Evolution is the continuous, random, natural process of change in genetic code and adaptation in life forms, that compete in an environment with limited resources and are constantly challenged by its dynamism. It is nature's method of trial and error, through which it creates different life forms, with varied genetic constitutions and therefore, varied characteristics and skills. It sustains those life forms that have the skills and natural abilities to survive and eliminates those, which cannot adapt. The ones that survive, reproduce successfully. They preserve their characteristics through genetic inheritance and their kind becomes more numerous, ultimately dominating that particular ecological system. In short, it is a game called 'Survival of the fittest and smartest'.
Divergent Evolution Explained
Divergent evolution is a gradual process. Organisms of the same species, with marginally different variations in genetic code, are subjected to vastly different environmental conditions due to voluntary or forced migration from the earlier familiar habitat. Over a period of time, every group and its succeeding generations face different environmental conditions and challenges. The criteria for survival are different for these groups now, who once belonged to the same ancestral stock. Therefore, different characteristics are promoted by natural selection in these groups.
Over a long period of time, small and gradual changes in the features and constitutions of their succeeding generations, cumulatively gives rise to a new species in both groups. They now look significantly different from their common ancestral stock. Thus, they 'diverge' from their original ancestral line and form their own new species.
To be classified as a separate species, there needs to be a significant difference in the new stock, from the original one, in more than one feature. As those significantly diverged groups, now classified as separate species, are subjected to increasingly divergent environmental conditions, they differ more and more in their appearance and instincts. The need for adaptation modifies succeeding generations by selecting conducive traits from the varied gene pool.
Ultimately, after millions of years, the result is that they diverge so much in all their features, in their appearance, mannerisms and functions, that it is difficult in some cases to even believe that they had the same ancestors. Examples of such divergences abound in plenty. Humans, apes, and monkeys had the same ancestor. One can imagine that the original creature, a tree shrew type of life form, the long lost ancestor of us humans, the apes, and the monkeys must have migrated. Over a time period of millions of years, it changed, adapted, in succeeding generations to become the Homo Sapiens or the 'Wise Man'.
The underlying machinery that makes this beautiful process possible is that of genetic variance and inheritance. It is a kind of 'genetic memory' that is passed along through the replicated strands of DNA (Deoxyribonucleic nucleic acid) molecule to each offspring, one each from the biological mother and father, creating the much-needed variance in the gene pool.
Imagine retracing evolutionary lines of each organism, back in time, joining back all the diverging species' lines and making them converge back to their ancestral stock. Every primal ancestor is again a descendant of another primal stock.
So, as you keep converging the lines together, you find that the birds, reptiles, mammals, insects, vertebrates, non-vertebrates, the plants and all other forms of life converge into a single primal ancestor, a unicellular form of life that was the first to appear on Earth. So, we are all related by this genetic link.
This diverging type of evolution process is something that never ceases as long as there is a change in the environment and there are mutations and variations in genetic structure. It is happening even today and who knows what our descendants will look like.
If we carefully observe the development of the limbs in vertebrates, we see a prime example of divergent evolution. The vertebrate arm in a human, the side fin of a whale (a mammal), the wing of a bat, and the paws of a cat - all these evolved from one primal stock of ancestors. One can see how it has undergone change in form and function over millions of years, adapting according to the need.
Another example are the Felines, the perfect predators on Earth. Felines are the only kind which come in two sizes, the diminutive domestic cat/wild cat and the big cats. If you compare a tiger and a cat, you can see that they have almost exactly similar features, but only the sizes are different. They shared the same ancestry, but became separate species. The cat evolved into the diminutive size since that aided its survival near human settlements, while the big cats remained big, which aided their survival in the wilderness of Africa and Asia.
More such examples can be found in almost every species, as we all ultimately owe our origin to a single ancestor. Thus, divergent evolution is a force of nature that creates the beautiful variety of form and structure in plants and animals. In future, man may outgrow this Earth and colonize other planets in our solar system. Groups of humans may settle on different planets. With this type of evolution at work, who knows what our succeeding generations will evolve into, trying to adapt to the harsher space environment. One can only wonder.