Today we see in various forms, a search for an organising force or an undiscovered "basic physical law" which can explain the complexity of life as we see it. The Gaian concept ( Goldsmith , 1992), Dynamic quality ( Pirsig , 1974), A Theory of Everything, such as super strings (Davies & Brown, 1988), and complexity theory (Lewin, 1993), all suggest an unidentified force at work. Natural selection leading to differential survival and complex organisms, is the evolutionary idea.
Proponents of the Gaia Hypothesis have included terminology that says that nature operates with a purpose ( discussed earlier ). This anthropomorphic approach, in the face of scientific objectivity, has led to some academic scorn for the holistic concept. This unfortunate and misleading use of terminology, saying that nature operates with a purpose, has turned away serious consideration of natural mechanisms. Gaia proponents have even attempted to hijack ecological science for their cause through statements such as "ecology is faith", "ecology is emotional" and "ecology is teleological" (Goldsmith, 1992).
Goldsmith's following statement illustrates the sticky tangle of
Gaian terminology: "A life process also evolves for a purpose, that of
fulfilling a specific function within the hierarchy of the biosphere,
so as to contribute to the maintenance of its critical order and hence
its stability." I have discussed this topic in greater detail under the
topic of teleology.
Genetics originated as a science only this century. Evolutionary biologists quickly used this science to build evolutionary theory upon genetic mechanisms. Molecular biology is the leading front of this endeavour today and still dominates the scene. Molecular biology can provide practical and commercial applications and may lead to new evolutionary mechanisms (Wilson, 1992). It has given birth to the rapidly progressing field of biotechnology . In relation to this, ecology and the effect of environmental selective pressures upon evolutionary processes have taken a back seat. This development of biotechnology illustrates a broader trend sweeping across science. Fundamental science, based on the urge to know more about nature and ourselves is shifting its emphasis. Scientists are abandoning basic science, or research for its own sake in favour of applied goals. America's National Science Foundation now requires that strategic research have priority to funding. Strategic science means investment in science that is focused on important national goals such as climatic change, advanced manufacturing and high-performance computing (Weisskopf, 1994).
The shift in emphasis to applied science, after the past 100 years of exploration and discovery, has some important implications. It is a form of adaptation through specialisation, building a dependency upon technological innovations. Having accumulated a vast body of information, sciences such as physics are approaching a "peak of sophisticated perception." To some extent, this has resulted in an absence of large theoretical ideas to challenge the mind and human endeavour. To replace this, we find both physics and biology creating innovative technologies. This has serious implications. Often, we apply technology to solve problems created by technology. Society is turning to science to solve environmental and other problems through technological fixes. In terms of the principles of natural selection we are becoming more specialised. Being specialised, we are becoming more dependent upon technology for our survival and less and less able to adapt. The intensity of our interaction with nature is causing irreversible damage to nature. We overcome this with technological fixes, but then become dependent upon the technology created. An animal that follows this route of specialisation in nature becomes extinct eventually. Social and economic factors are also putting demands upon scientists for technological solutions to our modern dilemma.
A typical example is the breeding of salt resistant crops to grow in areas where irrigation has lead to salination of the soil and made normal agriculture impossible . Another trap is the breeding of pesticide and herbicide resistant crops that can grow under the heavy chemical controls needed to sustain modern agricultural methods. By doing this we are accepting poisonous chemicals as a normal part of our future! Chemical manufacturers with vested interests want to make a quick profit, so promote these technological solutions. Economists seek the quick buck while nature bargains on long term viability. For the industrial capitalist, it does not matter that the solution will fail within 10 years if they can make a few billion dollars and develop new technologies through R&D in the interim. Nature will win this war. In evolutionary terms these are all extremely short term solutions. Insects have already shown their ability to become resistant to insecticides within our lifetime, let alone in the aeons ahead of humanity! In the field of medicine, many strains of bacteria have already developed resistance to antibiotics that were once very effective. Malaria is now showing a resurgence world-wide as it becomes resistant to chemical treatments. Many diseases are showing a resurgence or resistance. Aids viral strains are starting to show resistance to drugs that once offered some relief.
We need to step back and take stock of our situation, realise that we are an evolving species and see how we can better live with nature. "Perpetuity and compatibility" as a principle, offers an amazingly simple new theoretical idea to challenge the current progress of science. Societies need to give up their cultural resistance to the evolutionary perspective and develop a new approach when dealing with nature. Instead of forcing our way through with genetic engineering, biotechnology, nuclear fission reactors, deadly chemicals and the total replacement of ecosystems with highly mechanised and heavily fertilised monoculture type agriculture, we need to learn nature's constraints and adapt our lifestyles to these conditions. In effect we need to despecialise while maintaining educational and living standards as high as possible. Harnessing nature's forces is important. By placing humanity at the centre of ecosystems, we can set her free and ride with minimal control but much guidance. Solutions to our problems can be increasingly technological, but instead of technology conflicting with nature, it should work with and enhance natural processes.
How can the individual contribute to this process? It is already
happening through the trend of environmental awareness. My parents show
another route through planting various vegetables in amongst the
flowers of their suburban garden. Organic farming is becoming
increasingly popular in the USA and Europe (Flowerdew, 1993) (Lampkin,
1990). Green and diversity are beautiful. Working with nature is
Each species occupies and is adapted to an ecological niche. A NICHE
is the functional role of an organism within an ecosystem and its
position in time and space (Smith, 1974). A niche entails interaction
with biotic and abiotic elements and is multidimensional and dynamic.
To define a specific niche, one would have to define a species in its
dynamic and living form, for it is in this complex manner that the
species has dominated or defined its niche. This involves the animals
physical form, physiology and behaviour within the context of its
habitat. Mathematically it is a complex system and so no model can
completely predict its nature. Watch a dragonfly skirting back and
forth over a pond and figure out what it recognises that keeps it
within the area of its flight. The dragonfly flies as if tied to a
string, so that in flight it suddenly turns and flies back across its
niche space. This interesting creature is a Paleozoic
relict, with features such as stiff outstretched wings that date to the
dawn of flight, so in evolutionary terms it has been a very successful
form (Wilson, 1992). During the Carboniferous
period (360 to 286 Mya ago) dragonflies
as large as seagulls inhabited the forests of what is now the Czech
Republic (Benton, 1993).
A niche is however a model. One cannot go out into the field and find a new niche. One could compare the word "niche" to the word "game". Each game is different and the game is as it occurs at the time of play. Past games cannot be recovered. One can propose hypothetical games, with players and (environmental) conditions, but these do not exist "out there" waiting to be discovered. The term "game" is however still valid as a generalisation for a condition we understand.
No refinement of mathematics can describe an aquatic bird. Where the species is naturally found, that is the niche. A duck is not water and water is not a duck, but to fully understand a duck its natural habitat has to be considered. The organism has to be considered within the context of its whole environment for us to fully understand it. Dominance attained in interactions, described traditionally as competition, excludes other species from this niche. Savory (1988) sheds some light on the issue with his observation that "all living things share the power to change their micro environment by their mere presence." Dawkins (1983) calls the impact that an organism has on its environment its extended phenotype in that we can interpret this impact as the phenotypic expression of the creature's genes. A creature's ecological preference will have a genetic basis and be continually subject to selection for optimal fitness (Savory, 1989).
Where a niche is unoccupied, it must be quicker for a species adapted to a similar niche to adapt to, or occupy this niche than it is for another life form to evolve. If giraffes became extinct, evolving a longer neck would be easier and quicker in evolutionary terms for another buck species such as the kudu, to reach the higher uneaten leaves, than for another life form to evolve or for a member of the cat species to evolve a long-necked, leaf eating relative. Taxon cycles is the term for this principle. (Wilson, 1992). One may call this species cycles, for the taxon is a general term used for a taxonomic group (species, genus order etc.) of any rank. Evolution is as irrevocable as history. Once certain features and body plans evolve, many options are lost and the inherited design limits further evolution (Gould, 1993). Our flat feet might evolve into grasping appendages as in the chimpanzee, given the right selective factors and a few million years, but a giraffe is too specialised to evolve such appendages.
When humans disturb ecosystems there is a trend away from specialisation, but also reduced diversity. Specialised animals are generally the most sensitive to change and so the first to become extinct. Exploitation of complex systems makes them more simple. Humanity's disruption of natural systems is a recent occurrence, even if we are referring to the past 100,000 years, and is usually quite destructive. In complex ecosystems, such as tropical forests, or lake systems, where associations have evolved over very long periods, human disruption of the system usually leads first to the extinction of "sensitive" or specialised species. This trend is an indicator of ecosystem health. It is the first sign of pathology within a system that has existed for millions of years. Opportunistic, largely exotic forms often replace these species - generalists that have a broader (more general) niche (Rapport, 1992). However with humanity placed central to ecosystem processes we need to be more concerned with ecosystem integrity than the survival of specialised species. Gross effects such as erosion, water pollution, and the accumulation of pesticides within the system have to be countered while we conserve individual species. This requires a holistic approach, dealing with the ecosystem as a whole and carefully defining humanity's role within the system.
If you look at the bird species that live around your house, you should find such generalists that thrive in systems dominated and altered by humans. Around my house lives a small drab brown bird we call a mossie ( Passer domesticus indicus and P.d. domesticus , the house sparrow). This introduced species is a great generalist, even sharing in the dog food, but also hunting for and catching insects such as grasshoppers and eating budgie seed. Its beauty lies in its potential to evolve into any type of bird through adaptive radiation (see books). Nearby are some salt water prawn ponds where these birds live, scavenging on the wasted prawn feed that falls to the ground. While specialist birds may become extinct, generalists thrive around human habitations and have the potential of evolving to occupy many different habitats. Indigenous Passer sp. found in Southern Africa have more distinct plumage than the drab brown mossie and more specialised diets. Passer motitensis is more brightly coloured than the mossie and has very different habitat preferences. It is shy, keeping to the dry acacia savannah veld and never in towns. It eats grain and weed seeds (Liversidge & McLachlan, 1978).
Passer domesticus was introduced into North America from England and Germany in 1852. Since its introduction to America, P. domesticus has undergone geographic variation (morphological differentiation) in many characters, especially colour (Johnston & Selander, 1964). Various widely distributed native American species show a geographic pattern of colour variation in response to temperature and humidity. Introduced house sparrows, having been subject to the selective action of similar environmental factors show the same pattern of colour variation. Sparrows in Hawaii, introduced in 1870 or 1871, came via New Zealand (from England in 1866-1868). They have a very distinctive colour variation when compared with specimens from England, Germany and North America. Researchers think this is due to their separate evolutionary history and geographic isolation . Because of geographic isolation, the founder effect and genetic drift, the genetic histories of isolated groups are different and specimens from a locality can be separated or identified by colour and to some extent, size. Birds from regions with severe winters tend to have a larger body size than those of milder climates, a similar trend found in native species. This racial variation in the house sparrow over such a short period shows that evolution can occur within a short period.
Some organisms adapt to habitats or niches from which dispersal is easy, allowing them to "test" new environments and occupy new niches. Usually such animals will be widely dispersed. If the giraffe food niche were unoccupied, a generalist could adapt to this habitat and feeding niche, but at the expense of a greater chance of extinction if conditions change. Darwin's finches on the Galapagos islands evolved from a single species of seed-eating ground finch that arrived on these islands. Isolated on the islands, Darwin's finch had access to many food resources. The traditional explanation is that the present-day species arose due to "intense competition and to subsequent dietary specialisation" (McFarland, 1993). A significant observation is that on the isolated Crocos Island, north of the Galapagos Islands there is only one species of finch, while the Galapagos Islands, made up of at least 15 closely associated islands has 13 species of finch. This difference in species abundance introduces a principle recognised in evolution. On the Crocos Island no barriers to gene exchange were possible and the bird remained as one evolving species. On the Galapagos Islands, there is the possibility of geographical isolation on the different islands for a period. This allows for the possibility of genetic differentiation of the isolated populations and the eventual formation of new species.
In this chapter, I will provide a model showing how the intensity
of intraspecific interactions promotes speciation. If other species of
seed-eating or insect-eating birds had been present on the island, when
the ancestral Darwin finch arrived, the diversification of Darwin's
finch would have not been so wide. Competitive interaction would have
excluded the finch from certain niches. Is diversification then a
consequence of intense competition or the evolution of less intense
competition to improve the survival potential of the individual? In
fact, it is both. Intense interactions lead to the evolution of less
competition. One of Darwin's finches has even formed an association
with the large marine lizards that live on the island. When a finch
comes near, the lizard stands up, exposing all parts of the body. The
bird then hops around, pecking off parasites from the tough skin.
Patiently, the lizard waits for the service to end. A question is if
the lizard behaviour evolved over the short time during with the finchs
have been present?
Evolution is founded upon the life, death and differential survival of individuals. Ecosystems do not usually die, but show a slow and stable dynamic shift of interacting and mostly interdependent species in response to changing environmental conditions. Except natural calamities such as volcanic eruptions, meteorite impacts and other local events, complete destruction of whole ecosystems seldom occurs. It is only with human influence that widespread ecosystem destruction is occurring. There have been five main extinctions recorded in evolutionary or fossil history. (One period of global extinction led to the extinction of the dinosaurs.) Fossils do not always represent extinctions as the fossil may be the ancestor of a very successful species living today. ALL CREATURES have been evolving within an ecosystem throughout ALL TIME! There is no sudden change to another species, but at any moment an adapted fit to prevailing conditions.
Wilson (1992) describes this evolution on a large scale as a "succession of dynasties": an evolutionary lineage rises to dominance, expands its geographic range, and splits into multiple species. Some species evolve unique life cycles and ways of life. Groups that were replaced become relict species, or extinct, diminished by competition, disease and climatic or other environmental change. In time, evolutionary innovations bring another species to dominance. An endangered species may evolve a unique biological trait that allows it to survive and radiate again. As an example, one could study the evolution of herbivores' feet and limbs from the first terrestrial creatures to modern antelopes. Evolution of the horse 's limb is well represented in the fossil record as is the evolution of the vertebrate's pelvic girdle.
The modified Lotka Volterra ( MELV)
model, discussed in this chapter, presents a simple mechanism that
underlies this process of evolution through natural selection. This
mechanism dominates genetic influences, which become secondary in
influence, but still affect the whole process. I am referring to
genetical kinship theory or reciprocity theory. Kinship theory
accounts for evolution based on the genetic relatedness of organisms.
Many clear cases of altruism and social co-operation in nature occur
between closely related individuals. Geneticists explain these events
on the basis that the relative has many identical genes and the closer
the genetic relationship the more likely an individual is to sacrifice
itself or in some way promote the survival of its relative. In doing
so, the individual is promoting its own genes that are found in the
relative. This is a neat argument and must explain some animal
behaviour. The MELV model is based on the evolution of energetically
more efficient interactions driving diversification, specialisation and
In the early stages of the colonisation of the earth by life,
adaptation to the physical or abiotic environment must have
been the main process. Life forms interacting with the physical
environment need to adapt to the variety of conditions encountered or
perish. Fewer species around means that biotic interactions must have
been few and the selective forces would have been the abiotic extremes
of heat and cold, moisture and dryness. In population dynamics and
population regulation, ecologists term these influences
density-independent as their impact on the increase and decrease of an
animal population is not related to the population density (Smith,
1974). Population density does not affect extremes of temperature. Here
survival of the fittest would have been paramount. Using my
terminology, the drive for the perpetuity of the organism would have
become a strong instinct. All creatures have this drive for survival or
they do not exist - a simple reality of this material world - a basic
tautology (Thoday, 1958).
An example of a density-independent effect in nature is the effect of winter severity on the bobwhite quail populations. They lose from 4 percent of the population during mild month-long snow cover and 80 percent when the ground cover of snow lasts three months (Smith, 1974). Harsh environments illustrate the density independent influences on population growth that occurred early in evolutionary history. In deserts, the rate of increase of certain birds and rodents is related to rainfall received (Smith, 1974 ).
An important principle (Figure 1) to
observe here is that the environmental extremes which affect
survival are not random, but have a mean range that changes with the
seasons and the extremes of which have less probability of being found.
The animal is thus responding to a seasonally predictable range of
environmental variables and harmonises its behaviour, physiology and
life cycle to "anticipate" the likely range of changes that occur. As
with the bobwhite quail populations, when these extremes are exceeded,
al large proportion of the population dies.
In this shrimp pond climate (Fig. 1), it is practically impossible for winter temperatures to drop as low as ten degrees Celsius. None of the prawns died due to cold. Exotic Malawian cichlids kept in the same climatic regime suffered some mortality at the lowest temperatures experienced over this winter period. Historically, they had not encountered such low temperatures. Natural selection operated to eliminate those individuals not adapted to that temperature regime. The surviving stock (shoal) of fish had become better adapted to the environment, although less genetically diverse (heterozygous).
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