The species that is now Mitochondria was an entirely different species.
We carry Mitochondrial DNA, while the human side is Nuclear DNA…nucleus of every cell.
Birth as we know it wouldn’t have happened without a third species invading our cells. We know it as placenta.
Profound that we fight microbes, but without two (that we know about), our species literally (accurate use) would not exist.
At all.
Just, wow.