Editing Human–animal hybrid (section)

===Background and technological analyses===
{{see also|History of genetic engineering}}

[[File:Bluetomato.jpg|thumb|right|upright|These [[Blue tomato|blue-colored tomatoes]] are an example of a [[genetically modified food]].]]

Broadly speaking, a [[Hybrid (biology)|hybrid]] being has one cell line throughout its entire body and came originally from a mix of entities, with different species involved to make a new genetic combination. For instance, a [[liger]] has a lion father and a [[tigress]] mother, such a creature only existing in [[Captivity (animal)|captivity]]. Such hybridization has frequently caused difficult health problems that caregivers for the captive animals struggle with.<ref name=zonkey>{{cite web|last=Palmer|first=Roxanne|date=July 25, 2013|title=Zonkey, Wholphin, Liger, Tigon: Fascinating Animal Hybrids|url=http://www.ibtimes.com/zonkey-wholphin-liger-tigon-fascinating-animal-hybrids-photos-1359907|website=[[International Business Times]]|accessdate=August 8, 2015}}</ref>

A [[chimera (biology)|chimera]] is not the same thing as a hybrid because it is a being composed of two or more genetically distinct cell lines in one entity. The entity does not exist as a member of a separate species but has differing elements inside of it. An animal that has experienced an [[organ transplant]] or related surgery involving tissues from a different species is an example.<ref name=Mott/>

Throughout past [[human evolution]], hybridization occurred in many different instances, such as cross-breeding between [[Neanderthal]]s and ancient versions of what are now modern humans. Some scientists have believed that particular genes of the Neanderthal may have been key to ancient humans' adapting to the harsh [[climate]]s they faced [[Recent African origin of modern humans|when they left Africa]]. However, mixing between species in the wild both now and through natural history have generally resulted in [[Infertility|sterile offspring]], thus being a kind of dead end in reproductive terms.<ref name=zonkey/>

For much of modern history, the creation of [[genetically modified organism]]s in general was a topic rooted in fiction rather than practical research. This has changed significantly over the past few decades such that a number of plants and animals are commonly subject to [[genetic engineering]] for commercial purposes. For example, as of 2013 about 85% of the corn grown in the US as well as about 90% of its [[canola]] crops have been genetically modified.<ref name=foods/> As well, many Americans that have had cardiovascular surgery have had heart valves initially from pigs used in their procedures.<ref name=Weiss>{{cite news|url=https://www.washingtonpost.com/wp-dyn/articles/A19781-2005Feb12.html|last=Weiss|first=Rick|date=February 13, 2005|title=U.S. Denies Patent for a Too-Human Hybrid|newspaper=[[The Washington Post]]|accessdate=August 8, 2015}}</ref>

Issues relating to possible human-animal hybrids outside of a fictional, historical, or mythic context but as real, engineered beings received major international attention in 2003, after some Chinese scientists at the [[Shanghai Jiao Tong University School of Medicine|Shanghai Second Medical University]] managed to successfully fuse human cells with rabbit eggs. The embryos formed reportedly were the first stable human-animal chimeras in existence. Research in similar areas continued into 2004 and 2005, with the topic picking up coverage from publications such as ''[[National Geographic News]]''. The [[National Academy of Sciences]] soon began to look into the ethical questions involved.<ref name=Mott/> The [[U.S. Patent and Trademark Office]] additionally stirred interest into the topic by granting a patent request for a genetically modified mouse with a human [[immune system]].<ref name=Weiss/> Scientists announced in 2017 that they successfully created the first human-pig chimeric embryo. The embryo consisted mostly pig cells and some human cells. Scientists stated that they hope to use this technology to address the shortage of donor organs.<ref>{{Cite news|url=http://news.nationalgeographic.com/2017/01/human-pig-hybrid-embryo-chimera-organs-health-science/|title=Human-Pig Hybrid Created in the Lab—Here Are the Facts|date=2017-01-26|access-date=2017-01-27}}</ref><ref>{{Cite journal|last=Wu|first=Jun|last2=Platero-Luengo|first2=Aida|last3=Sakurai|first3=Masahiro|last4=Sugawara|first4=Atsushi|last5=Gil|first5=Maria Antonia|last6=Yamauchi|first6=Takayoshi|last7=Suzuki|first7=Keiichiro|last8=Bogliotti|first8=Yanina Soledad|last9=Cuello|first9=Cristina|last10=Valencia|first10=Mariana Morales|last11=Okumura|first11=Daiji|date=2017-01-26|title=Interspecies Chimerism with Mammalian Pluripotent Stem Cells|url=https://www.cell.com/cell/abstract/S0092-8674(16)31752-4|journal=Cell|language=English|volume=168|issue=3|pages=473–486.e15|doi=10.1016/j.cell.2016.12.036|issn=0092-8674|pmc=5679265|pmid=28129541}}</ref> In July 2019, Japanese scientist [[Hiromitsu Nakauchi]] got the approval of the Japanese government to experiment with inserting human [[stem cell]]s into animal (particularly [[rodent]]) embryos.<ref>{{Cite journal|last=Cyranoski|first=David|date=2019-07-26|title=Japan approves first human-animal embryo experiments|url=http://www.nature.com/articles/d41586-019-02275-3|journal=Nature|language=EN|doi=10.1038/d41586-019-02275-3}}</ref> Although its main use will be to make organ transplantation easier, this can be considered the first more effective step of making animal-human hybrids real.