Physical Anthropology

What is Evolution

Eddie French's image for:
"What is Evolution"
Image by: 

Watch a documentary on the origin of life and you will soon see if you are of the intensely inquisitive variety glaring gaps in the story of how life evolved from long chain molecules to multi-celled life forms, or indeed, how the long chain molecules got there in the first place.
I'd like to skip the story of how these molecules came into being at this time because for me the story of sexual reproduction is by far a much more interesting tale.

As this article progresses I will, out of necessity, resort to a little Ok, a lot of anthropomorphizing. This is a useful device to employ when the full explanation of the events happening and the mechanisms behind those events would take the completion of a university degree to even begin to explain here.

Right, that's the disclaimer out of the way where was I?
Ah yes, sexual reproduction.

We must go back a long way to get to where it all started, three and a half billion years or more. This was the time of the Prokaryote cell, a much simpler form of life than the one which gave rise to the likes of you and I, trees, plants and fish. You see where this list is going.
Prokaryotes are still with us in some forms but it's the Eukaryotes I'm interested in. You and me.

Let's imagine we are observers back at the dawn of multi-cellular life. What can we suppose happened back then, when the whole world was awash with these lakes and shallow seas which have been labelled so colourfully 'organic soups'. These soups were populated by many free floating long chain molecules, dashed together by electrical storms and solar energy. These complicated molecules only become positively viable after they formed a protective membrane around themselves - a cell wall.

Once enclosed inside this cell wall the molecule is no longer free floating, the molecule is imprisoned within a cell of its own making.

This imprisonment brings to mind all sorts of interesting questions
How does it now divide the long molecule chains' to reproduce?
How does it derive energy to survive?
How does it achieve locomotion?

The answers to at least some of these questions may begin to lead us in the right direction in our quest to find the truth about the first sexual act.

Let's suppose that this newly imprisoned chain of very complex molecules is floating around in a nice warm, if rather crowded organic soup, heated nicely by a nearby volcanic vent. Life is great. It's warm, there are no predators to speak of and no deadlines, just float along with the current. There's no danger of being carried to somewhere cold and hostile - those places just don't exist in these shallow lakes. Now let's suppose that the energy source which powers the cell is eclipsed for a time, let's say the light of the sun is blocked out we've all heard how this happens from time to time and energy levels subside.

Let's not forget that evolution has not really gotten started yet, at least not in the way that we understand it today.

So, here is this cell, fading fast and searching for a new energy source just like those little micro chip wheeled robots do on the partially electrified base you've seen them on telly. This particular cell has a weak spot in the cell wall which lets in other chemicals, chemicals which just keep it alive for a time. In effect it has become a sort of filter feeder. It has no way of venting waste yet except back out through the weak spot in the cell wall. It assimilates all that it 'eats' in order to grow and eventually divide, sharing the cell membrane with its clones'.

Then it eats something unusual, something a little more complicated than the usual fare. This new food has something to say about the assimilation process. The language is chemical numbers and incompatible molecule sizes and shapes but it talks nonetheless.

Now our cell has a problem. It just can't seem to fully assimilate the new food into the chain. Never mind, it's not giving too much trouble just now so maybe it'll all be alright.


Everything seems ok until the next division. It seems that the interloper is also trying to divide, inside the cell wall! Our cell now sends a chemical messenger that blocks this audacious act right away. The interloper evens the score by blocking the division of our cell when the time comes. We seem to have a Mexican stand off.

Not so.

What we have is the beginning of co-operation between species. The environment is so crowded that all life is virtually in contact with all other life in the shallow lake and soon our cell takes in another group which is compatible with the fragment within. The interloper is now more powerful (has more influence inside) than our little cell and begins to dictate terms. It also uses some our cell's innards to stay active (alive). Now both parties must look for matching chains to divide. This is not a matter of searching the seas for kindred souls, no, it's merely a matter of ignoring the mass of life which is brushing up against it constantly until just the right bit comes its way.
The right bit just happens to be similarly enclosed within a cell wall.
Our cell now has to chemically 'persuade' the latest player in this game of life to give up a bit of itself and somehow get this fragment through the cell wall.
Our luck is in. This new player has a similar weak spot and the deal is done.

You see where this is going don't you.

Some might think that this incredibly fortuitous meeting is just too impossible to even be considered - even as a hypothetical scenario - and it probably was for millions and millions of years. However, all the misses are done and dusted over previous aeons and our cell was the one to hit the home run.
We just happened to be there when it finally went down.

Back to the sex.

Now these cells all cloned from our lucky cell carry the same genetic material with them.
(I presume to call the material 'Genes' now because it was the result of the combination of two different life forms) These cells all have the weak spot in the cell wall and the interloper fragments inside. In fact, these cells are a blending of the two original cells on almost equal terms.

All that needs to happen now is that history repeats itself.

And it will, but not until many more useful elements have been carefully guided through the 'mouth' of the new species of cell which is mingling with the dense crowds in the warm organic soups of planet Earth.

As the cells specialise more and more in the previously random selection of dinner choices they begin to get more selective in the sensing and eventual assimilation of organisms that would give the most energy for the least effort, ignoring disparate organisms for more closely related cells.

In effect what we have now is the swapping of genetic material for the purpose of reproduction. Over time these new organisms could possibly chemically detect the required fragments if they were closer to the exterior cell wall of the prey and not buried deep within the nucleus. Over even more time the 'prey' might get fed up being eaten whole and offer up the genetic material, pushing it out toward the world outside the membrane. This protrusion might be recognised by the hunter and sought out. The bigger the protrusion containing the genetic material the better the chances are for reproduction.

Sound familiar?

Well, it's a mighty jump from these humble beginnings to full blown sexual reproduction and the human perception of man as the hunter but it all had to start somewhere and if all those sketchy documentaries on the subject are anything to go by then my theory is as good as the rest.

More about this author: Eddie French

From Around the Web