Editing Sexual differentiation (section)

== Humans==
{{Main|Sexual differentiation in humans}}
[[File:YChromShowingSRY2.png|thumb|200px|The Human Y Chromosome shows the SRY gene which codes for a protein regulating sexual differentiation.]]
The early stages of human differentiation appear to be quite similar to the same biological processes in other mammals—and the interaction of genes, hormones and body structures is fairly well understood. In the first weeks of [[gestation]], a [[fetus]] is anatomically indistinguishable as male or female and lacks the production of any particular [[sex]] hormones. Only a [[karyotype]] distinguishes males from females. Specific genes induce [[gonad]]al differences, which produce hormonal differences, which cause anatomic differences, leading to psychological and behavioral differences, some of which are innate and some induced by the [[society|social environment]].

Various processes are involved in the development of [[sex differences in humans]]. Sexual differentiation in humans includes the development of different genitalia—and the internal genital tracts, breasts, and body hair—and plays a role in gender identification.<ref>{{Cite web | url=http://www.gfmer.ch/Books/Reproductive_health/Human_sexual_differentiation.html |title = Human sexual differentiation}}</ref>{{Better source needed|date=June 2021}}

The development of sexual differences begins with the [[XY sex-determination system]] that is present in humans, and complex mechanisms are responsible for the development of the phenotypic differences between [[male]] and [[female]] [[human]]s from an undifferentiated [[zygote]].<ref>{{cite journal |doi=10.1007/BF01726695 |title=Determination of sex chromosomal constitution and chromosomal origin of drumsticks, drumstick-like structures, and other nuclear bodies in human blood cells at interphase by fluorescence in situ hybridization |year=1990 |last1=Mukherjee |first1=Asit B. |last2=Parsa |first2=Nasser Z. |journal=Chromosoma |volume=99 |issue=6 |pages=432–5 |pmid=2176962|s2cid=25732504 }}</ref> Atypical sexual development, and ambiguous genitalia, can be a result of genetic and hormonal factors.<ref>{{cite journal |pmid=16160410 |year=2005 |last1=Kučinskas |first1=Laimutis |last2=Just |first2=Walter |title=Human male sex determination and sexual differentiation: Pathways, molecular interactions and genetic disorders |volume=41 |issue=8 |pages=633–40 |journal=Medicina |url=http://medicina.kmu.lt/0508/0508-01e.htm |access-date=2014-05-22 |archive-date=2014-04-06 |archive-url=https://web.archive.org/web/20140406213835/http://medicina.kmu.lt/0508/0508-01e.htm |url-status=dead }}</ref>

The differentiation of other parts of the body than the [[sex organ]] creates [[secondary sex characteristic]]s. [[Sexual dimorphism]] of skeletal structure develops during childhood and becomes more pronounced in adolescence.