On the Origin of Stemness and Ancient Cell Lineages in Single-Celled Eukaryotes

It is clear the emergence of stem cells and their development was the prerequisite for the evolution of multicellularity [12], but the evolutionary origin of stem cells and their evolutionary history remain obscure and poorly understood [13].Unfortunately, microbial eukaryotes remained virtually unstudied.It was Ernst Haeckel 145 years ago who first considered singlecelled organisms as the phylogenetic ancestors of multicellular organisms [14].However, protist researchers in the past could not develop adequate experimental systems, with which to study and elucidate the evolutionary history of stem cells and functional multicellularity at the level of a single-celled organism.