Does Biology Constrain Culture?

Most social scientists would agree that the capacity for human culture was probably fashioned by natural selection, but they disagree about the implications of this supposition. Some believe that natural selection imposes important constraints on the ways in which culture can vary, while others believe that any such constraints must be negligible. This article employs a "thought experiment" to demonstrate that neither of these positions can be justified by appeal to general properties of culture or of evolution. Natural selection can produce mechanisms of cultural transmission that are neither adaptive nor consistent with the predictions of acultural evolutionary models (those ignoring cultural evolution). On the other hand, natural selection can also produce mechanisms of cultural transmission that are highly consistent with acultural models. Thus, neither side of the sociobiology debate is justified in dismissing the arguments of the other. Natural selection may impose significant constraints on some human behaviors, but negligible constraints on others. Models of simultaneous genetic/cultural evolution will be useful in identifying domains in which acultural evolutionary models are, and are not, likely to be useful.     

Does Cancer Solve an Optimization Problem?

Many cancers are characterized by a high degree of aneuploidy, which isbelieved to be a result of chromosomal instability (CIN). The precise role of CIN incancer is still the matter of a heated debate. We present a quantitative framework forexamining the selection pressures acting on populations of cells and weigh the \pluses"and \minuses" of CIN from the point of view of a sel¯sh cell. We calculate the optimalrate of chromosome loss assuming that cancer is initiated by inactivation of a tumorsuppressor gene followed by a clonal expansion. The resulting rate, p* ~ ¼ 10^-2 per celldivision per chromosome, is similar to that obtained experimentally by Lengauer et al(1997). Our analysis further suggests that CIN does not arise simply because it allowsa faster accumulation of carcinogenic mutations. Instead, CIN must arise because ofalternative reasons, such as environmental factors, epigenetic events, or as a directconsequence of a tumor suppressor gene inactivation. The increased variability aloneis not a su±cient explanation for the presence of CIN in the majority of cancers.     

Does streptomycin cause an error catastrophe?

We have examined the interpretation that streptomycin kills a bacterial culture by initiating the so-called error catastrophe. In particular, we asked whether the increased translational error rate induced by the antibiotic gives rise to an autocatalytic loss of functional fidelity of the devices responsible for gene expression, which ultimately causes the death of the culture. We have analyzed the performance characteristics of one of these devices, namely the ribosome in streptomycin-treated bacteria. We find that, although the treated ribosomes are constructed from error-containing proteins, they are not significantly different in elongation rate and fidelity from those ribosomes taken from untreated bacteria. We conclude that the bacteriocidal effect of streptomycin is not due to the initiation of an error catastrophe.     

Does acetylcholinesterase secretion involve an ADAMs-like metallosecretase?

The ADAMs (A Disintegrin And Metalloprotease-like) family is a large and rapidly expanding group of metalloproteinases with structural similarity. They are normally characterized by the presence of a proteolytic domain and disintegrin and signalling domains. Although 21 ADAMs proteins have been already cloned to date, in most cases their natural substrates are unknown. The best characterized representative of the mammalian ADAMs family is the TNF- converting enzyme (TACE). TACE is an integral membrane metalloproteinase that causes the secretion of the active form of TNF- from its plasma membrane precursor and thus can be regarded as a membrane protein secretase. Secretion of membrane proteins is a very well documented biological phenomenon and was demonstrated for a diverse range of membrane proteins, two examples being angiotensin converting enzyme (ACE) and Alzheimer's amyloid precursor protein (APP). ACE and APP secretion was shown to possess substantial similarity with the secretion of TNF-. In the present study, we have attempted to demonstrate that a metalloproteinase might be involved in the shedding of another membrane-bound protein – acetylcholinesterase (AChE). Secretion of AChE by human neuroblastoma SH-SY5Y cells was found to be inhibited by a selective hydroxamate metalloproteinase inhibitor batimastat (20 M), and stimulated by carbachol (20 M), which have previously been shown to regulate the activity of APP -secretase in a similar manner. The role of ADAMs proteins in the shedding of molecules from the cell surface is discussed.     

Does acetylcholinesterase secretion involve an ADAMs-like metallosecretase?

Summary The ADAMs (A Disintegrin And Metalloprotease-like) family is a large and rapidly expanding group of metallo-proteinases with structural similarity. The are normally characterized by the presence of a proteolytic domain and disintegrin and signalling domains. Although 21 ADAMs proteins have been already cloned to date, in most cases their natural substrates are unknown. The best characterized representative of the mammalian ADAMs family is the TNF-α converting enzyme (TACE). TACE is an integral membrane metalloproteinase that causes the secretion of the active form of TNF-α from its plasma membrane precursor and thus can be regarded as a membrane protein secretase. Secretion of membrane proteins is a very well documented biological phenomenon and was demonstrated for a diverse range of membrane proteins, two examples being angiotensin converting enzyme (ACE) and Alzheimer's amyloid precursor protein (APP). ACE and APP secretion was shown to possess substantial similarity with the secretion of TNF-α. In the present study, we have attempted to demonstrate that a metalloproteinase might be involved in the shedding of another membrane-bound protein—acetylcholinesterase (AChE). Secretion of AChE by human neuroblastoma SH-SY5Y cells was found to be inhibited by a selective hydroxamate metalloproteinase inhibitor batimastat (20 μM), and stimulated by carbachol (20 μM), which have previously been shown to regulate the activity of APP α-secretase in a similar manner. The role of ADAMs proteins in the shedding of molecules from the cell surface is discussed.     

Does codon bias have an evolutionary origin?

Background  

There is a 3-fold redundancy in the Genetic Code; most amino acids are encoded by more than one codon. These synonymous codons are not used equally; there is a Codon Usage Bias (CUB). This article will provide novel information about the origin and evolution of this bias.     

Does an opportunistic predator preferentially attack nonvigilant prey?

The dilution effect as an antipredation behaviour is the main theoretical reason for grouping in animals and states that all individuals in a group have an equal risk of being predated if equally spaced from each other and the predator. Stalking predators, however, increase their chance of attack success by preferentially targeting nonvigilant individuals, potentially making relative vigilance rates in a group relatively important in determining predation compared with the dilution effect. Many predators, however, attack opportunistically without stalking, when targeting of nonvigilant individuals may be less likely, so that the dilution effect will then be a relatively more important antipredation reason for grouping. We tested whether an opportunistically hunting predator, the sparrowhawk, Accipiter nisus, preferentially attacked vigilant or feeding prey models presented in pairs. We found that sparrowhawks attacked vigilant and feeding mounts at similar frequencies. Our results suggest that individuals should prioritize maximizing group size or individual vigilance dependent on the type of predator from which they are at risk. When the most likely predator is a stalker, individuals should aim to have the highest vigilance levels in a group, and there may be relatively little selective advantage to being in the largest group. In contrast, if the most likely predator is an opportunist, then individuals should simply aim to be in the largest group and can also spend more time foraging without compromising predation risk. For most natural systems this will mean a trade-off between the two strategies dependent on the frequency of attack of each predator type. Copyright 2003 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.     

Does beta-lactoglobulin denaturation occur via an intermediate state?

The denaturation of beta-lactoglobulin (BLG) in the presence of urea and GuHCl has been investigated at different pH values with various spectroscopic techniques. The equilibrium denaturation free energy values, obtained by linearly extrapolating the data to vanishing denaturant (DeltaG(D)(H2O)), are compared and discussed. The fit of the spectroscopic data monitoring the denaturation of BLG has been approached, at first, with a two-state model that describes the protein transition from the folded state (at each pH and in the absence of denaturant) to the denatured state, but in particular, along the GuHCl denaturation pathway some evidence is found of the presence of an intermediate state. Time-resolved fluorescence experiments performed on the BLG-ANS (1-anilino-8-naphthalenesulfonate) complex help to understand the results. Fluorescence polarization anisotropy (FPA) measurements accompanying the denaturation process show the presence of a fast rotational diffusion of the ANS probe, and the data are interpreted in terms of local fluctuations of a still structured tract of the denatured protein where the probe is bound.     

Freshman Undergraduate Biology Students�� Difficulties with the Concept of Common Ancestry

All life on earth descended from a single common ancestor that existed several billion years ago; thus, any pair of organisms will have had a common ancestor at some point in their history. This concept is fundamental to an understanding of evolution and phylogeny. Developing an understanding of this concept is an important goal of evolution education and a part of most high school and college biology curricula. This study examines freshman undergraduate biology majors’ understanding and application of the concept of common ancestry. We used a survey that asked students to provide a brief definition of common ancestry and to rate their confidence that different pairs of organisms shared a common ancestor. Our results show that, although many students in our sample could give a satisfactory definition of common ancestry, the overwhelming majority failed to apply their definitions correctly when assessing the likelihood that the pairs of organisms shared common ancestors. Instead, we found that these students do not treat common ancestry as a binary (yes/no) trait, but instead see it as a continuum from less probable to more probable. These students are more likely to think that closely related organisms have a common ancestor than those that are more distantly related and that humans are less likely to be connected to common ancestors than nonhuman organisms. This pattern is highly consistent from student to student and has important implications for teaching evolution.     

Does It Matter that Madagascar is an Island?

Being an island has been important for Madagascar's archaeology in two ways. First, its insularity was probably responsible for the lateness and some features of its first human colonizers, as well as for its highly endemic flora and fauna. The earliest coastal communities continued to interact with the Indian Ocean trade network, but the latterly settled interior eventually saw the greatest population increases, eclipsing the coastal communities in power. Second, it may be that as an island, archaeologists have unconsciously been predisposed to interpret Malagasy prehistory in terms of a tree-like model of evolution from a single ancestral culture. Yet if, as seems probable, Malagasy culture has seen contributions from many others, such a single proto-culture may never have existed.     

How Is Meaning Grounded in the Organism?

In this paper we address the interrelated questions of why and how certain features of an organism’s environment become meaningful to it. We make the case that knowing the biology is essential to understanding the foundation of meaning-making in organisms. We employ Miguel Nicolelis et al’s seminal research on the mammalian somatosensory system to enrich our own concept of brain-objects as the neurobiological intermediary between the environment and the consequent organismic behavior. In the final section, we explain how brain-objects advance the ongoing discussion of what constitutes a biosemiotic system. In general, this paper acknowledges Marcello Barbieri’s call for biology to make room for meaning, and makes a contribution to that end.     

Does Giardia intestinalis need glucose as an energy source?

Giardia intestinalis was grown in Diamond's TYI-S-33 medium containing either 50 mM-glucose or no added glucose to assess its dependence on glucose availability as an energy source. The parameters monitored included cell growth, glucose utilization and the accumulation of end products in the medium. In the medium containing no added glucose, G. intestinalis trophozoites achieved a cell density of about half that of the control, and produced the same end products, alanine, ethanol and acetate. Decreased amounts of both ethanol and alanine were observed (10 and 33% of controls, respectively after 4 days) while there was no change in acetate production. These observations indicate that G. intestinalis can utilize carbon sources other than glucose, and is not absolutely dependent upon glucose as an energy source.     

Does forest fragmentation cause an increase in forest temperature?

Forest fragmentation is considered by many to be a primary cause of the current biodiversity crisis. The underlying mechanisms are poorly known, but a potentially important one is associated with altered thermal conditions within the remaining forest patches, especially at forest edges. Yet, large uncertainty remains about the effect of fragmentation on forest temperature, as it is unclear whether temperature decreases from forest edge to forest interior, and whether this local gradient scales up to an effect of fragmentation (landscape attribute) on temperature. We calculated the effect size (correlation coefficient) of distance from forest edge on air temperature, and tested for differences among forest types surrounded by different matrices using meta-analysis techniques. We found a negative edge-interior temperature gradient, but correlation coefficients were highly variable, and significant only for temperate and tropical forests surrounded by a highly contrasting open matrix. Nevertheless, it is unclear if these local-scale changes in temperature can be scaled up to an effect of fragmentation on temperature. Although it may be valid when considering “fragmentation” as forest loss only, the landscape-scale inference is not so clear when we consider the second aspect of fragmentation, where a given amount of forest is divided into a large number of small patches (fragmentation per se). Therefore, care is needed when assuming that fragmentation changes forest temperature, as thermal changes at forest edges depend on forest type and matrix composition, and it is still uncertain if this local gradient can be scaled up to the landscape.     

Does the Segregation of Evolution in Biology Textbooks and Introductory Courses Reinforce Students’ Faulty Mental Models of Biology and Evolution?

The well-established finding that substantial confusion and misconceptions about evolution and natural selection persist after college instruction suggests that these courses neither foster accurate mental models of evolution’s mechanisms nor instill an appreciation of evolution’s centrality to an understanding of the living world. Our essay explores the roles that introductory biology courses and textbooks may play in reinforcing undergraduates’ pre-existing, faulty mental models of the place of evolution in the biological sciences. Our content analyses of the three best-selling introductory biology textbooks for majors revealed the conceptual segregation of evolutionary information. The vast majority of the evolutionary terms and concepts in each book were isolated in sections about evolution and diversity, while remarkably few were employed in other sections of the books. Standardizing the data by number of pages per unit did not alter this pattern. Students may fail to grasp that evolution is the unifying theme of biology because introductory courses and textbooks reinforce such isolation. Two goals are central to resolving this problem: the desegregation of evolution as separate “units” or chapters and the active integration of evolutionary concepts at all levels and across all domains of introductory biology.     

Does a top-predator provide an endangered rodent with refuge from an invasive mesopredator?

In arid environments, ecological refuges are often conceptualised as places where animal species can persist through drought owing to the localised persistence of moisture and nutrients. The mesopredator release hypothesis (MRH) predicts that reduced abundance of top-order predators results in an increase in the abundance of smaller predators (mesopredators) and consequently has detrimental impacts on the prey of the smaller predators. Thus according to the MRH, the existence of larger predators may provide prey with refuge from predation. In this study, we investigated how the abundance of an endangered rodent Notomys fuscus is affected by Australia's largest predator, the dingo Canis lupus dingo , introduced mesopredators, introduced herbivores, kangaroos and rainfall. Our surveys showed that N. fuscus was more abundant where dingoes occurred. Generalised linear modelling showed that N. fuscus abundance was associated positively with dingo activity and long-term annual rainfall and negatively with red fox Vulpes vulpes activity. Our results were consistent with the hypothesis that areas with higher rainfall and dingoes provide N. fuscus with refuge from drought and predation by invasive red foxes, respectively. Top-order predators, such as dingoes, could have an important functional role in broad-scale biodiversity conservation programmes by reducing the impacts of mesopredators.     

Does Help in Decision-Making in Biology Help in Decision-Making in Human Sciences and Conversely?

A link between biological and human sciences may be established, under the condition that we should admit the existence of reciprocal influences between them. The model for the regulation of agonistic antagonistic couples (MRAAC) is built from the study of biological systems and gives rise to specific types of control. This model can be helpful in decision processes in some human sciences such as management, economical and political strategies. The reason for such an opportunity lies in the fact that MRAAC is a general and phenomenological model able to incorporate the whole of the agonistic antagonistic systems. This type of regulation might be related to the concept of the viability of a system (yet also valid for human science systems) and to a functional and structural pattern which is the basis for agonistic antagonistic networks.