Editing Milk (section)

==Evolution of lactation==
{{main|Lactation}}
The [[mammary gland]] is thought to have derived from [[apocrine]] skin glands.<ref name="Oftedal 2002 225–252">{{cite journal |last=Oftedal |first=Olav T. |title=The mammary gland and its origin during synapsid evolution |journal=Journal of Mammary Gland Biology and Neoplasia |volume=7 |issue=3 |pages=225–52 |year=2002 |doi=10.1023/A:1022896515287 |pmid=12751889 |s2cid=25806501}}</ref> It has been suggested that the original function of lactation (milk production) was keeping eggs moist. Much of the argument is based on [[monotreme]]s (egg-laying mammals).<ref name="Oftedal 2002 225–252"/><ref>{{cite journal |last1=Oftedal |first1=Olav T. |title=The origin of lactation as a water source for parchment-shelled eggs |journal=Journal of Mammary Gland Biology and Neoplasia |volume=7 |issue=3 |pages=253–66 |year=2002 |pmid=12751890 |doi=10.1023/A:1022848632125 |s2cid=8319185}}</ref><ref>{{cite web |url=http://nationalzoo.si.edu/ConservationAndScience/SpotlightOnScience/oftedalolav20030714.cfm |archive-url=https://web.archive.org/web/20090414083919/http://nationalzoo.si.edu/ConservationAndScience/SpotlightOnScience/oftedalolav20030714.cfm |archive-date=April 14, 2009 |title=Lactating on Eggs |publisher=Nationalzoo.si.edu |date=July 14, 2003 |access-date=March 8, 2009}}</ref> The original adaptive significance of milk secretions may have been nutrition<ref>{{Cite journal |vauthors=Lefèvre CM, Sharp JA, Nicholas KR |title=Evolution of lactation: ancient origin and extreme adaptations of the lactation system |pmid=20565255 |journal=Annual Review of Genomics and Human Genetics |issue=1 |pages=219–38 |year=2010 |volume=11 |doi=10.1146/annurev-genom-082509-141806}}</ref> and immunological protection.<ref>{{Cite journal |vauthors=Vorbach C, Capecchi MR, Penninger JM |title=Evolution of the mammary gland from the innate immune system? |journal=BioEssays |volume=28 |pages=606–16 |year=2006 |pmid=16700061 |doi=10.1002/bies.20423 |issue=6}}</ref><ref>{{Cite journal |author=Goldman A.S. |title=Evolution of the mammary gland defense system and the ontogeny of the immune system |pmid=12751892 |url=http://pages.usherbrooke.ca/infosbio/PSL705/temp/evolution%20immune%20system.pdf |journal=Journal of Mammary Gland Biology and Neoplasia |issue=3 |pages=277–89 |year=2002 |volume=7 |doi=10.1023/A:1022852700266 |s2cid=19388426 |url-status=dead |archive-url=https://web.archive.org/web/20130620033141/http://pages.usherbrooke.ca/infosbio/PSL705/temp/evolution%20immune%20system.pdf |archive-date=June 20, 2013}}</ref><ref>{{cite web|last1=Stannard|first1=Hayley J.|last2=Old|first2=Julie J.|title=Wallaby joeys and platypus puggles are tiny and undeveloped when born. But their mother's milk is near-magical|url=https://theconversation.com/wallaby-joeys-and-platypus-puggles-are-tiny-and-undeveloped-when-born-but-their-mothers-milk-is-near-magical-207726|publisher=The Conversation|year=2023|access-date=October 25, 2023|archive-date=November 10, 2023|archive-url=https://web.archive.org/web/20231110202925/https://theconversation.com/wallaby-joeys-and-platypus-puggles-are-tiny-and-undeveloped-when-born-but-their-mothers-milk-is-near-magical-207726|url-status=live}}</ref><ref>{{cite journal|last1=Stannard|first1=Hayley J.|last2=Miller|first2=Robert D.|last3=Old|first3=Julie M.|title=Marsupial and monotreme milk – a review of its nutrients and immune properties|journal=PeerJ|year=2020|volume=8|page=e9335|doi=10.7717/peerj.9335 |pmid=32612884 |pmc=7319036 |doi-access=free }}</ref>

[[Tritylodontidae|Tritylodontid]] [[cynodont]]s seem to have displayed lactation, based on their dental replacement patterns.<ref>{{cite journal |last1=Hu |first1=Yaoming |last2=Meng |first2=Jin |last3=Clark |first3=James M |year=2009 |title=A New Tritylodontid from the Upper Jurassic of Xinjiang, China |journal=Acta Palaeontologica Polonica |volume=54 |issue=3 |pages=385–91 |doi=10.4202/app.2008.0053|doi-access=free}}</ref>