  After clambering over fossilised lava flows at 9,000ft, we duck into vegetation, my guide slashing his machete through tendrils that grip your legs like lassoes
  Finally, we see them – a family of  gorillas descended from those David ­Attenborough made famous in 1979
  Our hearts hammering in a silence only broken by the buzzing of insects, we watch the Rwanda mountain gorillas as they sit stock still, looming from lush vegetation like sculptures
  This is Ururabo, 22, with her sons, Nkurunziza, five, and Imena, 11, and in her strong arms daughter Wang Wang Uburumbuke, with a bootbrush head of fuzz, aged just one
  Ururabo is the daughter of Poppy, who was just 18 months old when she was filmed as she watched her pal Pablo playfully sit on an astonished David Attenborough
  Later, off camera, mischievous Poppy untied the naturalist’s boots.     In April, it will be 40 years since the film, in Sir David’s Life on Earth series, was screened on the BBC to an ­audience who knew more about gorillas from King Kong than wildlife shows
  Previously, not even the presenter himself had ever met one in the flesh, let alone filmed them
  When his encounter with the gorillas was broadcast, the creatures were precariously rare, numbering under 250 in the world and predicted to be extinct by the end of the century
  But there are now more than 1,004, making mountain gorillas the only ape on the planet, bar humans, rising in number
  Although they are still ­endangered, it is an extraordinary conservation success story, in large part thanks to Sir David
  We have come to Rwanda’s Volcanoes National Park in the Virunga mountains to retrace his steps, and try to understand his achievement and find descendants of the cheeky gorillas he met
      We are here with biologist Ian Redmond, 64, who, in the 1970s, worked in this dense jungle as a 22-year-old assistant to primatologist Dian Fossey, who had studied these groups, giving them each names
  Ian, who held the microphone as the gorillas gently teased Sir David like a brother, says the film “helped change the fate of a species”
  The gorillas were targeted by poachers, who cut off their hands and feet as trophies, and stole their babies to sell
  Ian says: “First, Sir David demolished the King Kong myth by being so clearly accepted by the gorillas
 He turned people’s opinions of them around.  “He never expected to get this close, but they took to him, although he certainly didn’t expect Pablo to sit on him
  “There was even a moment, when the lens was being changed, when Poppy’s sister, Puck, took hold of his head and peered right at his face
  “When you’re with a family of resting gorillas there is no fear. That’s what people saw and they loved them
  “Afterwards, he used his reputation to raise money and get organisations involved
”   The family tree of those gorillas is now long.  A census carried out exclusively for the Mirror reveals sisters Poppy, Puck and Tuck, the female gorillas in Attenborough’s film, have 26 children, 17 grandchildren, and one great-grandchild between them
  Our aim was to meet some of the youngest starlet Poppy’s brood.  Until last year, she was a regular face in the forest, at the age of 42 the last of the bunch alive
 Then she went missing, thought to have died from natural causes. As we watch, her daughter Ururabo’s family begin to move about
  Imena’s awesome hands, fingers like bananas, encircle crackling shoots as Ururabo strides gracefully through the butterflies with her baby on her back
  Later, crawling on our knees through goose grass and wild celery, we find silverback Agahebuzo, the strapping, 12-year-old grandson of Tuck
  As he sinks back for a snooze, he raises his leg and clutches it with his plate-sized hand, as if he’s doing yoga
 It is hard to believe anyone could knowingly hurt these serene beings, who share 98% of human DNA
   As Sir David said: “There is more meaning and mutual understanding in exchanging a glance with a gorilla than any other animal I know
”  After a little fearfully catching Agahebuzo’s knowing brown eyes, the same colour as my own, I understand
  But in the 1970s, they were prey. Just before Sir David arrived, a male christened Digit was speared to death, his hands and feet hacked off by poachers
  Ian says: “Two days later that’s how I found him. When Sir David arrived, we were angry and grieving
”  Six months after he left, a male and female were shot dead, and their baby, Kweli, who also appeared in the documentary, was left an orphan
 He later died.  Ian says: “He lost the will to live.”  Chief warden Prosper Uwingeli says the authorities needed to recognise the gorillas as a treasure in order to protect them
  After Sir David finished filming, he and the crew were shot at and strip-searched as they made their way down the mountain, the army suspicious they were trying to highlight poaching
   When they realised they had simply highlighted the beauty of these incredible creatures, their attitude changed
  Prosper says: “Attenborough’s message changed minds. We feel grateful to him.”  Later that year, the first habituated gorilla group for structured tourist visits was created
  In 1986, full-time veterinary care was ­established and today Gorilla Doctors operate in the forest, which also spans neighbouring Uganda and the Democratic Republic of Congo, checking for life-threatening wounds and diseases
  Prosper says: “Some don’t see tourism as a form of conservation, but it is low-intensity, kept to one visit a day, for an hour only
 It is working.”  Despite their familiarity with human faces, there is no doubt that the gorillas are wild
  We encounter Poppy’s daughter feeding her baby and the surprise elicits a hissing roar which forces us all to crouch into submissive poses
   Direct poaching has ceased in Rwanda and Uganda. But in the politically unstable DRC, gorillas are harder to protect and apes are still poached
  The latest positive phase in the gorilla’s protection is the Rwandan government’s decision last year to expand the forest, adding almost 4,000 hectares to its current 16,000
  I’m assured residents farming there will be re-homed, and given new means to earn a better living
  This must happen but, ultimately, forest expansion is for everyone’s sake.  The huge amount of carbon dioxide which forests absorb is crucial to battling climate change
  Just before we crawl back through the undergrowth, the trackers spy a newborn baby almost hidden in its mother’s arms, its umbilical cord still attached, fur still wet
  We are advised not to approach, but silently celebrate.  Ian says: “David has never been back, but he would be blown away to see what we have seen
”  To learn more and to help protect the gorillas, visit Ape Alliance: Action for Apes at 4apes
com.  
