https://en.wikipedia.org/wiki/Human_chimera https://en.wikipedia.org/wiki/Human_chimera It happens, although only when we are at a very early stage of developm

https://en.wikipedia.org/wiki/Human_chimera https://en.wikipedia.org/wiki/Human_chimera It happens, although only when we are at a very early stage of development, a time when we share some traits with jellyfish. The growth of an embryo tracks our evolution. If you ever see a dog, or a person (see the model taylor muhl) with a color split down the middle of their body, there is a reasonable chance they joined with a twin in utero. Absent a color split, no doubt many of us are totally unaware that we may contain multiple gene sets.