Mitochondrial merger Eukaryotes have a number of innovations compared to their more primitive archaeon ancestors. (scientificamerican.com)
The first option, called the big - bang or mitochondria - early theory, predicts that a primitive archaeon engulfed a bacterium, an event that drove the development of eukaryotes. (scientificamerican.com)
So, some 2 billion years ago, scientists think that one archaeon engulfed a bacterium. (washingtonpost.com)