Small changes take place within the different classifications of life forms. For example: cats speciate into different species of cats; dogs speciate into different species of dogs, etc. They can look very different from one another. We know a multitude of different life forms exist.
Do small changes within the classification level (dog kind, cat kind), eventually result in changes that go beyond the classification level, into a completely different classification kind? Do micro changes lead to macro change?
Many scientists believe they do: "Biologists therefore agree that change within species caused by natural selection (microevolution) eventually leads to the appearance of new species and even new kingdoms of organisms (macroevolution)." Biology Principles & Explorations - Holt, Rinehart and Winston - 1998, ch. 12, p. 266
My understanding is that not all biologists agree with that; nor have any biologists observed it happening. What does the evidence say?
Here is what we "know" about the world we live in: Things change within species. The major classifications of life forms such as dogs and cats appear to have the ability to speciate within their own classification built into them. Is there any evidence a dog or cat ever produced a non-dog or non-cat? Is there any evidence they are doing so now? Is there a different naturalistic answer that just hasn't been discovered yet, or do we look for an answer of a different kind?
Here are the two main hypotheses: 1. Small changes within life forms over time can result in a larger change into a completely different life form classification.
2. Although small changes take place within life forms, those changes never go beyond the classification of kind limits. Classification kinds are universally fixed.
1. If Micro to Macro is true, we should be able to look around us and observe millions of different life forms in all the different stages of change from one life form into a completely different one, as evidence it is currently happening.
We also should be able to look into the fossil record and observe millions of life forms that are in all different stages of change from one distinct life form into a completely different life form, as evidence it happened in the past.
2. If the fixity of species is true, if we look around us we should observe the different classification kinds of life forms to look basically the same as they always have been in recent history; with no life forms being observed in different stages of change.
If we look into the fossil record we should observe the different life forms basically as they look now; with no life forms being observed in all different stages of change.
Although small changes can be observed within life forms; the different stages of change between life forms cannot be observed in the world around us, or in the fossil record.
No evidence appears to exist as proof that micro types of changes within life forms translates into macro type changes from one distinct life form into a completely different life form; either in our current world, or in the fossil record of our past history on this planet. All the scientific evidence seems to point towards fixity of classification kinds.
Variation within species; and the fact that different classification kinds exist; is not proof that those classification kinds transitioned from previously existing classification kinds into completely different classification kinds.
Since no one doubts that change takes place within a classification system, only question that change takes place beyond classification systems, why don't we just refer to that type of change as "speciation" or "variation within classification kinds"?
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