Question

Compare and contrast three of Darwin's criteria for natural selection to creationist principles and explain which body of ideas are more applicable to deductive and inductive reasoning in science and why Explain and synthesize in detail how two of Darwin's 8 criteria for natural selections can be measured and explained through the steps of the scientific method, using principles of biology and inheritance

Answer 1

Darwin's theory of evolution by natural selection states that :

1. More individuals are produced each generation that can survive.
2. Phenotypic variation exists among individuals and the variation is heritable.
3. Those individuals with heritable traits better suited to the environment will survive.
4. When reproductive isolation occurs new species will form.

These are the basic tenets of evolution by natural selection as defined by Darwin. The following is a quote from Darwin.

"Variation is a feature of natural populations and every population produces more progeny than its environment can manage. The consequences of this overproduction is that those individuals with the best genetic fitness for the environment will produce offspring that can more successfully compete in that environment. Thus the subsequent generation will have a higher representation of these offspring and the population will have evolved."

Creationism most often refers to belief in special creation; the claim that the universe and lifeforms were created as they exist today by divine action, and that the only true explanations are those which are compatible with a Christian fundamentalist literal interpretation of the creation myths found in the Bible's Genesis creation narrative. Since the 1970s, the commonest form of this has been young Earth creationism which posits special creation of the universe and lifeforms within the last 10,000 years on the basis of Flood geology, and promotes pseudoscientific creation science. From the 18th century onwards, old Earth creationism accepted geological time harmonized with Genesis through gap or day-age theory, while supporting anti-evolution. Modern old-Earth creationists support progressive creationism and continue to reject evolutionary explanations Following political controversy, creation science was reformulated as intelligent design and neo-creationism.

While Darwin’s ideas initially challenged long-held scientific and religious belief systems, opposition to much of Darwin’s thinking among the scientific communities of the English-speaking world largely collapsed in the decades following the publication of On the Origin of Species. Yet evolution continued to be vigorously rejected by British and American churches because, religious leaders argued, the theory directly contradicted many of the core teachings of the Christian faith.

Darwin’s notion that existing species, including man, had developed over time due to constant and random change seemed to be in clear opposition to the idea that all creatures had been created “according to their kind” by God, as described in the first chapter of the biblical book of Genesis. Before Darwin, the prevailing scientific theory of life’s origins and development had held that species were fixed and that they never changed. This theory, known as “special creationism,” comported well with the biblical account of God creating the fish, fowl and mammals without mention of subsequent alteration.

Darwinian thinking also appeared to contradict the notion, central to Christianity and many other faiths, that man had a special, God-given place in the natural order. Instead, proponents of evolution pointed to signs in human anatomy – remnants of a tailbone, for instance – showing common ancestry with other mammals.

Finally, the idea of a benevolent God who cared for his creation was seemingly challenged by Darwin’s depiction of the natural world as a savage and cruel place – “red in tooth and claw,” as Darwin’s contemporary, Alfred Lord Tennyson, wrote just a few years before On the Origin of Species was published. Darwin’s theory challenged the idea that the natural world existed in benevolent harmony.

For investigating the laws of nature, Charles Darwin selected the deductive method of reasoning – and abandoned the inductive method of reasoning. The method of reasoning is critical when investigating the secrets of nature.

Unlike deductive reasoning, inductive reasoning minimizes the dogma and bias of the investigator. Inductive reasoning is the defining element of what has become known as the scientific method. Details of Darwin’s reasoning method are discussed in Darwin, Then and Now.

By the publication of the Origin of Species in 1859, the use of inductive reasoning – the scientific method – had become the standard method for scientists investigating the secret laws of nature.  The scientific method emerged as the driving force of the scientific revolution, starting with Nicolaus Copernicus.

Inductive reasoning reduces the risk of introducing bias into a hypothesis or theory – and provide a method of falsification.

Darwin’s use of deductive reasoning in The Origin of Species is a classic example of using non-falsifiable statements/premises when examined using twenty-first century technology has resulted in a litany of Darwin dilemmas – now validated scientific errors.

2.

Darwin’s theory of evolution entails the following fundamental ideas. The first three ideas were already under discussion among earlier and contemporaneous naturalists working on the “species problem” as Darwin began his research. Darwin’s original contributions were the mechanism of natural selection and copious amounts of evidence for evolutionary change from many sources. He also provided thoughtful explanations of the consequences of evolution for our understanding of the history of life and modern biological diversity.

• Species (populations of interbreeding organisms) change over time and space. The representatives of species living today differ from those that lived in the recent past, and populations in different geographic regions today differ slightly in form or behavior. These differences extend into the fossil record, which provides ample support for this claim.

• All organisms share common ancestors with other organisms. Over time, populations may divide into different species, which share a common ancestral population. Far enough back in time, any pair of organisms shares a common ancestor. For example, humans shared a common ancestor with chimpanzees about eight million years ago, with whales about 60 million years ago, and with kangaroos over 100 million years ago.   Shared ancestry explains the similarities of organisms that are classified together: their similarities reflect the inheritance of traits from a common ancestor.  

• Evolutionary change is gradual and slow in Darwin’s view. This claim was supported by the long episodes of gradual change in organisms in the fossil record and the fact that no naturalist had observed the sudden appearance of a new species in Darwin’s time. Since then, biologists and paleontologists have documented a broad spectrum of slow to rapid rates of evolutionary change within lineages.Let's look at an example to help make natural selection clear.

• Industrial melanism is a phenomenon that affected over 70 species of moths in England. It has been best studied in the peppered moth, Biston betularia. Prior to 1800, the typical moth of the species had a light pattern (see Figure 2). Dark colored or melanic moths were rare and were therefore collectors' items.

  Figure 2. Image of Peppered Moth

  During the Industrial Revolution, soot and other industrial wastes darkened tree trunks and killed off lichens. The light-colored morph of the moth became rare and the dark morph became abundant. In 1819, the first melanic morph was seen; by 1886, it was far more common -- illustrating rapid evolutionary change.

  Eventually light morphs were common in only a few locales, far from industrial areas. The cause of this change was thought to be selective predation by birds, which favored camouflage coloration in the moth.

  In the 1950's, the biologist Kettlewell did release-recapture experiments using both morphs. A brief summary of his results are shown below. By observing bird predation from blinds, he could confirm that conspicuousness of moth greatly influenced the chance it would be eaten.

  Recapture Success

  	light moth	dark moth
  non-industrial woods	14.6 %	4.7 %
  industrial woods	13 %	27.5 %

• Finally, we will look at a statistical way of thinking about selection. Suppose that each population can be portrayed as a frequency distribution for some trait -- beak size, for instance. Note again that variation in a trait is the critical raw material for evolution to occur.

  What will the frequency distribution look like in the next generation?

  Figures 5a-c Proportion of individuals with trait Height -

  First, the proportion of individuals with each value of the trait (size of beak, or body weight) might be exactly the same. Second, there may be directional change in just one direction. Third (and with such rarity that its existence is debatable), there might be simultaneous change in both directions (e.g. both larger and smaller beaks are favored, at the expense of those of intermediate size). Figures 5a-c capture these three major categories of natural selection.

  Figure 6 Infant Mortality (-log) Male Birth Weight (kg) Female Lower Mortality

  Under stabilizing selection, extreme varieties from both ends of the frequency distribution are eliminated. The frequency distribution looks exactly as it did in the generation before (see Figure 5a). Probably this is the most common form of natural selection, and we often mistake it for no selection. A real-life example is that of birth weight of human babies (see Figure 6).

  Under directional selection, individuals at one end of the distribution of beak sizes do especially well, and so the frequency distribution of the trait in the subsequent generation is shifted from where it was in the parental generation (see Figure 5b). This is what we usually think of as natural selection. Industrial melanism was such an example.

  Figure 7 Earty Eocene oligocene Late Pleisto- Upper molar teeth Forefeet front view) Forefeet (side view)

  The fossil lineage of the horse provides a remarkable demonstration of directional succession. The full lineage is quite complicated and is not just a simple line from the tiny dawn horse Hyracotherium of the early Eocene, to today's familiar Equus. Overall, though, the horse has evolved from a small-bodied ancestor built for moving through woodlands and thickets to its long- legged descendent built for speed on the open grassland. This evolution has involved well- documented changes in teeth, leg length, and toe structure (see Figure 7).

  Under diversifying (disruptive) selection, both extremes are favored at the expense of intermediate varieties (see Figure 5c). This is uncommon, but of theoretical interest because it suggests a mechanism for species formation without geographic isolation .