In spite of the usual convention of portmanteau words to describe hybrids, there is no consensus as to which word to use, though "chuman" or "humanzee" are used in popular speech. Geneticists adhere to the portmanteau word convention to indicate which species is the sire.(cf. tigon/liger) This is important because of the phenomenon of genomic imprinting where genes are expressed differently depending on which parent contributed them. Hybrids are named according to the convention first part of sire's name + second part of dam's name (except where the result is unwieldy). For geneticists, "Chuman" therefore refers to a hybrid of male chimpanzee and female human, while "Humanzee" or "manpanzee" refers to a hybrid of male human and female chimpanzee.
Humans have one fewer pair of chromosomes than other apes, since the ape chromosomes 2 and 4 have fused into a large chromosome (which contains remnants of the centromere and telomeres of the ancestral 2 and 4) in humans. 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.
The genetic structure of all the great apes is similar. Chromosomes 6, 13, 19, 21, 22, and X are structurally the same in all great apes. 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 will include Y as a match between gorillas, chimps, and humans, but chimpanzees (including bonobos) and humans have recently been found to share a large transposition from chromosome 1 to Y that is not found in other apes.
This level 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. 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 possessing between 44 and 62 depending upon species. In a direct parallel to the chimp-human case, the Przewalski horse (Equus przewalskii) with 33 chromosome pairs, and the domestic horse (E. caballus) with 32 chromosome pairs, have been found to be interfertile, and produce semi-fertile offspring, where male hybrids can breed with female domestic horses.).
In the 1920s the Soviet biologist Ilya Ivanovich Ivanov carried out a series of experiments to create a human/non human ape hybrid. At first working with human sperm and chimpanzee females, none of his attempts created a pregnancy. [來源請求] In 1929 he organized a set of experiments involving non human ape sperm and human volunteers, but was delayed by the death of his last orangutan. [來源請求] 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 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 man alone, it probably is restricted to the Hominoidea.
In 2006, research suggested that after the last common ancestor of humans and chimpanzees diverged into two distinct lineages, inter-lineage sex was still sufficiently common that it produced fertile hybrids for around 1.2 million years after the initial split.
However, despite speculation, no case of a human-chimpanzee cross has ever been confirmed to exist.[來源請求]
The Ivanov experiments[编辑]
Ilya Ivanovich Ivanov was the first to actually attempt to create a human-ape hybrid. As early as 1910 he had given a presentation to the World Congress of Zoologists in Graz, Austria in which he described the possibility of obtaining such a hybrid through artificial insemination.
In 1924, while working at the Pasteur Institute in Paris, Ivanov obtained permission from the Institute's directors to use its experimental primate station in Kindia, French Guinea, for such an experiment. Ivanov attempted to gain backing for his project from the Soviet government. He dispatched letters to the People's Commissar on Education and Science Anatoliy Vasilievich Lunacharsky and to other officials. Ivanov's proposal finally sparked the interest of Nikolai Petrovich Gorbunov, the head of the Department of Scientific Institutions. In September 1925 Gorbunov helped allocate US$10,000 to the Academy of Sciences for Ivanov's human-ape hybridization experiments in Africa.
In March 1926 Ivanov arrived at the Kindia facility, but stayed only a month without success. The Kindia site, it turned out, had no sexually mature chimpanzees. He returned to France where he arranged through correspondence with French Guinea's colonial governor to set up experiments at the botanical gardens in Conakry.
Ivanov reached Conakry in November 1926 accompanied by his son, also named Ilya, who would assist him in his experiments. Ivanov supervised the capture of adult chimpanzees in the interior of the colony, which were brought to Conakry and kept in cages in the botanical gardens. On February 28, 1927, Ivanov artificially inseminated two female chimpanzees with human sperm. On June 25, he artificially inseminated a third chimpanzee with human sperm. The Ivanovs left Africa in July with thirteen chimps, including the three used in his experiments. They already knew before leaving that the first two chimpanzees had failed to become pregnant. The third died in France, and was also found not to have been pregnant. The remaining chimps were sent to a new primate station at Sukhumi.
Although Ivanov attempted to organize the insemination of human females with chimpanzee sperm in Guinea, these plans met with resistance from the French colonial government and there is no evidence such an experiment was arranged there.
Upon his return to the Soviet Union in 1927, Ivanov began an effort to organize hybridization experiments at Sukhumi using ape sperm and human females. Eventually in 1929, through the help of Gorbunov, he obtained the support of the Society of Materialist Biologists, a group associated with the Communist Academy. In the spring of 1929 the Society set up a commission to plan Ivanov's experiments at Sukhumi. They decided that at least five volunteer women would be needed for the project. However, in June 1929, before any inseminations had taken place, Ivanov learned that the only postpubescent male ape remaining at Sukhumi (an orangutan) had died. A new set of chimps would not arrive at Sukhumi until the summer of 1930.
There have been occasional reports and rumors of humanzees throughout history. St. Peter Damian, in his 11th century De bono religiosi status et variorum animantium tropologia, tells of a Count Gulielmus whose pet ape became his wife's lover. One day the ape became "mad with jealousy" on seeing the count lying with his wife and it fatally attacked him. Damian claims he was told about this incident by Pope Alexander II and shown a creature named "Maimo", which was supposed to be the offspring of the countess and the ape.
There have been no scientifically verified specimens of a human/ape hybrid, although a performing chimp named Oliver was popularized during the 1970s as a possible Chuman/Humanzee. Genetic tests conducted at the University of Chicago concluded that, despite Oliver's somewhat unusual appearance and behavior, he was a normal chimpanzee; he had the same number of chromosomes as normal chimpanzees. The "hybrid" claims were possibly a promotional gimmick. As a result of being humanized (habituated to humans rather than to chimps), Oliver was said to be attracted to female humans, and did not mate with chimpanzees.
An episode of Unsolved History, Humanzee, originally broadcast on the Discovery Channel on March 27, 1998, discussed the controversies over Oliver the chimp and also detailed some of the rumors and urban legends about "humanzees". One claim was that a common chimpanzee was impregnated by human sperm in a laboratory in China, but died from neglect before giving birth during the Chinese Cultural Revolution in the 1960s. A similar story, reported by University at Albany psychologist Gordon Gallup, alleged that a human-chimp hybrid was successfully engendered and born during experiments by Robert Yerkes or his staff at the Yerkes National Primate Research Center in Orange Park, Florida in the 1920s, but was destroyed by the scientists soon after. Gallup claimed he heard the story as a young graduate student, when an elderly academic confided in him that he had been part of the team behind the experiment. Gallup added that he feels the colleague telling him of this genuinely believed the story to be true but that he, Gallup, has never been able to prove it one way or another.
Looking back millions of years into early human history, current research into human evolution tends to confirm that in some cases, interspecies sexual activity may have been a key part of human evolution. Analysis of the species' genes in 2006 provides evidence that after humans had started to diverge from chimps, interspecies mating between "proto-human" and "proto-chimps" nonetheless occurred regularly enough to change certain genes in the new gene pool:
- "A new comparison of the human and chimp genomes suggests that after the two lineages separated, they may have begun interbreeding... A principal finding is that the X chromosomes of humans and chimps appear to have diverged about 1.2 million years more recently than the other chromosomes."
The research suggests that:
- There were in fact two splits between the human and chimp lineages, with the first being followed by interbreeding between the two populations and then a second split. The suggestion of a hybridization has startled paleoanthropologists, who nonetheless are 'treating the new genetic data seriously.
- Naming Hybrid Big Cats from Messybeast.com accessed march 15, 2009
- IJdo JW, Baldini A, Ward DC, Reeders ST, Wells RA. Origin of human chromosome 2: an ancestral telomere-telomere fusion. Proc. Natl. Acad. Sci. U.S.A. 1991, 88 (20): 9051–5. . PMID 1924367. 已忽略未知参数
- Wimmer R, Kirsch S, Rappold GA, Schempp W. Direct Evidence for a Pan-Homo Clade. Chromosome Research: 55–61. doi:10.1023/A:1014222311431.
- Chandley, AC; Short, RV; Allen, WR. Cytogenetic studies of three equine hybrids. Journal of Reproductive Fertility. 1975, (23): 356–70. PMID 1060807.
- Bedford JM. Sperm/egg interaction: the specificity of human spermatozoa. Anat. Rec. 1977, 188 (4): 477–87. PMID 409311. doi:10.1002/ar.1091880407. 已忽略未知参数
- Brown, David. Human Ancestors May Have Interbred With Chimpanzees. Washington Post. May 18, 2006: A01 [2006-06-13].
- Rossiianov, Kirill. Beyond species: Il'ya Ivanov and his experiments on cross-breeding humans with anthropoid apes. Science in Context. 2002, 15 (2): 277–316. PMID 12467272.
- 10. Oliver the Mutant Chimp. [2006-03-11]. （原始内容存档于2005-12-28）.
- Wade, Nicholas. "Two Splits Between Human and Chimp Lines Suggested", The New York Times, 18 May 2006.