What is life? How do we define life?
One of the most fascinating questions that have bothered us since time memorable is what is life? What does it mean to be living? What distinguishes us from non-living? in this video we will seek how close we are to answering these questions? What are different scientific opinions on it?
What is life this question has fascinated us since time immemorable but no one has yet been able to give the correct answer? Different people say different answers to this question. There is no universally accepted explanation to this very fine and subtle question. But still, even though we don’t know the proper answer to this question it will be interesting to know what numerous thinkers and scientists have given their opinion on this problem. Let’s start with the ancient times, The Greek thinker Empedocles (430 BC) argued that everything in-universe is made up of a combination of four eternal elements or roots of all: earth, water, air, and fire. All change is explained by the arrangement and rearrangement of these four elements. The various forms of life are caused by an appropriate mixture of elements. So basically, he said that life is just like any other ordinary thing in-universe the only difference is that in what proportion these four elements are present in it and in non-living entities.
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| Empedocles (430 BC)
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But it is very vague and you cannot technically consider this statement as a definition. As it just says from what life is made but not tells anything about what is life. Another Greek thinker Democritus (460 BC) thought that the essential character of life is having a soul (psyche).
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Democritus (460 BC)
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Like other ancient writers, he was attempting to explain what makes something a living thing. His explanation was that fiery atoms make a soul in exactly the same way atoms and void account for any other thing. He elaborates on fire because of the apparent connection between life and heat, and because fire moves. In the early modern period the French philosopher, Rene Descartes(1596-1650) argued that animals and humans are assemblages of parts that together function as a machine. In the 19th century, the advances in cell theory in biological science encouraged this view.
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| Rene Descartes(1596-1650)
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Now coming to modern scientific approach and try to find out how close the science has come to answer of this question: When we ask “What is life?” we are in effect asking “what is the essence of a living organism, what distinguishes it from a non-living entity?”
The most common definition that we all study in our school the biological definition of life is much like a checklist that says that anything which ticks all the criteria in the list will be considered living. The definition goes like this:
Anything that breathes, eats, reproduces, tries to maintain its existence, evolves as per circumstances and possesses cell structure is living thing or in other it has life.
But the problem with this definition is that this is a list approach which says that any entity that has ticked all these features is alive I am sure that no one in this world will disagree on the fact that mules a hybrid offspring of a horse and a donkey is a living thing. But usually, they are sterile that they cannot produce any offspring this means the box of ability to reproduce remains unchecked but still we know that it is, in fact, a living organism without any doubt.
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virus
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Another problem with this biological definition is that some organisms at the very edge of the boundary between living and non-living called viruses don’t possess cellular structure they are practically just amalgamation of some proteins, RNA and DNA but they do reproduce and evolve. Some scientists say that they are not living due to the fact that they cannot reproduce independently as they need a host to reproduce themselves. But then the question arises why do parasites are considered living they also can’t live without a host. So, do we consider viruses living or we should remove parasites also from the list of living organisms based on the fact that it also does not fulfil the criteria of independent existence like viruses? But we can’t as we are very much sure due to our intuition that in fact, the parasites are living. But we have to rethink our definition that keeps viruses from the list of living because very large viruses such as Mimivirus are so large that they can be seen through microscopes and they look so much like a cell that you can mistake them for a bacterium. And another challenge for defining life comes from us humans itself. Human designed organisms like ‘Synthia’ which has few features of living but can’t survive outside a lab. Where they should be placed in living or non-living. Are viruses and other entities like this really living or just life-like?
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biology laboratory
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Using a list approach for defining life which itself is very arbitrary poses a problem as the answer to this question lies on what criteria you consider and what you leave. Charles Darwin in his theory of evolution said that life has the ability to adapt to its environment. This feature of adaptability is shared by all life on earth. Based on this renowned Biochemist George Joyce argues that life should be defined using the Darwinian theory of evolution of life. And he came up with a new working definition of life which says:
Life is a self-sustaining chemical system capable of Darwinian evolution.
Defining life isn’t easy because we can always find an entity that meets all criteria but is ‘clearly’ not alive such as thought it emerges, reproduces and evolves but not alive or we can also find some entity such as mule which lacks some of the features but still undoubtedly a living organism. So many other factors are also needed to be considered before we can define what is life?
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DNA illustration
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So many answers to be given one such factor is that should we consider molecules containing information for to assemble and reproduce a living entity such as DNA and RNA be considered while defining life or we should define life without them but defining life without them poses a problem because then a question will arise do artificial entities such as machines having Artificial Intelligence be considered living. But if we do consider DNA and RNA as a deciding factor to qualify as living then also that poses a great challenge as what about some probable extraterrestrial form of life which don’t have DNA and RNA but something different for the same purpose.
The quest is still open no one has yet been able to bring a proper definition of life but hope still lives in future we have really advanced a lot as our knowledge of science advances further we will have more advanced technologies than at that time we might come up with a much better answer to this epic question of ‘What is life?. Thank you
