Answers

2016-06-26T21:15:14+08:00
I think the devices people use to communicate with each other during prehistoric age are stones, and plants which are common around there surroundings. Maybe we cannot call it a device but a things used by the ancient people living in prehistoric age. 
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2016-06-27T07:51:39+08:00
No it was not plants and stones it was water and trees first you wrote it in the water and then put it on a tree 
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