If all or most of the above evolutionary mechanisms / processes exist then why do some scientists still claim natural selection is the prime mechanism in evolution?
Wow, I"m surprised by many responses to this, both pro and anti science. But to answer your question, what scientist ever claimed natural selection is the prime mechanism in evolution? Don't bore me with you heard or read, provide a scientific citation or forget I asked.
The Theory of Evolution proper has 4 laws. Speciation, or the Origin of Species, is a fifthe law.
1) Variation - within a species there is variation. Variation is appearent even among very closly related individuals. Even siblings have different heights, weights, eye color etc. Different populations may have more or less variation, but all populations have variation.
Unless you deny that everyone is different, then you believe in at least 25% of evolution.
2) Heritability - each species has traits that are strongly influenced by heredity. (Remember that wile Lineass had completed his work it was largly undistributed. Darwin had no clue about genetics.) Heritable traits pass from parent to offspring in a consistent manner.
Unless you deny that children inherit traits from their parents, you believe in another 25% of evolution.
3) Competition - Species produce more offspring each year than the environment can support. Individuals compete for resources (food, water, shelter). This competition for limited resources results in a high mortality rate. (As an example, the elephant has the slowest reproductive rate of any land animal. The female begins breeding at age 10, has one calve every 2 years, and lives for 50 years. This means she can have up to 20 young in her life time. If they all lived and reproduced, she would have over 700 descendents before she died at age 50. Many of them die very young, many die more die before they reach age 10 and breed. On average, if she has 2 descendents that survive to reproduce, then she has replaced her self in the population and the population will be stable.)
If you belive resources are limited, and individuals must compete for resources to survive, then you believe in another 25% of evolution.
4) Diferential Survival (aka natural selection) - Some individuals will survive the competition for resources, others will not. Those that have more traits that help them survive to reproduce, will survive at a higher rate. Those that fewer useful traits, will die before reproducing at a higher rate. If the traits which are useful and help to survive are inhereted, then the frequency of occurance of that trait in the population will increase.
If you believe that less fit (weaker, less attractive, not as good at finding food, etc.) die at a higher rate than more fit individuals, then you believe in the final 25% of evolution.
These 4 laws are all it takes and if they are true, then evolution is true. Evolution is the change in the frequency of heritable traits in a population.
There is no 'creative' part to it. But what might be confused with creativity is the first law, variation. Variation already exists in populations. But it is also very important that variation continues to arise. This occures in every individual when sperm and egg meet in what is called genetic crossover. It also occurs in random mutation, i.e. a tiny mistake in the transcribing of genetic code. This happens at an observable, measurable frequency.
The 5th law is reproductive isolation - When seperate populations of a species become reproductively isolated for a long enough time, each continues to evolve. Eventually they will have evolved to the point that they are no longer reproductivly compatable even if the populations at some time come back in contact with each other. Thus one species has given rise to 2 new species.
