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Encyclopedia > Sexual dimorphism
Female (left) and male Common Pheasant, illustrating the dramatic difference in both color and size, between the sexes
Female (left) and male Common Pheasant, illustrating the dramatic difference in both color and size, between the sexes

Sexual dimorphism is the systematic difference in form between individuals of different sex in the same species. Examples include size, color, and the presence or absence of parts of the body used in courtship displays or fights, such as ornamental feathers, horns, antlers or tusks. Male and female pheasant (Phasianus colchicus) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Male and female pheasant (Phasianus colchicus) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Binomial name Linnaeus, 1758 The Common Pheasant (Phasianus colchicus), otherwise known as the Ring-necked Pheasant or Chinese Pheasant is a gamebird in the pheasant family Phasianidae of the order Galliformes, gallinaceous birds. ... This article or section does not cite its references or sources. ... For other uses, see Species (disambiguation). ...

Contents

Examples

Peacock courting peahen
Peacock courting peahen

In many species, including most mammals, the male is larger than the female. In others, such as most spiders, birds, reptiles and amphibians, many insects and fish, and certain mammals such as the spotted hyena, the female is larger than the male. Other sex-specific differences include differences in colouration (sexual dichromatism), presence vs. absence of certain body parts such as horns, antlers, tusks or display feathers; size of the eyes (some insects); possession of stings (various kinds of Hymenoptera), and different thresholds for certain behaviors (aggression, infant care, etc). Download high resolution version (800x733, 148 KB)Fred the Peacock tries to woo an unsuspecting Peahen. ... Download high resolution version (800x733, 148 KB)Fred the Peacock tries to woo an unsuspecting Peahen. ... Peacock re-directs here; for alternate uses see Peacock (disambiguation). ... Peacock re-directs here; for alternate uses see Peacock (disambiguation). ... Subclasses & Infraclasses Subclass †Allotheria* Subclass Prototheria Subclass Theria Infraclass †Trituberculata Infraclass Metatheria Infraclass Eutheria Mammals (class Mammalia) are warm-blooded, vertebrate animals characterized by the presence of sweat glands, including those that produce milk, and by the presence of: hair, three middle ear bones used in hearing, and a neocortex... This article is about the Male sex. ... For other uses, see Female (disambiguation). ... Diversity 111 families, 40,000 species Suborders Mesothelae Mygalomorphae Araneomorphae  See table of families Wikispecies has information related to: Spiders Spiders are predatory invertebrate animals that have two body segments, eight legs, no chewing mouth parts and no wings. ... For other meanings of bird, see bird (disambiguation). ... Orders  Crocodilia - Crocodilians scary crocodiles. ... For other uses, see Amphibian (disambiguation). ... Orders Subclass Apterygota Archaeognatha (bristletails) Thysanura (silverfish) Subclass Pterygota Infraclass Paleoptera (Probably paraphyletic) Ephemeroptera (mayflies) Odonata (dragonflies and damselflies) Infraclass Neoptera Superorder Exopterygota Grylloblattodea (ice-crawlers) Mantophasmatodea (gladiators) Plecoptera (stoneflies) Embioptera (webspinners) Zoraptera (angel insects) Dermaptera (earwigs) Orthoptera (grasshoppers, etc) Phasmatodea (stick insects) Blattodea (cockroaches) Isoptera (termites) Mantodea (mantids) Psocoptera... For other uses, see Fish (disambiguation). ... Binomial name (Erxleben, 1777) Spotted Hyena range The Spotted Hyena, or Laughing Hyena, (Crocuta crocuta) is a mammal of the order Carnivora. ... Suborders Apocrita Symphyta Hymenoptera is one of the larger orders of insects, comprising the sawflies, wasps, bees, and ants. ...

Female (left) and male Greater Painted Snipe, displaying reverse sexual dimorphism
Female (left) and male Greater Painted Snipe, displaying reverse sexual dimorphism

Sexual dimorphism is particularly apparent in ducks, and most gamefowl perhaps most dramatically including peafowl. Male pheasants are notably larger than females and possess bright plumage; females are usually a drab brown irrespective of the particular species. In some birds (most of which are waders such as the phalaropes and painted snipes), females have brighter colors than males. As this is the opposite of the usual sexual dichromatism, it is termed reverse sexual dimorphism. In many predatory birds females are larger than males, often considerably so. This seems to reduce competition between members of a pair, as they have different optimal prey sizes. Some cases of sexual dimorphism in birds are so striking that males and females of the same species were originally taken to be members of entirely different species, as in the case of the Eclectus Parrot (Eclectus roratus), where the male is predominantly green with an orange beak and the female scarlet and deep blue with a black beak. Image File history File linksMetadata Painted_Snipe_hm. ... Image File history File linksMetadata Painted_Snipe_hm. ... Species Rostralata benghalensis Nycticryptes semicollaris Painted snipe are distinctive waders placed together in their own family Rostratulidae. ... Subfamilies Dendrocygninae Oxyurinae Anatinae Aythyinae Merginae Duck is the common name for a number of species in the Anatidae family of birds. ... Families Megapodiidae Numididae Odontophoridae Phasianidae Meleagrididae Tetraonidae Cracidae (?)Mesitornithidae Galliformes is an order of birds containing the turkeys, grouse, chickens, quails, and pheasants. ... Peacock redirects here. ... For other uses, see Species (disambiguation). ... Families Scolopacidae Rostratulidae Jacanidae Thinocoridae Pedionomidae Burhinidae Chionididae Pluvianellidae Ibidorhynchidae Recurvirostridae Haematopodidae Charadriidae Dunlin (Calidris alpina). ... Species Red Phalarope, Red-necked Phalarope, Wilsons Phalarope, The name Phalarope refers to any of three species of slender-necked shorebirds in the genus Phalaropus of the bird family Scolopacidae. ... Species Rostralata benghalensis Nycticryptes semicollaris Painted snipe are distinctive waders placed together in their own family Rostratulidae. ... Binomial name Eclectus roratus (Müller, 1776) The Eclectus Parrot, Eclectus roratus is a parrot native to the Solomon Islands, New Guinea, northeastern Australia and the Maluku Islands (Moluccas). ...


The Huia (Heteralocha acutirostris), a New Zealand bird species (now extinct), was another striking example of sexual dimorphism. The male's bill was short, sharp and stout while the female's was long, thin and crescent shaped. This beak dimorphism allowed mated pairs of Huia to avoid competing for the same food source, with males chiseling into and breaking apart rotting logs, while females were adept at probing into fresher wood for grubs. // Binomial name Heteralocha acutirostris (Gould, 1837) Synonyms Neomorpha acutirostris Neomorpha crassirostris (male) Heteralocha gouldi The Huia (Heteralocha acutirostris) was a bird endemic to New Zealand. ... Grub or GRUB can mean: a slang term for food a beetle larva that resembles a worm a distributed commercial search engine: see Grub (search engine) a number of places in Switzerland, Austria and Germany, such as: Grub, canton of Appenzell Outer Rhodes, Switzerland Grub, Germany for the GNU project...

Male (front) and female mallards. The male mallard has an unmistakable green head.
Male (front) and female mallards. The male mallard has an unmistakable green head.

Certain sexual dimorphisms have obvious utility beyond mate attraction, such as the Blue Wildebeest (and many other biungulates). The horns of the male are much larger, allowing the male to engage in combat more effectively as he competes with other bucks for mating privileges. Image File history File links Size of this preview: 800 × 532 pixel Image in higher resolution (1000 × 665 pixel, file size: 75 KB, MIME type: image/jpeg) Photo by David Stang. ... Image File history File links Size of this preview: 800 × 532 pixel Image in higher resolution (1000 × 665 pixel, file size: 75 KB, MIME type: image/jpeg) Photo by David Stang. ... For other uses, see Mallard (disambiguation). ... Binomial name (Burchell, 1823) The Blue Wildebeest is a large ungulate mammal of the genus Connochaetes which grows to 1. ... Highland cow, a very old long-horned breed from Scotland. ...


An extreme example of sexual dimorphism is found the genus Osedax of polychaete worms, which lives on whale falls. The females feed on the bones of the dead whale, but the males live inside the females and do not develop past their larval stage except to produce large amounts of sperm. In the echiuran Bonellia viridis, females force larvae which encounter them to develop into the tiny, semi-parasitic males. The argonauts also have males which are tiny compared to the female. In the parasitic barnacles Sacculina, the males are tiny, free-ranging animals, whereas the females only exist as a web-like tissue inside their hosts. Species Osedax frankpressi Osedax rubiplumus The osedax are a genus of whalebone-eating siboglinids (deep sea worms), first discovered in Monterey Bay, California, in June 2004. ... Subclasses Palpata Scoleoida Tomopteris from plankton The Polychaeta or polychaetes are a class of annelid worms, generally marine. ... Whale fall is the term used for a whale carcass that has fallen to the ocean floor. ... The Echiura, or spoon worms, are a small group of marine animals. ... Species Argonauta argo Argonauta bottgeri Argonauta cornuta Argonauta hians Argonauta nodosa Argonauta nouryi Argonauta pacifica Argonauts (genus Argonauta, the only genus in the Argonautidae family) are a kind of pelagic octopus that live close to the surface of warm seas rather than on the sea floor, as nearly all other... For other uses, see Barnacle (disambiguation). ... Species S. andersoni Sacculina is a genus of barnacles that are parasitic on crabs. ...

Female Triplewart seadevil, an anglerfish, with male attached near vent (arrow)

Some species of anglerfish also display extreme sexual dimorphism. Females are typical anglerfish, while males are tiny rudimentary creatures with no digestive systems. The males must find a female and fuse with her – he then lives parasitically, becoming little more than a sperm-producing body. A similar situation is found in the Zeus water bug Phoreticovelia disparata where the female has a cavity on her back where males live permanently attached.[1] Image File history File links Size of this preview: 800 × 484 pixelsFull resolution (2491 × 1506 pixel, file size: 47 KB, MIME type: image/gif) Cryptopsaras couesii (triplewart seadevil) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File links Size of this preview: 800 × 484 pixelsFull resolution (2491 × 1506 pixel, file size: 47 KB, MIME type: image/gif) Cryptopsaras couesii (triplewart seadevil) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Binomial name Cryptopsaras couesii Gill, 1883 The triplewart seadevil, Cryptopsaras couesii, is a seadevil of the family Ceratiidae, found in all oceans, from the surface to 2,000 m. ... Suborders Antennarioidei Lophioidei Ogcocephalioidei See text for families. ...


Psychological and behavioral differentiation

Sex steroid-induced differentiation of adult reproductive and other behavior has been demonstrated experimentally in many animals. In some mammals, adult sex-dimorphic reproductive behavior (e.g., mounting or receptive lordosis) can be shifted to that of the other sex by supplementation or deprivation of androgens in fetal life or early infancy, even if adult levels are normal. Sex steroids, also known as gonadal steroids, are steroid hormones which interact with vertebrate androgen or estrogen receptors. ... Orders Subclass Monotremata Monotremata Subclass Marsupialia Didelphimorphia Paucituberculata Microbiotheria Dasyuromorphia Peramelemorphia Notoryctemorphia Diprotodontia Subclass Placentalia Xenarthra Dermoptera Desmostylia Scandentia Primates Rodentia Lagomorpha Insectivora Chiroptera Pholidota Carnivora Perissodactyla Artiodactyla Cetacea Afrosoricida Macroscelidea Tubulidentata Hyracoidea Proboscidea Sirenia The mammals are the class of vertebrate animals primarily characterized by the presence of mammary...


Evolution of sexual dimorphism

Handicap principle

Main article: Handicap principle

The handicap principle is the evolutional force that gives males of some species traits that by the first glance seem to place the organism at a disadvantage. The handicap principle is an idea proposed by the Israeli biologist Amotz Zahavi. ...


Examples

For instance, the bright colouration of male game birds makes them highly visible targets for predators, while the drab females are better camouflaged. Other examples are bird of paradise and lyrebird, whose males have such large plumes that their flight is inhibited. Strong smells, loud cries and singing can also attract predators. This article is about protective camouflage used to disguise people, animals, or military targets. ... For the flowering plant of this name, see Strelitzia Genera Cicinnurus Diphyllodes Epimachus Lophorina Manucodia Paradisaea Parotia Ptiloris Seleucidis Lesser Bird of Paradise Paradisaea minor (c)Roderick Eime The birds of paradise are members of the family Paradisaeidae of the order Passeriformes, found in Oceania. ... Species Menura novaehollandiae Menura alberti A Lyrebird is either of two species of ground-dwelling Australian birds, most notable for their extraordinary ability to mimic natural and artificial sounds from their environment. ...


Explanation

The answer to this apparent paradox is that, at a biological level, the reproductive success of an organism is often more important than duration of life. This is particularly apparent in the case of game birds: a male Common Pheasant in the wild often lives no more than 10 months, with females living twice as long. However, a male pheasant's ability to reproduce depends not on how long he lives but whether females will select him to be their mate. Binomial name Linnaeus, 1758 The Common Pheasant (Phasianus colchicus), otherwise known as the Ring-necked Pheasant or Chinese Pheasant is a gamebird in the pheasant family Phasianidae of the order Galliformes, gallinaceous birds. ...


A brightly coloured and heavily plumed male demonstrates to the female that he is fit in evolutionary terms – he has been able to survive in spite of impediments and must therefore be a good choice to father her chicks (especially her daughters, who will have his "fit" genes, but will not be hampered by male plumage). This explanation was first proposed by Amotz Zahavi. Fitness (often denoted in population genetics models) is a central concept in evolutionary theory. ... Amotz Zahavi is an Israeli Evolutionary Biologist from Tel-Aviv University, and one of the founders of the Israeli Society for the Protection of Nature. ...


Development of such characters could not at first be explained in terms of simple natural selection. In 1871 Darwin advanced the theory of sexual selection, which related sexual dimorphism with sexual selection. For other uses, see Natural selection (disambiguation). ... Illustration from The Descent of Man and Selection in Relation to Sex by Charles Darwin showing the Tufted Coquette Lophornis ornatus, female on left, ornamented male on right. ... Illustration from The Descent of Man and Selection in Relation to Sex by Charles Darwin showing the Tufted Coquette Lophornis ornatus, female on left, ornamented male on right. ...


Polygamy

Comparison of sexual dimorphism in birds and their mating habits shows that the time spent in search for mates, staking territories and mating competes with the demands of taking care of young. For birds and in general, it can be stated that the stronger the dimorphism in a species, the more likely is it to be polygamous and the less is the task of caring for offspring shared among the sexes. This theory is developed by R. L. Trivers' in the parental investment theory. It applies to all ecology. Polygamy, literally many marriages in ancient Greek, is a marital practice in which a person has more than one spouse simultaneously (as opposed to monogamy where each person has a maximum of one spouse at any one time). ... Robert L. Trivers, (born 19 February 1943) is an American evolutionary biologist and sociobiologist, most noted for proposing the theories of reciprocal altruism (1971), parental investment (1972), and parent-offspring conflict (1974). ... Robert Trivers theory of parental investment predicts that the sex making the largest investment in lactation, nurturing and protecting offspring will be more discriminating in mating and that the sex that invests less in offspring will compete for access to the higher investing sex. ...


Sexual dimorphism in humans

Top: Stylised illustration of humans on the Pioneer plaque, showing both male (left) and female (right).
Above: Comparison between a male (left) and a female pelvis (right). Image File history File links Human. ... Image File history File links Gray241. ... Image File history File links Gray242. ... The illustration on the Pioneer plaque The Pioneer plaques are a pair of aluminum plaques which were placed on board the Pioneer 10 and Pioneer 11 spacecraft, featuring a pictorial message from humanity, in case either Pioneer 10 or 11 are intercepted by extraterrestrial beings. ... The pelvis (pl. ...

Main article: Sex differences in humans

Sexual dimorphism in humans is the subject of much controversy, especially relating to mental ability and psychological gender. (For a discussion, see biology of gender, sex and intelligence, gender, and transgender.) Obvious differences between men and women include all the features related to reproductive role, notably the endocrine (hormonal) systems and their physiological and behavioural effects. This article is about biological sex differences. ... Human Brain The biology of gender is the physical basis for behavioural differences between men and women. ... Sex and intelligence research investigates differences in the distributions of cognitive skills between men and women. ... Gender in common usage refers to the sexual distinction between male and female. ... A transgender woman at New York Citys gay pride parade Transgender (IPA: , from trans (Latin) and gender (English)) is a general term applied to a variety of individuals, behaviors, and groups involving tendencies that diverge from the normative gender role (woman or man) commonly, but not always, assigned at...


Such undisputed sexual dimorphism include gonadal differentiation, internal genital differentiation, external genital differentiation, breast differentiation and hair differentiation.


Some biologists theorise that a species' degree of sexual dimorphism is inversely related to the degree of paternal investment in parenting. Species with the highest sexual dimorphism, such as the pheasant, tend to be those species in which the care and raising of offspring is done only by the mother, with no involvement of the father (low degree of paternal investment). This would also explain the comparatively greater degree of sexual dimorphism in humans, who have a greater proportion of paternal investment than most other primates. Some biological text books, especially older sources, state that humans have a high degree of sexual dimorphism, but closer study by science fiction writer and biological theorist David Brin (2004) has shown that this is not the case.[Full citation needed] For other uses, see Parent (disambiguation). ... Science fiction is a form of speculative fiction principally dealing with the impact of imagined science and technology, or both, upon society and persons as individuals. ... Glen David Brin, Ph. ...


Among the proposed differences between the human sexes are sexually dimorphic behaviors, most especially dealing with sexual competition (both intrasexual and intersexual) and short- and long-term sexual strategies (David M Buss, 2007). However, there is a great degree of overlap between the sexes with regard to these behaviours.[Full citation needed]


The basal metabolic rate is about 6 percent higher in adolescent boys than girls and increases to about 10 per cent higher after puberty. Women tend to convert more food into fat, while men convert more into muscle and expendable circulating energy reserves. At age eighteen, men (on average) have about 50 percent more muscle mass than women in the upper body, 10 to 15 percent more in the lower. Men, on average, have denser, stronger bones, tendons, and ligaments. This allows for heavier work.[2] Structure of the coenzyme adenosine triphosphate, a central intermediate in energy metabolism. ... For other uses, see FAT. Fats consist of a wide group of compounds that are generally soluble in organic solvents and largely insoluble in water. ... For other uses of Muscles, see Muscles (disambiguation). ... This article is about the skeletal organs. ... A tendon (or sinew) is a tough band of fibrous connective tissue that connects muscle to bone and is built to withstand tension. ... In anatomy, the term ligament is used to denote three different types of structures:[1] Fibrous tissue that connects bones to other bones. ...


Men dissipate heat faster than women through their sweat glands. Women have a greater insulation and energy reserves stored in subcutaneous fat, withstanding cold better, and performing better in activities requiring extraordinary endurance. Sex differences in endurance events are less significant than for sprinting events. In humans, there are four kinds of sudoriferous or sweat glands which differ greatly in both the composition of the sweat and its purpose. ... It has been suggested that this article or section be merged into Adipose tissue. ...


Men typically have larger tracheae and branching bronchi, with about 30 percent greater lung volume per body mass. They have larger hearts, 10 percent higher red blood cell count, higher hemoglobin, hence greater oxygen-carrying capacity. They also have higher circulating clotting factors (vitamin K, prothrombin and platelets). These differences lead to faster healing of wounds and higher peripheral pain tolerance.[2] Windpipe redirects here. ... A bronchus (plural bronchi, adjective bronchial) is a caliber of airway in the respiratory tract that conducts air into the lungs. ... Lung Volumes The average pair of human lungs can hold about 6 liters of air, but only a small amount of this capacity is used during normal breathing. ... Body weight is simply the weight of anything, including humans. ... The heart and lungs, from an older edition of Grays Anatomy. ... “Red cell” redirects here. ... Structure of hemoglobin. ... This article is about the clotting of blood. ... Vitamin K1 (phylloquinone). ... Thrombin (activated Factor II) is a coagulation protein that has many effects in the coagulation cascade. ... A 250 ml bag of newly collected platelets. ... Superficial bullet wounds In medicine, a wound is a type of physical trauma wherein the skin is torn, cut or punctured (an open wound), or where blunt force trauma causes a contusion (a closed wound). ...


Women typically have more white blood cells (stored and circulating), more granulocytes and B and T lymphocytes. Additionally, they produce more antibodies and faster. Hence they develop fewer infectious diseases and succumb for shorter periods.[2] Ethologists argue that females, interacting with other females and multiple offspring in social groups, have experienced such traits as a selective advantage.[3] White Blood Cells redirects here. ... Eosinophil granulocyte Basophil granulocyte Granulocytes are a category of white blood cells characterised by the presence of granules in their cytoplasm. ... A scanning electron microscope (SEM) image of a single human lymphocyte. ... Each antibody binds to a specific antigen; an interaction similar to a lock and key. ... An infection is the detrimental colonization of a host organism by a foreign species. ... This article does not cite any references or sources. ... For other uses, see Natural selection (disambiguation). ...


[4] [5] [6] [7]


See also

Look up sexual dimorphism in
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Wikimedia Commons has media related to:
sexual dimorphism

Wikipedia does not have an article with this exact name. ... Wiktionary (a portmanteau of wiki and dictionary) is a multilingual, Web-based project to create a free content dictionary, available in over 150 languages. ... Image File history File links Commons-logo. ... In biology, Batemans principle is the theory that the sex which invests the most in producing offspring becomes a limited resource over which the other sex will compete. ... The digit ratio is the ratio of the lengths of different digits, fingers or toes, typically as measured from the bottom crease where the finger joins the hand to the tip of the finger. ... Illustration from The Descent of Man and Selection in Relation to Sex by Charles Darwin showing the Tufted Coquette Lophornis ornatus, female on left, ornamented male on right. ... Sexual differentiation is the process of development of the differences between males and females from an undifferentiated zygote (fertilized egg). ... The sexually dimorphic nucleus (SDN) is a cluster of cells in the preoptic area of the hypothalamus, an area of the human brain and that of other mammals, which is controversially considered by some studies to play a key role in the sexual differentiation of the brain. ... Although the subject of sexual dimorphism is not in itself controversial, the measures by which it is assessed differ widely. ... Sexual reproduction is a union that results in increasing genetic diversity of the offspring. ... Sex-limited genes are genes which are present in both sexes of sexually reproducing species but turned on in only one sex. ... This article is about gender differences in humans. ...

References

  1. ^ Arnqvist, Göran , Therésa M. Jones, Mark A. Elgar (2003)Reversal of sex roles in nuptial feeding. Nature 424:387 [1]
  2. ^ a b c A Glucksman, Sexual Dimorphism in Human and Mammalian Biology and Pathology, (Academic Press, 1981).
  3. ^ J Durden-Smith and D Desimone, Sex and the Brain, (New York: Arbor House, 1983).
  4. ^ ES Gersh and I Gersh, Biology of Women, (Baltimore: University Park Press, 1981).
  5. ^ J Stein (editor), Internal Medicine, 2nd edition., (Boston: Little, Brown and Company, 1987).
  6. ^ M McLaughlin and T Shryer, 'Men vs Women: The New Debate Over Sex Differences', U.S. News & World Report 8 August (1988): pp. 50-58.
  7. ^ BS McEwen, 'Neural Gonadal Steroid Action', Science 211 (1981): 1303–1311.
  • Bonduriansky, R. (2007) The evolution of condition-dependent sexual dimorphism. The American Naturalist, 169:1 pp9-19.
  • Biological Journal of the Linnean Society (1999), 67: 1–18.

Academic Press (London, New York and San Diego) was an academic book publisher that is now part of Elsevier. ... Little, Brown and Company is a publishing house established by Charles Coffin Little and his partner, James Brown. ... U.S. News & World Report is a weekly newsmagazine. ... Science is the journal of the American Association for the Advancement of Science (AAAS). ...

External links

  • MeSH Sex+dimorphism

  Results from FactBites:
 
Theoretical Background (12841 words)
Rice (1984), came to a different conclusion and, in a theoretical analysis of the effect of X-linkage on the evolution of sexual dimorphism, stated that "sex chromosomes facilitate the evolution of sexual dimorphism and that X-linked genes have a predominant role in coding for sexually dimorphic traits".
Sexual selection is thought to operate on males characters in two main ways: male competition where the winning male gains access to more matings, and female choice where the female chooses the male she deems more fit.
Ely, J. and Kurland, J. Spatial autocorrelation, phylogenetic constraints, and the causes of sexual dimorphism in primates.
  More results at FactBites »

 
 

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