Hi, again.
So, the idea that there's a common ancestor for all life. To my knowledge it isn't a foregone conclusion that every species alive descended from the same ancestor. It's possible that it isn't the case. What would you say you found to be circular in particular?
So although there are a number of examples, I'll give just a few.
The first idea started with - all life must have come from one common ancestor. The claim was made that comparing anatomy, and traits show that.
That's like having an idea, and then having another idea to support the first idea. Similarities of anatomy and traits does not automatically lead to one conclusion.
The idea that the process would have taken millions of years - a slow gradual process, was proposed. What was it based on? An assumption that the first idea is true.
The process of dating fossils and rock were both circular, and based on assumptions.
The fossil record did not support the claim that the first idea would require a slow gradual process. So punctuated equilibrium was proposed to fill gaping holes that the observed evidence was revealing.
What was not observed, was assumed to be the case, again, because the first idea is assumed to be true.
So it was claimed that change happens very quickly, not by a slow gradual process... alone.
Punctuated equilibrium would also explain the missing intermediate fossils, not found as proposed, in the fossil record.
Punctuated equilibrium would also fill the gap where new "species" seen in the fossil record appear suddenly, and then disappear, without any apparent morphological changes.
Here, circular reasoning is also used. Support for punctuated equilibrium is seen in fossil records they claim, but really, it is the case that punctuated equilibrium was hypothesized - an idea was created - in order to fill the large gaps in the fossil record. In other words, another idea was created in order to explains the observed evidence.
It's like finding evidence in a room. Not knowing the circumstances, but creating a story, and building all the evidence to fit that story.
Punctuated equilibrium is actually criticized for a number of reasons, and many still argue for gradualism, while searching for other explanations to fill the holes. It seems there is no end to this ongoing debate.
Edit
@Jaiket
Then there is punctuated gradualism...
Punctuated gradualism - Wikipedia
Studies use evidence to predict how organisms evolved in the past and apply this evidence to the present.
The study directly challenges phyletic gradualism and punctuated equilibrium. It shows how many factors can come into play when comparing the two modes of evolution.
All the evidence apparently points somewhere other than to the idea that all life came from one LUCA, but that evidence is interpreted to explain the idea.
What do you make of the opposite hypothesis? That there are multiple ancestors for the life at present. What do you think would be evidence of that?
This fits well with all the evidence imo.
From the design of DNA, to the sudden appearance of all major body plans in the fossil record, to living fossils... etc. etc. Everything seems to fit.
DNA and its code nature are amazing to me. Ok then. Let's say for the sake of discussion that DNA was designed, and it was God who designed it. Do you know anything about how it functions?
How DNA functions, is written all over the place. Here is a link to
a fascinating look at DNA's function.
Of course, if you are looking for more, you can find
animations, or if you like reading, just google DNA function.