Life as We Know It - and Its Evolution, Lead: Thomas Davis

2/11/2003

Summary by Connor Ahearn:

Life as We Know It and Its Evolution

We began the class with Kevin posing one last question referencing the cosmological physics that had been our primary focus. He wondered why, if motion through space and the expansion of spacetime are indistinguishable to an observer, we choose the spacetime view as our explanation for things like observed redshifts. Professor Mobius answered that observational evidence lends itself to the notion that spacetime is expanding. This was less than satisfactory to several people. However, at that point the discussion was tabled in the interest of moving into the day’s actual subject..

At this point Professor Davis began his lecture, which he described as an attempt to tackle “life as we know it.” He identified two stories that he could employ as a way of getting at our subject. The first was kind of a “Big Bang continued” that would trace evolution of all things in the universe, eventually arriving at life as a phenomenon that followed a similar progression. The second was to just jump headlong into a discussion of life and all the things that we may attribute to it. He wasn’t sure that either one was better than the other but instead took a bit from both perspectives over the course of the night. Also, almost as a side note, Prof. Davis planted a seed for thought by suggesting that if the history of life’s development on Earth were run in reverse you may not be able to pinpoint its beginning. Whether this would result from a blurring of what we assume was a single event or because it would be much too subtle to rigidly define, the idea drew some criticism from those insisting that there would be obvious differences that make it impossible to go unnoticed.

Prof. Davis then presented several cosmological questions of his own. He felt that the most important things to ask were: What is there? How do things work? Why are they the way they are? What’s it all about?

What seems to tie all of this together is the observer asking them. He suggested that things matter because we observe them. The idea is that, as observers, we give the universe whatever significance it has. It was noted that some thinkers have taken this a step further, not to say that the universe exists for us to observe, but rather that it exists because it is observed. This suggestion caused a bit of a digression into philosophical matters and definitions.

We were brought back to the world of life when Prof. Davis detailed several of the ways in which the word “life” is used. Although it wasn’t an exhaustive list, he chose six of the more common and perhaps diverse manners in which we make use of it.

   • 1. Presence/Absence of life in a place
   • 2. Presence/Absence of being alive
   • 3. Is the Earth alive or a living thing?
   • 4. The question of life versus death (as well as dead versus not alive)
   • 5. When does human life begin?
   • 6. Is there life after death?

These all seem to imply different aspects of what we attribute to life. In some ways we see life as a quality of things, as in numbers 2 and 3. We also want to draw boundaries for life: its beginning and ending as number 4 says, as well as distinguishing between the kind of life attributable to germ cells and the sense of life we feel to be intrinsic to humans in number 5. And in number 6 we aren’t talking about life in the biological sense at all. Prof. Davis would suggest later on that because life can encompass all of these notions for us, complications arise when we try to define what it is. These different definitions certainly caused a lot of confusion for us as we tried to discuss the topic but found that often times two of us were arguing with different conceptions of the term from the outset.

After being presented with this list the class began its inspection of the ideas. Sean asked if the Earth should be considered alive because it isn’t doing anything more than acting as a place for life to happen. This makes it no more alive than a rock with moss growing on the outside. Jayson, however, responded with a proposition from the reading that life may be defined as any self-sustaining process. So, in this sense, he thought the whole of Earth may be seen as alive. At this point, Josh and Bill combined to underscore the idea that “life” is used in so many manners that the term is not specific enough and perhaps only serves to confuse the argument. “Calling something life is not the same as calling something hydrogen,” was a recurring theme.

Prof. Davis decided to rein us in by focusing our efforts on one of the uses of the word life. By turning our attention to the idea of a presence or absence of being alive (number 2) we began to talk about what it means, biologically, to have life. The first step in a discussion of this sort would be to establish a list of characteristics of living things. Prof. Davis presented the list from the handout we had received as at least a beginning for this. The problem that list created for many was how stringently it needed to be applied. Several examples were given of organisms we know to be alive that may have at one time met the criteria but no longer do, as is the case with elderly humans with no reproductive capabilities. There also came the problem of whether or not things that were engineered to fulfill each aspect of the list were to be considered alive. It seemed that the creation of a list almost left us with more questions than answers. This was the point that someone suggested another popular opinion as an alternative; the notion that “I don’t know what life is, but I know it when I see it,” may be enough for us to use in identifying it. Prof. Davis felt that this worked fine for life in all its recognizable forms, but wondered if this may cause us to overlook the “yellow slime” that we’ve never encountered.

As the class came to an end a closely related topic came to the forefront of the discussion. Prof. Davis told us that the best estimate for when life first appeared on Earth is about four billion years ago. This event seems to immediately follow the emergence of the correct primordial conditions (such as a lack of oxygen in the atmosphere) for life to have occurred at all. The transition from an inhospitable environment to one of cooler temperatures and a stable climate was the crucial factor for life to begin to take root. Prof. Davis briefly mentioned the concept of panspermia, which proposes that life was transplanted here from an extraterrestrial source. This, of course, only postpones the problem of finding the origin of life.

Whether the organic material coalesced from substances that were previously here or if they were deposited by objects that fell to the surface, it is clear that three things were required to come together in order to arrive at life as we know it. The process of metabolism as well as some sort of genetic system needed to be housed within compartments or membranes. These three components were identified as the essential steps toward developing the sustainable form of life that we have come to recognize. Bringing up these points seemed to push the class into focusing on just what goes into a complex genetic system such as ours. This was where we left off as the class broke to allow those who needed to leave a gracious exit.