Once upon a time, millions of years ago, a single celled tube, Piet I think he..it was called, was floating around in the vast primordial sea. Piet wasn’t officially a tube as we now know tubes, because he was kind of amorphous in shape (actually an oxymoron because amorphous means shapeless), and didn’t really have any specific holes but rather took in nutrients and expelled wastes through his entire membrane via a process called osmosis. Piet didn’t have to be a tube because he was surrounded by the vast sea and always, from every which way, had an ocean view berth. Piet’s life was very simple and probably perfect and he didn’t really need to evolve into something else more complex but since simplicity is not considered a good thing in this world, things had to change. So, we are not really even sure that evolution was/is a step forward but without it there would be no legs to step any which way?
So, why did Piet make life more complicated by joining up with other cells? Are two cells better than one? Was he lonely and desirous of exchanging juices (and wastes) with someone else? Did the vast sea seem less vast with someone to share it with? Did he long for another to share his thoughts about the beautiful sunset? Did he just want someone else he could shit on? Or was it simply an accident? Perhaps while he was floating around another cell just accidently floated into him and they kind of grew on each other? We will probably never know, but it happened and Piet was no longer floating around all by himself and the two of them now had to figure out how to get along, whether they took his name, or the other cell’s name, or maybe they decided to hyphenate it like they do in modern marriages.
As they say, one thing leads to another, and once this pattern got set in motion it just kept going. There were all these cell couples floating around and two bumped into two and four bumped into four and eight into eight and life kept getting more and more complicated.
It probably wasn’t too difficult for the cells to get along so long as all of them still had ocean view berths, but eventually they stuck to each other in a way that some were outside and some were inside, landlocked actually, and that presented some serious problems because having no access to the sea around them, the inside ones had to shit on the outside ones and had no way to absorb the sea’s nutrients and started sucking on their outside neighbors! And somehow or other, these guys came up with an ingenious solution…THE TUBE! By arranging themselves into double rows, with space for the sea to flow between the rows, everyone had equal access! In biological terms these early tubal formations are called Coeloms.
This worked well for awhile, but, as we already know, all things must change and life loves to create increasingly complex problems for itself. So as more and more cells joined the ranks, they decided they had to specialize, develop different skills, responsibilities, etc. Also, being larger and more complex, their appetites’ increased. They needed more to eat and developed different tastes. Populations of different complex cellular arrangements increased and different tubular creatures began eating other tubular creatures and, well, there you have it!
Of course evolution is much more complex than this but to say anymore than, “there you have it” would be redundant and give all of us headaches. Suffice it to say that tubes developed within tubes and tubes learned how to eat other tubes, mate with other tubes, fight with other tubes. They developed systems to mobilize their tubes so they could chase and run away from other tubes.