Human Communication Systems Evolve by Cultural Selection

Human communication systems, such as language, evolve culturally; their components undergo reproduction and variation. However, a role for selection in cultural evolutionary dynamics is less clear. Often neutral evolution (also known as 'drift') models, are used to explain the evolution of human communication systems, and cultural evolution more generally. Under this account, cultural change is unbiased: for instance, vocabulary, baby names and pottery designs have been found to spread through random copying. While drift is the null hypothesis for models of cultural evolution it does not always adequately explain empirical results. Alternative models include cultural selection, which assumes variant adoption is biased. Theoretical models of human communication argue that during conversation interlocutors are biased to adopt the same labels and other aspects of linguistic representation (including prosody and syntax). This basic alignment mechanism has been extended by computer simulation to account for the emergence of linguistic conventions. When agents are biased to match the linguistic behavior of their interlocutor, a single variant can propagate across an entire population of interacting computer agents. This behavior-matching account operates at the level of the individual. We call it the Conformity-biased model. Under a different selection account, called content-biased selection, functional selection or replicator selection, variant adoption depends upon the intrinsic value of the particular variant (e.g., ease of learning or use). This second alternative account operates at the level of the cultural variant. Following Boyd and Richerson we call it the Content-biased model. The present paper tests the drift model and the two biased selection models' ability to explain the spread of communicative signal variants in an experimental micro-society

Anthropologie de l’environnement et des pratiques économiques

Nicolas Ellison, maître de conférences Praxis, perception et représentations de l’environnement : perspectives comparatistes Pour cette première édition partielle du séminaire (dix séances à partir de février, date de nomination), nous avons abordé la question, fondamentale pour l’anthropologie de l’environnement, des rapports entre les pratiques d’usage, la perception de l’environnement et les systèmes de représentations écologiques. En plus des étudiants de la formation en master « Anthropo..

Une écologie symbolique totonaque. Le municipe de Huehuetla (Puebla, Mexique)

Une écologie symbolique totonaque. Le municipe de Huehuetla (Puebla, Mexique). Cet article montre comment, dans le contexte de changements écologiques et de tensions interethniques régionales, les représentations cosmologiques – et notamment le symbolisme sylvestre – ont pris une nouvelle signification à partir des contrastes d’usage de l’environnement entre Totonaques et Métis. Les Totonaques s’identifient par leur relation privilégiée aux espaces boisés ou agroforestiers en mobilisant le système classificatoire chaud/froid. Ce principe dualiste est, comme on le sait, fondamental dans le domaine des pratiques thérapeutiques et culinaires, mais son application à la répartition symbolique des espaces est encore peu étudiée dans l’aire mésoaméricaine.A symbolic ecology of the Totonacs. The municipio of Huehuetla (Puebla, Mexico). This paper shows how, in the present context of ecological change and regional interethnic tensions, cosmological representations and especially forest symbolism find a new meaning in the contrast between Totonac found Mestizo use of the environment. Totonac found their identity on their special relation with wooded or agro-forestry areas, using a hot/cold classificatory system. Scholars have often focused on this dualistic principle in therapeutic and culinary practices, but its application at the level of symbolic classification of ecological spaces has rarely been studied in the Mesoamerican area.Una ecología simbólica totonaca. El municipio de Huehuetla (Puebla, México). Este artículo muestra cómo, en el contexto de cambios ecológicos y de tensiones interétnicas regionales, las representaciones cosmológicas y especialmente el simbolismo de la selva, toman una nueva significación a partir de los contrastes en los usos de los recursos naturales entre totonacas y mestizos. Los totonacas se identifican por su relación privilegiada con los espacios silvestres o agroforestales, movilizando para ello el sistema clasificatorio de la polaridad frío/caliente. Este principio dualista es, como cada uno sabe, fundamental en lo referente a las prácticas medicinales y culinarias, pero su aplicación a la repartición simbólica de los espacios ha sido poco estudiada para el área mesoamericana

Anthropologie de l’environnement et des pratiques économiques

Nicolas Ellison, maître de conférences Praxis, perception et représentations de l’environnement : perspectives comparatistes Cette année, le séminaire a poursuivi la réflexion engagée lors de sa première édition (2010-2011) sur la question, fondamentale pour l’anthropologie de l’environnement, des rapports entre les pratiques d’usage, la perception et les systèmes de représentations écologiques. Les diverses approches théoriques sur les rapports à l’environnement – notamment celles de l’écolo..

Anthropologie de l’environnement et des pratiques économiques

Nicolas Ellison, maître de conférences Praxis, perception et représentations de l’environnement : perspectives comparatistes Cette année, le séminaire a poursuivi la réflexion engagée lors de sa première édition (2010-2011) sur la question, fondamentale pour l’anthropologie de l’environnement, des rapports entre les pratiques d’usage, la perception et les systèmes de représentations écologiques. Les diverses approches théoriques sur les rapports à l’environnement – notamment celles de l’écolo..

Une propriété arithmétique équivalente à l'hypothèse de Riemann

International audienceLet h(n) denote the largest product of distinct primes whose sum is n. The main result of this article is that the property " for all n > 0, we have log h(n) 0 log h(n) < li^-1(n) " où li^-1 est la fonction réciproque du logarithme intégral est équivalent à l' l' Hypothèse de Riemann

The clustering of Luminous Red Galaxies around MgII absorbers

We study the cross-correlation between 212 MgII quasar absorption systems and \~20,000 Luminous Red Galaxies (LRGs) selected from the Sloan Digital Sky Survey Data Release 1 in the redshift range 0.4<z<0.8. The MgII systems were selected to have 2796 & 2803 rest-frame equivalent widths >=1.0 Angstrom and identifications confirmed by the FeII 2600 or MgI 2852 lines. Over comoving scales 0.05--13 h^-1 Mpc, the MgII--LRG cross-correlation has an amplitude 0.69+/-0.09 times that of the LRG--LRG auto-correlation. Since LRGs have halo-masses greater than 3.5 x 10^12 solar masses for M_R<-21, this relative amplitude implies that the absorber host-galaxies have halo-masses greater than 2--8 x 10^11 Msun. For 10^13 Msun LRGs, the absorber host-galaxies have halo-masses 0.5--2.5 x 10^12 Msun. Our results appear consistent with those of Steidel et al. (1994) who found that MgII absorbers with W_r>=0.3 Angstrom are associated with ~0.7 L^*_B galaxies.Comment: 7 pages, 3 figs; Accepted for publication in MNRAS Letters; Extended version with Appendix; Text version of MgII absorber catalogue (Table 1) can be found at http://www.ast.cam.ac.uk/~mim/pub.html. Minor changes to match the published tex

Insights into aphid prey consumption by ladybirds: Optimising field sampling methods and primer design for High Throughput Sequencing

Elucidating the diets of insect predators is important in basic and applied ecology, such as for improving the effectiveness of conservation biological control measures to promote natural enemies of crop pests. Here, we investigated the aphid diet of two common aphid predators in Central European agroecosystems, the native Coccinella septempunctata (Linnaeus) and the invasive Harmonia axyridis (Pallas; Coleoptera: Coccinellidae) by means of high throughput sequencing (HTS). For acquiring insights into diets of mobile flying insects at landscape scale minimizing trapping bias is important, which imposes methodological challenges for HTS. We therefore assessed the suitability of three field sampling methods (sticky traps, pan traps and hand-collection) as well as new aphid primers for identifying aphid prey consumption by coccinellids through HTS. The new aphid primers facilitate identification to species level in 75% of the European aphid genera investigated. Aphid primer specificity was high in silico and in vitro but low in environmental samples with the methods used, although this could be improved in future studies. For insect trapping we conclude that sticky traps are a suitable method in terms of minimizing sampling bias, contamination risk and trapping success, but compromise on DNA-recovery rate. The aphid diets of both field-captured ladybird species were dominated by Microlophium carnosum, the common nettle aphid. Another common prey was Sitobion avenae (cereal aphid), which got more often detected in C. septempunctata compared to H. axyridis. Around one third of the recovered aphid taxa were common crop pests. We conclude that sampling methodologies need constant revision but that our improved aphid primers offer currently one of the best solutions for broad screenings of coccinellid predation on aphids

c-di-GMP modulates type IV MSHA pilus retraction and surface attachment in Vibrio cholerae.

Biofilm formation by Vibrio cholerae facilitates environmental persistence, and hyperinfectivity within the host. Biofilm formation is regulated by 3',5'-cyclic diguanylate (c-di-GMP) and requires production of the type IV mannose-sensitive hemagglutinin (MSHA) pilus. Here, we show that the MSHA pilus is a dynamic extendable and retractable system, and its activity is directly controlled by c-di-GMP. The interaction between c-di-GMP and the ATPase MshE promotes pilus extension, whereas low levels of c-di-GMP correlate with enhanced retraction. Loss of retraction facilitated by the ATPase PilT increases near-surface roaming motility, and impairs initial surface attachment. However, prolonged retraction upon surface attachment results in reduced MSHA-mediated surface anchoring and increased levels of detachment. Our results indicate that c-di-GMP directly controls MshE activity, thus regulating MSHA pilus extension and retraction dynamics, and modulating V. cholerae surface attachment and colonization