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In this paper, we follow the evolutionary origins of cells as unicellular organisms and their evolution towards multicellularity, with a focus on plants and animals, both of which have two basic types of organismal self-identities: the immunological and the neuronal. Most cells of the animal immune system and its mesenchymal tissues are amoeba-like without flagella or cilia and form only loose cell–cell contacts. On the other hand, neuronal and epithelial cells are typically ciliated and assemble epithelial or neuronal synapses. In contrast, walled cells of higher plants lack flagella or cilia. However, lower plants up to the gymnosperm tree Ginkgo biloba have flagellated sperm cells. In our symbiotic concept of eukaryogenesis, the first ancient eukaryotic cells emerged from the merger of a large amoeba-like host cell with a small flagellated guest cell which later transformed into the eukaryotic nucleus. This duality at the …