The evolutionary tree of life is called as such because of the way species are interrelated to each other. From the base of the trunk, which represents the single-celled common ancestor that all life on earth shares, the tree grows and splits into branches: bacteria and other single-celled organisms split from the branch of the Eukaryotes, multi-celled organisms like plants, animals, fungi, etc. Then those branches split. Plants, animals, and fungus all go their own ways. And then again. Mammals end up on a different branch than reptiles, for instance, and then dogs, bears, and primates all end up on different smaller branches. On and on it goes until we end up with all the life we see on earth today. That's a gross simplification, but it works. Sort of. According to a recent paper published in the journal Nature, Canadian scientists have discovered an organism so vastly different from anything else alive that they believe it requires it's own own unique branch on the tree of life.
The organism, a microbe called Hemimastigophora, isn't a new discovery. While it is rare, scientists have known about its existence for some time. Ten species of Hemimastigophora have been known to scientists for over 100 years. While they knew it was weird, technology and genetic science hadn't progressed far enough to tell exactly how weird.
Hemimastigophora looks like one of the terrifying creatures you might see under a microscope. It moves, it hunts prey, and it utilizes microscopic body parts to get through it's day to day existence. It looks and behaves like a microscopic animal, but it's not. In fact, Hemimastigophora is farther away from any other living organism than humans are from mushrooms. According to Alastair Simpson, an author of the study:
"They represent a major branch… that we didn't know we were missing. There's nothing we know that's closely related to them."
The discovery was made by Dalhousie University graduate student Yana Eglit and a team of biologists after Eglit, on a whim, collected some soil samples on a hike in Nova Scotia. Upon examining the soil samples Eglit and fellow graduate student Gordon Lax found that they not only contained the rare microbe but contained two of them, including a previously undiscovered species of hemimastigophora which they named Hemastix kukwesjijk, after a hairy ogre from the legends of the local M'ikmaq people.
Genetic analysis of the Hemastix showed it's bizarre evolutionary lineage. Despite being a small micro-organism it's a complex multi-cellular creature which puts it in the kingdom of Eukaryotes, the kingdom that includes plants, fungi, and animals. Yet it doesn't fit in to any of those kingdoms. The scientists have now proposed adding an entirely new "supra-kingdom" to the tree of life to account for Hemimastigophora. A supra-kingdom is a fundamental separation. Again, human beings and portabello mushrooms are part of the same supra-kingdom.
Of course, proposing a new branch on the tree of life doesn't mean the rest of the scientific community will easily accept it, and if they do it will take a long time. Still this shows, once again, how much we have yet to learn about the this strange floating rock we call home.