Editing Development of the human body (section)

==After birth==
===Infancy and childhood===
{{Main|Infant|Child development|Child development stages}}
'''Childhood''' is the age span ranging from birth to [[adolescence]].<ref name="Students Macmillan 1981 page 173">''Macmillan Dictionary for Students'' Macmillan, Pan Ltd. (1981), page 173. Retrieved 2010-7-15.</ref> In [[developmental psychology]], childhood is divided up into the developmental stages of [[toddle]]rhood (learning to walk), [[early childhood]] (play age), middle childhood (school age), and adolescence (puberty through post-puberty). Various childhood factors could affect a person's attitude formation.<ref name="Students Macmillan 1981 page 173"/>

*Prepubescence 
** Neonate (newborn) 
**[[Infant]] (baby) 
**[[Toddler]] 
**[[Early childhood|Play age]] 
**[[Elementary school]] age, may coincide with [[preadolescence]] (preteen)
[[File:Child development stages.svg|thumb|center|800px|Approximate outline of development periods in [[child development]]]]

The [[Tanner stages]] can be used to approximately judge a child's age based on physical development.

{| class="wikitable" 
|- 
! For North American, Indo-Iranian (India, Iran) and European girls 
! For North American, Indo-Iranian (India, Iran) and European boys 
|- 
|  
*[[Thelarche]] (breast development) <br>age 10½ (8–13) 
*[[Pubarche]] (pubic hair) <br>age 11 (8½–13½) 
*Growth spurt <br>age 11¼ (10–12½) 
*[[Menarche]] (first menstrual bleeding) <br>age 12½ (10½–14½) 
*Wisdom tooth eruption<br>age 15½ (14–17)
*Adult [[Human height|height]] reached <br>age 15½ (14–17) 
|  
*[[Gonadarche]] (testicular enlargement) <br>age 11½ (9½–13½) 
*[[Pubarche]] (pubic hair) <br>age 12 (10–14) 
*Growth spurt <br>age 13 (11–15) 
*[[Spermarche]] (first ejaculation) <br>age 13 (11–15) 
*Wisdom tooth eruption <br>age 17 (15–19)
*Completion of growth <br>age 17 (15–19) 
|}

===Puberty===
{{Main|Puberty}}
'''Puberty''' is the process of physical changes through which a [[child]]'s [[Human body|body]] matures into an [[adult]] body capable of [[sexual reproduction]]. It is initiated by [[hormone|hormonal]] signals from the [[Human brain|brain]] to the [[gonad]]s: the [[ovary|ovaries]] in a girl, the [[testicle]]s in a boy. In response to the signals, the gonads produce hormones that stimulate [[libido]] and the growth, function, and transformation of the brain, [[bone]]s, [[muscle]], [[blood]], [[Human skin|skin]], [[human hair growth|hair]], [[breast]]s, and [[sex organ]]s. [[Human development (biology)|Physical growth]]—height and weight—accelerates in the first half of puberty and is completed when an adult body has been developed. Until the maturation of their reproductive capabilities, the pre-pubertal physical differences between boys and girls are the external sex organs.

On average, girls begin puberty around ages 10–11 and end puberty around 15–17; boys begin around ages 11–12 and end around 16–17.<ref name="Kail">{{cite book |last=Kail |first=RV |author2=Cavanaugh JC |title=Human Development: A Lifespan View |isbn=978-0495600374 |publisher=[[Cengage Learning]] |year=2010 |access-date=September 11, 2014 |page=296 |edition=5th |url=https://books.google.com/books?id=E-n5E7oyCgoC&pg=PA296 |archive-date=January 10, 2023 |archive-url=https://web.archive.org/web/20230110011825/https://books.google.com/books?id=E-n5E7oyCgoC&pg=PA296 |url-status=live }}</ref><ref name="pamf.org">"For girls, puberty begins around 10 or 11 years of age and ends around age 16. Boys enter puberty later than girls-usually around 12 years of age-and it lasts until around age 16 or 17." {{Cite news |url=http://www.pamf.org/parenting-teens/health/growth-development/pre-growth.html |title=Teenage Growth & Development: 11 to 14 Years |publisher=[[Palo Alto Medical Foundation]]/pamf.org |access-date=2013-11-09 |archive-date=2018-04-05 |archive-url=https://web.archive.org/web/20180405141025/http://www.pamf.org/parenting-teens/health/growth-development/pre-growth.html |url-status=live }}</ref><ref name="Pamf.org">{{Cite news |title=Teenage Growth & Development: 15 to 17 Years |publisher=[[Palo Alto Medical Foundation]]/pamf.org |url=http://www.pamf.org/parenting-teens/health/growth-development/growth.html |access-date=2013-11-09 |archive-date=2018-03-17 |archive-url=https://web.archive.org/web/20180317214045/http://www.pamf.org/parenting-teens/health/growth-development/growth.html |url-status=live }}</ref><ref name="Puberty">{{cite web |title=Puberty and adolescence |publisher=[[University of Maryland]] |url=http://umm.edu/health/medical/ency/articles/puberty-and-adolescence |archive-url=https://web.archive.org/web/20130924134845/http://umm.edu/health/medical/ency/articles/puberty-and-adolescence |access-date=December 8, 2020|archive-date=2013-09-24 }}</ref><ref name="Marshall17677">Marshall (1986), pp. 176–177{{Full citation needed|date=October 2022}}</ref> The major landmark of puberty for females is [[menarche]], the onset of menstruation, which occurs on average between ages 12 and 13;<ref name="Tanner">Tanner, 1990.{{Full citation needed|date=October 2022}}</ref><ref name="U.S. menarche">{{cite journal |vauthors=Anderson SE, Dallal GE, Must A|title=Relative weight and race influence average age at menarche: results from two nationally representative surveys of US girls studied 25 years apart |journal=Pediatrics |volume=111 |issue=4 Pt 1 |pages=844–850 |date=April 2003 |pmid=12671122 |doi=10.1542/peds.111.4.844 }}</ref><ref name="Canadian menarche">{{cite journal |vauthors=Al-Sahab B, Ardern CI, Hamadeh MJ, Tamim H|title=Age at menarche in Canada: results from the National Longitudinal Survey of Children & Youth |journal=BMC Public Health |volume=10 |page=736 |year=2010 |pmid=21110899 |pmc=3001737 |doi=10.1186/1471-2458-10-736 |doi-access=free }}</ref><ref name="UK menarche">{{cite book |url=http://vstudentworld.yolasite.com/resources/final_yr/gynae_obs/Hamilton%20Fairley%20Obstetrics%20and%20Gynaecology%20Lecture%20Notes%202%20Ed.pdf |title=Obstetrics and Gynaecology |series=Lecture Notes |first=Diana |last=Hamilton-Fairley |edition=Second |publisher=Blackwell Publishing |access-date=2013-11-09 |archive-date=2018-10-09 |archive-url=https://web.archive.org/web/20181009065351/http://vstudentworld.yolasite.com/resources/final_yr/gynae_obs/Hamilton%20Fairley%20Obstetrics%20and%20Gynaecology%20Lecture%20Notes%202%20Ed.pdf |url-status=dead }}</ref> for males, it is the first [[ejaculation]], which occurs on average at age 13.<ref name="Jorgensen & Keiding">Jorgensen & Keiding 1991.{{Full citation needed|date=October 2022}}</ref>  In the 21st century, the average age at which children, especially girls, reach puberty is lower compared to the 19th century, when it was 15 for girls and 16 for boys.<ref>{{cite news |url=https://www.telegraph.co.uk/health/healthnews/7824699/Girls-now-reaching-puberty-before-10-a-year-sooner-than-20-years-ago.html |archive-url=https://web.archive.org/web/20100614195534/http://www.telegraph.co.uk/health/healthnews/7824699/Girls-now-reaching-puberty-before-10-a-year-sooner-than-20-years-ago.html |url-status=dead |archive-date=2010-06-14 |location=London |work=[[The Daily Telegraph]] |first=Richard |last=Alleyne |title=Girls now reaching puberty before 10—a year sooner than 20 years ago |date=2010-06-13}}</ref> This can be due to any number of factors, including improved nutrition resulting in rapid body growth, increased weight and fat deposition,<ref name="Guillette_2006">{{cite journal |vauthors=Guillette EA, Conard C, Lares F, Aguilar MG, McLachlan J, Guillette LJ|title=Altered breast development in young girls from an agricultural environment |journal=Environ. Health Perspect. |volume=114 |issue=3 |pages=471–5 |date=March 2006 |pmid=16507474 |pmc=1392245 |doi=10.1289/ehp.8280 }}</ref> or exposure to [[endocrine disruptor]]s such as [[xenoestrogen]]s, which can at times be due to food consumption or other environmental factors.<ref name="Louis_2008">{{cite journal |vauthors=Buck Louis GM, Gray LE, Marcus M, Ojeda SR, Pescovitz OH, Witchel SF, Sippell W, Abbott DH, Soto A, Tyl RW, Bourguignon JP, Skakkebaek NE, Swan SH, Golub MS, Wabitsch M, Toppari J, Euling SY|title=Environmental factors and puberty timing: expert panel research needs |journal=[[Pediatrics (journal)|Pediatrics]] |volume=121 |issue=Suppl 3 |pages=S192–207 |date=February 2008 |pmid=18245512 |doi=10.1542/peds.1813E |doi-access=free }}</ref><ref name="Mouritsen_2010">{{cite journal |vauthors=Mouritsen A, Aksglaede L, Sørensen K, Mogensen SS, Leffers H, Main KM, Frederiksen H, Andersson AM, Skakkebaek NE, Juul A|title=Hypothesis: exposure to endocrine-disrupting chemicals may interfere with timing of puberty |journal=Int. J. Androl. |volume=33 |issue=2 |pages=346–59 |date=April 2010 |pmid=20487042 |doi=10.1111/j.1365-2605.2010.01051.x }}</ref> Puberty which starts earlier than usual is known as [[precocious puberty]], and puberty which starts later than usual is known as [[delayed puberty]].

Notable among the [[morphology (biology)|morphologic]] changes in size, shape, composition, and functioning of the pubertal body, is the development of [[secondary sex characteristic]]s, the "filling in" of the child's body; from girl to woman, from boy to man.{{Clarify|reason=What exactly does "filling in" involve, for female and for male bodies? What are the secondary sex characteristics?|date=October 2022}}

===Adulthood===
Biologically, an adult is a human or other organism that has reached sexual maturity. In human context, the term adult has additional meanings associated with social and legal concepts. In contrast to a [[Minor (law)|legal minor]], a legal adult is a person who has attained the age of majority and is therefore regarded as independent, self-sufficient, and responsible. The typical age of legal majority is 18 years in most contexts, although the definition of majority may vary by legal rights and country.

Human adulthood encompasses psychological adult development. Definitions of adulthood are often inconsistent and contradictory; an adolescent may be biologically an adult and display adult behavior but still be treated as a child if they are under the legal age of majority. Conversely, a legal adult may possess none of the maturity and responsibility that is supposed to define them; the mental and physical development and maturity of an individual has been proven to be greatly influenced by their life circumstances.