Before the development of complex Human society we would have led a more primitive lifestyle, displaying more simple behaviours and using more basic forms of language than the ones we recognise today. Despite this massive contrast with life in the modern world, there are still people that actually live in the wild and seem to have adapted well to their new surroundings.
Although thankfully quite rare, cases of feral children have been reported from all around the world, with over 100 cases having been recorded today. Feral children are young children that have lived away from Human contact for so long that they have little or no understanding of Human care or social behaviour, and even language (many never learn how to speak once back in Human society).
The circumstances for which the child has been abandoned differ, with some having been deliberately isolated by other people and others living in the wild completely on their own, but some are taken in and are actually brought up by animals. Numerous cases of children being found in the wild with varying species have cropped up, with the child displaying behaviours more similar to the animal than to a Human child.
Some of the most famous cases of feral children having been adopted by animals include:
Kamala and Amala - also known as the Indian Wolf Girls they were found to have been living with a pack of Wolves near Calcutta in 1920. They were nocturnal with eyes that shone in the dark, moved around on all fours and had an acute sense of both smell and hearing. Oxana Malaya - was found to have lived most of her life with Dogs, in the Ukraine in 1991 when she was only eight years old. She growled, barked, moved around and crouched like a Dog, and smelt her food before she ate it. She had extremely good smell, sight and hearing but found it difficult to master language.