Cosmology and our View of the World
Life and Evolution
Lead: Mary Awad &Greg Hilston
Summary by Matthew Kimball
When, where, how did life start - How did it evolve
The seminar on March 19th was led by Mary Awad and Greg Hilston, the topic of the night being Life and Evolution as we know it.
To start off the seminar, two definitions of life were presented to the class to attempt to make discussion easier:
In addition to the definitions, 7 characteristics of living things were provided:
Interestingly enough after giving these definitions and characteristics, the question arose, “Are viruses alive?” This is a debate which was also brought up in a previous class session, led by Prof. Davis, because viruses have six of the seven characteristics of living things, the only exception being that they do not have cellular organization. In addition, when outside of a host, the virus does not have the ability to reproduce or metabolize. Is having six of seven characteristics of living things enough to be considered “living” at all? Some debate arose about the inability of the virus to adapt to an environment outside of another living organism as precluding it from being a living thing itself, since a virus cannot grow and develop unless within a host. Greg started the discussion as being in favor of viruses being alive, as the host is their environment. The point was brought up that viruses can adapt evolutionarily, however if they must do so in an environment defined as “free-standing” (outside of a host) then they would not be living. Some argued that the point is moot as to whether or not they are alive, and Dr. Davis argued that because a virus only injects part of itself (it’s DNA) into a host, that it would not be alive because the DNA itself is not living. It only commands more viruses to be made from the host cell.
The debate about viruses brought about the question of how life should be defined. An interesting point was brought up by a student saying, “Since there is even a question about viruses being alive, that would mean that the definition itself is incorrect.” This was well-received by others, and any students had the mindset that ambiguity when defining life is okay. It was stated multiple times that there could be something outside of “life as we know it” which doesn’t fit all of our current categories, and yet is still alive beyond our current understanding. I believe this is an important point to consider because we are able to leave Earth with scientific instruments or even manned missions, and that brings about the potential to find other forms of life, that didn’t evolve under the same circumstances as those organisms found here on Earth. Our definition seems to be very limiting considering how much about the universe we don’t know.
Following the debates about viruses and how to define life, a brief overview of when life started was provided by Mary and Greg:
In addition, Greg shared an infographic representation of the Universe from the Big Bang to present day as a single terrestrial year. The solar system and life did not occur until “September”, and it is not until 11:58PM on “December 31st” that humans even evolve. This clever diagram helped to show just how little time it has taken for life as we know it to have developed and evolved on the cosmic timescale.
After learning when life is thought to have originated, the discussion turned to the different theories of how and where life originated. Mary presented to the class via slides that, “for the origination of life on Earth we need water, a source of free energy, and an organic molecular species capable of self-assembly.” Currently science is not able to definitively explain how the proper conditions for the origin of life arose, so there are many theories concerning the occurrence of these conditions. The oceanic origins were discussed first, starting with the thought that life could have originated in deep sea vents, which postulates that hydrogen-rich fluids emerged out of the sea floor and mixed with the carbon-dioxide rich water, and the combination of the two may have given life as we know it a kick-start. The second theory of oceanic origins posed the idea of a “foamy shoreline”, in which the foam present on the seashore was a perfect place for the components of life to come together.
Next, possible extraterrestrial origins of life were discussed, focusing on theories of meteorite-delivery and pseudo-panspermia. The meteorite theory arose due to the discovery of the Murchison meteorite in 1969. It was discovered that within the meteorite were microfossils which led scientists to believe that it originated on a water-rich world with evidence of 15 amino acids. It was postulated that similar amino acids from outside of Earth could have landed on the Earth’s surface, and provided the building blocks of life. Pseudo-panspermia is the hypothesis that pre-biotic compounds were present at the formation of the solar system, and so were incorporated when Earth itself formed, and thus are present outside of Earth locked away in meteorites which scientists can study when they land on the surface. It was brought up during the discussion that the organic compounds required for life are known to exist even outside our own solar system, and are ubiquitous throughout the known universe.
The next theory about the origins of life was the “Soup Theory” which states:
It was shown in the lab that uracil, guanine, adenine, and cytosine, which are the building blocks of DNA and RNA, could be made using conditions similar to that found on prebiotic earth. The counter-argument was brought up that it is still hard to see how nucleotides could have formed from these component parts, and some scientists argue that the “further transformations” from the soup theory cannot be explained with current scientific knowledge or technology.
Within the theory of the origins of life, three main “worlds” have been proposed, in which the first life could have first formed and been replicated. These three “worlds” are:
Encompassed in the RNA world theory is the thought that RNA was able to form templates of itself, mutate, and undergo Darwinian evolution, leading to more and more complex organisms. The Lipid world theory postulates that the first self-replicating molecules were much like the lipids that we see today, and were called “lipozymes”. The comment was made, “it is interesting that all life came from fat”. The clay world theory says that clay was the perfect place for early life to form, because it is a good housing against the harsh elements and clay is able to form crystals which preserve their arrangement as they grow, and as pieces break off the early life formed from it could have used these crystals as a template to further mutate and eventually replicate.
The final three topics concerning life discussed during the class session were Panspermia, religious theories, and artificial forms of life. Panspermia is the theory that life formed outside of Earth and was transported here on meteors. This is similar to pseudo-panspermia mentioned earlier, but in this case the complex organisms themselves are transported to Earth, rather than just the component building blocks of life. Nearly every religion has its own creation story, and during the discussion the Christian and Buddhist theories of the origin of life were discussed. According to Christianity, life, the world and universe were created by god in seven days. Some in the class clarified that within the Bible the use of “day” could simply be a measure of time greater than the Earth day that we know, which would not negate the scientific evidence for life appearing on Earth 3.5BYA. Buddhism states that the universe has, and always will, exist. An agnostic theory of the origins of life was brought up in the slides, but the discussion didn’t touch upon it, as most agnostics rely on science to describe the origins of the universe.
Artificial forms of life were discussed, and were defined as life that is either created in the lab or simulated. The hope is that although simulations are not life in their own right, the traits and information exhibited by them could be used to the benefit of scientific research into life as we currently know it. Many in the class stated that computer programs such as Conway’s Game of Life, or viruses such as Stuxnet are not life in themselves. It was agreed however, that computer simulations and viruses do exhibit some of the traits of life, such as replication, environmental adaptation, and “evolution”. This again brought up the question of how complete our definition of life is, and possibly whether different “worlds” (nature vs. computer networks) should have differing definitions of life. Science currently has one set of characteristics for what defines something as living.
Unless we can adapt that definition upon the potential discovery of other organisms which don’t fit our current criteria, there is potential for new life outside of Earth to be ignored or ill-defined. The world of the Matrix movies was brought up, since the simulation within it was so “real” that it was hard to differentiate between actual people and simulations. The question was then asked, “What is the difference between you and an artificial you if both respond, develop, and act in the same way?” In response, the statement was made that “artificial coffee is not coffee”.
In conclusion, the class period left the students with a few questions to ponder in the future and to utilize in future class sessions: