However, the animal that’s arguably helped us the most in understanding both our biology and evolution more broadly is the ...

The hybrid is what scientists call a human-animal chimera, a single organism that’s made up of two different sets of cells — in this case, a mouse embryo that has both mouse cells and human cells.

Scientists have engineered a hybrid mouse with a gene that predates all animal life. The team replaced a single gene in the mouse stem cells with a version from an ancient, single-celled ancestor ...

The genes were injected during the mouse’s embryonic state and created a chimera, which is the term for an animal that sports two distinct sets of DNA. Related Story Scientists Grew a Mouse ...