At which point I guess we agree to disagree. You don't believe in a balance and I do.....and it doesn't appear either of us is about to change the other's mind. Ironically, I guess that's a kind of balance.
The thing that always strikes me about "agreeing to disagree" is that it applies quite well to opinions, but rather less well to facts. "Nature exists in a balance" is an empirical statement of fact, not an opinion, provided you've defined what the word "balance" means. You may 'disagree' with the notion that any so-called "balance" in nature is transient and temporary at best, and that the reality of nature is constant change and constant extinction...but the facts are against you if you do.
Predator-prey "balance," for instance, holds only so long as absolutely nothing changes. It's a precarious situation, like sand growing in an hourglass. The moment anything changes, whether it be weather or mutation or the introduction of new disease or parasites, that so-called "balance" collapses, and species go extinct. This happened before man came to be. It will happen after man is gone.
As to the Gaia hypothesis that I referred to in my previous post (i.e., that the earth is similar to a multicellular organism), that was an analogy. On the other hand, our definition of a multicellular organism is constantly evolving. It is now known, for example, that the human body has more bacterial cells than human cells, and we cannot live without these symbionts. They provide digestive enzymes, compete with pathogens (preventing them from establishing themselves) and produce many vitamins. Since this is the case, are we really organisms or small ecosystems? I doubt that humans are unique in this way.
I get the analogy. I just don't think it's very strong.
It's flawed for two reasons. First, the earth does not behave in any meaningful way like a single organism. It behaves like a complex web of different organisms with different survival strategies, some of which are cooperative, some of which are competitive, and the vast majority of which are parasitic. (Like I said before, the study of evolutionary biology is the study of parasites; parasites outnumber free-living species of life on this planet by *at least* four to one.)
So comparing the earth with a person falls flat. We are home to a large number of organisms, a small handful of which are symbiotic, many of which are parasitic, and a great bulk of which are just along for the ride, but in no meaningful sense does our body behave like a complex set of interdependent ecosystems the way the planet does.
Second, the earth-as-Gaia model neglects the fact that this complex web of interconnected ecosystems does not behave, react, or change in unison in any way like a single organism. There is no central organization. There is no single system. There is overarching structure.
Instead, there is a whole lot of DNA being expressed in a whole lot of organisms, and whatever changes work in the short term are propagated, regardless of their effect on other organisms or on the ecosystem as a whole. There is no long-term plan. Every mutation, every adaptation, is local and specific. And, more important, the forces of adaptation and natural selection are utterly, completely without forethought or destination, and entirely without any sort of long-term plan.
Contrary to popular misconception, evolution is not an upward curve in the direction of greater complexity, greater sophistication, or greater "balance;" the human immunodeficiency virus is, by any reasonable understanding of evolutionary biology a more "highly evolved" organism than human beings are. And it doesn't give a toss about "balance" or anything else.
I talked about this conversation with my evolutionary biologist girlfriend last night. Her opinion, which I think is a good one, is that anyone who argues in favor of "natural balance" or that the world's ecosystems would be "better off" without humans in it should read two books:
Parasite Rex: Inside the Bizarre World of Nature's Most Dangerous Creatures by Carl Zimmer, and
The Blind Watchmaker: Why the Evidence of Evolution Reveals a Universe without Design by Richard Dawkins.
The first is an exploration of how any sort of Walt Disney idea of nature is deeply, profoundly flawed, and why one of the single most driving forces of nature isn't predator-prey relationships but rather the unceasing, never-ending warfare of parasite-host relationships. I'm going to Canada to visit her this week, and her science book club will be discussing this book; the discussion is being led by Dr. Rosemary Redfield, who
recently published a paper refuting the notion of organisms adapted to metabolisms built on arsenic.
The second is without question the single best introduction to the ideas of evolutionary biology I have ever encountered. It neatly demolishes many deeply-cherished ideas about "natural order" and debunks most of the common misconceptions about how nature and evolutionary adaptation works; I dearly wish that there could be a law saying nobody is allowed to talk about how evolution is "random" or is about "survival of the fittest" (to cite two of the most common misperceptions) without first reading this book.
