“The results were pretty astounding. All non-bacterial life on Earth – called eukaryotic life – can now be divided into four main groups instead of the five groups that we have been working with up to now,” says Kamran Shalchian-Tabrizi, an associate professor from the University of Oslo’s Department of Biology
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All life on Earth can be divided into two essentially different life forms—eukaryotes and prokaryotes. The eukaryotes gather their genetic material in a nucleus, while the prokaryotes (bacteria and archaea) have their genetic material floating freely in the cell. Eukaryotic organisms—such as humans—can, as a result of the new findings, be divided into the following four categories:

• Plants (green and red algae, and plants)
• Opisthokonts (amoebas, fungi, and all animals—including humans)
• Excavates (free-living organisms and parasites)
• SAR (the new main group, an abbreviation of Stramenophiles, Alveolates, and Rhizaria, the names of some of its members)

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Three billion years ago, there was only bacteria and Archaea. Eukaryotic life, which comprises all multi-celled organisms, developed in the sea—probably between 1.2 and 1.6 billion years ago. It was not before about 500 million years ago that the first creatures crept onto land.