Oldest human ancestor found in Norway lake
By Lee Ji-eun
Norwegian scientists found a unique single-celled organism, which is not involved in any branch of the tree of life, LiveScience.com reported Monday.
Researchers in the University of Oslo said that they discovered a new category of organism called Collodictyon as it is not an animal, plant, parasite, fungus or alga, in the latest edition of journal Molecular Biology Evolution,
They expect that it may provide insight into what life looked like on earth hundreds of millions of years ago as the organism is concerned a world’s oldest living organism and man’s remotest relative.
The organism, a type of protozoan or a very small living thing that has only one cell, has been known to science since 1865. However, scientists haven’t been able to get a grip on its genetic makeup because it was difficult to culture in the lab. It was placed in the protist kingdom on the tree of life mostly based on observations of their size and shape.
Lately, researchers were able to grow enough of Collodictyon in the lab to analyze its genome. They found it doesn’t genetically fit into any of the previously discovered the five main groups of eukayotes or an organism whose cells contain complex structures enclosed within membranes although it has membrane-bound internal structures.
Collodictyon is about 30 to 50 micrometers long, which is about the width of a human hair. It eats algae and doesn't like to live in groups. It is also unique because it has four tail-like propellers called flagella instead of one or two like other protozoa.
It also has unique characteristics usually associated with protists and amoebas, two different branches. This left researchers wondering where the microorganism fits into the tree of life.
The scientists analyzed its genetic code to see how similar it is to organisms that have already been genetically catalogued. They compared its genome with those in hundreds of databases around the world. In all that looking they "have only found a partial match with a gene sequence in Tibet." They think this organism belongs in a new group on the tree of life.
"It is conceivable that only few other species exist in this family branch of the tree of life, which has survived all the many hundreds of millions of years since the eukaryote species appeared on Earth for the first time," a researcher said.
The researchers said that the ancestors of this group might be the organisms that gave rise to these other kingdoms including the amoeba and the protist. ”If that's true, they would be some of the oldest eukaryotes, giving rise to all other eukaryotes, including humans,” said a researcher.