Ed Yong

In more than 3 billion years of existence on Earth, this merger happened once—and resulted in the complex life we have today:

There are many possible explanations, but one of these has recently gained a lot of ground. It tells of a prokaryote that somehow found its way inside another, and formed a lasting partnership with its host. This inner cell—a bacterium—abandoned its free-living existence and eventually transformed into the mitochondria. These internal power plants provided the host cell with a bonanza of energy, allowing it to evolve in new directions that other prokaryotes could never reach.

If this story is true, and there are still those who doubt it, then all eukaryotes—every flower and fungus, spider and sparrow, man and woman—descended from a sudden and breathtakingly improbable merger between two microbes. They were our great-great-great-great-…-great-grandparents, and by becoming one, they laid the groundwork for the life forms that seem to make our planet so special. The world as we see it (and the fact that we see it at all; eyes are a eukaryotic invention) was irrevocably changed by that fateful union—a union so unlikely that it very well might not have happened at all, leaving our world forever dominated by microbes, never to welcome sophisticated and amazing life like trees, mushrooms, caterpillars, and us.

A couple has trouble finding a treatment for their 13-year-old daughter’s undiagnosed illness. Sequencing her genome provided a promising path to an answer:

“The family has a mantra: It’s a marathon not a sprint. They were battle-hardened from a long road of possible fixes and disappointments. ‘We thought: This is great but it’s probably just going to be another data point that we add to the binder,’ says Steve. ‘Lilly’s already had a lot of bad news in her life,’ says Gay. ‘Her biggest fear was that we wouldn’t find anything. Not knowing would be the worst thing.'”

A look at ecologist Bob Paine, whose mentorship has produced a long line of influential scientists throughout his five-decade career:

“Soon, Paine’s students were growing up and embarking on careers of their own. Few have spawned as rich a legacy as Jane Lubchenco and Bruce Menge. They met as graduate students in Paine’s lab in 1969, married two years later and began a partnership that has generated more than 31 students and 19 postdocs. After the pair left Paine’s lab, they took his experimental approach to the US east coast; she focused on plants and herbivores, while he concentrated on predators. By enclosing, excluding and removing species at different points along the New England shore, they showed that fierce waves can keep predators such as starfish at bay, allowing mussels to dominate. But in sheltered areas, predators kept mussels under control, allowing Irish moss (Chondrus crispus), a type of red alga, to take over. The work revealed how the environment can control interactions between species.”