"There is more meaning and mutual understanding in exchanging a glance with a gorilla than any other animal I know," whispered David Attenborough during his memorable encounter with the mountain gorillas of central Africa during filming for the groundbreaking BBC Life on Earth series in 1978.
That short scene of a family group of gorillas - playing, resting, feeding and reflecting ourselves back through the camera lens - cemented our affection for a creature with which mankind shares around 98 per cent of our DNA. They are, as Attenborough suggested so effectively, our cousins in the wild.
And it is that unique relationship which underpinned the horror felt by many last week when it was revealed that one and possibly two of the remaining 700 mountain gorillas, confined to a small area bordering three central African countries, had been killed and probably eaten by Congolese rebel soldiers. And these were not just some anonymous wild creatures: they had names, ages, personalities and were adult male members of one of the most closely observed and documented communities of the animal kingdom. This was akin to cannibalism.
Now, following the intervention of two wildlife conservation groups, it has been announced that the rebels have agreed to stop the killing of primates. For the time being, at least, the conservation groups hope their future is secure. "We are fairly optimistic that the agreement will hold. But at the moment, we do not know how many other gorillas might have died," said Emmanuel de Merode, the Congo director of Wildlife Direct, one of the organisations involved.
The killings illustrate the precarious position of the population of mountain gorillas - a community that has, remarkably, managed to thrive despite living in an area that is plagued by war, famine, disease and genocide.
So, what are mountain gorillas? And why are we so concerned about the loss of only two of these animals, in an area that has seen the deaths of millions of people? Mr de Merode believes that they are as important as any human beings. "The mountain gorillas are extremely vulnerable and the death of only a handful could have a significant impact on the population as a whole," he said.
David Jay, who works for the United Nations-backed Great Apes Survival Project and the Born Free Foundation, puts the argument another way: "Compared to the millions of humans, these are the last remaining creatures of this type on the planet. They don't live anywhere else. The death of even one adult male can affect the vitality of the entire population."
Gorillas, the largest of the great apes, only live in central Africa, mostly in and around the Congo basin. There are two species - eastern and western gorillas - each divided into two further sub-species. The mountain gorilla, a sub-species of the eastern gorilla, is now only found in two highland areas.
One is on the borders of Rwanda, Uganda and the Democratic Republic of Congo, in what is generally known as the Virunga area, which is home to around 380 gorillas. The second, to the north, is the Bwindi National Park in the Ugandan highlands, where a further 320 mountain gorillas live. Both sites are relatively small by African standards.
All gorillas face three serious threats: poaching for bushmeat, the Ebola virus and the erosion of their habitats. Mountain gorillas, mainly distinguished from their lowland compatriots by their longer hair, which protects against the cold, are not the most endangered gorilla sub-species. That distinction belongs to the Cross River gorilla, with just 280 or so individuals left. But both are among the world's most threatened primates.
Like all gorillas, they live mostly in family groups of between five and 30, overseen by dominant adult males called silverbacks, after the silver hair on their backs. Younger males leave the group when they are about 11 years old to begin groups of their own. They can live to between 30 and 50 years old, and their diet is mostly vegetarian, with a few insects thrown in.
We know so much about the mountain gorillas mainly because of the work of such pioneers as Dian Fossey, the American animal behaviourist who along with Jane Goodall, the chimpanzee expert, went to Africa in the late 1960s to work for archaeologist Dr Louis Leakey, who believed that primate behaviour held the key to human evolution. Both were known as "Leakey's Angels". Fossey began work on the mountain gorillas in the Virunga, created in 1925 as Africa's first national park and now a UN World Heritage Site.
When, more than a decade later, Attenborough arrived in the area on the Rwandan side to film for Life on Earth, he was wary that the famously fierce and protective Fossey might not let him have access to "her gorillas", as she called them. She did, eventually, let the crew in, giving them strict instructions on how to approach the animals: keep low and grunt a lot. Attenborough's famous sequence with the gorillas, shot with a young gorilla lounging on his chest and a baby taking off his shoe, became rightly celebrated. But it was the film of Fossey's life, based on her autobiography Gorillas in the Mist, starring Sigourney Weaver, that brought her work and her gorillas to a global audience. Fossey's murder, in 1985, which has never been completely explained and has been attributed to both the poachers she waged war against and those who felt she had become an obstacle to the tourism industry that she herself had done much to bring about.
Fossey's work ensured that, throughout the years of the Rwandan civil war and genocide in the mid-1990s, the Virunga gorillas would become closely monitored by conservationists and the local national park rangers - so much so that David Attenborough was able to discover recently that Pablo, the youngster who was filmed with him, was now a 200kg silverback and group leader.
The legacy of that earlier era continues through such people as Ian Redmond, once Fossey's assistant and now chief consultant to the Great Apes Survival Project, who helped to re-install some of the national park staff when peace returned to Rwanda. Dr Leakey's son, Richard Leakey, also became a renowned archaeologist - for his discoveries of fossils in Ethiopia - and conservationist, for his campaign against elephant poaching.
The gorillas have become famous and gorilla-related tourism, which has sporadically continued amid the conflicts, has become a huge earner in countries otherwise stricken by poverty.
But tourism, and the close monitoring by national park rangers, is a double-edged sword because it also means that the animals become accustomed to - and therefore more trusting of - human beings, which can be their downfall. Nevertheless, Mr Jay believes both are crucial: "Tourism is a major source of income for a deprived area. So ensuring the survival of the gorillas is an investment for the future of the local people."
And so the story comes full circle as Leakey, who has had a career as both a wildlife expert and politician/administrator in east Africa, now runs the Africa Conservation Fund and Wildlife Direct, whose intervention in the latest deaths led to the current agreement with the rebels. That took place on the DRC side of the Virunga, where, despite ceasefire agreements, areas are still controlled by rebel fighters loyal to renegade Congolese army general Laurent Nkunda.
The DRC itself was devastated by civil war and famine between 1998 and 2003, in which more than 4 million people died. Despite the conflicts on both sides of the border, the deforestation of their habits for fuel and farming, the number of gorillas has risen by 14 per cent since the war began.
Last week, the national park rangers learned that one solitary male gorilla, later identified as Karema, who was 18 years old, had been killed and butchered, his remains, principally his head, dumped in a pit latrine. On the Wildlife Direct website, there was a short and poignant obituary for Karema, written by one of the senior rangers, Paulin Ngobobo, and typical of the close, familial regard these men have for the gorillas. Entitled "Farewell To A Friend", it said: "Karema was born in 1989 to Mukechuru and Rugendo, a large silverback. His mother, Mukechuru, died of old age in 1991, when Karema was still very dependant on her care. His father looked after him thereafter. The word Karema means 'handicapped'. He lost his left hand, most likely to a snare. Men plagued his existence to the end, and yet he was known for his exceptionally calm personality. The first recorded contact with Karema was by the biologist Conrad Aveling, who noted his friendly disposition. He was a calming influence on the gorilla group, which was frequently visited by tourists in those days. He disappeared from his family in February 2002, reappearing as a young blackback a few months later, living a life of solitude. He died at the hands of a species he trusted completely, aged 18." Another solitary male, whose details have not been released was also believed to have been killed.
After worldwide publicity about the deaths was generated by Wildlife Direct and the Frankfurt Zoological Society, which works with the charity in the area, the rebel movement even went so far as to issue a press release denying any involvement. UN peacekeeping troops in the area then set up a meeting on Tuesday between Ngobobo, a representative of the society and both sides in the military conflict. The result was an agreement by the local rebel commander, known as Colonel Makenga, to allow the rangers into the area in order to check on the welfare of the gorillas and, on the part of the rebels, to refrain from killing more gorillas. The rangers hope to return next week.
Paulin Ngobobo said afterwards: "This is a very positive result. We weren't expecting to succeed given the overwhelming odds against. However, this is just another small step. We must keep up international pressure to ensure this doesn't happen again next week, next month or next year."
Why all this is so important to us is perhaps best explained by Redmond, who has known the mountain gorillas since he first started working with Dian Fossey in the 1970s. He said yesterday: "When you catch the eye of a gorilla, you realise that there is someone - as distinct to something - in there. If human beings are defined by a sense of self-awareness, then without a doubt that is something the great apes share with us. When you see a gorilla, it is a gorilla being. And you realise that humans are not the only self-conscious and aware creatures on the planet."