You would probably think any leprechaun claims I made were far-fetched, but have you ever heard of the Orang pendek? Every now and again someone reports having found evidence of a new, extant, human-like species. Someone returns from an expedition with ‘evidence’ of the yeti, Bigfoot or the Orang pendek: a bipedal ape that is alleged to live in remote mountainous forests in Sumatra. The same pattern of events is then repeated. The returning adventurer presents their evidence of the new species, be it a sasquatch, skunk ape or batutut, and a media frenzy follows. The story quickly blows itself out and the media move on to a misbehaving politician or celebrity – anything else that can fill the ‘and finally’ slot of news programmes. Once out of the public spotlight, it gradually becomes apparent that the evidence in support of the new species is weak: a grainy photograph that could be of pretty much anything, a dubious plaster cast of a footprint, a hair that is thought to belong to the beast, or some unverifiable accounts from members of the local population. In some cases, the hair may be examined by geneticists who conclude it comes from a cow, goat or dog, or they are unable to extract any DNA (deoxyribonucleic acid, the molecule in which the instructions to build an organism are encoded) at all from it. The person who collected the weak evidence is often convinced of what they saw, but they do not always understand that most scientists require more compelling evidence, and ideally a specimen such as a skeleton from an individual of the species.
I once attended a talk describing insights into the Orang pendek at the Institute of Zoology, the research arm of London Zoo. The speaker was convinced by the evidence they presented, but the audience was not. In discussion afterwards, it became clear that most people in the audience wanted the Orang pendek to exist. The discovery of a new great ape would be a major biological advance, and the discoverer would be rightly feted. However, most of the audience felt that the photos projected were too blurred to count as evidence, and they gave little weight to an interview with a member of the local community whose testimony was presented as evidence of the Orang pendek’s existence. The interviewee was clearly an expert in the native flora and fauna, having spent many years in the forest. But he was unable to return to the site where he claimed to have buried an Orang pendek he had found dead, and his statement that the species could remove their feet and put them on backwards to confuse trackers lacked credibility, as no other apes or, for that matter, any animal species, can do this. It would be a strange thing to evolve, as such a trait is highly unlikely to give the bearer any advantage in producing babies, the currency of evolution, compared to a firmer-ankled individual. One member of the audience felt the interviewee’s claim to have been a pigeon in a former life was more believable than the foot-switching trick. We wished the researcher luck in collecting more data while explaining that we were unconvinced and describing what would be required to persuade most of us. I still hope to hear one day of a specimen of a new species of great ape found to be living in Sumatra, but I am not holding my breath. I would also love to learn that sasquatch and yetis roam remote parts of our planet but, once again, I suspect it is unlikely.
You don’t always need much material to provide strong evidence of the existence of a species. Leprechauns don’t exist, Orang pendek probably don’t exist, but woman X did exist, and she was from a group of individuals called Denisovans. The Denisovans were an ancient people, like Neanderthals, but they lived in Central Asia rather than Europe, and were closely related to us. Scientists have not found enough material to classify the Denisovans as a new species, but what they have discovered is remarkable. Much of the story we know comes from a single finger bone that was subjected to high-tech analyses which have shed a lot of light on the history of our own species.
The story starts in a cave in the Altai Mountains in Siberia, which used to be the home of a Russian hermit. The hermit, called Dionisij, made the cave his home in the eighteenth century. Denis is the English translation of Dionisij, and this led to the cave being named the Denisova Cave.
Denis was not the first human to use this cave. Russian archaeologists who have worked in the cave have found evidence that Neanderthals, ‘woman X’ and, more recently, modern humans, used the cave over a period of at least 100,000 years. Woman X was identified by a bone from the finger of a child that was neither Neanderthal nor Homo sapiens – the Latin name of modern-day humans. It was not the structure of the bone that revealed this but the DNA sequences that were extracted from the finger.
The girl whose bone it was used the cave sometime between 30,000 and 50,000 years ago. Biologists are yet to conclude whether the girl is a different species to us, or whether she is from the population of a subspecies, and this means that her scientific name is yet to be decided. Biologists classify organisms as belonging to species, but what defines a species can be challenging because individuals of the same species can vary quite substantially among different populations across the species range. For example, the Bengal tiger (Panthera tigris tigris), the Sumatran tiger (Panthera tigris sumatrae) and the Siberian tiger (Panthera tigris altaica) all look a little different from one another, they are genetically distinct, and their populations have evolved away from one another for potentially hundreds of generations. Nonetheless, they are all tigers and can mate with one another to produce viable offspring. They are consequently described as subspecies. Woman X is usually referred to as a Denisovan, and if I were asked to make a call, I would classify Denisovans, Neanderthals and modern-day humans as subspecies of one another rather than as separate species, but this may irritate some palaeontologists.
We know little about woman X’s life, but DNA has been extracted from her finger bone and sequenced, with great care, using state-of-the-art technology. The genome from this girl has been compared with genomes from modern-day humans from around the world, and with Neanderthals. DNA revealed she was not a Neanderthal, nor a modern human. Woman X’s passing may have been unremarkable, although I have no doubt she was mourned by her relatives and friends, but the discovery of her finger bone has left an astonishing legacy: scientists have had to revisit the history of us.
The discovery of Denisovans caused much scientific excitement, but it was not the first time evidence of an extinct subspecies so similar to us caused interest. In 1856, three years before Darwin published On the Origin of Species, bones were discovered in a cave in the Neander Valley in Germany. They clearly differed from those of modern humans, and they caused excitement when the find was announced in the Elberfeld newspaper. Over the following years learned researchers argued that the bones were from a Russian Cossack, a Native American, a soldier from Attila’s army, a man who suffered from and was pained by rickets, or a member of an extinct tribe of primitive villagers that inhabited Europe before modern people arrived. William King published a paper in 1864 that drew similarities between the fossilized bones and those of apes like chimpanzees and gorillas, and proposed that they belonged to a new species he called Homo neanderthalensis. Scientists began to accept that another species (or subspecies) with similarities to humans once existed in Europe, and the Neanderthals were generally assumed to be simple, brutal savages. It took most of the following 150 years for scientists to overturn this view.