The mysterious microbes shifting humanity's place in the tree of life

Puzzling, slow-living microbes named after
 Loki, the trickster of Norse mythology, are helping solve
one of evolution's biggest mysteries:
the origin of complex life

LIFE

By THE_D_R_SINH

Tiny microbes called archaea, shown

 here with the thread-like flagella used

 for locomotion, are shining new light

 on life’s earliest evolutionary history

Eye of Science/Science Photo Library

EVEN the gods struggled to cope with Loki, the trickster of Norse mythology. So it may have been foolhardy to beckon the notorious schemer into the world of modern science – but that’s what a team of researchers did in 2008. They had struggled to find a group of hydrothermal chimneys at the bottom of the Norwegian Sea because the heat signature seemed to keep shifting. When they finally tracked down the rocky spires, they thought it would be apt to name them Loki’s Castle in reference to Loki’s ability to confound those around him by shape-shifting.

The castle’s smallest residents soon began stirring up trouble too. Strange microbes living there (inevitably dubbed the Lokis) are shedding light on one of evolution’s biggest mysteries: the origin of complex life. What is more, they have reignited an argument about the shape of the tree of life, one of biology’s most fundamental ways of describing the rise of life on Earth, with implications for all of us. The discovery of the Lokis may leave humanity lumped together with a group of weird single-celled organisms called archaea, dramatically redefining our species.

Textbooks will tell you that shortly after biological cells appeared on Earth more than 3.5 billion years ago, there was a parting of the ways that sent life down three distinct branches. One led to bacteria – single-celled organisms only visible through a microscope. A second led to similarly simple but biologically distinct microbes called …