Evolution and Survival of the Fittest

chillibreeze writer — Anand C R

We all studied in school that the giraffe's neck elongated because it kept reaching for leaves that were slightly higher up. This gave us all an impression that if an organism or a species kept trying at something, it will evolve its anatomy to suit its needs. I also wondered, not aloud to my teacher though, if humans kept wishing for wings, would we be able to fly one day? Darwin and his theory of evolution do not say it happens this way. If it did, then a cow or a horse or any other leaf eater could also have developed a long neck.

So what did happen after all? How come the giraffe developed a long neck and not the other leaf eaters? Let’s take a quick look at what science actually says about the Origin of Species and Natural Selection.

The current explanation from science about the origin of life is that of the “primordial soup”. Early earth had no facilities to support life, as it exists today. As it cooled down and other factors made it conducive, there may have been a soup of organic compounds, which, with some stretching of imagination and serendipity, could have come together in such a way that they made a molecule. Now this molecule could have been such that it attracted certain other molecules of its own type, with a physical mechanism perhaps as simple as positive charges attract negative charges. So imagine a molecule in the shape of a strand that attracted chemical compounds within the soup in such a way that another strand similar to the first got formed adjacent to it.

If we realize what just happened, it turns out to be reproduction in its most primitive form. The word used though is replication. This also means that we have looked at life in its most primitive form. After all, organisms are but a huge collection of molecules.

Now further imagine that the soup had a strand (molecule) of type-A and also of type-B. Let’s say the soup has limited resources in terms of compounds available for replication. Given this scenario, if type-B is built such that it can attract soup compounds better than type-A, type-B can produce more replicas than type-A. So type-B molecules become more prevalent in the soup. The phrase survival of the fittest implies this.

We should note that there is no conscious thought from type-B molecules to improve their 'attraction' facilities. It so happens that type-B attracts more and is better than type A for that environment. And so the type-B population is more in the soup. Now suppose that by a freak accident, the term mutation is used, a particular type of A molecule's structure got changed. And by this accident, this molecule’s structure became such that its attraction power became greater than that of type B molecules. Let’s call this one particular molecule as A'. A' will now start replicating, reproducing, type-A' strands, which are faster than type-B at replicating. You can now imagine that, given enough time, type-A' will overtake type-B in population within the soup.

So in the struggle for existence in the soup with limited resources, different types of molecules started developing different strategies to survive better. Always remember that in this hypothesis there is no scope for "conscious thought" as it exists in human strategies. Strategy here implies a series of freak accidents called mutations within the structure of a particular molecule that improves the attraction or survival capacity of that molecule and its progeny. The mutations can also deteriorate the capacity to attract, in which case, the molecule reproduces less any way. Its progeny will lose the struggle for existence anyway in the soup, eventually. So that kind of molecule will be wiped out. This is called 'natural selection', because it happens naturally, without an external entity, like for example, God.

Now further imagine that these molecules, by a series of further accidents, start developing their structure in such a way that they form a physical sheath around them. This sheath could give them protection against rival molecules, which could have developed strategies to break other molecules. Do not interpret the word 'rival' as in human rivalries and ego. If we analyze this, this is the first trivial 'body' that encapsulates genetic content or what we have so far been calling strands or molecules. The genetic content, when mutating, may improve or screw up the body built so far. However, only the improved versions, with improved facilities, get to reproduce better and improved genes are passed on to progeny. In this way, the "fittest genes" survive and continue to change for the better.

All modern day organisms such as the humans, cats, dogs etc are but 'bodies' for the 'molecules' which have undergone a series of lucky accidents, or "favorable mutations", from time immemorial.

Our genes keep changing continuously. One way in which they change is mutation, where DNA is exposed to external factors such as UV rays. Also when an egg or sperm is formed, something called crossing over happens, making each sperm and each egg produced by an individual - unique. That is the reason you look and feel different from your brother or sister.

The giraffe too is a kind of body that encapsulates its genes. It was also a leaf eater like the other leaf eating animals, with a normal neck. But it could have so happened that one giraffe with a slightly longer neck, either because of a favorable mutation in her gene structure or due to a favorable crossing over, could reach out better for the leaves at the top. So she could eat better even in places where leaves at the bottom were scarce. So food, and hence survival, became easier for her than for her kin. She probably spent more time reproducing than groping for leaves. Her offspring who inherited her long-neck trait also inherited her advantage and so did their offspring. Soon, a population of long necked giraffes came in to the picture and eventually emerged as a species in its own right.

To summarize, an organism or a species' gene structure keeps changing. Those whose gene changes agree with the available environment survive, while others whose changes disagree with the environment collapse. After all, the giraffe did not develop a long neck by "wishing" for it. It happens using the two random variables:

1. Surrounding environmental changes and

2. Lucky changes to the gene structure that match the changes in the environment by mutation or crossing over.

Further Reading: "The Selfish Gene" by Richard Dawkins
For a detailed exposition of the subject, this is an excellent book.

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Anand writes for chillibreeze.

Evolution and Survival of the Fittest

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