Published on April 26th, 2012 | by James Ayre
Rare Protozoan Confirmed as Most Distant Relative of Humans
Humankind’s most distant relative has been found to be a very rare micro-organism living in the sludge at the bottom of a Norwegian lake.
The discovery may give insight into what life looked like one billion or more years ago.
The protozoan lives in a small lake 30 km south of Oslo, Norway. After the researchers analyzed and compared its genes to all other known species in the world, they found that it did not fit on any of the branches of the tree of life. It is not a fungus, alga, parasite, plant, or animal.
“We have found an unknown branch of the tree of life that lives in this lake. It is unique! So far we know of no other group of organisms that descend from closer to the roots of the tree of life than this species. It can be used as a telescope into the primordial micro-cosmos,” an enthusiastic Kamran Shalchian-Tabrizi, head of the Microbial Evolution Research Group (MERG) at the University of Oslo, is quoted as saying.
The tree of life is easily divided based on whether the organism has one or two flagella. Animals, fungus, and amoebas have one. And plants, algae, and single celled parasites called excavates, originally had two.
The protozoan in the Norwegian lake has four.
“Were we to reconstruct the oldest, eukaryote cell in the world, we believe it would resemble our species. To calculate how much our species has changed since primordial times, we have to compare its genes with its nearest relatives, amoebae and excavates,” says Shalchian-Tabrizi.
The protozoans are only 30-50 micrometers long and only viewable under a microscope. They have not been found anywhere other than this lake, and aren’t present in large quantities.
“We are surprised. Enormous quantities of environmental samples are taken all over the world. We have searched for the species in every existing DNA database, but have only found a partial match with a gene sequence in Tibet. So it is conceivable that only a 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.”
“They are not sociable creatures. They flourish best alone. Once they have eaten the food (algae), cannibalism is the order of the day,” notes Professor Dag Klaveness of MERG.