I'm today uploading an article I wrote 22 years ago, in 1986! I was in the 11th standard then, full of questions about what we were learning in science. We were studying evolution, which I found quite intriguing. Some questions I had then were: Why did evolution occur at all? What is it that was responsible for 'more advanced' life forms to emerge as the years went by? These and other reflections are part of this article. Our lecturers simply gave us information. They didn't have answers to these questions. I'm not sure if my understanding is better now, but I have read a little bit of Richard Dawkins, Stephen Jay Gould, James Lovelock and Lewis Thomas. These books, together with my own thinking, have helped me along the way...
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Evolution
These days, we are learning about evolution of life on earth. For me, this is a new topic and it surprises me a little that we did not encounter it in school. Anyway, I find the idea of evolution fascinating and I guess it will take some time for me to appreciate its complexity. The big question is: Why did it happen in the first place? And how did it give rise to such an incredible variety of organisms, small and big? The way we are discussing it in class, looks like have taken this mind boggling phenomenon for granted to be just read with the upcoming examinations in mind. The guy who is dealing with this topic is killing it, literally! I wonder why they don’t feel excited about it.
Whether life originated on the earth, or came from outer space, piggy riding some asteroid or meteor a few billion years ago is still being debated but the former hypothesis is more widely established. It is generally accepted that the Viruses were the first ‘organisms’ on the earth, churned out by that process called evolution. It is a bit like magic – the magician keeps stirring this pot containing the ‘primordial soup’ containing air, water and some rag tag chemicals and suddenly, at some point in time, we have these really tiny weeny self-replicating organisms (discovered only in 1898 as microscopes became powerful enough to reveal them) popping out! How did this happen?
The classification of viruses defies taxonomists (the people who classify living things, based on some criteria) till this day. They are ‘common’ to the plant and animal kingdoms (by the way, ‘kingdom’ is a kind of category that taxonomists use), and secondly, they exhibit both living and non-living characteristics! In the laboratory, you can put the virus in deep freeze and it will behave like its dead. When conditions become ‘favourable’ it will thrive and show the characteristics of living cells. Viruses possess the basic materials needed for life – proteins and nucleic acids. The proteins form a capsule or coat around the nucleic acids. The jargon given to us in the class recently is: ‘Viruses are obligate, intracellular parasites’, i.e., they can replicate themselves only in a host cell.
This tiniest of the tiny living thing causes untold damage to the rest of the living species, whatever their pretensions to size and complexity and power may be – we have heard of the HIV which has already brought us much grief and then, I have read somewhere about an even more devastating virus called the Ebola virus which exists in some place in Africa.
From what we have learnt so far, it seems that the evolution of various forms of life ‘began’ from the viruses and it took thousands of millions of years for evolution to ‘make’ us. Our textbooks tell us that Mycoplasmatales (also known as Mycoplasmas) were the next products of evolution after the viruses. This is the message I get because the Mycoplasmas chapter comes after the one on viruses! They look a little more intricate that the viruses. However, Mycoplasmas, like the viruses, cannot be classified definitely as belonging to the plant or animal kingdom.
How did Mycoplasmas come on the scene? What were the factors that caused this change? It is tempting to think of a change in the environment which ‘forced’ the viruses to adapt themselves in order to ‘become’ mycoplasmas! It is difficult to think of any other reasons at this stage and I do not see the viruses ‘feeling’ something inside of themselves as a result of which they ‘evolved’ to give rise to the new, slightly more advanced organism. It is interesting to note that we humans also change when something external to us, changes. And I suppose that we ‘grow’ as a result of the things that we learn from these changes – in this sense, we too evolve. Or so I think! We cannot live alone.
Let us take this further. The blue-green algae, which contain the bluish green pigment, came next. All the three forms of life mentioned so far – viruses, mycoplasmas and the algae -- are examples of very ‘primitive’ (or ‘prokaryotic’) organisms. They do not contain the specialized structures that a well-developed cell contains, and their metabolism is not very complicated. However, the algae are more intricate than the mycoplasmas which in turn look more complicated under the microscope than the viruses. We are given to understand that ‘animal like’ cells, like the Euglena, would have appeared next. These were followed by ‘proper’ animal cells, like the shapeless Amoeba and later, the Paramecium, which has a definite shape.
Again, I come back to the question raised earlier – what changed in the environment for this diversification to occur along two well defined routes? And what was the distinction at that stage – that animal cells cannot make food like the plant cells do…?
As we went along, we realized that the process of evolution witnessed a turning point of sorts, with the emergence of the Bacteria. Structurally and functionally, the bacterial cells are more complicated than the others discussed so far. The presence of different elements or parts in the bacterial cell -- the cell wall, protoplast, cell membrane, cytoplasm, nucleoid, ribosomes, etc. point out to a well organized cellular set-up. It is a bit like comparing the difference between nomadic man and the chap who settled down much later inside a home and started doing some agriculture. Life then became a little more organized and one didn’t have to live only on instinct.
Now these Bacteria may also be ‘photosynthetic’ – that is, they can make food using a pigment called chlorophyll. There is general agreement that these organisms belong to the plant kingdom. Does this mean that plants appeared before the animals on earth? More specifically -- did ‘plant like’ characteristics appear first? What were the reasons for this to happen? Only more questions! We have been taught that plants and animals have to depend on each other for survival. Does this interdependence apply even to the most primitive organisms, perhaps extending to the furthest reaches of evolutionary time? It is then striking that the characteristics of plants appeared first.
It is indeed tempting to believe that these evolutionary processes (including the diversification along the two different paths – the plants and the animals) were the result of accident. I wonder how it can be explained. It is equally attractive to consider the proposition that everything was ‘pre-determined’ (by whom?!).
The formation of the sexes was a very important event, for, it ensured species propagation. Prokaryotic cells can reproduce only asexually, whereas the more advanced (eukaryotic as they are called) cells can reproduce through conjugation. Humans do it this way! However, in the case of the earliest organisms, it is difficult to distinguish the sexes morphologically (meaning, it is not very obvious from physical appearance). As we climb the ladder of evolution, it is not difficult to differentiate between plants and animals. The identification of the sexes also becomes easier.
We have very briefly touched upon this thing called evolution with these examples. The question that keeps coming back to us is about the role of the environment, and the interaction between changes in this environment and the living organisms, which over a period of time actually resulted in more diversity, intricacy and complication of forms – and, I would also like to add, abilities as well. This seems to be a dynamic process which I do not think has stopped to this day. Why was diversity important? In addition to diversity, we also see a progressive complication of living forms from the tiniest, most primitive organisms, to this human who is self aware and conscious, who is in a position to ask such questions and probe into the nature of things. How did this happen?
I asked this question in class today but our lecturer did not have any satisfactory answer. He mumbled something about ‘survival of the fittest’ (that famous Darwinian slogan of sorts!) but I couldn’t make out who was fitter – the viruses, the mycoplasmas or the bacteria? All the three organisms exist even today! If one of them had been fitter and more powerful, the others may not have existed. The issue, therefore, cannot be explained away as easily.
My answer would be – the earth has been continuously changing since the time it was formed 5 billion years ago. Its surface has undergone major upheavals through earthquakes, volcanic eruptions, etc. and temperatures have kept changing, becoming progressively cooler. It is quite possible that the molecules of life must have felt (what does this mean though?!) these changes. Through complex chemical reactions, these molecules would have adapted to these changes. And adaptation is perhaps the basis for complex forms to get generated as the aeons go by.
The central question which I never tire of asking, is why did evolution take place at all? Was it inevitable, given the conditions available as the earth passed through different stages after its formation? And again -- why would changes in the environment necessarily lead to the formation of ‘better’, or ‘more advanced’ organisms? Why, for instance, should the Paramecium evolve as the next organism in the evolutionary ladder after the amoeba?
There ends my quest for answers at present. It is possible that if evolution is viewed from a different perspective, these questions can be answered. Who knows, I may be the one who will do it at a later stage…
May 1986
Bangalore
