 It has also been hypothesized that vampire legends were influenced by individuals being buried alive because of shortcomings in the medical knowledge of the time . In some cases in which people reported sounds emanating from a specific coffin , it was later dug up and fingernail marks were discovered on the inside from the victim trying to escape . In other cases the person would hit their heads , noses or faces and it would appear that they had been " feeding . " A problem with this theory is the question of how people presumably buried alive managed to stay alive for any extended period without food , water or fresh air . An alternate explanation for noise is the bubbling of escaping gases from natural decomposition of bodies . Another likely cause of disordered tombs is grave robbing . 
