Hypothetical chimpanzee–human hybrid
|Hybrid:||Homo sapiens × Pan troglodytes|
The humanzee (Homo sapiens × Pan) is a hypothetical hybrid of chimpanzee and human. Serious attempts to create such a hybrid were made by Soviet biologist Ilya Ivanovich Ivanov in the 1920s, and possibly by researchers in the People's Republic of China in the 1960s, though neither succeeded. The portmanteau word humanzee for a human–chimpanzee hybrid appears to have entered usage in the 1980s.
The possibility of hybrids between humans and other apes has been entertained since at least the medieval period; Saint Peter Damian (11th century) claimed to have been told of the offspring of a human woman in Liguria who had mated with an ape, and so did Antonio Zucchelli, an Italian Franciscan capuchin friar who was a missionary in Africa from 1698 to 1702, and Sir Edward Coke in "The Institutes of the Lawes of England".
Chimpanzees and humans are closely related, sharing 95% of their DNA sequence and 99% of coding DNA sequences. The closest known data is that hybridization between chimpanzees and bonobos, which share 99.6% of the genome (and see the chart) is easily possible. Some authors even say that "the population split between bonobo and chimpanzee occurred relatively close in time to the split between the bonobo–chimpanzee ancestor (i.e., the ancestor of the genus Pan) and humans", or that Pan, especially bonobos, are a "living fossil" close to our ancestors, "Pan prior". Genetic similarity, and thus the chances of successful hybridization, is not always correlated with visual similarity. For example, pugs and huskies look quite dissimilar (perhaps more so than some chimpanzees, bonobos, or even gorillas look compared to humans), but belong to the same species and subspecies and can hybridize freely. On the other hand, rabbits and hares look very similar, but are only distantly related and cannot hybridize.
Humans have one pair fewer chromosomes than other apes, with ape chromosomes 2 and 4 fused in the human genome into a large chromosome (which contains remnants of the centromere and telomeres of the ancestral 2 and 4). Having different numbers of chromosomes is not an absolute barrier to hybridization; similar mismatches are relatively common in existing species, a phenomenon known as chromosomal polymorphism.
All great apes have similar genetic structure. Chromosomes 6, 13, 19, 21, 22, and X are structurally the same in all great apes. Chromosomes 3, 11, 14, 15, 18, and 20 match between gorillas, chimpanzees, and humans. Chimps and humans match on 1, 2p, 2q, 5, 7–10, 12, 16, and Y as well. Some older references include Y as a match between gorillas, chimps, and humans, but chimpanzees, bonobos, and humans have recently been found to share a large transposition from chromosome 1 to Y not found in other apes.
This degree of chromosomal similarity is roughly equivalent to that found in equines. Interfertility of horses and donkeys is common, although sterility of the offspring (mules) is nearly universal (with only around 60 exceptions recorded in equine history). Similar complexities and prevalent sterility pertain to horse–zebra hybrids, or zorses, whose chromosomal disparity is very wide, with horses typically having 32 chromosome pairs and zebras between 16 and 23 depending on species. In a direct parallel to the chimp–human case, the Przewalski's horse (Equus ferus przewalskii) with 33 chromosome pairs, and the domestic horse (E. f. caballus) with 32 pairs, have been found to be interfertile, and produce semi-fertile offspring: male hybrids can breed with female domestic horses.
In 1977, researcher J. Michael Bedford discovered that human sperm could penetrate the protective outer membranes of a gibbon egg. Bedford's paper also stated that human spermatozoa would not even attach to the zona surface of non-hominoid primates (baboon, rhesus monkey, and squirrel monkey), concluding that although the specificity of human spermatozoa is not confined to Homo sapiens sapiens alone, it is probably restricted to the Hominoidea. However, in the opposite direction of closely related species, it has been found that human sperm binds to gorilla oocytes with almost the same ease as to human ones.
Hybridization between members of different, but related genera is sometimes possible, as in the case of cama (camel and llama), wholphin (common bottlenose dolphin and false killer whale), and some felid hybrids, for example.
Reports of attempted hybridization
There have been no scientifically verified specimens of a human–chimp hybrid, but there have been substantiated reports of unsuccessful attempts at human/chimpanzee hybridization in the Soviet Union in the 1920s, and various unsubstantiated reports on similar attempts during the second half of the 20th century.
Ilya Ivanovich Ivanov was the first person to attempt to create a human–chimp hybrid by artificial insemination. Ivanov outlined his idea as early as 1910 in a presentation to the World Congress of Zoologists in Graz. In the 1920s, Ivanov carried out a series of experiments, culminating in inseminating three female chimpanzees with human sperm, but he failed to achieve a pregnancy. (For comparison with known cama statistics, in the case of male camel - female guanaco cross the probability that insemination would lead to pregnancy was approximately 1/6:) In 1929 he organized a set of experiments involving nonhuman ape sperm and human volunteers, but was delayed by the death of his last orangutan. The next year he fell under political criticism from the Soviet government and was sentenced to exile in the Kazakh SSR; he worked there at the Kazakh Veterinary-Zootechnical Institute and died of a stroke two years later.
In the 1970s, a performing chimp named Oliver was popularized as a possible "mutant" or even a human–chimpanzee hybrid. Claims that Oliver had 47 chromosomes—midpoint between the normal 46 for humans and 48 for chimpanzees—were disproven after an examination of his genetic material at the University of Chicago in 1996. Oliver's cranial morphology, ear shape, freckles, and baldness fall within the range of variability exhibited by the common chimpanzee. Results of further studies with Oliver were published in the American Journal of Physical Anthropology.
In the 1980s, there were reports on an experiment in human–chimpanzee crossbreeding conducted in the People's Republic of China in 1967, and on the planned resumption of such experiments. In 1981, Ji Yongxiang, head of a hospital in Shenyang, was reported as claiming to have been part of a 1967 experiment in Shengyang in which a chimpanzee female had been impregnated with human sperm. According to this account, the experiment came to nothing because it was cut short by the Cultural Revolution, with the responsible scientists sent off to farm labour and the three-months pregnant chimpanzee dying from neglect. According to Timothy McNulty of Chicago Tribune, the report was based on an article in the Wenhui Bao paper of Shanghai. Li Guong of the genetics research bureau at the Chinese Academy of Sciences was cited as confirming both the existence of the experiment prior to the Cultural Revolution and the plans to resume testing.
In 2019, unconfirmed reports surfaced that a team of researchers led by Professor Juan Carlos Izpisua Belmonte from the Salk Institute for Biological Studies in the U.S. successfully produced the first human-monkey chimeras. Belmonte and others had previously produced pig and sheep embryos containing a small percentage of human cells. As with those embryos, the human-monkey chimeras were reportedly only allowed to develop for a few weeks. Although development was stopped prior to the formation of a nervous system or organs, avoiding more severe ethical concerns, the research was reportedly carried out in China to avoid legal issues. Due to the much larger evolutionary distance between humans and monkeys, vs. humans and chimpanzees, it is considered unlikely that true human-monkey hybrids could be brought to term. However, it is feasible that human-compatible organs for transplantation could be grown in these chimeras.
Evidence for early hominin hybridization
There is evidence for a complex speciation process for the Pan–Homo split. This concerns times pre-dating the emergence of Homo and would concern hybridization between Pan and Ardipithecus or Orrorin, not Homo. Different chromosomes appear to have split at different times, suggesting that large-scale hybridization may have taken place over a period of as much as four million years leading up to the two emerging ("human" and "chimp") lineages as late as six million years ago. The similarity of the X chromosome in humans and chimpanzees might suggest hybridization taking place as late as four million years ago. This latter conclusion should be regarded as uncertain, with alternative proposals available to explain the apparent short divergence time in the X chromosome.
Humanzees in fiction
- Almost Human (2015) ISBN 1478752394 and Becoming Human (2018) by Kenneth L. Decroo, ISBN 0648417123
- "Chromosome 6" (1998) by Robin Cook.
- Gor Saga by Maureen Duffy (1982). It was adapted into the 1988 television serial First Born. The novel and serial concern, not a chimpanzee-human hybrid, but a genetic gorilla-human hybrid, who appears human.
- Humanzee by Susan Gates (1998), ISBN 978-0192717962.
- Leopold & Brink by Christopher Alan Fink (1997-). Brink is a human/bonobo hybrid.
- Les orchidées de Staline (2017) by Corinne De Vailly and Normand Lester, ISBN 978-2374532325.
- Lucy by Laurence Gonzales (2010), ISBN 978-0307473905.
- Next (2006) by Michael Crichton, ISBN 978-0060873165.
- Sims by F. Paul Wilson
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- "Darwin's Incident" (2020) by Shun Umezawa, ISBN 978-4-06-521398-8.
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- Damiani, Saint Petri (1853). Constantinus Caietanus (ed.). Chap. 29: De simia, et quo pacto simia capi possit.. Patrologia Latina. Opus 52: De Bono Religiosi Status et Variarum Animantium Topologia (in Latin). 145. pp. 789, 790. Retrieved 4 September 2019.
Ait [Alexander papa] enim quia nuper comes Gulielmus in Liguriae partibus habitans marem habebat simiae, qui vulgo maimo dicitur, cum quo et uxor eius, ut erat impudica prorsus ac petulans, lascivius jocabatur. Nam et ego duos eius filios vidi, quos de episcopo quodam plectibilis lupa pepererat; ... cum femina fera concubuit; ... Enimvero nuper allatus est praefato papae, et simul et nobis grandiusculus quidam puer; et si jam, ut dicitur, vicennalis, tamen prorsus elinguis et maimoni forma consimilis, ita ut eodem vocabulo nuncupetur. ("For [ Pope Alexander II ] says that recently Count William who lived in the area of Liguria had a male ape, who was called maimo [?], with which also his wife, as she was exceedingly impudent and wanton, played in a more lascivious manner. For I also have seen two sons of hers which the punishable whore bore of a certain bishop. ... the beast mated with the woman; ... So then, according to the pope's account, at the same time as for us, a rather large boy was born; and although, as it is said, he is already 20 years old, he is still unable to speak and looks like the maimo, so he is called by that same name.")
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- Wong, Kate (2014). "The 1 Percent Difference". Scientific American. 311 (3): 100. Bibcode:2014SciAm.311c.100W. doi:10.1038/scientificamerican0914-100. PMID 25211913.
- "The bonobo, the non-murderous version of the chimpanzee, gets its genome mapped". Christian Science Monitor. 2012-06-13.
- "Hybrids between common chimpanzees (Pan troglodytes) and pygmy chimpanzees (Pan paniscus) in captivity".
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- An example of a pug-husky hybrid: https://i.redd.it/n1775c7jjkhz.jpg
- Darren. "Can Rabbits And Hares Breed?". Bunny Advice. Retrieved August 11, 2021.
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- Hill, WCO; in Bourne, GH (1969). Anatomy, behavior, and diseases of chimpanzees (The Chimpanzee. 1. S. Karger. pp. 22–49.
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- "The Baltimore Sun from Baltimore, Maryland on February 12, 1981 · 3".
- "Li Guong, of the genetics research bureau of the Academy of Science treats it seriously. 'My personal view is that it is possible [...] We also did experimental work on this before the Cultural Revolution, but we were stopped. At the moment, we plan to arrange further tests.'" Timothy McNulty, "Chinese Aim To Implant Human Sperm In Chimps", St. Petersburg Independent 12 February 1981, p. 19. "Chinese May Resume Experiments to Create 'Near-Human' Ape", Houston Post (from Chicago Tribune), 15 February 1981, p. 19, cited after Justin Leiber, Can Animals and Machines be Persons?: A Dialogue, Hackett Publishing, 1985 p. 71.
- Davis, Nicola (2019-08-03). "First human-monkey chimera raises concern among scientists". The Guardian. ISSN 0261-3077. Retrieved 2019-09-14.
- Patterson N, Richter DJ, Gnerre S, Lander ES, Reich D (June 2006). "Genetic evidence for complex speciation of humans and chimpanzees". Nature. 441 (7097): 1103–8. Bibcode:2006Natur.441.1103P. doi:10.1038/nature04789. PMID 16710306. S2CID 2325560.
- Wakeley J (March 2008). "Complex speciation of humans and chimpanzees". Nature. 452 (7184): E3–4, discussion E4. Bibcode:2008Natur.452....3W. doi:10.1038/nature06805. PMID 18337768. S2CID 4367089. "Patterson et al. suggest that the apparently short divergence time between humans and chimpanzees on the X chromosome is explained by a massive interspecific hybridization event in the ancestry of these two species. However, Patterson et al. do not statistically test their own null model of simple speciation before concluding that speciation was complex, and—even if the null model could be rejected—they do not consider other explanations of a short divergence time on the X chromosome. These include natural selection on the X chromosome in the common ancestor of humans and chimpanzees, changes in the ratio of male-to-female mutation rates over time, and less extreme versions of divergence with gene flow. I therefore believe that their claim of hybridization is unwarranted." Wade, Nicholas. "Two Splits Between Human and Chimp Lines Suggested", The New York Times, 18 May 2006. For a chromosomal homology map between these species see. Pratas, D; Silva, R; Pinho, A; Ferreira, P (May 18, 2015). "An alignment-free method to find and visualise rearrangements between pairs of DNA sequences". Scientific Reports. 5: 10203. Bibcode:2015NatSR...510203P. doi:10.1038/srep10203. PMC 4434998. PMID 25984837.