Gerry Ellis / Western Lowland Gorilla (Gorilla gorilla gorilla) silverback, Limbe Wildlife Centre, Cameroon

Gerry Ellis / Chimpanzee (Pan troglodytes) orphan Larry playing in tree, Ape Action Africa, Mefou Primate Sanctuary, Cameroon

Gerry Ellis / Chimpanzee (Pan troglodytes) orphans, Larry investigating Daphne's tongue, Ape Action Africa, Mefou Primate Sanctuary, Cameroon

Gerry Ellis / Chimpanzee (Pan troglodytes) orphan Larry, Ape Action Africa, Mefou Primate Sanctuary, Cameroon

Gerry Ellis / Chimpanzee (Pan troglodytes) orphan Larry playing in forest nursery, Ape Action Africa, Mefou Primate Sanctuary, Cameroon

Gerry Ellis / Chimpanzee (Pan troglodytes) orphan Larry scratching, Ape Action Africa, Mefou Primate Sanctuary, Cameroon

Anup Shah / Eastern Chimpanzee (Pan troglodytes schweinfurthii) fourteen year old sub-adult male, named Fundi, making submissive facial gesture, Gombe National Park, Tanzania

Anup Shah / Eastern Chimpanzee (Pan troglodytes schweinfurthii) forty-three year old female, named Gremlin, scratching face, Gombe National Park, Tanzania

Anup Shah / Eastern Chimpanzee (Pan troglodytes schweinfurthii) twenty-five year old female, named Nasa, Gombe National Park, Tanzania

Anup Shah / Eastern Chimpanzee (Pan troglodytes schweinfurthii) four year old infant male, named Gizmo, foraging for insects in log, Gombe National Park, Tanzania

Fiona Rogers / Eastern Chimpanzee (Pan troglodytes schweinfurthii) twenty year old male, named Titan, Gombe National Park, Tanzania

Fiona Rogers / Eastern Chimpanzee (Pan troglodytes schweinfurthii) seven year old juvenile male, named Siri, feeding on vines, Gombe National Park, Tanzania

Fiona Rogers / Eastern Chimpanzee (Pan troglodytes schweinfurthii) twenty-five year old female, named Tanga, Gombe National Park, Tanzania

Fiona Rogers / Eastern Chimpanzee (Pan troglodytes schweinfurthii) four year old infant male, named Gizmo, Gombe National Park, Tanzania

Fiona Rogers / Eastern Chimpanzee (Pan troglodytes schweinfurthii) eighteen year old male, named Sampson, Gombe National Park, Tanzania

Fiona Rogers / Eastern Chimpanzee (Pan troglodytes schweinfurthii) four year old infant male, named Gizmo, Gombe National Park, Tanzania

Anup Shah / Eastern Chimpanzee (Pan troglodytes schweinfurthii) sixteen month old baby female, named Gossamer, in tree, Gombe National Park, Tanzania

Fiona Rogers / Eastern Chimpanzee (Pan troglodytes schweinfurthii) five year old juvenile female, named Fadhila, playing with her three year old brother, named Fifty, Gombe National Park, Tanzania

Tim Fitzharris / Sumatran Orangutan (Pongo abelii) male, native to Sumatra

Thomas Marent / Bonobo (Pan paniscus) staring, native to central Africa

Fiona Rogers / Eastern Chimpanzee (Pan troglodytes schweinfurthii) mother, twenty-three years old, holding less than one day old newborn, Gombe National Park, Tanzania

Cyril Ruoso / Bonobo (Pan paniscus) young in day nest, Democratic Republic of the Congo

Anup Shah / Eastern Chimpanzee (Pan troglodytes schweinfurthii) juvenile male, five years old, Gombe National Park, Tanzania

Theo Allofs / Mountain Gorilla (Gorilla gorilla beringei) juvenile male, Volcanoes National Park, Rwanda

Theo Allofs / Mountain Gorilla (Gorilla gorilla beringei) juvenile male, Volcanoes National Park, Rwanda

Thomas Marent / Bonobo (Pan paniscus) hooting, Lola Ya Bonobo Sanctuary, Democratic Republic of the Congo

Thomas Marent / Bonobo (Pan paniscus) walking through water, Lola Ya Bonobo Sanctuary, Democratic Republic of the Congo

Thomas Marent / Bonobo (Pan paniscus) feeding on leaves, Lola Ya Bonobo Sanctuary, Democratic Republic of the Congo

Thomas Marent / Bonobo (Pan paniscus), Lola Ya Bonobo Sanctuary, Democratic Republic of the Congo

Anup Shah / Eastern Chimpanzee (Pan troglodytes schweinfurthii) female, thirteen years old, playing with her two month old baby daughter, Gombe National Park, Tanzania

Gerry Ellis / Orangutan (Pongo pygmaeus) sub-adult male in trees in haze caused by forest clearing, West Kalimantan, Borneo, Indonesia. October, 2015

Sean Crane / Orangutan (Pongo pygmaeus) juvenile investigating camera, Tanjung Puting National Park, Borneo, Indonesia

Sean Crane / Mountain Gorilla (Gorilla gorilla beringei) mother and young, Bwindi Impenetrable National Park, Uganda

Hiroya Minakuchi / Sumatran Orangutan (Pongo abelii) juvenile playing with branch, native to Sumatra

Thomas Marent / Eastern Chimpanzee (Pan troglodytes schweinfurthii) mother with baby, Gombe Stream National Park, Tanzania

Thomas Marent / Eastern Chimpanzee (Pan troglodytes schweinfurthii) mother with baby, Gombe Stream National Park, Tanzania

Thomas Marent / Eastern Chimpanzee (Pan troglodytes schweinfurthii) baby with mother grooming juvenile, Gombe Stream National Park, Tanzania

Thomas Marent / Eastern Chimpanzee (Pan troglodytes schweinfurthii) baby hanging on branch, Gombe Stream National Park, Tanzania

Thomas Marent / Eastern Chimpanzee (Pan troglodytes schweinfurthii) parent grooming juvenile feeding on fruit, Gombe Stream National Park, Tanzania

Thomas Marent / Eastern Chimpanzee (Pan troglodytes schweinfurthii) mother with baby, Gombe Stream National Park, Tanzania

Adri de Visser / Mountain Gorilla (Gorilla gorilla beringei) in rain, Bwindi Impenetrable National Park, Uganda

Roland Seitre / Orangutan (Pongo pygmaeus) female, native to Borneo

Roland Seitre / Western Lowland Gorilla (Gorilla gorilla gorilla) silverback male, native to central Africa

Roland Seitre / Western Lowland Gorilla (Gorilla gorilla gorilla) silverback male appearing to pout, native to central Africa

Roland Seitre / Western Lowland Gorilla (Gorilla gorilla gorilla), albino male named Snowflake, Barcelona Zoo, Spain

ZSSD / Western Lowland Gorilla (Gorilla gorilla gorilla) juvenile

Fiona Rogers / Sumatran Orangutan (Pongo abelii) twenty-four year old female, named Ratna, playing with her female baby, named Global, Gunung Leuser National Park, Sumatra, Indonesia

Fiona Rogers / Sumatran Orangutan (Pongo abelii) twenty-six year old male, named Halik, biting lip, Gunung Leuser National Park, Sumatra, Indonesia

Fiona Rogers / Sumatran Orangutan (Pongo abelii) twenty-six year old male, named Halik, Gunung Leuser National Park, Sumatra, Indonesia

Cyril Ruoso / Eastern Chimpanzee (Pan troglodytes schweinfurthii) , Frodo the dominant male and hunter, eating a Red River Hog (Potamochoerus porcus) piglet with two females begging, Gombe National Park, Tanzania

Cyril Ruoso / Eastern Chimpanzee (Pan troglodytes schweinfurthii) eating leaves, Gombe National Park, Tanzania

Cyril Ruoso / Sumatran Orangutan (Pongo abelii) mother and young, Gunung Leuser National Park, Sumatra, Indonesia

Cyril Ruoso / Chimpanzee (Pan troglodytes) baby playing with keeper, Pandrillus Drill Sanctuary, Nigeria

Cyril Ruoso / Chimpanzee (Pan troglodytes) adults and young, Pandrillus Drill Sanctuary, Nigeria

Cyril Ruoso / Bonobo (Pan paniscus), bath time for orphan infants with their adoptive mother, Sanctuary Lola Ya Bonobo Chimpanzee, Democratic Republic of the Congo

Cyril Ruoso / Bonobo (Pan paniscus) female with newborn, Sanctuary Lola Ya Bonobo Chimpanzee, Democratic Republic of the Congo

Cyril Ruoso / Bonobo (Pan paniscus) pair of orphans hugging, Sanctuary Lola ya Bonobo, Democratic Republic of the Congo

Cyril Ruoso / Chimpanzee (Pan troglodytes) female looking into the camera curiously, Gabon

Cyril Ruoso / Bonobo (Pan paniscus) female playing in the grass, ABC Sanctuary, Democratic Republic of the Congo

Cyril Ruoso / Bonobo (Pan paniscus) portrait of female standing, ABC Sanctuary, Democratic Republic of the Congo

Cyril Ruoso / Mountain Gorilla (Gorilla gorilla beringei) large silverback continuing to display after attacking a tourist, Virunga Mountains, Rwanda

Cyril Ruoso / Mountain Gorilla (Gorilla gorilla beringei) female with her three month old newborn, Parc National Des Volcans, Rwanda

Cyril Ruoso / Mountain Gorilla (Gorilla gorilla beringei) close-up portrait of a silverback in the rain, Parc National Des Volcans, Rwanda

Cyril Ruoso / Chimpanzee (Pan troglodytes) using tools to crack nuts, Gabon

Cyril Ruoso / Chimpanzee (Pan troglodytes) using tools to crack nuts, Gabon

Cyril Ruoso / Chimpanzee (Pan troglodytes) adult female with orphan baby she has adopted, Gabon

Cyril Ruoso / Chimpanzee (Pan troglodytes) young using a leaf to drink, Gabon

Cyril Ruoso / Chimpanzee (Pan troglodytes) resting on a liana vine, Gabon

Cyril Ruoso / Chimpanzee (Pan troglodytes) adult female calling, Gabon

Cyril Ruoso / Bonobo (Pan paniscus) juvenile pair making funny faces, Democratic Republic of the Congo

Cyril Ruoso / Bonobo (Pan paniscus) smiling while laying on ground, ABC Sanctuary, Democratic Republic of the Congo

Duncan Usher / Western Lowland Gorilla (Gorilla gorilla gorilla) mother walking with young holding on, Arnhem, Netherlands

Martin Willis / Mountain Gorilla (Gorilla gorilla beringei) male feeding, Volcanoes National Park, Rwanda

Suzi Eszterhas / Mountain Gorilla (Gorilla gorilla beringei) silverback feeding, Parc National des Volcans, Rwanda

Suzi Eszterhas / Mountain Gorilla (Gorilla gorilla beringei) mother holding five month old twin babies, Parc National des Volcans, Rwanda

Suzi Eszterhas / Mountain Gorilla (Gorilla gorilla beringei) mother holding five month old twin babies, Parc National des Volcans, Rwanda

Paul D Stewart / Engraving of an ape-like cave man accompanying an article by Boitard in the French 'Magasin Universel' (April 1838). This is the earliest reconstruction of a pre-historic human. It is striking that it...

Suzi Eszterhas / Sumatran Orangutan (Pongo abelii) two and a half year old baby calling, Gunung Leuser National Park, north Sumatra, Indonesia

Suzi Eszterhas / Sumatran Orangutan (Pongo abelii) mother and playful one and a half year old baby, Gunung Leuser National Park, north Sumatra, Indonesia

Suzi Eszterhas / Sumatran Orangutan (Pongo abelii) nine month old baby playing in tree, Gunung Leuser National Park, north Sumatra, Indonesia

ZSSD / Bonobo (Pan paniscus) female playing with youngster by throwing him up in the air, native to Africa

ZSSD / Western Lowland Gorilla (Gorilla gorilla gorilla) scratching its head, native to Africa

Thomas Marent / Orangutan (Pongo pygmaeus) female with baby on back, Camp Leaky, Tanjung Puting National Park, Indonesia

Thomas Marent / Mountain Gorilla (Gorilla gorilla beringei) silverback, Volcanoes National Park, Rwanda

ZSSD / Western Lowland Gorilla (Gorilla gorilla gorilla) baby clinging to mother's back, critically endangered, native to Africa

Ingo Arndt / Chimpanzee (Pan troglodytes) juvenile fishing for termites, endangered, Gombe Stream National Park, Tanzania

Ingo Arndt / Mountain Gorilla (Gorilla gorilla beringei) juvenile, Parc National Des Volcans, Rwanda

Ingo Arndt / Mountain Gorilla (Gorilla gorilla beringei) baby, Parc National Des Volcans, Rwanda

Ingo Arndt / Mountain Gorilla (Gorilla gorilla beringei) Susa group showing male silverback, two females and two juveniles, Parc National Des Volcans, Rwanda

Suzi Eszterhas / Mountain Gorilla (Gorilla gorilla beringei) 10 month old infant playfully climbing bamboo pole, endangered, Parc National Des Volcans, Rwanda

Suzi Eszterhas / Mountain Gorilla (Gorilla gorilla beringei) 10 month old infant riding on mother's back, endangered, Parc National Des Volcans, Rwanda

ZSSD / Western Lowland Gorilla (Gorilla gorilla gorilla) mother walking away with 48 day old baby on back, native to Africa

ZSSD / Western Lowland Gorilla (Gorilla gorilla gorilla) male vocalizing, native to equatorial West Africa

ZSSD / Western Lowland Gorilla (Gorilla gorilla gorilla) male portrait, native to Africa

Konrad Wothe / Mountain Gorilla (Gorilla gorilla beringei) males fighting, Virunga National Park, Democratic Republic of the Congo

Konrad Wothe / Mountain Gorilla (Gorilla gorilla beringei) baby rolling on forest floor, Virunga National Park, Congo