We’re all mutants. Or largely mutant.

Science News has the results of a new study that shows healthy “normal” humans have a “large patches” of mutated cells in lots of different kinds of healthy tissues:

About 95 percent of healthy people had patches of mutated cells in at least one of the 29 tissues examined, including kidney, muscle and liver, researchers report in the June 7 Science. Most of those mutations found in the 488 people in the study are harmless, but some have been linked to various cancers.

About 40 percent of tissues had at least one big patch of mutated cells, and about 5 percent of the studied samples had five or more mutant patches, Keren Yizhak of the Broad Institute of MIT and Harvard and colleagues discovered.

Skin, esophagus and lung tissues had more of these mutant patches than other tissues, the researchers found. Those three tissue types are exposed to more ultraviolet light, pollution, smoke or other environmental factors that may cause mutations than internal organs, which are not directly exposed to these external factors.

The Science study is here.