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Secondary sex characteristics are features that appear during
puberty Puberty is the process of physical changes through which a child Biologically, a child (plural children) is a human Humans (''Homo sapiens'') are the most abundant and widespread species In biology Biology is the natur ...

puberty
in
human Humans (''Homo sapiens'') are the most abundant and widespread species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A speci ...

human
s, and at
sexual maturity Sexual maturity is the capability of an organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxono ...
in other animals. These characteristics are particularly evident in the
sexually dimorphic Sexual dimorphism is the condition where the sexes of the same species exhibit different characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most animals and some plants. Differences may in ...
phenotypic trait A phenotypic trait, simply trait, or character state is a distinct variant of a phenotypic In genetics Genetics is a branch of biology Biology is the natural science that studies life and living organisms, including their ...
s that distinguish the
sex Sex is either of two divisions, typically male Male (♂) is the sex of an organism that produces the gamete known as sperm. A male gamete can fuse with a larger female gamete, or ovum, in the process of fertilization. A male cannot sexual r ...
es of a species, but unlike the
sex organ A sex organ (or reproductive organ) is any part of an animal or plant that is involved in sexual reproduction. The reproductive organs together constitute the reproductive system. In animals, the testis in the male, and the ovary in the female, a ...
s (primary sex characteristics), are not directly part of the
reproductive system The reproductive system of an organism, also known as the genital system, is the biological system made up of all the anatomical organs An organ is a group of tissues with similar functions. Plant life and animal life rely on many organs tha ...
. Secondary sex characteristics are believed to be the product of
sexual selection Sexual selection is a mode of natural selection Natural selection is the differential survival and reproduction of individuals due to differences in phenotype right , Here the relation between genotype and phenotype is illustrat ...
for traits which display fitness, giving an organism an advantage over its rivals in
courtship Courtship is the period of development towards a sexual relationship An intimate relationship is an interpersonal relationship that involves Physical intimacy, physical or emotional intimacy. Although an intimate relationship is commonly a ...

courtship
and in
aggressive Aggression is overt or covert, often harmful, social interaction with the intention of inflicting damage or other harm upon another individual. It may occur either reactively or without provocation. In humans, aggression can be caused by various ...
interactions. Secondary sex characteristics include, for example, the manes of male
lion The lion (''Panthera leo'') is a large cat The cat (''Felis catus'') is a domestic Domestic may refer to: In the home * Anything relating to the human home A home, or domicile, is a space used as a permanent or semi-perma ...

lion
s, the bright facial and rump coloration of male
mandrill The mandrill (''Mandrillus sphinx'') is a primate of the Old World monkey (Cercopithecidae) family. It is one of two species in the genus ''Mandrillus,'' along with the Drill (animal), drill. Although they superficially resemble baboons, they ...

mandrill
s, and horns in many
goat The domestic goat or simply goat (''Capra hircus'') is a domesticated species of typically kept as . It was from the (''C. aegagrus'') of and . The goat is a member of the animal family and the subfamily , meaning it is closely related ...

goat
s and
antelope The term antelope is used to refer to many species of even-toed ruminant Ruminants (suborder In biological classification, the order ( la, wikt:ordo#Latin, ordo) is # a taxonomic rank used in the classification of organisms and recognized by ...

antelope
s. These characteristics are believed to be produced by a
positive feedback Positive feedback (exacerbating feedback, self-reinforcing feedback) is a process that occurs in a feedback loop Feedback occurs when outputs of a system are routed back as inputs as part of a chain Image:Kettenvergleich.jpg, Roller c ...
loop known as the
Fisherian runaway Fisherian runaway or runaway selection is a sexual selection Sexual selection is a mode of natural selection Natural selection is the differential survival and reproduction of individuals due to differences in phenotype right ...
produced by the secondary characteristic in one sex and the desire for that characteristic in the other sex. Male birds and fish of many species have brighter coloration or other external ornaments. Differences in size between sexes are also considered secondary sexual characteristics. In humans, visible secondary sex characteristics include enlarged
breast The breast is one of two prominences located on the upper ventral Standard anatomical terms of location deal unambiguously with the of s, including s. Terms used generally derive from or roots and used to describe something in its . Th ...

breast
s and widened
hips In vertebrate anatomy, hip (or "coxa"Latin ''coxa'' was used by Celsus in the sense "hip", but by Pliny the Elder in the sense "hip bone" (Diab, p 77) in medical terminology) refers to either an anatomical region or a joint. The hip region is ...

hips
of females,
facial hair Facial hair is hair Hair is a protein filament In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molec ...
and
Adam's apple The Adam's apple or laryngeal prominence, is the lump or protrusion in the human neck The neck is the part of the body on many vertebrate Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular ...
s on males, and
pubic hair Pubic hair is terminal body hair that is found in the genital area of adolescent and adult humans. The hair is located on and around the sex organs and sometimes at the top of the inside of the thighs. In the pubic region around the pubis ...

pubic hair
on both.


Evolutionary roots

Charles Darwin Charles Robert Darwin (; ; 12 February 1809 – 19 April 1882) was an English naturalist Natural history is a domain of inquiry involving organism In biology, an organism () is any organic, life, living system that fu ...

Charles Darwin
hypothesized that
sexual selection Sexual selection is a mode of natural selection Natural selection is the differential survival and reproduction of individuals due to differences in phenotype right , Here the relation between genotype and phenotype is illustrat ...
, or competition within a species for mates, can explain observed differences between sexes in many species.
Ronald Fisher Sir Ronald Aylmer Fisher (17 February 1890 – 29 July 1962) was a British polymath A polymath ( el, πολυμαθής, , "having learned much"; la, homo universalis, "universal human") is an individual whose knowledge spans a subs ...
, the English
biologist A biologist is a professional who has specialized knowledge in the field of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Mol ...
, developed a number of ideas concerning secondary characteristics in his 1930 book ''
The Genetical Theory of Natural Selection ''The Genetical Theory of Natural Selection'' is a book by Ronald Fisher Sir Ronald Aylmer Fisher (17 February 1890 – 29 July 1962) was a British statistician, geneticist, and academic. For his work in statistics, he has been describ ...
'', including the concept of
Fisherian runaway Fisherian runaway or runaway selection is a sexual selection Sexual selection is a mode of natural selection Natural selection is the differential survival and reproduction of individuals due to differences in phenotype right ...
which postulates that the desire for a characteristic in females combined with that characteristic in males can create a positive feedback loop or runaway where the feature becomes hugely amplified. The 1975
handicap principle The handicap principle is a hypothesis A hypothesis (plural hypotheses) is a proposed explanation for a phenomenon. For a hypothesis to be a scientific hypothesis, the scientific method The scientific method is an Empirical evidence, ...
extends this idea, stating that a
peacock Peafowl is a common name for three bird species in the genera Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology, taxonomy () is the scientific study of naming, def ...

peacock
's tail, for instance, displays fitness by being a useless impediment that is very hard to fake. Another of Fisher's ideas is the
sexy son hypothesis The sexy son hypothesis in evolutionary biology and sexual selection, proposed by Patrick J. Weatherhead and Raleigh J. Robertson of Queen's University at Kingston, Queen's University in Kingston, Ontario in 1979, states that a female's ideal mat ...
, whereby females will desire to have sons that possess the characteristic that they find sexually attractive in order to maximize the number of grandchildren they produce. An alternative hypothesis is that some of the genes that enable males to develop impressive ornaments or fighting ability may be correlated with fitness markers such as disease resistance or a more efficient
metabolism Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life Life is a characteristic that distinguishes physical entities A bubble of exhaled gas in water In common usage and classical mechanics, a phys ...

metabolism
. This idea is known as the good genes hypothesis.


In non-human animals

Secondary sex characteristics in non-human animals include manes of male
lion The lion (''Panthera leo'') is a large cat The cat (''Felis catus'') is a domestic Domestic may refer to: In the home * Anything relating to the human home A home, or domicile, is a space used as a permanent or semi-perma ...

lion
s and long feathers of male
peafowl Peafowl is a common name for three bird species in the genera ''Pavo (genus), Pavo'' and ''Afropavo'' within the tribe Pavonini of the family Phasianidae, the pheasants and their allies. Male peafowl are referred to as peacocks, and female pe ...

peafowl
, the tusks of male
narwhal The narwhal, also known as a narwhale (''Monodon monoceros''), is a medium-sized toothed whale The toothed whales (also called odontocetes, systematic name Odontoceti) are a parvorder of cetacea Cetaceans (from la, Cetus (mythology), ...

narwhal
s, enlarged
proboscis Convolvulus hawk-moth (''Agrius convolvuli'') feeding with extended proboscis">Agrius_convolvuli.html" ;"title="Convolvulus hawk-moth (''Agrius convolvuli">Convolvulus hawk-moth (''Agrius convolvuli'') feeding with extended proboscis A probosci ...

proboscis
es in male
elephant seal Elephant seals are large, oceangoing earless seals in the genus Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such ...
s and
proboscis monkey The proboscis monkey (''Nasalis larvatus'') or long-nosed monkey is an arboreal Old World monkey with an unusually large nose, a reddish-brown skin color and a long tail. It is Endemism, endemic to the southeast Asian island of Borneo and is foun ...

proboscis monkey
s, the bright facial and rump coloration of male
mandrill The mandrill (''Mandrillus sphinx'') is a primate of the Old World monkey (Cercopithecidae) family. It is one of two species in the genus ''Mandrillus,'' along with the Drill (animal), drill. Although they superficially resemble baboons, they ...

mandrill
s, and horns in many
goat The domestic goat or simply goat (''Capra hircus'') is a domesticated species of typically kept as . It was from the (''C. aegagrus'') of and . The goat is a member of the animal family and the subfamily , meaning it is closely related ...

goat
s and
antelope The term antelope is used to refer to many species of even-toed ruminant Ruminants (suborder In biological classification, the order ( la, wikt:ordo#Latin, ordo) is # a taxonomic rank used in the classification of organisms and recognized by ...

antelope
s. Biologists today distinguish between "male-to-male combat" and "mate choice", usually female choice of male mates. Sexual characteristics due to combat are such things as antlers, horns, and greater size. Characteristics due to mate choice, often referred to as ''ornaments'', include brighter
plumage Plumage ( "feather") is a layer of feather Feathers are epidermal growths that form a distinctive outer covering, or plumage Plumage ( "feather") is a layer of feather Feathers are epidermal growths that form a distinctive outer ...
, coloration, and other features that have no immediate purpose for survival or combat. Male
jumping spider Jumping spiders or the Salticidae are a family In human society A society is a Social group, group of individuals involved in persistent Social relation, social interaction, or a large social group sharing the same spatial or soci ...

jumping spider
s have visual patches of UV reflectance, which are ornamentations used to attract females.Lim, Matthew L. M., and Daiqin Li. "Courtship and Male-Male Agonistic Behaviour of Comsophasis Umbratica Simon, an Ornate Jumping Spider (Araneae: Salticidae)." The Raffles Bulletin of Zoology (2004): 52(2): 435-448. National University of Singapore. 20 September 2015


In humans

Sexual differentiation Sexual differentiation is the process of development of the sex Sex is either of two divisions, typically male Male (♂) is the sex of an organism that produces the gamete known as sperm. A male gamete can fuse with a larger female gamete ...
begins during
gestation Gestation is the period of development Development or developing may refer to: Arts *Development hell, when a project is stuck in development *Filmmaking#Development, Filmmaking, development phase, including finance and budgeting *Development ...
, when the
gonads A gonad, sex gland, or reproductive gland is a mixed gland that produces the gametes A gamete ( /ˈɡæmiːt/; from Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the classical antiqu ...
are formed. The general structure and shape of the body and face, as well as
sex hormone Sex hormones, also known as sex steroids, gonadocorticoids and gonadal steroids, are steroid hormone A steroid hormone is a steroid that acts as a hormone. Steroid hormones can be grouped into two classes: corticosteroids (typically made in the ...
levels, are similar in
preadolescent Preadolescence, also commonly known as pre-teen, is a stage of Human development (biology), human development following early childhood and preceding adolescence.New Oxford American Dictionary. 2nd Edition. 2005. Oxford University Press. It commo ...
boys and girls. As
puberty Puberty is the process of physical changes through which a child Biologically, a child (plural children) is a human Humans (''Homo sapiens'') are the most abundant and widespread species In biology Biology is the natur ...

puberty
begins and sex hormone levels rise, differences appear, though some changes are similar in males and females. Male levels of
testosterone Testosterone is the primary sex hormone and anabolic steroid in males. In humans, testosterone plays a key role in the development of Male reproductive system, male reproductive tissues such as testes and prostate, as well as promoting secondar ...
directly induce the growth of the
genitals A sex organ (or reproductive organ) is any part of an animal or plant that is involved in sexual reproduction Sexual reproduction is a type of reproduction Reproduction (or procreation or breeding) is the biological process Biological ...
, and indirectly (via
dihydrotestosterone Dihydrotestosterone (DHT, 5α-dihydrotestosterone, 5α-DHT, androstanolone or stanolone) is an endogenous Endogenous substances and processes are those that originate from within a system such as an organism, Tissue (biology), tissue, or Cell ...
(DHT)) the
prostate The prostate is both an accessory gland of the male reproductive system The male reproductive system consists of a number of sex organ A sex organ (or reproductive organ) is any part of an animal or plant that is involved in sexual repr ...

prostate
.
Estradiol Estradiol (E2), also spelled oestradiol, is an estrogen steroid hormone and the major female sex hormone. It is involved in the regulation of the estrous cycle, estrous and menstrual cycle, menstrual female reproductive cycles. Estradiol is resp ...

Estradiol
and other
hormones A hormone (from the Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is appr ...
cause
breast The breast is one of two prominences located on the upper ventral Standard anatomical terms of location deal unambiguously with the of s, including s. Terms used generally derive from or roots and used to describe something in its . Th ...

breast
s to develop in females. However, fetal or neonatal
androgen An androgen (from Greek ''andr-'', the stem of the word meaning "man") is any natural or synthetic steroid hormone A steroid hormone is a steroid , hypothetical a steroid with 32 carbon atoms. Its core ring system (ABCD), composed of 17 c ...
s may modulate later breast development by reducing the capacity of breast tissue to respond to later
estrogen Estrogens or oestrogens, are a class of natural or synthetic sex hormone Sex hormones, also known as sex steroids, gonadocorticoids and gonadal steroids, are steroid hormone A steroid hormone is a steroid that acts as a hormone. Steroid ho ...

estrogen
.
Underarm The axilla (also, armpit, underarm or oxter) is the area on the human body directly under the joint A joint or articulation (or articular surface) is the connection made between bones in the body which link the skeletal system into a functional ...
hair and
pubic hair Pubic hair is terminal body hair that is found in the genital area of adolescent and adult humans. The hair is located on and around the sex organs and sometimes at the top of the inside of the thighs. In the pubic region around the pubis ...

pubic hair
are usually considered secondary sex characteristics, but they may also be considered non-secondary sex characteristics because they are features of both sexes following puberty.


Females

In females,
breasts The breast is one of two prominences located on the upper ventral region of the torso of primates. In females, it serves as the mammary gland, which produces and secretes milk to feed infants. Both females and males develop breasts from the ...

breasts
are a manifestation of higher levels of
estrogen Estrogens or oestrogens, are a class of natural or synthetic sex hormone Sex hormones, also known as sex steroids, gonadocorticoids and gonadal steroids, are steroid hormone A steroid hormone is a steroid that acts as a hormone. Steroid ho ...

estrogen
; estrogen also widens the pelvis and increases the amount of body fat in hips, thighs, buttocks, and breasts. Estrogen also induces growth of the
uterus The uterus (from Latin "uterus", plural ''uteri'') or womb () is the main female hormone-responsive, sex organ, secondary sex organ of the reproductive system in humans and most other mammals. Things occurring in the uterus are described with t ...

uterus
, proliferation of the
endometrium The endometrium is the inner epithelial Epithelium is one of the four basic types of animal Tissue (biology), tissue, along with connective tissue, muscle tissue and nervous tissue. It is a thin, continuous, protective layer of compactly pac ...

endometrium
, and
menstruation Menstruation (also known as a period and many other Colloquialism, colloquial terms) is the regular discharge of blood and Mucous membrane, mucosal tissue from the endometrium, inner lining of the uterus through the vagina. The menstrual cycl ...
. Female secondary sex characteristics include: * Enlargement of
breasts The breast is one of two prominences located on the upper ventral region of the torso of primates. In females, it serves as the mammary gland, which produces and secretes milk to feed infants. Both females and males develop breasts from the ...

breasts
and erection of
nipples The nipple is a raised region of tissue on the surface of the breast The breast is one of two prominences located on the upper ventral region of the torso of primates. In females, it serves as the mammary gland, which produces and secret ...

nipples
. * Growth of
body hair Body hair, or androgenic hair, is the terminal hair that develops on the human body during and after puberty. It is differentiated from the head hair and less visible vellus hair, which is much finer and lighter in color. The growth of androgenic ...
, most prominently underarm and pubic hair. * Widening of
hip In vertebrate Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, ...
s; lower
waist to hip ratio The waist is the part of the Human abdomen, abdomen between the rib cage and Hip (anatomy), hips. On people with slim bodies, the waist is the narrowest part of the torso. The waistline refers to the horizontal line where the waist is narrowes ...

waist to hip ratio
than adult males. * Elbows that
hyperextend Motion Image:Leaving Yongsan Station.jpg, 300px, Motion involves a change in position In physics, motion is the phenomenon in which an object changes its position (mathematics), position over time. Motion is mathematically described in terms of ...
5–8° more than male adults. * Upper arms approximately 2 cm longer, on average, for a given height.Manwatching: A Field Guide to Human Behaviour, 1977,
Desmond Morris Desmond John Morris FLS ''hon. caus.'' (born 24 January 1928) is an English zoologist Zoology ()The pronunciation of zoology as is usually regarded as nonstandard, though it is not uncommon. is the branch of biology that studies the Anim ...
*
Labia minora The labia minora (Latin for ''smaller lips,'' singular: ''labium minus'' "smaller lip"), also known as the inner labia, inner lips, vaginal lips or nymphae, are two flaps of skin on either side of the human Humans (''Homo sapiens'') are th ...

Labia minora
, the inner lips of the
vulva The vulva (plural: vulvas or vulvae; derived from Latin for wrapper or covering) consists of the external female sex organs. The vulva includes the mons pubis In human anatomy The human body is the structure of a human being. It is com ...

vulva
, may grow more prominent and undergo changes in color with the increased stimulation related to higher levels of estrogen.


Males

The increased secretion of testosterone from the testes during puberty causes the male secondary sexual characteristics to be manifested. In males,
testosterone Testosterone is the primary sex hormone and anabolic steroid in males. In humans, testosterone plays a key role in the development of Male reproductive system, male reproductive tissues such as testes and prostate, as well as promoting secondar ...
directly increases size and mass of
muscle Skeletal muscles (commonly referred to as muscles) are organs An organ is a group of tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given organ's tissues can be broadly cat ...

muscle
s,
vocal cord In humans, vocal cords, also known as vocal chords, vocal folds or voice reeds, are folds of tissue in the throat that are key in creating sounds through vocalization. The size of vocal cords affects the pitch of voice. Open when breathing and ...
s, and
bone A bone is a rigid tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a specific function * ''Triphosa haesitata'', a species of geometer moth found in North America * ''Triphosa dubit ...

bone
s, deepening the
voice The human voice consists of sound In physics Physics is the that studies , its , its and behavior through , and the related entities of and . "Physical science is that department of knowledge which relates to the order of natu ...
, and changing the shape of the
face The face is the front of an animal's head that features the eyes Eyes are organs An organ is a group of tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given organ's ti ...

face
and
skeleton A skeleton is a structural frame that supports an animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consu ...

skeleton
. Converted into DHT in the skin, it accelerates growth of
androgen An androgen (from Greek ''andr-'', the stem of the word meaning "man") is any natural or synthetic steroid hormone A steroid hormone is a steroid , hypothetical a steroid with 32 carbon atoms. Its core ring system (ABCD), composed of 17 c ...
-responsive facial and body hair but may slow and eventually stop the growth of head hair. Taller stature is largely a result of later
puberty Puberty is the process of physical changes through which a child Biologically, a child (plural children) is a human Humans (''Homo sapiens'') are the most abundant and widespread species In biology Biology is the natur ...

puberty
and slower epiphyseal fusion. Male secondary sex characteristics include: * Growth of
body hair Body hair, or androgenic hair, is the terminal hair that develops on the human body during and after puberty. It is differentiated from the head hair and less visible vellus hair, which is much finer and lighter in color. The growth of androgenic ...
, including
underarm The axilla (also, armpit, underarm or oxter) is the area on the human body directly under the joint A joint or articulation (or articular surface) is the connection made between bones in the body which link the skeletal system into a functional ...
,
abdominal The abdomen (colloquially called the belly, tummy, midriff or stomach) is the part of the body between the thorax The thorax or chest is a part of the anatomy of humans, mammals, other tetrapod animals located between the neck and the abdomen. I ...
,
chest hair Chest hair is hair that grows on the chest of a male in the region between the neck and the Human abdomen, abdomen. Chest hair develops during and after puberty along with other types of androgenic hair. Development and growth Although vellus ...
and
pubic hair Pubic hair is terminal body hair that is found in the genital area of adolescent and adult humans. The hair is located on and around the sex organs and sometimes at the top of the inside of the thighs. In the pubic region around the pubis ...

pubic hair
. * Growth of
facial hair Facial hair is hair Hair is a protein filament In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molec ...
. * Enlargement of
larynx The larynx (), commonly called the voice box, is an organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with similar functions. Plant life and animal life rely on many organs that co-exist ...

larynx
(Adam's apple) and deepening of
voice The human voice consists of sound In physics Physics is the that studies , its , its and behavior through , and the related entities of and . "Physical science is that department of knowledge which relates to the order of natu ...
.Sexual reproduction
* Increased
stature Human height or stature is the distance Distance is a numerical measurement of how far apart objects or points are. In physics or everyday usage, distance may refer to a physical length or an estimation based on other criteria (e.g. "two c ...
; adult males are taller than adult females, on average. * Heavier
skull The skull is a bone A bone is a rigid tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a specific function * ''Triphosa haesitata'', a species of geometer moth found in North A ...

skull
and
bone A bone is a rigid tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a specific function * ''Triphosa haesitata'', a species of geometer moth found in North America * ''Triphosa dubit ...

bone
structure A structure is an arrangement and organization of interrelated elements in a material object or system A system is a group of Interaction, interacting or interrelated elements that act according to a set of rules to form a unified whole. ...

structure
. * Increased
muscle Skeletal muscles (commonly referred to as muscles) are organs An organ is a group of tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given organ's tissues can be broadly cat ...

muscle
mass and strength. * Broadening of
shoulder The human shoulder is made up of three bones: the clavicle The clavicle, or collarbone, is a slender, S-shaped long bone approximately 6 inches (15 cm) long that serves as a strut between the scapula, shoulder blade and the sternum (bre ...

shoulder
s and chest; shoulders wider than hips. * Increased secretions of oil and
sweat gland Sweat glands, also known as sudoriferous or sudoriparous glands, , are small tubular structures of the skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate Vertebrates () comprise all species of an ...
s.


References

{{DEFAULTSORT:Secondary Sex Characteristic * Sexual selection