Medical doctors, psychologists, and social scientists are able to observe and describe the insides of our brains, our states of mind including our emotions, our memories, our physical bodies, our families, our neighborhoods and communities, our societies and cultures.
There are questions about LIFE that we are all curious about. What exactly is life? What does it mean for something to be alive? How can we be sure that a thing is truly alive, such as a cat or a tomato plant? And how do we know for sure that something is not alive, like a rock or a chair? There is widespread disagreement in the scientific community as to exactly what causes something to be alive.
Everything is made of atomic elements. The objects around us, from plants to planets, are composed of different combinations of atoms and molecules. So how are we able to tell which things are alive and which aren’t?
There are at least four things to look for. First, in order for something to be alive, it must be able to make copies of itself. Second, it must be able to respire, or breathe. Third, it must take in nutrients, and convert them to energy. And finally, it must be able to regulate itself, maintaining basic bodily functions.
Different organisms reproduce, respire, input nutrients and output waste, and regulate their bodily systems in different ways. Animals breathe in oxygen and exhale carbon dioxide, and, because they have the freedom to move around, hunt, gather and consume food and liquids. Plants, which stay in one place, gather nutrients and water from their roots. They also capture light with their leaves and convert it to useable energy. Plants breathe-in carbon dioxide and exhale oxygen, the opposite of animals.
In addition to the four basic conditions for life, living things tend to grow and develop, just as we do. And all organisms learn to adapt to their environment. Some species adapt better than others, and these will tend to reproduce at a greater rate overall. New species that are not adaptive, or existing species that are no longer adaptive, don’t survive.
It is my view that things that don’t fulfill the four basic requirements for life are not alive; they are inanimate. Inanimate objects may posses one or more of the conditions of life, but all of the requirements need to be present and functional for an organism to be alive. For example, a washing machine is a self-regulating system, but it can’t make copies of itself and it doesn’t adapt to the environment. Some objects, such as crystals and mountains, can grow and develop, but they can’t breathe and they don’t metabolize, which means they don’t convert food into energy. A bird is alive; a rock is not. Interestingly, a virus is alive when it invades and occupies a host cell, but is patently not alive when it is floating along on its own.
Scientists have several interesting theories about the beginning of life on Earth. One idea is that life originated somewhere else in our galaxy and was transported to Earth by an asteroid. This is known as panspermia.
A classic theory presented in the 1950’s suggests that a kind of ‘primordial soup’ formed the first chemical basis of life and was triggered by a lightning flash, creating the initial conditions necessary for life to occur.
Another ‘creationist’ theory suggests that life was spontaneously generated from a simple set of conditions. This theory is supported by computer models which produce a variety of self-generating programs. The computer programs are able to create complex ‘organic’ forms from a simple set of rules.
The most popular theory among scientists today is that life began over 3 billion years ago with an organic, gooey slime that covered most of the planet. Eventually, small bits or pieces of the metabolizing slime split off, later folding over on itself, creating the first single-celled organism.
It wasn’t until another billion years had passed that the first green algae appeared in the world’s oceans. Later, more complex single-celled organisms evolved in the oceans, followed, on land, by fungi, animals and plants.
Complex life forms, such as flowers, trees, insects, birds and all other animals are made up of cells that communicate with one another. Different groups of cells cooperate to form everything that is a whole living system, whether it is a tree, mouse, elephant, or person.
As we know, all of life has evolved from a simple common ancestor. When one of the first single-celled organisms made copies of itself, there was a slight copying error that changed part of its genetic instructions. This resulted in the creation of a slightly different creature. The new creature reflected this change as it made new copies of itself. If it successfully adapted to its surroundings, it became a new species; if not, it died out. This process has occurred over and over, creating the diversity of life that we see throughout the world.
Living things are newly formed, grow, age, and die. Some organisms live to be over a thousand years old, such as the giant redwood trees of northern California. Others, such as tiny insects, live out their entire lifetime in a few days or weeks. Usually, the larger a species is, the longer its average lifespan. Just south of Australia, on the island of Tasmania, there is a giant bush that extends for miles. This plant has been alive for 40 thousand years, the age of modern humans. It is the oldest known living thing on Earth.
Recently, scientists have made great headway in examining the possibility of life beyond Earth. Many astro-biologists today believe that anywhere in the universe where there could be life, there probably is. Part of this optimism is due to the extraordinary discoveries of organisms living and reproducing in hostile environments here on Earth, especially in places where no light can penetrate. These microbes, known as ‘extremaphiles’, have been found living in dark ocean vents, deep caves and frozen blocks of Antarctic ice.
With the routine discovery of new planets in the Milky Way and other galaxies occurring almost on a daily basis, the idea that an existing climate for life may exist not only somewhere, but in many places throughout the universe seems quite plausible. Scientists argue that the origin of carbon-based life is inevitable due to the larger forces in the universe. Discovering life in other worlds would, of course, move the dialog from the safety of science fiction to one that would profoundly change human perspective for better or worse. (for more on this subject, see Marc Kaufman’s stimulating book First Contact)
For some, the death of a pet, for example, is a sadness we may experience in early childhood. For most of us, it is not until later that we are confronted with the overwhelming sorrow of the death of a loved one, such as a grandmother or grandfather, aunt or uncle, parent or sibling.
We know that all living things on Earth must eventually die. Yet why is this? What makes the certainty of death a reality? How and when did death originate? Is there some reason that everything has to die?
All things eventually decay and disappear. It is the physical nature of objects that they break down over time. The classical physicist Isaac Newton referred to this phenomenon as entropy – the tendency of things and events over time to lose more energy than they gain. Historically, not too few experiments have been created in an attempt to defy this principle. Many have tried. None have succeeded. My own thoughts on this subject led me to the idea that even though each of us must eventually die, we continue to pass on our genes to the next generation. This process of protecting the human genome, our DNA, from extinction has gone on for tens of thousands of years, and may prove, at least for the near future, a promising challenge to Newton’s famous second law of thermodynamics. There is a modern idea in the biology world that the human body acts as a ‘vehicle’ for the transmission of DNA, suggesting that humans are biologically expendable, while DNA lives on from generation to generation. (google Richard Dawkins for more.)
Death, as we know it, originated with biological sex. When genetically complex creatures such as plants and animals reproduce, as opposed to bacteria that clone themselves, the resulting offspring contains two sets of genes, one provided by the male, the other by the female. This amount of genetic material is capable of creating different kinds of cells (blood cells, body cells, immune cells, nerve cells, etc.) that are useful for adaptation, but can be harmful if the cells are allowed to divide and grow indefinitely.
The natural death of an organism, whether it is a potato, a parrot, or a person is due to an ageing process caused by the breakdown of individual cells in the body. From the time we are born, new cells continue to replace old cells. Cells in the body continually divide, making more cells, and replacing old ones. But there is a limit to the number of replacement cells that a person can have over a lifetime.
Early in the evolution of plants and animals, organisms evolved a method of controlling the amount of cells that can divide and grow. If there are too many cells growing too fast, the result is an unwanted cancer killing off parts of the body, eventually leading to the early death of the organism.
The ‘solution’ that nature selectively ‘invented’ for the problem of too much natural growth in our bodies was to limit the number of cell divisions from birth. Once the number of cell divisions is reached, which is different for different species, and for different individuals, the cells are chemically ‘turned-off’, and our bodies begin the process of breaking down.
As we age, and are no longer producing new cells, our body is not able to maintain itself in the same way it did when we were younger. Illness and injury become more frequent and severe. Our natural defenses become increasingly weaker, and finally we succumb to death.
So, our bodies don’t die naturally from being worn out by age, they are genetically programmed to stop replacing cells once we have reached the age of maturity. This process of programmed cell death is known as apoptosis and the cells that have been turned off are referred to as ‘suicide cells’.
Lynn Margulis has famously said: ‘Death is a sexually transmitted disease’.
The good news is that eating well, sleeping and exercising regularly, and finding ways of lowering stress in our normal routines can extend our lifetime by a number of years. Also current medical research promises to slow the ageing process, and the availability of gene therapies and the wholesale replacement of body parts will soon become part of standard medical care. While we wait, a process of sustained body freezing, known as Cryogenics, promises to suspend life until average life expectancy is significantly greater. Nobody knows for sure.
Strangely, there is an exception to the finality of death. It is simple bacteria, the kind that makes food spoil. These free and independent single-celled creatures, known as prokaryotes, roam about freely, or they may attach themselves to another organism. These bacteria are immortal. Barring a mishap or random accident, they may live for millions of years, continually reproducing themselves.
As we mentioned, scientists have recently discovered the chemical switches used by the cells in our body to turn-off the ability to make more cells. This means that in the future we may be able to control how long we live, and maybe even whether we die or not. New medical experiments on fruit flies and other small creatures have resulted in greatly extending the lives of these organisms.
Biogerontologist Aubrey de Grey despises death. He believes that ageing is a curable disease. Through the pioneering efforts of de Grey, George Church at Harvard Medical School and others, researchers are currently mining the secrets of death, hoping to curb or eliminate the ageing process for multicellular creatures like ourselves.
As eerie as this may seem, it is truly astonishing that for the first time in history, we are able to conceive of the idea of human immortality. This is a big idea and if it becomes a reality, it would force us to think about ourselves and others in a profoundly different way. Our private, spiritual, and social lives would be forever changed.
Naturally, human immortality brings with it a whole host of frightening challenges, moral concerns, and ethical issues and responsibilities. If immortality becomes a reality in the future, and nobody plans on dying, where are we going to put everybody? The world is already crowded and growing bigger. Who will get to live, and who won’t, and who will decide.
As emotionally painful and difficult as death may be to endure and cope with, there is a bright side. Death reminds us of the unity of nature, of something larger than ourselves. Following death, the very atoms and molecules that give life its form and function, return to the surrounding space from which they came. They are recycled into the inanimate world of energy and matter, perhaps forming new life once again. It is a comforting thought to realize that you may be breathing some of the same atoms that were once exhaled by Leonardo de Vinci or the Queen of Sheeba.
to learn more about Programmed Cell Death, view the Prose Poem: