But as Johns Hopkins' Cristian Tomasetti most of these mutations don't crop up in sensitive spots. Some might manage to occur in, for instance, an oncogene, and might make those cells better at dividing, but the Atlantic notes that one mutation isn't often enough to make a cell cancerous. "Evolution has built in a formidable number of safety nets," Albert Einstein College of Medicine's Jan Vijg tells it.
The Atlantic adds that which kinds of cells these mutations occur within is also important, as some tissue types have higher turnover rates than others, and that environmental factors affecting different cells like UV radiation and skin also have a role. The number of mutations a person's cells hold is also influenced by that person's age, as older people have had more time to accumulate changes.
Additionally, other cells might not have accrued the same set of mutations. "[Y]our body slowly becomes a mosaic of different cell groups, each with their unique mutations," the Atlantic writes.