Cosmology and our View of the World
The Questions of Life
Lead: Thomas Davis
2/10/2009
Summary by Austin Purves
Life as we Know it
The three major themes in this course are “life as we know it,” “consciousness,” and “our universe.” Davis asserts that consciousness plays a very important role in the universe, since in the absence of consciousness, the universe would have no meaning whatsoever. If life is the medium through which consciousness exists, then life is equally important.
For the purpose of this discussion, life as we know it can include several sub-topics, including origin of life, diversification of life, extraterrestrial life, synthetic life, death, life after death.
In order to discuss these aspects of life, we will first attempt to define what life is. Life can be understood as a category, that is, an ontologically significant distinction between fundamentally different kinds of things: living things and non-living things. Or it can be understood as a property that some things have; some things are alive, and some things are not. In any case, we can acknowledge some common properties of living beings (or things which are alive). They all have a complex structure, which is made up of cells, and which is dynamic (not static, as in a computer). On this basis, biologists don’t consider viruses to be alive, they are simply a package of genetic material. All living things also exhibit metabolism, a complex of biochemical processes harnessing energy from the environment for use by the living thing. Another common property is a genetic system, a repository of information needed to synthesize functional proteins. Living things usually exhibit growth and reproduction, but not necessarily at any given moment. Some living things may be dormant for a time, and some may be unable to reproduce (although all living things are the product of reproduction). Some definitions of life may include other properties such as responsiveness to external stimuli or Darwinian evolution.
Once we have some sort of definition of life, can we recognize it when we see it? Would we be able to recognize life if we found it on Mars, or create it in a lab? To gain some insight into this question, the class is issued a challenge to recognize life. The first subject is Professor Davis, who the class quickly agrees is alive. This agreement is based on the universal assumption that Professor Davis is not a virtual reality simulation or “android.” We can see some of the properties of life in Professor Davis.
The next subject is a strawberry plant. The class is at first silent. It does have some properties that suggest that it is alive, such being edible and having a sweet taste, resembling something that we already expect from past experience to be alive, and also having some seeds. To make a more confident decision one would have to look very closely at the strawberry plant. This is illustrated by the fact that a portion of the plant, including the visible strawberries, are actually made of plastic and not alive at all, despite appearing to be alive according to our initial observation.
The third subject is a giant cockroach. The class agrees that it is alive and probably not a sophisticated robot. It seems to respond to external stimuli, and at times spontaneously start to move. We could look more closely and see if it metabolizes and has a cellular structure. We note that for the Dalai Lama, a key property would be the existence of sentience or the ability to experience pain and pleasure.
A question is posed by Professor Moebius: is a robot running on a fuel cell metabolizing? Professor Davis responds that metabolism in living things usually functions to actively maintain the structure of the living thing, so this is not metabolism in the usual sense.
Other questions are raised. The sun’s metabolism maintains its structure, does the sun then metabolize as living things do? Professor Davis responds that the sun’s structure is not developmentally programmed enough to be the kind of structure found in living things. What about some “cybernetic” organism maintained by “nano-machines,” which are constantly repairing or maintaining the organism? Professor Davis responds that this could be crossing the border between a non living thing and a living thing. Could we make a distinction between this and true life based on organic materials? Professor Davis responds that processes similar to those found in life could conceivably be manifested by different chemical constituents.
Another question is raised. What of this certain species of frog that can be frozen during the winter, such that there is no metabolism or other dynamic process maintaining it, but can still be thawed and go on living? When it’s frozen is it dead? Or is there some way we can distinguish its frozen state and a truly dead state?
Another question. According to our definitions of life, could earth itself be a living thing? Does this have some connection to the Gaia hypothesis?
While we do have some sense and agreement over what exactly life is, we can see the problems that arise in trying to develop a rigorous definition.
Can we put an upper-bound on how long ago life could have originated? We know that the elements which compose life-as-we-know-it, Hydrogen, Carbon, Oxygen, Nitrogen, and Phosphorus, did not all exist in the early universe, there was only Hydrogen and Helium. Terrestrial life apparently began about 3.5 billion years ago, but in principle life could have begun elsewhere at an earlier time before coming to Earth. This hypothesis is called panspermia. Astrobiologists believe that life could potentially propagate around the solar system, lending credibility to the panspermia idea.
A question is raised: what about a natural intelligent designer? Is this considered as a possible origin of terrestrial life? Professor Davis responds that this is not an unreasonable hypothesis. Professor Moebius points out that even if there is a natural intelligent designer, presumably its own origin would be need in of an explanation, so this only moves the question “one step back.” Eventually the regression will have to be terminated with a natural explanation of the origin of life, or a supernatural one.
Professor Davis comments that all species share the same genetic code, a fact that is quite remarkable to professor Davis. Perhaps it implies that all life on Earth has a common origin, lending more credibility to panspermia.
Other points are raised. Terrestrial life has already existed for a large fraction of the life of the universe, the age of the universe being only a factor of two or three times longer than the age of terrestrial life. Can we establish the timescales available for life to originate? For how long have there been galaxies and planets orbiting stars?
Another question; to what extent can we mathematically model the spontaneous formation of life to see how likely it would have been during the “window” of time that Earth is hospitable to life?
We can ask the question of how life originates on Earth now. So far as we observe, life only comes from life. It may be necessary here to distinguish between life, and “a life.” One person invokes the “law of Bio-Genesis.” If life only comes from life, don’t we have to conclude that at some point there must have existed something other than carbon based life? Professor DeVries claims that we observe this now only because of our circumstances. We cannot be certain that Bio-Genesis is a general law, nor can we eliminate the possibility of some unfamiliar form of life being a predecessor to life-as-we-know-it.
Some questions are raised. Can we eliminate certain kinds of pre-life scenarios using the physics that we know now? Does explaining life-as-we-know-it by the existence of some other kind of life lead us potentially into an infinite regress? The threat of an infinite regress doesn’t necessarily mean we are entering one. The end of the regress could be only a few steps away.
More questions are raised. Does life have to ultimately create itself or be created? Or is there a possibility that life is infinite? Why are we so worried about the creation of life when we don’t worry about the creation of matter? What’s the distinction between these two creations and why is one more important? Maybe life has a degree of complexity that is not paralleled in other aspects of the material world.
A recipe for life (as we know it) is proposed. All life is cellular, so we will begin our recipe for life with a cellular compartment. Next, we know that life requires some kind of metabolism, so the recipe calls for some biochemical process to manifest metabolism. This process must somehow support the dynamic molecular structure of life. We also need some way to encode genetic information, such as the DNA used in life as we know it. Finally there must be some means for the perpetuation of life, such as reproduction.
This recipe sums up the basic ingredients that would be necessary for life originating on Earth, or being created in a lab, but gives little credit to some of the incredible complexities found in the components of life. These incredible complexities mean that generation of life is much more difficult than our brief recipe might suggest.
One of these complex components is the cell membrane, or the cellular compartment called for in our recipe. This is the easiest problem, as simple ones have already been created in laboratories. Life today has much more complicated ones, however. The second complex component is metabolism. This is a process of extracting energy from molecules, usually starting from the glucose molecule. This is generally a very complicated multi-step process, sometimes using heavy elements such as iron, sulfur, and/or magnesium as catalysts and the proton pump. Perhaps the most complex component of life as we know it is the storage and copying of genetic information.
Information is stored in the DNA molecule as a sequence of nucleotides. The information is used to make proteins, which become the army of functional molecules. Information is copied from the DNA molecule into messenger RNA. Ribosomes read the messenger RNA and synthesize proteins. Transfer RNA brings amino-acids, the building blocks of proteins, so that the proteins can be synthesized. There are at least 60 kinds of transfer RNAs, and 20 kinds of amino-acids are used to make proteins. Proteins are used throughout the process (within the ribosome, there are about 70 distinct kinds of proteins) but are also the product of the process. This leads to the chicken and egg problem, one potential solution of which is the “RNA world,” which is a hypothesized state of “pre-life” that used only RNA, not DNA. Some catalytic properties today found in proteins must have been found in RNA molecules for the RNA world to work.
A question is raised. The more difficult part to explain in the origin-of-life is the origin of functioning multi-cellular organisms after cells existed, correct? Professor Davis thinks that right now the existence of genetic systems (genetic “information” encoded in DNA, transcribed into RNA, and translated into proteins by ribosomes) is the hardest part of the origin-of-life to explain right now. But every few years we discover a new degree of complexity.
“The human race is just a chemical scum on a moderate-sized planet” –Stephen Hawking
One can wonder exactly what Stephen Hawking meant by this, but Professor Davis believes we must be a very special chemical scum because we are conscious.
“In the absence of observers, our universe is dead” –Andrei Linde (quoted by Paul Davies)
This statement comes from an interpretation of quantum mechanics. Professor Davis asserts that if there is meaning in the universe, it comes through the existence of conscious observers.
“Regardless of how persuasive the Darwinian account of the origins of life may be, as a Buddhist, I find that it leaves on crucial area unexamined. This is the origin of Sentience – the evolution of conscious beings who have the capacity to experience pain and pleasure.” –Dalai Lama, Pp 115
Some closing questions: Consciousness is a prerequisite for meaning, is life a prerequisite for conciousness? In consciousness somehow fundamental and irreducible?