You probably remember the taxonomy chart from science class (whether or not you can recite it): kingdom, order, phylum, etc. You probably don't remember the tree of life, though, also known as the phylogenetic tree. That's a chart created to try and piece together how species evolved into other species, like a large-scale family tree.
Well, scientists in Norway think they've found something that is further towards the roots of that tree than just about anything else. 20 years ago, a tiny little microorganism was found in a tiny little lake about 30 kilometers south of Oslo. The University of Oslo has been trying to figure out what it is ever since, and they've just concluded that that microorganism is, in fact, mankind's oldest relative. They're giving it a new genus on the taxonomy chart, Collodictyon, and note that of everything that they cross-referenced the organism with over 20 years of searching, they only got a single partial match with something in Tibet. The organism itself hasn't been found anywhere outside that one lake.
The second link in that last paragraph, which goes to Science Daily, will be able to give you the nitty-gritty on what the Collodictyon is made of and all its various parts, as well as its daily life, which basically consists of living in the muck, waiting for some algae to float by, popping up, eating it, and then sinking back into the muck to munch. When they run out of algae, they start eating each other.
I'll leave to you the inevitable humanity's-oldest-relative jokes about who or what else that description might fit.