 A great debate had existed between Alzheimer's disease researchers about the relevance of amyloid prior to the 1990s – many scientists believed amyloid was a tombstone of the disease and was not critical to the development of the disease.However, because the only difference between the family members who developed Alzheimer's disease and those that did not in these families was the inheritance of the mutation in the amyloid gene, this suggested that the amyloid protein itself could cause the disease.The idea that amyloid could cause the disease influenced scientific research until this day.