Evolution has always been a source of fascination for many, primarily because many of the questions we ask about ourselves can be answered with a single concept.
It is important to remember when asking such questions, especially for people who aren’t familiar with the way biology works, that we have to work with what we have. That is, we observe, we ask questions, and answer them as best as we can. The problem is that there’s nobody to tell you if you’re right. So to ask questions like ‘Why don’t we have three arms?’ and ‘Why is our nose where it is?’ can best be answered by bringing up complications that would have happened otherwise, and this doesn’t fully satisfy anybody, anymore than ‘We do because we do’ does. The point to remember here is that scientists don’t have a telephone connection to Nature, and therefore, nothing you say can ever be fully justified by anybody, so we rely on mutual agreement. This arrangement is far from satisfactory, but it’s the best we’ve got.
Evolution however, is a genius concept that explains everything with one stroke. ‘We do because we do’ is also absolutely the correct answer to everything, but then, it explains nothing.
The father of modern evolution theory is Charles Darwin. His historical five year voyage on the HMS Beagle and his classical study on the Galapagos Islands are talked about widely, even today. There is a need to mention Alfred Russell Wallace, who also came up with the same idea and requested a joint publication. However, Darwin’s theory was much more extensively developed, which led to Wallace, an admirer of Darwin to agree that he should be known as its main architect. (Biology by Campbell and Reece)
Most people have an instinctive tendency to believe that evolution is guided, that it is directed towards complex organism that are equipped to deal with life better. And indeed it does seem so. This classic picture is probably to blame for this misconception.
There is nothing further from the truth. When you think about evolution being directed towards making the perfect organism, it suggests that evolution is some sort of all powerful entity with a mind and will. Stepping clear of religious explanations, it’s important to understand that evolution cannot see ahead and make decisions based on which models might fail.
Evolution is trial and error.
Evolution is a process that spans billions of years, and that puts into perspective the ‘massive changes’ that we see when we visualize a single cell morphing into a human being, which is what most of us see. However, humans are not the end of a chain of evolution, and indeed, if they were, no other organism would exist today.
The concept of evolution lies in natural selection which, in simple terms means survival of the fittest. This implies automatically non-survival of the unfit, and every species alive today, all 9 billion, are the survivors of evolution so far. A common misconception is that ‘fitness’ refers to physical strength. In terms of Darwinian evolution, ‘fitness’ refers to competitive superiority, so anything that enables a species to survive and propagate its line under the given environment in that space and time falls under Darwinian fitness. The difference may not seem very apparent immediately, but if you think about a population of rats and a population of ants in the desert, the difference becomes more apparent.
For there to be the ‘fittest’, there need to be physical differences between the ‘fit’ and the ‘unfit’ that causes one to survive and thrive better than the other. There is a vital necessity for diversity in an ecosystem: diversity of species and diversity of physical attributes. Anything might support survival, and there are times when surprise events have lead to the extinction of the bigger and stronger. The reason mammals have a free reign today is because of the extinction of the dinosaurs.
A question you may ask is why coexistence cannot be achieved. When there is a finite amount of basic resources, like food, water and space, and one population is more successful at surviving and expanding in size, it follows automatically that the extra food, water and space is being taken from somebody else’s domain; some species more ill equipped to survive and defend its domain.
Therefore, evolution does not work on a single being, it only applies to a population that has differences in their ability to survive and reproduce.
You may ask why evolution is trial and error. The differences that are generated among populations, that have all descended ultimately from a single cell arise due to mutations and sexual recombination. Mutations are changes in the genetic code. Sexual recombination is the shuffling of the genetic code when genes from a male and female are selectively recombined in their offspring. Genes dictate everything about how an organism develops from an embryo to what it will end up as.
Mutations are random events and could be caused by a number of factors. A mutation is like a shot in the dark, it is not possible to predict how it will alter DNA and what its effects will be. If a mutation is in a vital gene, it could alter the development or physiology of an organism, which is what generates differences. If this mutated gene is passed on to the next generation organism, it’s a viable candidate for natural selection.
In summary, evolution is not a pre-planned, guided, linear development of a single cell to human beings. It starts when a random mutation affects the physiology of an organism, which helps it to survive better than its ‘normal’ counterparts. This organism reproduces, creating more like itself, which can thrive on the resources, ultimately growing to an extent, over several generations that leads to the extinction of the unmutated organism. On the flipside, if the mutation causes a change in the physiology that is harmful to the organism, the reverse happens, and that the genes of that organism die out with its descendants several generations later.
‘That’s one small step for a man, a giant leap for mankind.’ – Neil Armstrong’s words on first setting foot on the moon (1969)
References :
1. Biology by Cambell and Reece