Archive for April 2010

On Progress: Philosophical Ramblings on the Nature of Evolution

April 10, 2010

Let us consider, for a moment, the pinnacle of evolution.  This group of organisms builds its own cities, engages in organized labor, builds stratified, complex societies, and even practices agriculture in a sense.  I am referring to ants.  You might argue that my momentary classification of ants as the pinnacle of evolution demonstrates a level of inane stupidity on my part, but please allow me a moment to explain myself.

What would you replace ants with in my model? Most likely, you are thinking “well humans, of course”.  But why?  What justifies the classification of humanity as the ultimate pinnacle of evolution? One might argue that we are currently the “dominant” species on Earth, but “dominant” is a tricky term.  Yes, we shape the environment itself in an extremely tactile and observable manner, but even the humble stromatolite has altered Earth’s atmosphere on a global scale (by releasing oxygen early on in life’s history on Earth).  Yes, we use tools and make war with each other, but chimps do the same thing.  Is it perhaps because we are still alive today? This seems like an even worse reason to assume human superiority than the previous ones.  Given the diversity of life on Earth today, the assumption that humans are somehow the pinnacle of an evolutionary process, while perhaps a nice idea from our perspective, is not a scientifically tenable hypothesis.

Of course, I am not implying that there is nothing special about the human species when Earth’s long history is considered.  Yes, we have technological and intellectual capacities far greater than that of other species here on Earth.  Our species has achieved great things, and this should not be overlooked.  However, on the same note, our connections to the world around us must also not be overlooked.  The human species is clearly a biological phenomenon at some deep and fundamental level; we are part of nature, one with the natural world.  If one reads evolution as a progressive ladder trending inherently towards human excellence, it is far to easy to overlook our connection to the greater world around us.  How does this ideology of progress work?

The ideology of progress is actually quite simple to grasp.  If one reads evolution as a progressive process in the sense we are focusing on, then one accepts that evolution inherently operates as follows:

first, nice simple life

then, more complex life

then, even more complex life

finally, upright, bipedal, conscious organisms with social capabilities.

Of course, the fossil record mirrors this trend to an extent. We start with invertebrates, then fish, amphibians, reptiles, mammals, primates, and ultimately humans as a late arrival on the scene.  However, the ideology of progress attempts to place a directional framework around life’s evolution on Earth.  A Progressivist would argue that life somehow inherently evolves in a directional sense, ultimately tending towards consciousness.  This mindset is reflected in many popular (as opposed to academic) texts dealing with paleontology, as well as in the depiction of evolution as a tree.  First, fish appear, and then disappear as amphibians appear. Then it’s reptiles replacing amphibians. And so on.  Such a mindset is culturally constructed rather than demonstrated by scientific data. In the model of evolution as a tree, humanity is ultimately placed at the top and center of the tree, with other lineages, such as reptilia, as side branches.  The message in such a presentation is clear: humans are the most important species on Earth.  Ernest Haeckel’s own evolutionary tree is perhaps the most beautiful illustration of such an idea. The illustration is public domain, so I’ll upload it in a minute, but here’s the wikipedia page where I borrow the image itself from. Anyway, here’s the image:

Haeckel's tree of life

However, Haeckel’s tree of life is extremely problematic. Species do not stop evolving once a more “advanced” group appears on the scene.   When amphibians first evolved during the Devonian, fish did not disappear, never to be heard from again. Nor did they stop diversifying.  Indeed, evolution still shapes new piscine permutations, even today.  If we were self-aware fishes rather than mammalian in nature, perhaps we would shape our evolutionary ladder in such a way that our fishy heritage would be the defining trunk of the tree of life, with humans off on some side branch of their own. Of course, we are not really fish, we are humans. Therefore, we understandably view our own species as the most important product of evolution (as demonstrated by Haeckel’s tree).  Such an anthropocentric model of evolution, while understandable, is not scientific in nature.

In fact,  Darwin rejected the ideology of progress inherent in Haeckel’s tree.  Darwin preferred the analogy of a coral, rather than a tree.  On p. 25 of the B Notebook (available here), Darwin states that “The tree of life should perhaps be called the coral of life, base of branches dead; so that passages cannot be seen.” Darwin was contemplating  tree-like models, but his tree, or coral, was inherently nonprogressive (image from here):

Darwin's tree, or "coral" of life

Note that in contrast to Haeckel’s tree, Darwin’s own illustration (although superficially tree-like) has no obvious pinnacle. Branches “A”, “B”, “C”, and “D”, each branch off in their own separate direction, with no single branch occupying an obviously central position on top of a well-defined trunk.  Thus, no progress inherent in Darwin’s own illustration of how natural selection works.

But what does this all mean? Is there a reason for my posting of these beautiful yet archaic images?  Trees, branches, corals, and progress…who cares?  This line of inquiry is useful for multiple reasons.  First, Darwin’s coral and Haeckel’s tree offer a wonderfully clear illustration of how one’s own biases can influence one’s science.  While Darwin’s coral suggests natural selection as a wholly non-progressive enterprise, inherent in Haeckel’s tree is his own, and indeed our own, anthropocentrism.  Haeckel’s tree places humans exactly where most of us view ourselves, at the top of the ladder and central to all life on Earth.  In Haeckel’s tree, non-human lifeforms are portrayed as inherently “lower” than humans. In Darwin’s coral, we are relegated to one branch of the larger model, diverging from other lifeforms in a similar manner to that of Haeckel’s tree, but merely away from other lifeforms rather than inherently upward.

So what?  Darwin drew corals to illustrate evolution but Haeckel drew trees. This split, in itself, signifies a far greater split within human society.  Most mainstream Western religious belief systems uphold a view of humanity similar to that presented in Haeckel’s tree.  Humans are presented as beings “Created in God’s image”, at the pinnacle of all life on Earth.  Darwin’s coral, being non-progressive in nature, seems to contradict these belief systems.

However, is such a contradiction between evolution and religious belief really necessary?  While religiously inspired anti-evolution movements see such a contradiction as inherent and deadly to either evolution or religion (choosing, of course, evolution as the ideology to reject), is such a contradiction really there?  Not necessarily.  While some evolutionary biologists, such as Richard Dawkins, are ardent atheists, others, such as Kenneth Miller, are devoutly religious.  As I argue in Gould’s Hopeless Monster, evolutionary theory can, in fact, co-exist with religious belief.  However, the two magisteria DO overlap in some cases, forcing some level of compromise in the zones where this overlap occurs in order to maintain coexistence.

Of course, if one wants to truly accept all implications of modern science, then religious beliefs will often end up shifting to accommodate science in these contested zones.   But this is not to imply that science disproves God.  Indeed, God is a supernatural hypothesis outside the magisteria of science; one cannot scientific prove or disprove the existence of the supernatural.  What science can and must do is to follow the available evidence where it leads in search of natural explanations for natural phenomenon.  So is Darwin’s coral or Haeckel’s tree the correct model for the diversity of life? The fact that the history of life on  Earth has followed a relatively contingent path of development over the past few billion years lends credibility to Darwin’s coral rather than Haeckel’s tree.

But what does this mean for religious belief? Surprisingly, not as much as one might initially think.  While such a model suggests that we are deeply tied to the web of life surrounding us, it does not necessarily exclude the existence of God.  As much as one might argue that a rejection of the ladder of progress somehow “lowers” the significance of human existence, why is such a statement necessary? One could just as easily argue that such a position rather elevates the position of non-human lifeforms, perhaps focusing on the unity of all lifeforms as part of God’s creation, if one wanted to debate the issue in theological terms.  Of course, such a discourse, while influenced by science, is not in itself scientific in any sense, since science cannot, by nature, answer theological questions dealing with the supernatural.

Now, moving away from the question of religion, let’s finally focus on the implications for science as a whole.  The ladder of progress is heavily embedded within the scientific community, even though, as we have seen, it is a non-scientific concept.  In fact, Michael Ruse (1996) has published an entire book, Monad to Man: the Concept of Progress in Evolutionary Biology, focusing on the subject.  If you’re at all interested in the question of progress after reading this post, I strongly suggest checking it out.  Regardless of whether we embrace Darwin’s coral or Haeckel’s tree, our choice has major implications for how we view life as a whole.  If we are to embrace Haeckel’s tree, then consciousness is likely to be the end result of an evolutionary programme, suggesting that self-aware life is likely to be ubiquitous, or at least fairly common throughout the universe.  If we are to rather embrace Darwin’s coral, then consciousness is likely to be far rarer in the universe.  So perhaps ironically, while Darwin’s coral seems to de-emphasize the importance of human life here on Earth, it may prove to be foundational to the importance of human existence in the cosmos as a whole.  If evolution does not necessarily trend towards consciousness, and if it is therefore plausible to argue that we are one of only a few (if not the only) “conscious”, self-aware species in the universe as a whole, then that is an intriguing thought.  If we are indeed organisms of an exceedingly rare nature within the cosmos as a whole, then perhaps such a plausibility is worth contemplating.