral alleles maintained by a balance of migration and Dobzhansky-type epistatic selection acting on two diallelic loci. I show that Dobzhansky-type epistatic selection can build up a very strong barrier to neutral gene flow. I describe properties of clines that are indicative of Dobzhansky-type selection.     

Experimental analysis of the migration and differentiation of neuroblasts of the autonomic nervous system and of neurectodermal mesenchymal derivatives, using a biological cell marking technique

By isotopic and isochronic transplantations of fragments of quail neural tube into chick, it has been previously shown that enteric ganglion cells arise from the “vagal” (somites 1–7) and the “lumbo-sacral” (behind somite 28) levels of the neural crest, while the trunk region (somites 8–28) gives rise to orthosympathetic ganglion chain and adrenomedullary cells. The latter originate precisely from the neural crest corresponding to somites 18–24 (i.e., “adrenomedullary” level of the crest). Heterotopic transplantations of fragments of quail neural tube into chick have been carried out in the present work. When the “adrenomedullary” level of the quail neural tube is grafted into the “vagal” region of a chick, the crest cells colonize the gut and differentiate into enteric ganglia of Auerbach's and Meissner's plexi. If quail cephalic neural crest is transplanted in the “adrenomedullary” level of a chick, quail cells migrate into the suprarenal glands and differentiate into adrenomedullary cells. Mesectodermal cells migrate laterally, and differentiate into cartilage, dermis and connective tissues. Thus it appears that preferential pathways located at precise levels of the embryo lead crest cells to their definitive sites. On the other hand the differentiation of the autonomic neuroblasts is controlled by the environment in which crest cells are localized at the end of their migration. On the contrary, mesenchymal derivatives of the cephalic neural crest appear to be early determined since they differentiate according to their presumptive fate when transplanted into the trunk.     

Ecological theatre and the evolutionary game: how environmental and demographic factors determine payoffs in evolutionary games

In the standard approach to evolutionary games and replicator dynamics, differences in fitness can be interpreted as an excess from the mean Malthusian growth rate in the population. In the underlying reasoning, related to an analysis of “costs” and “benefits”, there is a silent assumption that fitness can be described in some type of units. However, in most cases these units of measure are not explicitly specified. Then the question arises: are these theories testable? How can we measure “benefit” or “cost”? A natural language, useful for describing and justifying comparisons of strategic “cost” versus “benefits”, is the terminology of demography, because the basic events that shape the outcome of natural selection are births and deaths. In this paper, we present the consequences of an explicit analysis of births and deaths in an evolutionary game theoretic framework. We will investigate different types of mortality pressures, their combinations and the possibility of trade-offs between mortality and fertility. We will show that within this new approach it is possible to model how strictly ecological factors such as density dependence and additive background fitness, which seem neutral in classical theory, can affect the outcomes of the game. We consider the example of the Hawk–Dove game, and show that when reformulated in terms of our new approach new details and new biological predictions are produced.     

A new criterion for confounder selection

Summary We propose a new criterion for confounder selection when the underlying causal structure is unknown and only limited knowledge is available. We assume all covariates being considered are pretreatment variables and that for each covariate it is known (i) whether the covariate is a cause of treatment, and (ii) whether the covariate is a cause of the outcome. The causal relationships the covariates have with one another is assumed unknown. We propose that control be made for any covariate that is either a cause of treatment or of the outcome or both. We show that irrespective of the actual underlying causal structure, if any subset of the observed covariates suffices to control for confounding then the set of covariates chosen by our criterion will also suffice. We show that other, commonly used, criteria for confounding control do not have this property. We use formal theory concerning causal diagrams to prove our result but the application of the result does not rely on familiarity with causal diagrams. An investigator simply need ask, “Is the covariate a cause of the treatment?” and “Is the covariate a cause of the outcome?” If the answer to either question is “yes” then the covariate is included for confounder control. We discuss some additional covariate selection results that preserve unconfoundedness and that may be of interest when used with our criterion.     

Metaphors in search of a target: the curious case of epigenetics

Carrying out research in genetics and genomics and communicating about them would not be possible without metaphors such as “information,” “code,” “letter” or “book.” Genetic and genomic metaphors have remained relatively stable for a long time but are now beginning to shift in the context of synthetic biology and epigenetics. This article charts the emergence of metaphors in the context of epigenetics, first through collecting some examples of metaphors in scientific and popular writing and second through a systematic analysis of metaphors used in two UK broadsheets. Findings show that while source domains for metaphors can be identified, such as our knowledge of electrical switches or of bookmarks, it is difficult to pinpoint target domains for such metaphors. This may be indicative both of struggles over what epigenetics means for scientists (natural and social) and of difficulties associated with talking about this, as yet, young field in the popular press.     

162 Dominant forces in protein folding

In the first part of this talk, I will discuss the need for a paradigm shift from hydrophobic (HφO) to a hydrophilic ((HφI) based theory of protein folding. Next, I will discuss the various types of solvent-induced forces that are exerted on various groups on the protein. It is argued, both theoretically and by simulations, that the HφI–HφI solvent-induced forces are likely to be the strongest. Therefore, it is suggested that these forces are also the forces that force the protein to fold, in a short time, along a narrow range of pathways. This paradigm shift also answers Levinthal’s question about the factors that “speed” and “guide” the folding of proteins.     

Type I interferon in neurological disease—The devil from within

The members of the type I interferon (IFN-I) family of cytokines are pleiotropic factors that have seminal roles in host defence, acting as antimicrobial and antitumor mediators as well as potent immunomodulatory factors that bridge the innate and adaptive immune responses. Despite these beneficial actions there is mounting evidence that link inappropriate or chronic production of IFN-I in the CNS to the development of a number of severe neuroinflammatory disorders. The most persuasive example is the genetically determined inflammatory encephalopathy, Aicardi–Goutières syndrome (AGS) in which patients have chronically elevated IFN-α production in the CNS. The presentation of AGS can often mimic congenital viral infection, however, molecular genetic studies have identified mutations in six genes that can cause AGS, most likely via dysregulated nucleic acid metabolism and activation of the innate immune response leading to increased intrathecal production of IFN-α. The role of IFN-α as a pathogenic factor in AGS and other neurological disorders has gained considerable support from experimental studies. In particular, a transgenic mouse model with CNS-restricted production of IFN-α replicates many of the cardinal neuropathologic features of AGS and reveal IFN-I to be the “devil from within”, mediating molecular and cellular damage within the CNS. Thus, targeting IFN-I may be an effective strategy for the treatment of AGS as well as some other autoimmune and infectious neurological “interferonopathies”.     

Experimental Identification of “Songlan” (Isatis indigotica) and Woad (I.tinctoria) Introduced into China

“Song Lan” is a source of Chinese drugs such as “Daqingye”, “Banlangen” or “Qingdai”. We have discovered that the two species, “Song Lan” (Isatis indigotica Fort.) and woad (I. tinctoria L.), were mistakenly described in the literature due to their morphological polymorphism. In order to clarify the two species, cytology examination, pollen analysis, electrophoretic analysis of isoenzymes and soluble protein were performed. The results show that previous non-trichiferous type of woad is a “Song Lan”. As in woad, “Song Lan” is also morphologically of great variability. The base of canline leaves in this species may be sagittate or auriculate. We have not found the non-trichiferous type of woad in our country. It is reported for the first time that the chromosome number for “Song Lan” is 2n=14. The content of the indole glucoside in fresh leaves of “Song Lan” is about five timeshigher than in woad. For medicine cultivation of “Song Lan” is favorable.