Watch Cousins online: Episode 1 The First Primates

In Rwanda, Dr Charlotte Uhlenbroek finds herself grunting to a group of mountain gorillas for the first time. Accepted by these gentle giants, Charlotte finds herself the target for some laddish behaviour by two young black-back male gorillas. In the dry forests of Madagascar, Charlotte meets the smallest primate in the world, a pygmy mouse lemur that would fit in the palm of her hand. Apes and monkeys never got across to the island of Madagascar, and in their place some weird and wonderful primitive primates flourish here. Bamboo lemurs live off shoots of giant bamboo, which is heavily laced with cyanide. Golden bamboo lemurs consume what should be 12 times their lethal dose of cyanide every day and survive. In northern Madagascar, Charlotte tackles one of the hardest landscapes in the world, the limestone tsingy. Her reward is to meet some crowned lemurs that scale the vertical rock faces with apparent ease. Deep in the caves beneath she unravels the mystery of the giant

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