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Multiple experimental evidences have confirmed that at the molecular level, cancer is caused by lesions in cellular DNA.
For about 100 years, scientists thought that peptic ulcers were caused by stress, spicy food, and alcohol. Later, researchers added stomach acid to the list of causes and began treating ulcers with antacids. Now it is known that peptic ulcers are predominantly caused by Helicobacter pylori, a spiral-shaped bacterium that normally exist in the stomach.
It is believed that the Incas used anesthesia. Evidence supports the theory that shamans chewed cocoa leaves and drilled holes into the heads of patients (letting evil spirits escape), spitting into the wounds they made. The mixture of cocaine, saliva, and resin numbed the site enough to allow hours of drilling.
Blood is approximately twice as thick as water because of the cells and other components found in it.
The U.S. Preventive Services Task Force recommends that all women age 65 years of age or older should be screened with bone densitometry.