Summary: The totality of characteristics of reproductive structure, functions, PHENOTYPE, and GENOTYPE, differentiating the MALE from the FEMALE organism.

Top Publications

  1. Otto S, Nuismer S. Species interactions and the evolution of sex. Science. 2004;304:1018-20 pubmed
    The Red Queen hypothesis posits that sex has evolved in response to the shifting adaptive landscape generated by the evolution of interacting species...
  2. Narra H, Ochman H. Of what use is sex to bacteria?. Curr Biol. 2006;16:R705-10 pubmed
    ..Bacterial sex differs from that of eukaryotes in that it is unidirectional and does not involve gamete fusion or reproduction...
  3. Renaut S, Replansky T, Heppleston A, Bell G. The ecology and genetics of fitness in Chlamydomonas. XIII. Fitness of long-term sexual and asexual populations in benign environments. Evolution. 2006;60:2272-9 pubmed
    ..Recombination between these genotypes reduces mean fitness and creates genetic variance for fitness. This may provide fuel for continued selection should the environment change. ..
  4. Young E, Korszun A. Sex, trauma, stress hormones and depression. Mol Psychiatry. 2010;15:23-8 pubmed publisher
    ..It may be the constantly changing steroid milieu that contributes to these phenomena and vulnerability to depression. ..
  5. Cohen Bendahan C, van Goozen S, Buitelaar J, Cohen Kettenis P. Maternal serum steroid levels are unrelated to fetal sex: a study in twin pregnancies. Twin Res Hum Genet. 2005;8:173-7 pubmed
    Increased prenatal exposure to testosterone (T) in females of an opposite-sex (OS) twin pair may have an effect on the development of sex-typical cognitive and behavioral patterns...
  6. Nielsen R. Evolution. Why sex?. Science. 2006;311:960-1 pubmed
  7. Shirangi T, McKeown M. Sex in flies: what 'body--mind' dichotomy?. Dev Biol. 2007;306:10-9 pubmed
    ..fruitless (fruM) is a major component inducing male behaviors, but recent work indicates key roles for other sex-specific and sex-non-specific components...
  8. Schmitt D, Realo A, Voracek M, Allik J. Why can't a man be more like a woman? Sex differences in Big Five personality traits across 55 cultures. J Pers Soc Psychol. 2008;94:168-182 pubmed publisher
    Previous research suggested that sex differences in personality traits are larger in prosperous, healthy, and egalitarian cultures in which women have more opportunities equal with those of men...
  9. Otto S. Unravelling the evolutionary advantage of sex: a commentary on 'Mutation-selection balance and the evolutionary advantage of sex and recombination' by Brian Charlesworth. Genet Res. 2007;89:447-9 pubmed publisher

More Information


  1. Watson R, Weinreich D, Wakeley J. Genome structure and the benefit of sex. Evolution. 2011;65:523-36 pubmed publisher
    ..We conclude that there are conditions in which sexuals can systematically evolve high-fitness genotypes that are essentially unevolvable for asexuals. ..
  2. Gorelick R, Heng H. Sex reduces genetic variation: a multidisciplinary review. Evolution. 2011;65:1088-98 pubmed publisher
    For over a century, the paradigm has been that sex invariably increases genetic variation, despite many renowned biologists asserting that sex decreases most genetic variation...
  3. Magi R, Lindgren C, Morris A. Meta-analysis of sex-specific genome-wide association studies. Genet Epidemiol. 2010;34:846-53 pubmed publisher
    ..Such sex-differentiated effects are common in model organisms, and are becoming increasingly evident in human complex traits ..
  4. White K, Loughlin L, Maqbool Z, Nilsen M, McClure J, Dempsie Y, et al. Serotonin transporter, sex, and hypoxia: microarray analysis in the pulmonary arteries of mice identifies genes with relevance to human PAH. Physiol Genomics. 2011;43:417-37 pubmed publisher
    ..To further investigate these sex differences, microarray analysis was performed in the pulmonary arteries of normoxic and chronically hypoxic female ..
  5. Gardner D, Wale P, Collins R, Lane M. Glucose consumption of single post-compaction human embryos is predictive of embryo sex and live birth outcome. Hum Reprod. 2011;26:1981-6 pubmed publisher
    ..Analysis of glucose was performed by microfluorimetry. The sex of children born was recorded. Clinical pregnancy and live birth rates were 58 and 56%, respectively...
  6. Lehtonen J, Jennions M, Kokko H. The many costs of sex. Trends Ecol Evol. 2012;27:172-8 pubmed publisher
    Explaining the evolution of sex is challenging for biologists. A 'twofold cost' compared with asexual reproduction is often quoted...
  7. Igbigbi P, Nanono Igbigbi A. Determination of sex and race from the subpubic angle in Ugandan subjects. Am J Forensic Med Pathol. 2003;24:168-72 pubmed
    The accurate determination of sex and race are important tools to forensic and physical anthropologists...
  8. Yamada H, Benedict M, Malcolm C, Oliva C, Soliban S, Gilles J. Genetic sex separation of the malaria vector, Anopheles arabiensis, by exposing eggs to dieldrin. Malar J. 2012;11:208 pubmed publisher
    ..develop SIT for mosquitoes, female elimination prior to release is essential as they are the disease-transmitting sex. A genetic sexing strain (GSS) of Anopheles arabiensis was created based on resistance to dieldrin, and methods of ..
  9. Pizzari T, Gardner A. The sociobiology of sex: inclusive fitness consequences of inter-sexual interactions. Philos Trans R Soc Lond B Biol Sci. 2012;367:2314-23 pubmed publisher
  10. Meerkerk G, van den Eijnden R, Garretsen H. Predicting compulsive Internet use: it's all about sex!. Cyberpsychol Behav. 2006;9:95-103 pubmed
    ..On a longitudinal basis, spending a lot of time on erotica predicted an increase in CIU 1 year later. The addictive potential of the different applications varies; erotica appears to have the highest potential. ..
  11. Yamauchi A, Kamite Y. Facultative sexual reproduction under frequency-dependent selection on a single locus. J Theor Biol. 2003;221:411-24 pubmed
    ..This indicated that the evolution of sex should be considered carefully with respect to the possibility of invasion of facultative sex.
  12. Miura I, Ohtani H, Ogata M. Independent degeneration of W and Y sex chromosomes in frog Rana rugosa. Chromosome Res. 2012;20:47-55 pubmed publisher
    The frog Rana rugosa uniquely possesses two different sex-determining systems of XX/XY and ZZ/ZW, separately in the geographic populations...
  13. AboZaid H, Wessels S, Hörstgen Schwark G. Effect of rearing temperatures during embryonic development on the phenotypic sex in zebrafish (Danio rerio). Sex Dev. 2011;5:259-65 pubmed publisher
    In zebrafish, Danio rerio, a polygenic pattern of sex determination or a female heterogamety with possible influences of environmental factors is assumed...
  14. Hayward A, Gillooly J. The cost of sex: quantifying energetic investment in gamete production by males and females. PLoS ONE. 2011;6:e16557 pubmed publisher
    ..Together, these results suggest that understanding the heterogeneity in rates of gamete production among species requires joint consideration of the effects of gonad mass and metabolism. ..
  15. Otto S. The advantages of segregation and the evolution of sex. Genetics. 2003;164:1099-118 pubmed
    ..This article is the first to investigate the possibility that sex might have evolved and been maintained to promote segregation, using a model that incorporates both a general ..
  16. Doyal L. Sex and gender: the challenges for epidemiologists. Int J Health Serv. 2003;33:569-79 pubmed
    ..quot; It begins by exploring the concepts of biological "sex" and social "gender" and assesses their implications for the health of both women and men...
  17. Setchell J, Huchard E. The hidden benefits of sex: evidence for MHC-associated mate choice in primate societies. Bioessays. 2010;32:940-8 pubmed publisher
    ..These findings underline the importance to females of selecting a sexual partner of high genetic quality, as well as the generality of the role of MHC genes in sexual selection. ..
  18. Lively C. An epidemiological model of host-parasite coevolution and sex. J Evol Biol. 2010;23:1490-7 pubmed publisher
    ..The results suggest that epidemiological feedbacks, combined with frequency-dependent selection, could lead to the long-term persistence of sex under biologically reasonable conditions.
  19. Barton N. Why sex and recombination?. Cold Spring Harb Symp Quant Biol. 2009;74:187-95 pubmed publisher
    b>Sex and recombination have long been seen as adaptations that facilitate natural selection by generating favorable variations...
  20. Agrawal A. Spatial heterogeneity and the evolution of sex in diploids. Am Nat. 2009;174 Suppl 1:S54-70 pubmed publisher
    Much of the theoretical work on the evolution of sex has focused on the effects of recombination. In diploids, segregation also occurs during sexual reproduction...
  21. Berman J, Hadany L. Does stress induce (para)sex? Implications for Candida albicans evolution. Trends Genet. 2012;28:197-203 pubmed publisher
    Theory predicts that stress is a key factor in explaining the evolutionary role of sex in facultatively sexual organisms, including microorganisms...
  22. Kunitz S. Sex, race and social role--history and the social determinants of health. Int J Epidemiol. 2007;36:3-10 pubmed
  23. Maxfield J, Van Tassell J, St Mary C, Joyeux J, Crow K. Extreme gender flexibility: using a phylogenetic framework to infer the evolution of variation in sex allocation, phylogeography, and speciation in a genus of bidirectional sex changing fishes(Lythrypnus, Gobiidae). Mol Phylogenet Evol. 2012;64:416-27 pubmed publisher
    The genus Lythrypnus is a group of marine gobies that exhibit extreme gender flexibility as bidirectional sex changers. The genus consists of 20 described species and several undescribed species that are distributed in the Americas...
  24. Groenewald M, Groenewald J, Harrington T, Abeln E, Crous P. Mating type gene analysis in apparently asexual Cercospora species is suggestive of cryptic sex. Fungal Genet Biol. 2006;43:813-25 pubmed publisher
    ..beticola, C. zeae-maydis and C. zeina populations, in contrast to single mating types in C. apii (MAT1) and C. apiicola (MAT2), suggests that a sexual cycle may be active in some of these species...
  25. Bell P. Sex and the eukaryotic cell cycle is consistent with a viral ancestry for the eukaryotic nucleus. J Theor Biol. 2006;243:54-63 pubmed
    The origin of the eukaryotic cell cycle, including mitosis, meiosis, and sex are as yet unresolved aspects of the evolution of the eukaryotes...
  26. Callaghan T, Degnan B, Sellars M. Expression of sex and reproduction-related genes in Marsupenaeus japonicus. Mar Biotechnol (NY). 2010;12:664-77 pubmed publisher
    ..At PL110, seven of the ESTs were detected in females only, and seven ESTs were detected in males only. Sex-specific expression at this developmental stage indicates that these ESTs act as important gonadal development ..
  27. Sørensen J, Kristensen T, Kristensen K, Loeschcke V. Sex specific effects of heat induced hormesis in Hsf-deficient Drosophila melanogaster. Exp Gerontol. 2007;42:1123-9 pubmed
    ..However, the results also suggest that other processes are involved and that different mechanisms might have marked sex specific impact.
  28. Mogil J, Bailey A. Sex and gender differences in pain and analgesia. Prog Brain Res. 2010;186:141-57 pubmed publisher
    ..Research in this field has now begun to concentrate on finding explanations for this sex difference...
  29. Otto S, Gerstein A. Why have sex? The population genetics of sex and recombination. Biochem Soc Trans. 2006;34:519-22 pubmed
    ..with those of another individual? Mathematical models are especially important in developing predictions about when sex and recombination can evolve, because it is difficult to intuit the outcome of evolution with several interacting ..
  30. Sato S, Beakes G, Idei M, Nagumo T, Mann D. Novel sex cells and evidence for sex pheromones in diatoms. PLoS ONE. 2011;6:e26923 pubmed publisher
    ..We also report experimental evidence for sex pheromones that reciprocally stimulate sexualization of compatible clones and orientate motility of the male ..
  31. Misevic D, Kouyos R, Bonhoeffer S. Predicting the evolution of sex on complex fitness landscapes. PLoS Comput Biol. 2009;5:e1000510 pubmed publisher
    Most population genetic theories on the evolution of sex or recombination are based on fairly restrictive assumptions about the nature of the underlying fitness landscapes...
  32. Ramesh M, Malik S, Logsdon J. A phylogenomic inventory of meiotic genes; evidence for sex in Giardia and an early eukaryotic origin of meiosis. Curr Biol. 2005;15:185-91 pubmed
    ..evolutionary innovation in eukaryotic cells, and delineating its history is key to understanding the evolution of sex. Meiosis arose early in eukaryotic evolution, but when and how meiosis arose and whether all eukaryotes have ..
  33. Becks L, Agrawal A. Higher rates of sex evolve in spatially heterogeneous environments. Nature. 2010;468:89-92 pubmed publisher
    ..However, direct experiments of the evolution of sex within populations are extremely rare (but see ref. 12)...
  34. Lively C. A review of Red Queen models for the persistence of obligate sexual reproduction. J Hered. 2010;101 Suppl 1:S13-20 pubmed publisher
    ..An early simulation model by Hamilton (Hamilton WD. 1980. Sex versus non-sex versus parasite. Oikos. 35:282-290...
  35. Riaz S, Krivanek A, Xu K, Walker M. Refined mapping of the Pierce's disease resistance locus, PdR1, and Sex on an extended genetic map of Vitis rupestris x V. arizonica. Theor Appl Genet. 2006;113:1317-29 pubmed
    ..5 cM. Ninety-four of the 210 markers on the consensus map were new. The 'Sex' expression locus segregated as single major gene was mapped to linkage group 2 on the consensus and the male map...
  36. Goddard M, Godfray H, Burt A. Sex increases the efficacy of natural selection in experimental yeast populations. Nature. 2005;434:636-40 pubmed
    Why sex evolved and persists is a problem for evolutionary biology, because sex disrupts favourable gene combinations and requires an expenditure of time and energy...
  37. Nedelcu A, Michod R. Sex as a response to oxidative stress: the effect of antioxidants on sexual induction in a facultatively sexual lineage. Proc Biol Sci. 2003;270 Suppl 2:S136-9 pubmed
    The evolution of sex is one of the long-standing unsolved problems in biology...
  38. Heitkemper M, Jarrett M, Bond E, Chang L. Impact of sex and gender on irritable bowel syndrome. Biol Res Nurs. 2003;5:56-65 pubmed
    ..This review addresses the topic of possible sex (genetic, biological) and gender (experiential, perceptual) differences in individuals with and without IBS...
  39. Colegrave N. Sex releases the speed limit on evolution. Nature. 2002;420:664-6 pubmed
    Explaining the evolutionary maintenance of sex remains a key problem in evolutionary biology...
  40. Roze D. Disentangling the benefits of sex. PLoS Biol. 2012;10:e1001321 pubmed publisher
    ..Most of the current hypotheses rely on the fact that sex increases genetic variation, thereby enhancing the efficiency of natural selection; an important body of ..
  41. Agrawal A. Differences between selection on sex versus recombination in red queen models with diploid hosts. Evolution. 2009;63:2131-41 pubmed publisher
    The Red Queen hypothesis argues that parasites generate selection for genetic mixing (sex and recombination) in their hosts. A number of recent papers have examined this hypothesis using models with haploid hosts...
  42. Franco H, Yao H. Sex and hedgehog: roles of genes in the hedgehog signaling pathway in mammalian sexual differentiation. Chromosome Res. 2012;20:247-58 pubmed publisher
    ..Here, we review current findings on the roles of hedgehog signaling in the sexually dimorphic development of the reproductive organs with an emphasis on mammals and comparative evidence in other species...
  43. Artieri C, Haerty W, Gupta B, Singh R. Sexual selection and maintenance of sex: evidence from comparisons of rates of genomic accumulation of mutations and divergence of sex-related genes in sexual and hermaphroditic species of Caenorhabditis. Mol Biol Evol. 2008;25:972-9 pubmed publisher
    ..Here, we examine the advantages of dioecy versus hermaphroditism by comparing the rate of evolution in sex-related genes and the rate of accumulation of deleterious mutations using a large number of orthologs (11,493) in ..
  44. Dorken M, Mitchard E. Phenotypic plasticity of hermaphrodite sex allocation promotes the evolution of separate sexes: an experimental test of the sex-differential plasticity hypothesis using Sagittaria latifolia (Alismataceae). Evolution. 2008;62:971-8 pubmed publisher
    ..nuclear inheritance when unisexuals have more than twice the reproductive fitness of hermaphrodites through one sex function (e.g., when females have more than twice the seed fertility of hermaphrodites)...
  45. Kumpulainen T, Grapputo A, Mappes J. Parasites and sexual reproduction in psychid moths. Evolution. 2004;58:1511-20 pubmed
    ..the life-history traits of these species in two locations where they coexist to test predictions of the cost-of-sex hypothesis...
  46. Dorken M, Neville K, Eckert C. Evolutionary vestigialization of sex in a clonal plant: selection versus neutral mutation in geographically peripheral populations. Proc Biol Sci. 2004;271:2375-80 pubmed
    ..These observations suggest that selection has facilitated the vestigialization of sex, and thus do not support the neutral mutation hypothesis...
  47. Järvelä I, Zácková T, Laitinen P, Ryynanen M, Tekay A. Effect of parity and fetal sex on placental and luteal hormones during early first trimester. Prenat Diagn. 2012;32:160-7 pubmed publisher
    ..The placental function already differs between primigravid and multigravid women during the first weeks of pregnancy, which reflects the corpus luteal function. ..
  48. de Visser J, Elena S. The evolution of sex: empirical insights into the roles of epistasis and drift. Nat Rev Genet. 2007;8:139-49 pubmed
    Despite many years of theoretical and experimental work, the explanation for why sex is so common as a reproductive strategy continues to resist understanding...
  49. Balfour M, Yu L, Coolen L. Sexual behavior and sex-associated environmental cues activate the mesolimbic system in male rats. Neuropsychopharmacology. 2004;29:718-30 pubmed
    ..Specifically, the effects of sexual experience and sex-related environmental cues on the activation of several components of the mesolimbic system were studied...
  50. Becks L, Agrawal A. The evolution of sex is favoured during adaptation to new environments. PLoS Biol. 2012;10:e1001317 pubmed publisher
    Both theory and experiments have demonstrated that sex can facilitate adaptation, potentially yielding a group-level advantage to sex...
  51. Bushman B, Moeller S, Crocker J. Sweets, sex, or self-esteem? Comparing the value of self-esteem boosts with other pleasant rewards. J Pers. 2011;79:993-1012 pubmed publisher much value? Do people value self-esteem more than other pleasant activities, such as eating sweets and having sex? Two studies of college students (Study 1: N=130; Study 2: N=152) showed that people valued boosts to their self-..
  52. Turner P. Searching for the advantages of virus sex. Orig Life Evol Biosph. 2003;33:95-108 pubmed
    b>Sex (genetic exchange) is a nearly universal phenomenon in biological populations. But this is surprising given the costs associated with sex...
  53. Doyal L. Biological sex and social gender: challenges for preventive and social medicine. Soz Praventivmed. 2003;48:207-8 pubmed
  54. Cavalier Smith T. Origin of the cell nucleus, mitosis and sex: roles of intracellular coevolution. Biol Direct. 2010;5:7 pubmed publisher
    ..Discussions on the origin of sex typically overlook its association with protozoan entry into dormant walled cysts and the likely simultaneous ..
  55. Hadany L, Comeron J. Why are sex and recombination so common?. Ann N Y Acad Sci. 2008;1133:26-43 pubmed publisher
    The abundance of sex and recombination is still one of the most puzzling questions in the theory of evolution: Most models find that recombination can evolve, but only under a limited range of parameters...
  56. Campos Ramos R, Harvey S, Penman D. Sex-specific differences in the synaptonemal complex in the genus Oreochromis (Cichlidae). Genetica. 2009;135:325-32 pubmed publisher
    Total synaptonemal complex (SC) lengths were estimated from Oreochromis aureus Steindachner (which has a WZ/ZZ sex determination system), O. mossambicus Peters and O. niloticus L. (both of which have XX/XY sex determination systems)...
  57. Riffell J, Zimmer R. Sex and flow: the consequences of fluid shear for sperm-egg interactions. J Exp Biol. 2007;210:3644-60 pubmed
    ..The shears maximizing fertilization success in the lab typically characterized natural flow microenvironments of spawning red abalone. Gamete behavior thus emerges as a critical determinant of sexual reproduction in the turbulent sea. ..
  58. Gandon S, Otto S. The evolution of sex and recombination in response to abiotic or coevolutionary fluctuations in epistasis. Genetics. 2007;175:1835-53 pubmed
    Evolutionary biologists have identified several factors that could explain the widespread phenomena of sex and recombination...
  59. Busch J, Neiman M, Koslow J. Evidence for maintenance of sex by pathogens in plants. Evolution. 2004;58:2584-90 pubmed
    ..This pattern is consistent with the hypothesis that pathogen-mediated selection may contribute to the maintenance of outcrossing in species of seed plants. ..
  60. Morris S, Klausner J, Buchbinder S, Wheeler S, Koblin B, Coates T, et al. Prevalence and incidence of pharyngeal gonorrhea in a longitudinal sample of men who have sex with men: the EXPLORE study. Clin Infect Dis. 2006;43:1284-9 pubmed
    The prevalence of gonorrhea of the pharynx among select samples of men who have sex with men (MSM) ranges from 9% to 15%...
  61. Piwoz E, Humphrey J, Marinda E, Mutasa K, Moulton L, Iliff P. Effects of infant sex on mother-to-child transmission of HIV-1 according to timing of infection in Zimbabwe. AIDS. 2006;20:1981-4 pubmed
    We examined the relationship between sex and the risk of intrauterine, intrapartum and postnatal HIV transmission among 4495 infants born to HIV-infected mothers in Harare, Zimbabwe. Intrauterine transmission was 8...
  62. Agrawal A. Evolution of sex: why do organisms shuffle their genotypes?. Curr Biol. 2006;16:R696-704 pubmed
    Sexual processes alter associations among alleles. To understand the evolution of sex, we need to know both the short-term and long-term consequences of changing these genetic associations...
  63. Hadany L, Feldman M. Evolutionary traction: the cost of adaptation and the evolution of sex. J Evol Biol. 2005;18:309-14 pubmed
    ..But the advantage of sex for large populations, low mutation rates, and rare or mild environmental changes remains a conundrum...