It turns out that parasitic bacteria may be to blame for the eventual evolution of mitochondria, the powerhouses of animal and plant cells. Scientists have found that these bacteria first acted as energy parasites before becoming beneficial.
The origin of mitochondria began about 2 billion years ago. This event helped spur further evolution as it powered animal and plant cells. Yet very little is known about the circumstances surrounding the origin of mitochondria, which is why scientists decided to take a closer look.