Hybrids have always fascinated cryptozoologists and, as we shall see, they are still implicated in the creation of les bêtes ignorées. Hybrid appeal is nothing new. Between the thirteenth and fifteenth century fabulous creatures from the union of one or more different species inhabited all medieval bestiaries. Among the favourites were the griffon, with the body of a lion and the wings of an eagle, the leucrota, having the haunches of a stag, the breast and shins of a lion and the head of a horse, and the yale, sporting the tail of an elephant and the face of a boar.
However, contrary to what you might now think after reading the previous chapter or browsing through early manuscripts, successful hybridisation through interbreeding is actually very rare in most mammals, especially in the wild. Whereas it is, in theory anyway, comparatively uncomplicated for two closely related species to breed in captivity, the offspring are generally not as fit and healthy as their parents. In the wild, without the care and attention of the zookeepers, they would be eliminated in the face of competition from the two parent species who have had, after all, millions of years of adaptive evolution to come to terms with their environment. However in captivity, protected from this fatal competition, hybrids can thrive. Famous examples are the offspring of tigers and lions, the liger (lion father, tiger mother) and the tigon with the opposite parentage. They are healthy, indeed typically the liger is larger than either of its parents. The trouble begins when they come to breed, as the males of both hybrids have very low sperm counts, though the females are normally fertile. This follows what has become known as Haldane's rule, named after the evolutionary biologist J.B.S. Haldane who formulated it in 1922. Haldane's rule states that in a hybrid the heterogametic sex is disadvantaged by low fitness or sterility. It governs all sorts of hybrids, both plant and animal.
The mechanisms behind Haldane's rule are complex, and need not concern us here, but the consequences for ligers and tigons, not to mention theoretical hybrids between different human species, is that males (the heterogametic sex, as males have X and Y chromosomes while females have two identical X chromosomes) are usually infertile while female hybrids are not. In a Homo neanderthalensis x sapiens hybrid, whichever way round the parentage is arranged, the girls will have a better chance of being fertile than the boys.
Haldane's rule is not the only problem for hybrids. In all species, nuclear DNA is carried on chromosomes. While different species vary in their numbers of chromosomes, typically between ten and fifty, there is no tolerance of variation in chromosome count. One chromosome too many or one too few always leads to a serious medical condition, like Down's syndrome in humans, where sufferers carry an extra chromosome number 21. If the two parent species of a hybrid have different numbers of chromosomes, breeding is ruled out altogether as both sexes will be infertile. That female ligers and tigons can produce offspring at all is because their parents have the same numbers of chromosomes. It is not just that the lion and tiger parents are genetically fairly close, being two species in the same genus, but the equality in their chromosome count that allows the hybrids to breed. If the parental chromosome numbers of a hybrid are different, then it will be infertile. The most famous example is the mule, a hybrid between a horse and a donkey, each of which have different numbers of chromosomes. Although perfectly fit and healthy themselves, mules cannot produce viable germ cells – that is, eggs or sperm. The reason here is that the hybrid mule has an odd number of chromosomes. In this situation, any germ cells that are formed will have either one too many or one too few chromosomes. What generally happens is that the germ cells give up trying to sort this out and fail to form at all.
When it comes to humans and the sapiens x neanderthalensis hybrids that the DNA tells us have introduced the Neanderthal component into modern European genomes, both parents must have the same chromosome count. Although we and our Neanderthal cousins are far more closely related than tigers and lions, chromosomal compatibility does not necessarily follow from this evolutionary proximity. Our nearest primate relatives, chimpanzees, gorillas and orang-utans, have one extra pair of chromosomes compared to humans because, at some point in our evolution after we split from the great apes, two ancestral chromosomes fused to become our chromosome number 2. This chromosome imbalance is the reason why a chimp x human hybrid, the so far only theoretical humanzee, would certainly be infertile. Like the mule, a humanzee would not form sperm or eggs. Until very recently we did not know where on the tree of human evolution this chromosome fusion occurred. If it was during the last half million years, that is after humans and Neanderthal last shared a common ancestor, the two human species would have different chromosome counts and any hybrids would be infertile, like the mule. If the chromosome fusion occurred before the split between the two human lines, then both H. sapiens and H. neanderthalensis would have the same number of chromosomes and fertile hybrids would not be ruled out by numerical incompatibility. But what is the answer? The best way to find out is to look at the chromosomes under a microscope, but to do that requires having live cells which is, of course, impossible with Neanderthals – or at least it is until one is found alive.
Of more immediate importance to our own interest in the question of hybridisation is that the high-quality Denisovan genome sequence contained information about the chromosome number. Chromosomes are essentially very long linear strands of DNA made up of only four chemical units abbreviated A, T, C and G. DNA is a code which conveys instructions on how to build and run an organism from one generation to the next. As in any code, like a word, it is not so much the letters themselves but the order in which they occur that matters. Although the DNA alphabet has only four letters, the possible combinations are almost infinite. The sequence is all. At both ends of human and primate chromosomes there is a stretch of DNA with the sequence GGGGTT. When the ends of the two primate chromosomes fused to form human chromosome 2, these sequences of GGGGTT met head to head at the join to create the sequence GGGGTTTTGGGG. This joining segment has remained in the genome of Homo sapiens ever since. A search of the Denisovan genome found these head-to-head fragments, presumably from the fused chromosome 2, but the same search in the chimpanzee genome, where the chromosomes are still separate, found none. While perhaps not quite as conclusive as counting the chromosomes of living cells under a microscope, it is pretty good evidence that the ancestral chromosome fusion had already occurred by the time the Denisovans appeared on the scene. As that was probably half a million years before the Neanderthals, it looks as though the barrier of numerical incompatibility between the different hominids had never been erected. We were all free to breed with each other and live to see our daughters at least, remembering Haldane's rule, produce healthy grandchildren.
Even if hybrids between ourselves and our great ape cousins would not be fertile, would they ever be conceived, let alone born live? Bernard Heuvelmans was especially fascinated by the prospect, as I discovered in his archive in Lausanne when I looked through his bulging box files of press cuttings and scientific papers on the topic. One file, coloured pink and intriguingly entitled ‘Hybrides: Vrais, présumes et fabuleux’ (Hybrids: True, presumed and fabulous), contained a wide range of material from, at one extreme, academic papers, such as Richard Van Gelder's essay on the classification of genera and species written for the American Museum of Natural History in New York1 to, at the other, a tabloid French magazine's coverage of ‘Queen Kong: The Liberated Lady Gorilla’ illustrated by a picture of the firmly-bosomed pongid, hair swept back under a golden hairband, perched on top of a skyscraper under attack by fighter planes while clasping a hapless man in her giant hands.
In between these two extremes were cuttings of newspaper reports of actual human-ape hybrids, the most famous of which was Oliver. But before we come to him, I was astonished to come across an article in Heuvelmans' files written in 1908 by one Herman Bernolet-Moens and titled ‘Experimental Researches about the descent of Man’.2 Bernolet-Moens was a Dutch amateur scientist and scholar who, in this article, announced that he was on his way to the French Congo, which at the time covered the present-day Republic of the Congo, Gabon and the Central African Republic, in order to undertake experiments into human evolution. He had, so he said, the full support of the French government in this endeavour.
In one section of the article called ‘The Artificial Fecundation of Mature Female of the Anthropoid Apes with the Sperm of Man’ he made his intentions abundantly clear, stating the ‘gorilla and chimpanzee will be especially fecundated with negro sperm’. In a space reserved for the anticipated results he placed a large question mark and the undertaking that ‘when my work in the Congo shall be over I will substitute the result of my experiments for this point of interrogation’. This intriguing publication was a declaration of intent, a prospectus with an invitation for readers to contribute. It finished with an appeal: ‘. . . I trust to be favoured with the help of my readers who feel sympathy for my enterprise’ adding that he had already received a donation from none other than Her Majesty the Queen of the Netherlands and from other members of the Dutch royal family. As far as I have been able to discover, Bernolet-Moens never did fill in the space reserved by the question mark. In fact, it's unclear whether he even began what to us now seems an abhorrent experiment.
Bernolet-Moens was later involved in a scandal when, in 1919, he was indicted for taking photographs of African-American schoolchildren in Washington DC, ostensibly to progress his anatomical studies. From being admired as a scholar his reputation rapidly plummeted to revulsion as a suspected paedophile. With time public perception of Bernolet-Moens swung back to respectability and he was one of the first to promote inter-racial mixing as a way to improve the prospects for our species. This view was in complete contrast to the prevailing eugenic philosophy, which we would now see as rabidly racist, which was to discourage interbreeding across ethnic boundaries and to eliminate ‘inferior’ types. Just this philosophy was later used to justify the atrocities of the Third Reich.
Even if Bernolet-Moens experiments in the Congo never materialised, there are a number of travellers' tales of half-ape, half-human intermediates from Africa all meticulously catalogued in Heuvelmans' files. For example, on 6 June 1926, the South African Sunday Times printed the following account from the prospector Paul de Chaillu who was camping near a village in the Congolese province of Katanga.
One day an extraordinary individual appeared. I say ‘individual’ but he looked more like a gorilla than a human. He stood about 5ft. 9in. in height judging from my own height. His legs were slightly thicker than the ordinary native's, and his arms were a good deal stronger. His body was covered in hair. But it was not as thick as that of a baboon, while his head much resembled that of the very intelligent apes one sees in zoos; yet there was a very human expression about it, too. It was a half-native type of countenance, with protruding jaw, and low receding forehead: neither man nor monkey. The nose was flat; the normal type of native nose. He had startling black eyes, brighter and more searching than those of a native. His hair was similar to a native's, except that it was longer.
When de Chaillu enquired which tribe the unusual individual belonged to, he was told that it was ‘the offspring of a native woman and a gorilla father. He had come to the tribe as a boy; had just wandered in, as it were, and no one knew whence he came. He had, however, lived with the tribe since the day of his arrival, and had in time acquired all the tribal ways. I spoke through the interpreter to the chief, who informed me that he had seen similar specimens in the forest, and thought that there were many such crosses in gorilla country.’
I later came across the same story in Hedley Chilvers' book The Seven Lost Trails of Africa, which puts the year of de Chaillu's encounter as 1913 and adds a comment by the anthropologist Raymond Dart. Professor Dart, based in Johannesburg, who was the first to describe the species Australopithecus afarensis, is quoted as saying that there was nothing impossible in the abduction and impregnation of a human female by a male gorilla leading, by implication to the birth of a hybrid child.3
Somewhat less credible is the story carried in the Kansas Daily Globe of 7 July 1921 that described the elopement of a beautiful New York socialite with a strange-looking man who had come from South Africa to live in the Eastern US. He was described as being large and thickset with a muscular and powerful frame, and arms that hung down to his knees. The girl's brother, alarmed at his sister's choice of fiancé, confronted the man who broke down and explained that his mother had been abducted by a gorilla on the East Coast of Africa and that he was the result.
A brother's concern for the fate of his sister turned to revenge in another story carried by the Kansas Daily Globe. The heroine of the tale had been abducted by a gorilla while a tourist in Africa, carried into the forest and forced to live with the creature for a month. She somehow managed to escape and described her captor as having two toes missing from his left foot. With this key feature in mind, the girl's brother, a millionaire apparently, set out for Africa with a party of expert marksmen intent on hunting down and killing the three-toed violator of his sister's chastity. Unfortunately the Globe did not report what happened when, and if, the vengeful sibling confronted the malefactor.
Other pongids with amorous intent towards human females have also faced the wrath of their protectors. The Massachusetts-based Middlesex News of 13 February 1991 carried one such story under the headline ‘Killed for a Kiss’. An orang-utan grabbed an Indonesian woman as she was undressing to bathe in a river. She screamed and fainted, and the ape ran off. Even so, it was enough for one of the villagers to track the orang-utan and kill it, despite its legally protected status. Recently I was told by a primatologist that rape by orang-utans is a known occupational hazard for female field workers in Sumatra but she did not know of any records of offspring.
In December 1980 a press report from the London Times correspondent in Peking (Beijing) quotes an announcement in the Shanghai newspaper Wen Aui Bao that Chinese authorities were considering renewing a breeding programme involving humans and chimpanzees to ‘found a strain of helots for economic and technical purposes’. According to the newspaper, thirteen years previously a female chimpanzee in a medical research laboratory became pregnant after being inseminated with a man's sperm. The laboratory was later smashed up by the Red Guard and the chimp died. Mr Qi Yongxiang, the man behind the new project, was quoted as saying that the proposed humanzees would be able to drive a car, protect forests and be used for space exploration. Mr Qi's grip on the ethics of the proposal appeared a little slack. When asked whether creating such a hybrid was unethical he replied that ‘semen was of no account once it had left the body and could be disposed of like manure. The hybrid would be classed as an animal, so there need be no qualms about killing it when necessary.’
An equally ambitious, and chilling, series of experiments to create ape-human hybrids was started in the early years of the Soviet Union, but only came to light after Soviet archives were opened in the 1990s.4 The instigator was Ilya Ivanovich Ivanov, a gifted and respected zoologist and an early pioneer of artificial insemination as an aid to improved efficiency in the breeding of horses. He announced his intentions to create human–chimpanzee hybrids at the 1910 World Congress of Zoology in Graz, Austria but only after the 1917 revolution was he able to attract official backing. His plans received enthusiastic backing from Bolshevik intellectuals who saw the opportunity for anti-religious propaganda in the project. There was also support from Americans eager for a practical demonstration of Darwin's evolutionary theory, now widely accepted, that humans were descended from apes. Ivanov was given a large grant to set up a research facility at Kindia in French Guinea in West Africa. There he set about capturing chimpanzees and to arrange for the insemination of females by human sperm and, for the reverse cross, inseminate local women with ape sperm in exchange for payment. He did succeed in capturing a number of chimpanzees but found no volunteers among the local population for insemination by ape sperm. He explained this reluctance down to their fear of being ostracised by the community, as was the fate of women that had been raped by chimpanzees in the wild. He did not give up and planned to inseminate women without their consent during faked medical examinations for other purposes but this was stopped by the governor. With no pregnancies among the captive female chimps, Ivanov moved back to Russia to continue his experiments at a specially constructed research facility at Sukhumi in Abkhazia. He took twenty chimpanzees with him, but only four survived the trip.
He did find five female volunteers willing to be inseminated but was rapidly running out of male apes to provide the necessary sperm and no pregnancies resulted. Ivanov persisted until 1930 but the mood of his political supporters shifted and he was arrested and exiled to Kazakhstan where he died two years later.
I did not find any material specifically relating to the Ivanov experiments among Heuvelmans' papers, but in a book written with Boris Porchnev he tells the story of a Russian doctor who claimed he knew of a Soviet concentration camp where a new race of man was being created by hybridisation between humans and apes.5
Let me now return to the hybrid story which occupied most space in Heuvelmans' pink folder, that of Oliver. He was born in the Congo in about 1968 but spent most of his life in America until he died, aged around thirty, at a retirement home for circus and medical research chimps near San Antonio, Texas. Unlike most chimpanzees who habitually walk on both arms and legs, Oliver was consistently bipedal. He was intended to be part of a well-known touring animal act with three other chimps brought over from Africa at the same time. But the other chimps wanted nothing to do with Oliver, so he was left out of the shows. According to his owners, Frank and Janet Burger, Oliver was much brighter than their other apes and was soon helping around the house. ‘You could send him on chores. He would take the wheelbarrow and empty the hay and straw from the stalls. And when it was time to feed the dogs, he would get the pans and mix the dog food for me. I'd get it ready and he'd mix it,’ Janet said.
As Oliver grew older he adopted some more human habits. ‘This guy Oliver, he enjoyed sitting down at night and having a drink and watching television. He'd mix his own. He'd put a shot of whiskey and put some Seven-Up in there, stir it and drink it.’ Oliver looked different too, with a smaller head, shorter arms and less hair than a regular chimp. He had a squarer face, and a more human-like expression than other chimps. The Burgers were forced to sell when Oliver was approaching sexual maturity. As Mrs Burger explained to reporters: ‘He had sex on his mind. The old hormones flared up. He didn't care about the female chimps we had, he started trying to have sex with me and any other woman.’ Oliver's next owner was a New York City lawyer who saw his new charge's earning potential. He took Oliver on tour all over the world and indeed, during his period of ownership, tried to pass him off as a Bigfoot.
What was Oliver? Was he just an unusual chimpanzee, or was he really a human–chimp hybrid from the Congo? Recalling the difference in the chromosome number between humans and chimps, it should have been an easy thing to establish. All that was needed was to grow some of Oliver's cells in a culture dish and look at them under a microscope when they were about to divide. At this stage, chromosomes are at their most condensed and can be individually recognised and counted. Normal chimpanzees have forty-eight chromosomes and humans only forty-six because of the ancestral fusion of two chromosomes to form human chromosome 2, as we saw earlier in this chapter. According to reports in The Sunday Times of 5 Sept 1976, the testing was carried out at the University of Chicago and counted forty-seven chromosomes in Oliver's cells, the number expected in a chimp–human hybrid. If these reports were accurate, Oliver may well have been a genuine humanzee.
The same Sunday Times report revealed a plan to breed from Oliver, carried under the headline ‘Girl plans to mate with Ape’. The proposed encounter was to take place in a Tokyo hotel after Oliver and Miss Hiroko Tagawa, a nineteen-year-old actress temporarily working in a sushi restaurant, had been properly introduced.
Though I have been unable to find confirmation that their anticipated conjugation ever took place, I have been able to find out more about the background to Oliver's chromosome count. According to other press reports in the Heuvelmans archive, Oliver's cells were to be sent to Dr David H. Ledbetter, a geneticist at the University of Chicago. During my time in medical genetics, I had come across a Dr Ledbetter and knew his work on a rare genetic disorder called Fragile X syndrome, whose unusual causation became a key part of my genetics lectures to the Oxford medical students.
I tracked Dr Ledbetter down through a former colleague in Chicago and got a swift reply that he was indeed the man who had examined Oliver's cells. He had grown them on a cell-culture slide and counted the chromosomes as they condensed during cell division. Oliver did not have forty-seven chromosomes, as widely reported, but the regular forty-eight. In Dr Ledbetter's words, he was ‘just a chimp that liked to stand up’. He also told me that he had intended to write this investigation up as a paper, but never got round to it. He felt, as I would have done in the circumstances, that it was a negative result of no importance that was unlikely ever to be published in a serious journal. The press meanwhile completely lost interest in Oliver on hearing that he was a regular chimp, but the myth that his hybrid status had been confirmed by chromosome analysis has continued.
Heuvelmans' bulging pink file held many more tales of hybrids between animals of all descriptions. They must have held a particular fascination for the father of cryptozoology, a fascination that for many of his followers continues to this day, as we shall see. But let us close the file at this point and return to our own species.
One point that has so far been overlooked in the excitement of finding significant chunks of Neanderthal and Denisovan DNA in our genomes, with the promise of more to come is this. Where does it leave us, Homo sapiens, as a species? The biological definition insists that a species can only breed successfully in the wild with itself. It is an important evolutionary principle for the Darwinian concept of the origin of species, which requires that at some point there must be some sort of barrier to interbreeding. Often this barrier is geographical. There are many examples, including Darwin's original work on the finches living on the scattered islands of the Galapagos archipelago. It was through his observations of these birds that Darwin consolidated and developed his ideas on the origin of species through natural selection. In the Galapagos Darwin noticed that the finches looked quite different on each island. In fact he thought they were completely different birds altogether until the ornithologist John Gould examined the specimens Darwin had brought back with him and pointed out that they were all closely related. Darwin eventually realised that these distinguishing features may have evolved through isolation, something that would not have happened had the finches continually interbred with birds from other islands.
Because of Darwin's somewhat delayed insight into the Galapagos finches, and hundreds of examples since that time, species definition has become very strict. Speciation, the process of creating new species, in populations of wild animals requires that something happens to make interbreeding between them impossible, a good example being the chromosome fusion in the human ancestral line that prevents interbreeding in the wild between humans and chimps. It follows that if what are thought of as two different species of animals do successfully interbreed in the wild and produce healthy fertile offspring that are able to survive, then they are not strictly-speaking two species but one.
Where does that leave us? Collateral human species, like the Neanderthals, have traditionally been defined by their appearance deduced from fossils. However, it is quite impossible to tell from the appearance of the skeleton whether Neanderthals were a different species from Homo sapiens by the strict biological definition of genetic incompatibility. But now all that has changed. We now believe that Neanderthals, Denisovans and our own Homo sapiens did interbreed both successfully and in the wild. If the offspring of the occasional inter-species human x chimp liaisons, possibly like the unusual individual encountered by Paul de Chaillu in the Congo, chromosome incompatibility would have prevented the parental DNA being passed on to the next generation and we would not have been able to detect it in modern humans. But with the Neanderthals and Denisovans, we can. So, to my mind, this means that by the strictly applied biological criteria insisted on by modern taxonomy, we are all, Neanderthals, Denisovans and the rest that have left a trace of their DNA in our genomes, members of the same species. While this will appear to many to be a semantic distinction, there is one very practical implication. While it is not illegal to kill an unknown species or indeed a hybrid, if we are all in the same species then there can be no hybrids. By this reasoning, to kill a Bigfoot, a yeti, a Neanderthal or a Denisovan, as well as being a travesty, might also be classed as homicide.