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Let鈥檚 begin with the obvious. You are the product of billions of years of evolution, the accumulation of trillions of gene-copying errors. That鈥檚 what led single cells to evolve into jellyfish, ferns, warthogs and humans. Without mutations, life would never have evolved into Darwin鈥檚 鈥渆ndless forms most beautiful鈥�, and you would never have seen the light of day.

Today, while most of our genes are undeniably Homo sapiens, many of us also carry DNA from other species. We have known for a decade that people of non-African descent inherit between 2 and 4 per cent of their DNA from Neanderthals. And we now know that DNA from several other extinct human species is also still in circulation, on every continent including Africa.

Not only do you carry DNA from other species, you probably also play host to other people鈥檚 cells. Before you were born, your mother鈥檚 cells crossed the placenta into your bloodstream. Decades later, some of these migrants are still there in your blood, heart, skin and other tissues. This 鈥渕icrochimeric鈥� exchange was mutual: if you are a mother, your children may still be inside you in the form of their embryonic stem cells.

You may even be carrying cells from your grandmother and any older siblings. Because microchimeric cells persist for a long time, there is a chance that during pregnancy, your mother was still carrying cells from any previous children she had, as well as cells from her own mother 鈥� and she may have shared some with you.

Maternal microchimerism is extensive, says at the University of Washington in Seattle, and probably useful too. 鈥淭here are so many examples in biology where organisms thrive as a result of exchange 鈥� why wouldn鈥檛 it also be useful for humans to exchange cellular material?鈥� Fetal cells may help to repair a mother鈥檚 damaged heart tissue and . Other research shows that mothers can end up with their child鈥檚 DNA in their brains, something that may even be linked to a .

In future, we could become mutants by design. Gene-editing tools like CRISPR should allow genetic diseases to be treated by injecting genes into the body. For example, a small number of people with a mutation in the CCR5 gene, which supplies a protein to the surface of white blood cells, are resistant to HIV. CRISPR opens the possibility of inserting that mutation into the DNA of others, giving them a genetic vaccine against the virus.

From there, it鈥檚 only a baby-step to genetic superpowers. Ethical questions notwithstanding, future generations could be enhanced with genes for extra-strong bones, lean muscles and a lower risk of cardiovascular disease and cancer. A mutation in the ABCC11 gene currently found in about 1 in 50 Europeans . Think of the savings on deodorant. Be warned, however: this mutation also makes your ear wax dry up. Swings and roundabouts.

This article appeared in print under the headline 鈥淵ou are鈥� a mutant鈥�