On the shapes of leaves

" When you are a Bear of Very Little Brain, and you Think of Things, you find sometimes that a Thing which seemed very Thingish inside you is quite different when it gets out into the open and has other people looking at it " ― A.A. Milne, Winnie-the-Pooh

On one of my walks as usual I begun to ponder the limitation of human perception in our culture and the frameworks we apply to sensory data. This came about when I found a very interesting looking tree at the side of the road. It wasn't unusual in sense of the word - it was just very old and stood out from others in a kind of majesty.

It had already begun to loose most of its branches to old age but was still retaining some really sturdy ones going up. The kind I liked to climb up when I was a younger and dared such feats. The view from the top of this one would be amazing as it was already some elevation from the rest of its surroundings at the side of a hill.

Lost in thought and admiration of its thick bark I began to wonder the process by which that bark is formed, and ultimately shed by the elements - and that it was this process which defined the shape of its bark and why it was different from the nearby trees whose bark was relatively young.

Life of an organism like a tree is mainly concentrated in two key locations of active growth - the tips of the branches which form annual buds and are responsible for flowers for reproduction, leaves for photosynthesis and the ultimate upward growth towards sunlight - and a thin layer of spongy tissue left behind on all surfaces just under the outermost bark which keeps thickening the inside truck with water and nutrient carrying channels and also forms the outer bark which protects this whole operation from the elements, pests and disease.

The scales of bark covering this old gentleman were tough as shields. Each one having endured countless cycles of harsh weather and extremes of annual climate. Only paper thin slices of dried bark would occasionally come loose and float gently to the ground - or ripped off by heavy rain and wind. Yet this old tree had seen its formative years, now slowly but surely shrinking, loosing a branch here and there, taking a beating after another. With every shedding the shields would get thinner, polished by the elements.

It was in their shape I saw all this. Yet when you think about it I didn't really see any of that. It was all a story I made up to explain away what I saw. If given a similar piece of plastic painted pink, I probably wouldn't have recognize it as a shape of a tree bark and wouldn't have made any of the conclusions about its formation - and wouldn't use words like 'shield like' to describe the shape.

In the Middle age European theologians, especially popular ones, formed many such stories to explain away things - their shapes, their meanings, purpose, existence. A cow was there to provide milk for humans and its udders were shaped specifically to fit between the fingers of the man woman milking it. Even predators were there to teach us about courage (lions), cunning (fox) or the importance of washing (parasites). This was at the time made sense to some extent because most people had not the time to really observe and examine nature.

Naturalists who came long after begun to distance themselves from such anthropocentric explanations and begun to see multiple reasons for why things appeared a certain way and even some of the processes by which they came about. Modern evolutionary biology with its basis of chemistry and ultimately physics unified and made our understanding rigorous. No longer could we judge anything by their appearances - almost any process of nature had an inner life which we could only discover ones we delved deep into its hidden processes and interactions with its surroundings.

Thus the random ramblings and walks of the naturalists became quite boring and almost irrelevant. Apart from the occasional discovery of a new species or phenomenon which the biologist and chemist would then rush to examine, verify and dissect there was nothing much the old master could with his limited senses but be nostalgic for the old days when there was still some mysteries and secrets one could discover on your own.

So turning from my rigid framework of limited perception towards the next tree I was stunned to see it covered from branch to roots with velvety silk gown. A species of months had invaded several local trees that summer and was in the process of engulfing them. Every leaf was gone leaving a bare wintery looking tree - with a web like continuous translucent white cloth neatly woven by perhaps thousands or even millions? of Bird-cherry Ermine moth caterpillars (Yponomeuta evonymella). In fact the ground under the trees was quite full of dead moths and loose wings, bright white like petals from a cherry tree.

My thoughts were: OK, here is another process. But how would I see this phenomenon if I lacked the framework of explanations for each part. Surely I would have no idea about the role of the netting in the reproductive cycle of the months - or would probably make up some sort of quite imaginative explanation for it.

Then I thought my point of view was also quite biased in that I was looking at individual months and projecting myself 'in their shoes'. Many insects are 'hive-beings' as in they only survive in groups and it is their collective effort which defines their existence. Examining a single moth, let alone trying to find its process, its motives and purpose, without the whole of its swarm would be impossible or inaccurate.

In fact the border between the 'individual' and the 'collective' is very fuzzy in reality. From the anthill down to the smallest of bacteria and viruses, we too are composed of primordial collective agreements between interacting cells - even the our cells themselves are a union of two 'organisms' - molecular cluster called mitochondria and the outer cell with its nucleus distantly related to a single bacteria. The evolutionary development of early forms of life indicates that even these components were once 'individual' lifeforms that at some point merged to form a complete symbiosis - to the extent that we no longer hardly see them as entities on their own. 

To what extent can we then examine the behavior of a species, or any phenomenon in general, when we have this bias of differentiating entities into 'actors', individuals, and then assigning them with motives or purposes - when in fact we could just as easily see them as parts of a process with many interacting levels. In fact when you think about it the 'collectivity' or the 'individuality' of the moths to the cells in the tree bark are just degrees or levels of categorization. We cannot assign them 100% into either category.

This makes observation of nature particularly challenging - and disturbing when noticing that this applies to ourselves too.  We want to assign ourselves some level of free-will, yet always at a closer examination any such 'freedom' appears uncertain and elusive.

To think that we are no more free to choose the aspects of our behavior in every day life then a tree has in forming the shape of its leaf. Both are ultimately limited by the biochemistry (signals in brains and cell division in leaves) and environmental factors (sensory and other signals to the brains and the environmental signals like direction of sunlight to the leaf). On top of all these we have our conceptual and cultural biases - I guess the leaf would have some pretty restrictive biases too about what form to try to grow under the circumstances.

Approaching storm clouds cause my brain chemistry to switch to 'seek-shelter' -mode and my brain creates an illusion to myself that I have made a decision to return to home supposedly because of a rational choice about not getting wet. This all seems very satisfying to me and I congratulate myself on my decisiveness :3

Refs:
The Biography of a Tree - James Jackson,
Free Will - Sam Harris