Evolution: a never ending process
Most scientists date the appearance of life on our planet at around 3.5 billion years ago. A fraction of these life forms left traces, or fossil forms, for us to find. If there is one conclusion we can draw from reviewing the story of life, it is the fact that it was subject, and continues to be subject, to change.
It is safe to say that as long as there is life on our planet, it will change over time. In other words, it will evolve.
This notion of an ongoing process of change has important implications. It renders the expression of “missing link,” or “intermediate fossil” meaningless.
Quite often, scientists who study and teach evolution are challenged to show such intermediate fossils, with questions like “Mommy, Did Apes Evolve from Dogs?” Questions like these are then followed by statements like “Scientists cannot produce the fossils of half-evolved dinosaurs or other creatures.”
The challenge is clear: unless one can produce these half-evolved creatures, whatever they are supposed to look like (an ape with a dog’s head?), then the concept of evolution must be wrong. One needs to realize, however, that the way in which the question is posed is misleading.
In an earlier blog I referred to all of us a being mutants. This tongue-in-cheek statement makes the point that we are all unique because of a small number of mutations that set us apart from our parents. The mechanism that supports evolution resides in the tiny genetic changes that occur as a result of mutations – not from a sudden appearance of a different body type or part.
However, when these small changes are allowed to accumulate over vast amounts of time – say millions of years – the results can be significant. The fossil record tells us that these results were, in fact, very significant: hundreds of thousands of animal and plant species flourished and perished over the last 3.5 billion years.
Each species exhibited tiny mutations in each generation. Sometimes, the results of the mutation gave that species an advantage that allowed it to survive where others did not – thus allowing it to continue to impact the story of life on Earth.