Hasil untuk "Evolution"

H. Selye

Z. Peng, Xiaogang Peng

N. Prantzos, E. Vangioni‐Flam, M. Cassé

W. Williams

T. Bouchard, J. Loehlin

R. Trivers, H. Hare

T. Ohta

P. Erd6s, A. R~nyi

G. Kauffmann, M. Haehnelt

We incorporate a simple scheme for the growth of supermassive black holes into semi-analytic models that follow the formation and evolution of galaxies in a cold dark matter-dominated Universe. We assume that supermassive black holes are formed and fuelled during major mergers. If two galaxies of comparable mass merge, their central black holes coalesce and a few per cent of the gas in the merger remnant is accreted by the new black hole over a time-scale of a few times 107 yr. With these simple assumptions, our model not only fits many aspects of the observed evolution of galaxies, but also reproduces quantitatively the observed relation between bulge luminosity and black hole mass in nearby galaxies, the strong evolution of the quasar population with redshift, and the relation between the luminosities of nearby quasars and those of their host galaxies. The strong decline in the number density of quasars from z∼2 to z=0 is a result of the combination of three effects: (i) a decrease in the merging rate; (ii) a decrease in the amount of cold gas available to fuel black holes, and (iii) an increase in the time-scale for gas accretion. The predicted decline in the total content of cold gas in galaxies is consistent with that inferred from observations of damped Lyα systems. Our results strongly suggest that the evolution of supermassive black holes, quasars and starburst galaxies is inextricably linked to the hierarchical build-up of galaxies.

A. Sugden

A. Norenzayan, A. Shariff

Junhong Liu, J. Lampinen

R. Sage

T. Embley, W. Martin

R. Bellah

Religion in Human Evolution is a work of extraordinary ambition--a wide-ranging, nuanced probing of our biological past to discover the kinds of lives that human beings have most often imagined were worth living. It offers what is frequently seen as a forbidden theory of the origin of religion that goes deep into evolution, especially but not exclusively cultural evolution. How did our early ancestors transcend the quotidian demands of everyday existence to embrace an alternative reality that called into question the very meaning of their daily struggle? Robert Bellah, one of the leading sociologists of our time, identifies a range of cultural capacities, such as communal dancing, storytelling, and theorizing, whose emergence made this religious development possible. Deploying the latest findings in biology, cognitive science, and evolutionary psychology, he traces the expansion of these cultural capacities from the Paleolithic to the Axial Age (roughly, the first millennium BCE), when individuals and groups in the Old World challenged the norms and beliefs of class societies ruled by kings and aristocracies. These religious prophets and renouncers never succeeded in founding their alternative utopias, but they left a heritage of criticism that would not be quenched. Bellah's treatment of the four great civilizations of the Axial Age--in ancient Israel, Greece, China, and India--shows all existing religions, both prophetic and mystic, to be rooted in the evolutionary story he tells. Religion in Human Evolution answers the call for a critical history of religion grounded in the full range of human constraints and possibilities.

A. Traulsen, M. Nowak

We propose a minimalist stochastic model of multilevel (or group) selection. A population is subdivided into groups. Individuals interact with other members of the group in an evolutionary game that determines their fitness. Individuals reproduce, and offspring are added to the same group. If a group reaches a certain size, it can split into two. Faster reproducing individuals lead to larger groups that split more often. In our model, higher-level selection emerges as a byproduct of individual reproduction and population structure. We derive a fundamental condition for the evolution of cooperation by group selection: if b/c > 1 + n/m, then group selection favors cooperation. The parameters b and c denote the benefit and cost of the altruistic act, whereas n and m denote the maximum group size and the number of groups. The model can be extended to more than two levels of selection and to include migration.

J. Leskovec, L. Backstrom, Ravi Kumar et al.

H. Kokko, R. Brooks, M. Jennions et al.

B. Hansson, M. Stensmyr

P. Sereno