“I use the term Struggle for Existence in a large and metaphorical sense, including dependence of one being on another, and including (which is more important) not only the life of the individual, but success in leaving progeny.”
“there is a frequently recurring struggle for existence,”
“Every being, which during its natural lifetime produces several eggs or seeds, must suffer destruction during some period of its life, and during some season or occasional year,”
“each at some period of its life, during some season of the year, during each generation or at intervals, has to struggle for life, and to suffer great destruction. When we reflect on this struggle, we may console ourselves with the full belief that the war of nature is not incessant, …and that the vigorous, the healthy, and the happy survive and multiply.” (Emphasis added.)
It was within that framework of recurring struggle, not constant struggle, that he applied a Malthusian approach to the question of population growth. But his conclusion was not that lack of food would stabilize or reduce populations, but that
The amount of food for each species of course gives the extreme limit to which each can increase; but very frequently it is not the obtaining food, but the serving as prey to other animals, which determines the average numbers of a species.” And “Climate plays an important part in determining the average numbers of a species, and periodical seasons of extreme cold or drought, I believe to be the most effective of all checks.
In short, environmental factors often limit population growth before starvation from overpopulation steps in.
Despite Darwin’s clear instruction to the contrary, his Struggle for Existence has been twisted into a metaphor for life itself. In particular, the concept of scarcity has been installed not only as the driving force behind the struggle for existence, but as the basis of economic studies.
So how important is scarcity as a factor in natural selection? Darwin rarely used the word, preferring the Struggle for Existence metaphor. He overstated the significance of the metaphor a little, as he apparently had to overcome a prevailing attitude of the time, to the effect that the natural world was all about lazy summer afternoons with birds singing and bees buzzing.
Nothing is easier than to admit in words the truth of the universal struggle for life, or more difficult--at least I have found it so--than constantly to bear this conclusion in mind. Yet unless it be thoroughly engrained in the mind, I am convinced that the whole economy of nature, with every fact on distribution, rarity, abundance, extinction, and variation, will be dimly seen or quite misunderstood. We behold the face of nature bright with gladness, we often see superabundance of food; we do not see, or we forget, that the birds which are idly singing round us mostly live on insects or seeds, and are thus constantly destroying life; or we forget how largely these songsters, or their eggs, or their nestlings, are destroyed by birds and beasts of prey; we do not always bear in mind, that though food may be now superabundant, it is not so at all seasons of each recurring year.
Note that even while justifying the importance of the struggle, Darwin balanced that concept with the fact of regular periods of abundance. It’s that regular abundance that theorists have ignored, but which must be discussed.
Let’s consider a product of natural selection – a forest. Are the individual trees struggling for existence? Not at all. Constant struggle entails debilitating hardship, it results in a loss of vigor, we would see considerable signs of stress, survivors and failures, yet the vast bulk of trees in a forest are flourishing pictures of health.
For this situation to arise there must be adequate resources for most of the trees. Furthermore, forests could not have developed to the point where they have dominated landscapes for millennia if abundant resources were not the norm.
Some forest trees are struggling. Those on the upper and lower limits of a forest on a mountain slope, or those on the northern and southern limits of a forest that might stretch for a thousand or more kilometers, struggle with climatic extremes for which the species is not well adapted.
It will no doubt be argued that the individual trees in a forest are competing with each other for resources. This is simply anthropomorphism. How can they compete? Are they even aware that another tree is nearby? Trees side by side are not competing, they are simply living. I have trees in my yard that have roots intermeshing. Are they competing, or supporting each other?
Unless either of these viewpoints is backed by evidence they are no more than idle speculation.
In a forest where there are adequate resources for all, again, as shown by the health of the forest, the concept of competition is ludicrous. But, some people argue, the trees struggle upwards for a share of the available sunlight. Not so. If a seedling from one of these forest trees was planted in an open area it would grow to much the same size as in a forest, without the need to strive for sunlight. Its form would be slightly stunted due to a lack of protection from other trees, so the height of forest trees can be seen as an indication of favorable conditions rather than unfavorable.
Which view is correct? Are the forest trees engaged in a competitive struggle, or are they benefitting from close association? I think the general better health of a forest tree compared to one growing in isolation, suggests the latter. There is no upward struggle.
As Darwin himself put it in pursuing a different thought; “For in such cases, we may believe, that a plant could exist only where the conditions of its life were so favorable that many could exist together, and thus save each other from utter destruction.”
When we consider the life of a forest, the health of the majority of trees and the stressed appearance of trees at the extremes of its range, a general rule of natural selection comes to mind.
The struggle for existence takes place at the margins.
It therefore cannot be a metaphor for life in general, nor can it be the defining feature of evolution.
That view is supported by the fact that it is not necessary that competition takes place, in order that favorable variations increase within a population. Those individuals that are better able to access resources when resources are abundant, will tend to leave greater numbers of progeny. Their progeny will in turn pass on those traits and thus create a trend, an increase within the population of the traits, in the absence of scarcity and competition.
So we see another general rule;
The increase of traits in a population does not require scarcity, nor does it require competition for scarce resources.
The significance of scarcity has been greatly overstated.
My view is that the regular abundance that has created great forests on every continent, is seen also in many other ecosystems around the world. For example, the Great Barrier Reef that stretches for over a thousand kilometers, in which tiny immobile marine organisms rely on tidal currents to provide them with nutrients, and which in turn become a resource for an entire ecosystem. Those currents have provided those nutrients for eons. And the cold northern and southern oceans in which staggering annual explosions of biomass occur that are a resource for countless life forms. So abundant is this food source that whales feeding on it can store enough energy to last until the next annual harvest.
This abundance is a key factor in evolution. For variation to occur in a population, you first need a population. An increase in numbers requires reliable resources. Those resources must be plentiful most of the time, although “most of the time” will vary with the capability of particular groups. Scarcity certainly has a role; occasional periods of scarcity would accelerate the increase and decrease of traits in a population, and would be significant in extinctions, but scarcity must play a secondary role to abundance.
Theorists will argue that the growth of populations creates scarcity that then produces competition. That’s not clear thinking, that’s paranoia. Instances of scarcity and competition can occur, but such are infrequent compared to periods of abundance. And as Darwin pointed out, an increase in a population creates a resource for another organism, whether that be a predator, a parasite, or a virus. Scarcity is secondary to abundance.
To summarize, Darwin overstated the significance of the struggle for existence because he believed that if natural selection was to be properly understood, he had to overcome a perceived, popular, sentimental view of nature.
Despite his clear instruction that his Struggle for Existence was a broad metaphor, and that the real story of life is that “The vigorous, the healthy, and the happy survive and multiply,” evolutionary theorists that followed, who call themselves Darwinists, have twisted the metaphor into an alleged fact of constant scarcity. Their failure to understand that biological struggle is a figure of speech has progressed step by step into the greatest absurdity in biology – the struggling genes of selfish gene theory.
A metaphor to explain a metaphor. No wonder confusion reigns.