For the first time in one billion years, two lifeforms truly merged into one organism

Evolution is quite a wondrous and lengthy process, with some random bursts of activity that are responsible for the diversity of life on our planet today. These can happen on large scales like with the evolution of more efficient limbs. They also occur at microscopic cellular level, such as when different parts of the cell were first formed.
Now, a team of scientists have detected a sign of a major life event that has likely not occurred for at least one billion years. They’ve observed primary endosymbiosis–two lifeforms merging into one organism. This incredibly rare event occurred between a type of abundant marine algae and a bacterium was observed in a lab setting. For perspective, plants first began to dot our planet the last time this happened. The results are described in two papers recently published in the journals Cell and Science.