Cosmology and our View of the World
Life as we Know it and its Origins
Lead: Thomas Davis
Summary by Sarah Brown
Life as we Know it and its Origins
Before delving into our discussion on Life as We Know It and Its Origins, Professor Davis introduced a few topics that often trouble biologists and philosophers alike. Some questions are brought up, such as: How did life originate on earth? Was life brought to earth from another area of the universe? How did life on earth, with a single common ancestor of a simple organism, diversify enough to achieve the incredible complexity of what it is today? What about life and death? What is the transition between the two? Is there a possibility for life after death? And where does consciousness fit into the picture? What meaning can be derived from Life as We Know It?
To begin, Professor Davis divided “life” into two separate roles that this elusive concept can play for us:
Life as a category: This aspect references living versus non-living things. On earth, we divide this section into the biological Kingdoms of Life: animals, plants, fungi, and microbes (and maybe viruses – though they are not generally regarded as ‘living’, they are an integral part of life). We can also speculate as to extra-terrestrial life (Is it like life on earth? Do we share any part of our genetic code with extra-terrestrial organisms?), though at this point the answers remain unclear.
Life as a property: This aspect examines the properties commonly
associated with (earthly) life, and though the list is not comprehensive, includes
- cellular structural complexity: single-celled or a community of cells
- metabolism: the ability to process and store energy
- a genetic system: DNA/RNA
- growth and reproduction: this is a feature of life: not all living things can reproduce, though all living things are a product of reproduction
- evolution: though individuals do not tend to evolve over time, the evolution of a species is characteristic of Life.
However, it may sometimes be difficult to recognize life when we see it. We discussed examples such as laboratory robot-bugs that exhibit REAL bug-like behavior, or REAL bugs that move almost mechanically, leading the observer to question whether or not it is truly living. After a brief discussion, we concluded ‘life’ to be biochemical, not electronic (eliminating the possibility of ‘living’ robots).
Professor Davis stated: “A living thing is a structurally complex physical entity, that dynamically maintains its organic molecular structure via the internal use of chemical energy.”
This is to say that all living things operate within a cell membrane. Cells have complex, dynamic organic structures that must be maintained within this membrane. Cells are extremely dynamic (and contain ‘vibrational’, ‘rotational’, and ‘run-around’ energy), and expend tremendous amounts of energy to control their own molecular energy.
We then moved on to discuss the Origin of Life:
We concluded that life has probably NOT always existed in the universe, because there are certain key elements necessary to support life (as we know it), which were not present in the early stages of the universe. Some of these elements include Hydrogen, Carbon, Oxygen, Nitrogen, and Phosphorus. Scientists speculate that only Hydrogen existed in the early universe. As the universe grew older, heavier elements were produced through a series of nuclear reactions inside stars, in particular in supernovas.
Let's briefly examine a basic timeline of the universe:
- The Big Bang: ~3.7 billion years ago (bya)
- The first stars: ~2.7 bya
- The formation of a primitive earth: ~4.5 bya
- The first life on earth: ~3.5 bya
Scientists, through fossil evidence, believe the first life on earth to have appeared about 3.5 billion years ago. Before this, the conditions on earth were believed to be too inhospitable to life. Some hypotheses contend that life may have tried to start multiple times and was wiped out, before it truly ‘began’ about 3.5 bya.
The theory of Panspermia suggests that life originated somewhere else in the universe, and was brought to earth as a result of a collision between the earth and some other object, such as a meteorite. However, seeing as we have not yet found other evidence of life in the universe, we can only speculate as to whether or not this theory is true.
Professor Davis went on to explain that life is no longer being created on earth. We do not have the capacity to create life, because it has already been created. This idea is analogous to the fact that one can no longer invent the wheel or the telescope. However, we should not confuse this with things such as human reproduction, where a life is created, not life.
Next, we discussed a Recipe for Life:
These ideas had already been introduced at the beginning of the class. Lipids form the membrane of the cellular compartment, with water acting as a thermodynamic stabilizer for the structure of the cell membrane. The cell membrane allows nutrients to pass through its walls, in and out of the cell. The self-maintenance of this complex, dynamic molecular structure is achieved through cell metabolism. The cell metabolizes energy through the use of many different proteins. Some functions include transfer of:
- ADP > ATP
- CH2O > H2O + CO2
The cell must also include some sort of genetic system. Through a complex series of biological ‘triggers’, cells synthesize RNA based on information in DNA, and protein with the help of RNA. Finally, in order to perpetuate life, reproduction is necessary. Through Darwinian evolution, which is possible only through reproduction, life is able to diversify.
Professor Davis was sure to express the astounding complexity of life. Cell membranes, for example, are unbelievably complex systems of molecules that perform incredible tasks. Within the cell membrane rests the nucleus and nuclear membrane of the cell, where DNA is copied into RNA with the help of a multitude of proteins. These cell attributes are so complex, that it is hard to imagine such an advanced system having come from nothing.
So, the next question is: How did we get from no life on earth, to where we
Scientists refer to LUCA, or the Last Universal Common Ancestor. According to Charles Darwin, species experience evolution as they change from one form to another over time. He believed that through natural selection, a species would gradually evolve in a way that best perpetuates its existence, while other species gradually disappear. The extinction of a certain species may be a result of a particular weakness of the species, or just unlucky chance. Many scientists believe that there are some ‘neutral’ factors that may lead to the extinction or evolution of one particular species over another. For example, suppose there was a chance extinction of a species of red fish in a pond. No longer having to compete to survive, this could lead to the survival and development of other blue fish, even if they are not ‘genetically superior’ to the red ones.
Hereditary variation of a species occurs through a variety of mechanisms. There is natural selection, as we already discussed. Mutations (a change in DNA from one structure to another) are also a common product of reproduction, along with ‘recombinations’ produced by the reshuffling of chromosomes passed from parents to offspring. These variations produced will ultimately lead to the survival or extinction of a species, depending on its suitability to the environment in which it resides. Drift is a term that refers to what happens by chance, rather than to natural or artificial selection, and includes events such as natural disasters, etc.
Along with natural selection, mutations are an inevitable and indispensable aspect of life. Though they may seem ‘random’ at times (with respect to the adaptive value of the organism), it is hard to say whether they are truly ‘random’ or if we simply cannot understand the natural laws and processes behind these mutations. A highly disputed topic tries to understand what is ‘random’ versus what is inexplicable.
Genetic engineering and selective breeding were both brought up during this
discussion as unnatural methods of hereditary variation. Both practices entail
conscious human intervention, though they are fundamentally different:
Genetic engineering is the deliberate modification of the characteristics of an organism by manipulating its genetic material.
Selective breeding is the selection of certain seeds or animals for reproduction in order to pass desirable traits from one generation to the next.
Are either of these methods ethical? Should we be manipulating natural processes? How far can we push the development of life on earth?
Now these evolutionary theories may be helpful, but can they sufficiently account for the incredible diversity and biological complexity of life on earth? There are two contradicting viewpoints that attempt to explain this diversity:
The Intelligent Design Argument: This view holds that if an organism or object has the appearance of having been designed, than they must have been designed by some superior being. Since living, breathing beings are so complex, they must have been specifically designed to be this way, as it is improbable they would have reached that state through their own, slow, evolutionary means.
The Darwinian (Evolutionary) Argument: This view contends that natural evolutionary processes are enough, and have taken place over such a long span of time, to give the appearance of having been designed.
This topic is extremely complex and highly disputed by scientists and philosophers. Since earthly life is the only type of life available for us to study, we can only speculate as to the possibilities of life elsewhere in the universe. We cannot understand the life, consciousness, and the universe from an objective viewpoint, since we can only experience and rationalize subjectively. Francis Bacon’s “Idol of the Tribe” encapsulates our limitations as members of the human race. We see in a sort of ‘tunnel vision’, restricted by our own senses and capabilities.
Professor Davis closed the class with the following quote from Stephen Hawking: “The human race is just a chemical scum on a moderate-sized planet.” This quote leads us to wonder, are we just a ‘trivial embellishment to the physical world’, of no particular significance in the overall scheme of things? Is our existence a result of chance biological processes or can we attribute some meaning to Life, the Universe, and Everything? Though we may never be able to fully understand the universe and our role in it as conscious beings, we believe that devoid of consciousness, the universe would have no meaning.