Earth's complex life began with a fungus

"On Earth, biological organisms are getting more and more interesting as the years tick by. As the unbroken chain of life continues, the combined factors of inheritance, random mutations, and horizontal gene transfer serve to increase the total amount of genetic information found in the genomes of the most complex organisms. This results in them gaining more specialized features, and many new characteristics begin emerging."

"Some organisms thrive together in colonies, with identical unicellular lifeforms binding to one another to ensure that the majority of them survive and thrive. Other organisms develop multicellularity: the ability for a single organism to produce multiple component parts - cells - that all remain bound together as part of the original, parent organism. And still other organisms become differentiated, where new subcomponents develop within an organism, conferring features and abilities onto it that it didn't possess before."

"Evolving well before plants or animals arise on our planet, these early fungi likely thrive in aquatic environments and possess flagella: tiny, thread-like tails that allow them to control their motion through water. The fungi are all eukaryotic organisms that reproduce through the creation of spores, which mature atop microscopic, soft-tissue structures known as fruiting bodies. In aquatic environments, flagella are required to transport spores away from the parent body, towards locations where they can gain nutrients, thrive, and survive until they reach reproductive age."

At roughly 12.5 to 12.6 billion years after the Universe began, biological organisms on Earth increase in complexity through inheritance, random mutations, and horizontal gene transfer, which raise total genetic information in complex genomes and produce specialized traits. Some unicellular organisms form colonies of identical cells to improve survival. Other lineages evolve multicellularity, producing multiple bound cells from one parent. Additional lineages undergo differentiation, developing internal subcomponents that confer new functions. One result is the emergence of fungi as a distinct kingdom: early aquatic, flagellated eukaryotes that reproduce via spores atop microscopic fruiting bodies, using flagella to move spores through water toward nutrient-rich locations.

Read at Big Think