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Researchers Luella and Winthrop Kellogg were inspired by an article about the wolf-children of India whom everyone assumed lacked intelligence, but he believed the children simply adapted to their environment from a young age.

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The unusual siblings were treated as similarly as possible.

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Gua the chimp developed human behaviors much faster than her "brother," testing ahead of him in tasks like using a spoon or cup and responding to simple commands.

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But she was less independent than Donald the human when it came to human interaction, often clinging to her researcher for comfort and affection.

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The experiment was meant to last for 5 years, following the growth of each child, but after just 9 months, Kellogg decided to end it.

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Donald, on the other hand, had begun mimicking Gua's chimpanzee sounds, such as her "food bark."

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Donald was adapting to his surroundings the way humans do, which in this case meant learning how the chimp communicated.

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Donald was adapting to his surroundings the way humans do, which in this case meant learning how the chimp communicated.

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