-
2007-03-09
Sexual reproduction in Nature requires two sexes, which raises the question
why the reproductive scheme did not evolve to have three or more sexes. Here we
construct a constrained optimization model based on the communication theory to
analyze trade-offs among reproductive schemes with arbitrary number of sexes.
More sexes on one hand lead to higher reproductive diversity, but on the other
hand incur greater cost in time and energy for reproductive success. Our model
shows that the two-sexes reproduction scheme maximizes the recombination
entropy-to-cost ratio, and hence is the optimal solution to the problem.
Author(s):
Bo Deng
-
2006-07-03
In 1960s V.Geodakian proposed a theory that explains sexes as a mechanism for
evolutionary adaptation of the species to changing environmental conditions. In
2001 V.Iskrin refined and augmented the concepts of Geodakian and gave a new
and interesting explanation to several phenomena which involve sex, and sex
ratio, including the war-years phenomena. He also introduced a new concept of
the "catastrophic sex ratio." This note is an attempt to digest technical
aspects of the new ideas by Iskrin.
Author(s):
Boris D. Lubachevsky
-
2008-08-29
The two classic theories for the existence of sexual replication are that sex
purges deleterious mutations from a population, and that sex allows a
population to adapt more rapidly to changing environments. These two theories
have often been presented as opposing explanations for the existence of sex.
Here, we develop and analyze evolutionary models based on the asexual and
sexual replication pathways in Saccharomyces cerevisiae (Baker's yeast), and
show that sexual replication can both purge deleterious mutations in a static
environment, as well as lead to faster adaptation in a dynamic environment.
This implies that sex can serve a dual role, which is in sharp contrast to
previous theories.
Author(s):
Pavel Gorodetsky
Emmanuel Tannenbaum
-
2001-03-02
Recently Quantum Battle of The Sexes Game has been studied by Luca Marinatto
and Tullio Weber. Yet some important problems exist in their scheme. Here we
propose a new scheme to quantize Battle of The Sexes Game, and this scheme will
truly remove the dilemma that exists in the classical form of the game.
Author(s):
Jiangfeng Du
Hui Li
Xiaodong Xu
Mingjun Shi
Xianyi Zhou
Rongdian Han
-
1998-07-14
The celebrated Foata combinatorial model for Hermite polynomials, and his
seminal and beautiful proof of the Mehler formula, are straightened to deal
with two sexes rather than one, with the exclusion of same-sex relationships
(both marital and non-marital).
Author(s):
Doron Zeilberger
-
2001-06-23
We present a detailed recipe for making movies from multi-epoch radio
observations of astronomical sources. Images are interpolated linearly in time
to create a smooth succession of frames so that a continuous movie can be
compiled. Here, we outline the procedure, and draw attention to specific
details necessary for making a successful movie. In particular, we discuss the
issues pertaining specifically to making polarization movies. The procedure
described here has been implemented into scripts in NRAO's AIPS package
(Brandeis AIPS Movie Maker -- BAMM) that are available for public use
(http://www.astro.brandeis.edu).
Author(s):
C. C. Cheung
D. C. Homan
J. F. C. Wardle
D. H. Roberts
-
2008-08-23
Sex is considered as an evolutionary paradox, since its evolutionary
advantage does not necessarily overcome the two fold cost of sharing half of
one's offspring's genome with another member of the population. Here we
demonstrate that sexual reproduction can be evolutionary stable even when its
Darwinian fitness is twice as low when compared to the fitness of asexual
mutants. We also show that more than two sexes are always evolutionary
unstable. Our approach generalizes the evolutionary game theory to analyze
species whose members are able to sense the sexual state of their conspecifics
and to switch sexes consequently. The widespread emergence and maintenance of
sex follows therefore from its co-evolution with even more widespread
environmental sensing abilities.
Author(s):
Alexander Feigel
Avraham Englander
Assaf Engel
-
2003-03-14
Why sex evolved and it prevails in nature remains one of the great puzzles of
evolution. Most biologists would explain that it promotes genetic variability,
however this explanation suffers from several difficulties. What advantages
might sex confer? The present communication aims at certain investigations
related to this question, in this way we introduce sexual recombination on the
H\"otzel model (with males and females) and we compare these results with those
from asexual reproduction without recombination.
Author(s):
A. O. Sousa
-
2001-10-16
We analysed quantum version of the game battle of sexes using a general
initial quantum state. For a particular choice of initial entangled quantum
state it is shown that the classical dilemma of the battle of sexes can be
resolved and a unique solution of the game can be obtained.
Author(s):
Ahmad Nawaz
A. H. Toor
-
2008-09-30
A trivariate Weibull survival model using competing risks concept is applied
on studying recidivism of committing 3 types of crimes - sex, violent and
others. The assumption of independence of time to commit each type of crimes is
relaxed so that the association of the time to recidivism between any two types
of crimes can be evaluated. We found that the correlation of time to recidivism
between sex crimes and violent crimes are more correlated than other pairs.
Probability of experiencing a charged arrest of other crimes is greater than a
charged arrest of violent crimes followed by a charged arrest of sex crimes for
an individual after release.
Author(s):
Jenq-Daw Lee
Cheng K. Lee
-
2008-07-18
The nature of epistasis has important consequences for the evolutionary
significance of sex and recombination. Recent efforts to find negative
epistasis as source of negative linkage disequilibrium and associated long-term
sex advantage have yielded little support. Sign epistasis, where the sign of
the fitness effects of alleles varies across genetic backgrounds, is
responsible for ruggedness of the fitness landscape with implications for the
evolution of sex that have been largely unexplored. Here, we describe fitness
landscapes for two sets of strains of the asexual fungus \emph{Aspergillus
niger} involving all combinations of five mutations. We find that $\sim 30$% of
the single-mutation fitness effects are positive despite their negative effect
in the wild-type strain, and that several local fitness maxima and minima are
present. We then compare adaptation of sexual and asexual populations on these
empirical fitness landscapes using simulations. The results show a general
disadvantage of sex on these rugged landscapes, caused by the break down by
recombination of genotypes escaping from local peaks. Sex facilitates escape
from a local peak only for some parameter values on one landscape, indicating
its dependence on the landscape's topography. We discuss possible reasons for
the discrepancy between our results and the reports of faster adaptation of
sexual populations.
Author(s):
J. Arjan G. M. de Visser
Su-Chan Park
Joachim Krug
-
1999-06-04
I review the observational properties of SW Sex stars. I show that they can
be explained by an accretion stream overflowing the disc, combined with an
accretion disc wind. I suggest that SW Sex behaviour is caused by episodes of
very high mass transfer, which are balanced by VY Scl low states.
Author(s):
Coel Hellier
-
2002-12-17
We modify the Penna Model for biological aging, which is based on the
mutation-accumulation theory, in order to verify if there would be any
evolutionary advantage of triploid over diploid organisms. We show that this is
not the case, and that usual sex is always better than that involving three
individuals.
Author(s):
A. O. Sousa
S. Moss de Oliveira
J. S. Sa Martins
-
2004-08-01
Evolutionary role of the separation into two sexes from a cyberneticist's
point of view. [I translated this 1965 article from Russian "Nauka i Zhizn"
(Science and Life) in 1988. In a popular form, the article puts forward several
useful ideas not all of which even today are necessarily well known or widely
accepted. Boris Lubachevsky, bdl@bell-labs.com ]
Author(s):
Vigen A. Geodakian
-
2009-06-02
We present the unique solution to the Quantum Battle of the Sexes game. We
show the best result which can be reached when the game is played according to
Marinatto and Weber's scheme. The result which we put forward does not
surrender the criticism of previous works on the same topic.
Author(s):
Piotr Frcackiewicz
-
1997-09-17
We present spectrophotometry of the eclipsing nova-like variable SW Sex. The
continuum is deeply eclipsed and shows asymmetries due to the presence of a
bright spot. We derive a new ephemeris and, by measuring the eclipse width, we
are able to constrain the inclination to i > 75^o and the disc radius to R_D >
0.6 L_1. In common with other members of its class (of which it is the
proto-type), SW Sex shows single-peaked emission lines which show transient
absorption features and large phase shifts in their radial velocity curves. In
addition, the light curves of the emission lines show a reduction in flux
around phase 0.5 and asymmetric eclipse profiles which are not as deep as the
continuum eclipse. Using Doppler tomography, we find that most of the line
emission in SW Sex appears to originate from three sources: the secondary star,
the accretion disc and an extended bright spot. The detection of the red star
allows us to constrain the radial-velocity semi-amplitude of the secondary to
K_R > 180 km/s and hence the component masses to M_1 = 0.3-0.7 Msun and M_2 <
0.3 Msun.
Author(s):
V. S. Dhillon
T. R. Marsh
D. H. P. Jones
-
2000-11-15
We report on the discovery of variable circular polarization in the SW Sex
star LS Pegasi. The observed modulation has an amplitude of ~0.3 % and a period
of 29.6 minutes, which we assume as the spin period of the magnetic white
dwarf. We also detected periodic flaring in the blue wing of Hbeta, with a
period of 33.5 minutes. The difference between both frequencies is just the
orbital frequency, so we relate the 33.5-min modulation to the beat between the
orbital and spin period. We propose a new accretion scenario in SW Sex stars,
based on the shock of the disk-overflown gas stream against the white dwarf's
magnetosphere, which extends to the corotation radius. From this geometry, we
estimate a magnetic field strength of B(1) ~ 5-15 MG. Our results indicate that
magnetic accretion plays an important role in SW Sex stars and we suggest that
these systems are probably Intermediate Polars with the highest mass accretion
rates.
Author(s):
P. Rodriguez-Gil
J. Casares
I. G. Martinez-Pais
P. Hakala
D. Steeghs
-
2004-12-01
Introduction: Two key dimensions of the mind are understanding and responding
to another's mental state (empathizing), and analysing lawful behaviour
(systemizing).
Methods: Two questionnaires, the Systemizing Quotient (SQ) and the Empathy
Quotient (EQ), were administered to a normal control group and a group of
individuals with Asperger Syndrome (AS) or High-Functioning Autism (HFA). The
multivariate correlations of the joint scores were analysed using principal
components analysis.
Results: The principal components were well-approximated by the sums and
differences of the SQ and EQ scores. The differences in the scores corresponded
to sex differences within the control group and also separated out the AS/HFA
group, which showed stronger systemizing than the control group, but
below-average empathy. The sums of the scores did not show sex differences, but
did distinguish the AS/HFA group.
Conclusions: These tests reliably sex the brain, and their correlations show
that empathizing and systemizing are not independent, but compete neurally.
Their combined score (EQ + SQ) quantifies the deficit in autism spectrum
conditions.
Author(s):
Nigel Goldenfeld
Sally Wheelwright
Simon Baron-Cohen
-
2006-07-12
No abstract given. Confirms earlier simulatiobns of the self-organization of
dominance in the sexual Penna model, and the advantage of hermaphroditic over
sexual reproduction.
Author(s):
Klaus Blindert
-
2009-02-11
We present time-resolved spectroscopy and circular spectropolarimetry of the
SW Sex star RX J1643.7+3402. We find significant polarisation levels exhibiting
a variability at a period of 19.38 +- 0.39 min. In addition, emission-line
flaring is found predominantly at twice the polarimetric period. These two
findings are strong evidences in favour of the presence of a magnetic white
dwarf in the system. We interpret the measured periodicities in the context of
our magnetic accretion model for SW Sex stars. In contrast with LS Pegasi -the
first SW Sex star discovered to have modulated circular polarisation- the
polarisation in RX J1643.7+3402 is suggested to vary at 2(omega - Omega), while
the emission lines flare at (omega - Omega). However, a 2omega/omega
interpretation cannot be ruled out. Together with LS Peg and V795 Her, RX
J1643.7+3402 is the third SW Sex star known to exhibit modulated circular
polarisation.
Author(s):
P. Rodriguez-Gil
I. G. Martinez-Pais
J. de la Cruz Rodriguez