Umuntu omdala wesilisa womuntu . Ngaphambi kokuba mdala, umuntu wesilisa ubizwa ngomfana ( ingane yesilisa noma eyeve eshumini nambili ). Njengazo zonke izilwane ezincelisayo zesilisa, ufuzo lomuntu ngokuvamile luthola i- X<span typeof="mw:Entity" id="mwIw"> </span>i-chromosome evela kumama kanye no- Y<span typeof="mw:Entity" id="mwJQ"> </span>i-chromosome evela kubaba. Umbungu wesilisa ukhiqiza amanani amakhulu ama- androgens namanani amancane ama- estrogens kunombungu wesifazane.Lo mehluko kumanani ahlobene nalawa ma- steroids ezocansi ubhekene nomehluko womzimba ohlukanisa amadoda kwabesifazane .Ngesikhathi sokuthomba, ama-hormone akhuthaza ukukhiqizwa kwe-androgen aholela ekukhuleni kwezici zesibili zobulili, ngaleyo ndlela kukhombisa umehluko omkhulu phakathi kobulili.Lokhu kufaka phakathi ubukhulu bemisipha, ukukhula kwezinwele zobuso nokwakheka kwamafutha omzimba aphansi. Anatomy Male is zihlukaniswa kusukela anatomy zesifazane yi uhlelo besilisa zokuzala, ehlanganisa umthondo, amasende, isidoda imbobo, wendlala indlala kanye epididymis, kanye seconday ubulili izici. Kukhona okuhlukile okungenhla ngokuphathelene kobakhe futhi bulilimbili amadoda. Kubantu, ubulili bomuntu bunqunywa ngesikhathi sokukhulelwa ngezinto zofuzo ezithwelwe esitokisini sesidoda. Uma ingqamuzana lesidoda eliphethe i- X chromosome livundisa iqanda, inzalo ngokujwayelekile iyoba ngowesifazane (XX).Ngakolunye uhlangothi, uma isidoda sesidoda esithwele i- Y chromosome sifaka iqanda, inzalo iyoba ngowesilisa (XY).Isici sangempela sokunquma yisakhi sofuzo se-SRY, esivame ukutholakala ku-Y chromosome.