K.Rose in Message 107 writes:
I’ll accept that Evolutionism includes a broad category of studies, but there are a couple of essential components in in the Evolutionary process that go beyond mere natural selection and variance within like lifeforms. The notion of a random, non-directed, continuing common ancestry for all life forms is the most critical of these, critical in that it is the prerequisite for refuting Biblical Creation.
This is the first time you've mentioned a religious motivation. No one here is trying to refute Biblical creation. Creationism only receives attention from scientists in response to efforts to teach it as accepted science in public schools.
What you're calling "random, non-directed, continuing common ancestry" does not "go beyond" descent with modification combined with natural selection. Descent with modification already means random, non-directed mutations. Common ancestry is a necessary implication of the process.
My effort here is to understand the evidence showing that this is possible. How does one life form evolve into another?
Gradually, one generation at a time.
What is the mechanism?
Descent with modification combined with natural selection.
Can or has it been observed? Can it be reproduced in the laboratory?
Has the origin of a new species been observed? Maybe at the single-celled level where generations are short. There are some claims of speciation being observed in real time at much higher classification levels, but I'm not convinced.
But we'll never observe the origin of a new species of fish, amphibian, reptile, bird or mammal because each generation takes too long. For example, the changes in Eohippus ("dawn horse") that gradually became Orohippus ("mountain horse") probably took a couple million years. Each Eohippus/Orohippus birth included a number of mutations, and with many births every year there would be millions and millions of mutations over a couple millions years. Each Eohippus/Orohippus would live out its life in its environment and be selected or not to contribute its genes to the next generation, i.e., its mutations would either be passed on or not. It would not be possible to duplicate such a lengthy process in the laboratory. Especially it wouldn't be possible to accelerate the mutation rate.
We could of course exert strong selection pressures in the lab, but your own example of the dog shows that strong selection pressures do not produce speciation. Domestically bred pigeons are another example of huge variation within a single species.
There's another more subtle reason why it would be difficult to observe speciation, and that's that speciation is a very gradual process. One way that speciation is thought to happen is when a species population becomes divided into two separate populations, for example by a river changing course. The separate populations evolve independently and only gradually become less and less capable of interbreeding.
This means that there is no exact point where the two populations become two different species. There's a point where interbreeding is 90% successful, then 80%, then 70%, and so on until finally they'll incapable of interbreeding at all. At what point do they become two different species? At 50%? 20% 0%?
Examples are helpful in considering this question. Even though the lion and the tiger are two different species, a male lion can mate with a female tiger to create a liger. A male donkey and a female horse can mate to create a mule. Species are not hard boundaries but a continuum. Some species are closely related and can interbreed to some extent, others are less closely related and can interbreed less successfully, and distantly related species cannot interbreed at all.
DNA can provide us a measure of relatedness. Chimp and human share 98.8% of their DNA and yet cannot interbreed at all.
Note that Scientific Fact has a pretty high Certainty bar: Zero Error, 100% Probability, 100% Confidence.
One widely held viewpoint is that everything in science is tentative, including facts. Stephen Jay Gould (paleontologist and evolutionary biologist at Harvard) had this to say about facts:
Stephen Jay Gould:
In science, 'fact' can only mean 'confirmed to such a degree that it would be perverse to withhold provisional assent.' I suppose that apples might start to rise tomorrow, but the possibility does not merit equal time in physics classrooms.
These days the Great Deceit of many scientific theories lies in their presentation to the public as implied fact, and in allowing the misconception of factuality to stand.
"The Great Deceit of many scientific theories?" Now you sound anti-science. This isn't really the topic, but which theories do you think science has been deceitful about?
If Evolutionism can meet the high bar of Scientific Fact, then it should be presented as such. If not, then the Certainty of Evolutionary conclusions must be divulged front and center.
Evolutionism? Is that analogous to religionism?
The theory of evolution is a theory, not a fact, but it
*is* a fact that one little step of evolution takes place with nearly every reproductive event.
--Percy
™ Version 4.2
(1)