Biological Origins

Abstract

The emergence of multicellular organisms was a necessary step for human evolution. A key to the development of multicellularity was the appearance of proteins promoting cell adhesion, an energy-expensive feature. At least two events facilitated the emergence of such proteins: increased oxygen levels in the early earth environment and the ability of symbiotic organisms to extract energy from oxygen (e.g., via mitochondria). Multicellularity enabled multifunctionality in which an organism could dedicate subsets of cells to specialized functions, like circulation, digestion, respiration, and sexual reproduction. Other subsets of cells could specialize in seeking better and more helpful habitats, elude predators, and chase down prey. Overall, multicellularity provided significant survival advantages to these newly emerging organisms.