Spontaneous human combustion (SHC) is a name used to describe cases of the burning of a living human body without an apparent external source of ignition. Some[who?] regard SHC as a unique and currently unexplained phenomenon, others feel that cases described as SHC can be understood using current generally-accepted scientific principles, but the most common view by far is extreme skepticism. While there have been about 200 cited cases worldwide over a period of around 300 years, most of the alleged cases are characterized by the lack of a thorough investigation, or rely heavily on hearsay and oral testimony. In many of the more recent cases, where photographic evidence is available, it is alleged that there was an external source of heat present , and nothing occurred spontaneously.