This theory states that an important part of aging is determined by what happens to our genes after we inherit them. From the time of conception, our body's cells are continually reproducing. Each time a cell divides, there is a chance that some of the genes will be copied incorrectly, this is called a mutation. Additionally, exposures to toxins, radiation or ultraviolet light can causes mutations in your body's genes. The body can correct or destroy most of the mutations, but not all of them. Eventually the mutated cells accumulate, copy themselves and cause problems in the body's functioning related to aging.
Genetic theories of aging are only concerned with the genes in sperm and egg cells. Those are the genes that can be passed down from generation to generation. Somatic mutations are changed in the genes that occur after you have inherited them, but cannot be passed down to your children.
Like all the aging theories, the somatic mutation theory only explains a piece of the puzzle. Of course, there is evidence of gene mutations causing damage and even death, but it cannot be said that this is the most important factor in aging.
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