How is this different from what chance does?
What kind of variation is available for selection depends purely on chance cannot be predicted.
Edit: frankly, i dont see much difference from many chance based explanation (such as the one for antifreeze in fish) and saying God chose to do it that way.
Thatās a problem for you. First, evolution isnāt just chance. Thereās selection too. Second, this isnāt even about how innovations arise; itās about common descent. An innovation, however it arises, is inherited by subsequent generations, and the pattern of inheritance makes a nested hierarchy. The single genetic code is at the base of that hierarchy. Common descent explains why thereās a single code. āGod chose to do it that wayā explains nothing; itās a substitute for explanation and leads nowhere.
How does evolution predict that there can be only one tree of life?
Why not two or threeā¦ does evolution somehow ensure life can arise from unknown processes only once?
Universal common ancestry is not predicted by evolution. Itās one of the possibilities.
Thatās why I said an evolutionary explanation is similar to one involving God as it can account for any scenario.
Going with the consensus view is a good rule of thumb, agreed. However, science is like all other human activities a social activity, with group-think, subconsious assumptions, etc. It wouldnāt be the first time the consensus had favored seeing a simple form as being ancestral to more complex forms, only to find out that the simple form had been secondarily reduced (e.g. microsporidia and placozoa).
This is a circular āpredictionā. We observe a (nearly) universal genetic code, therefore the code must have been āfrozenā in LUCA. Had we observed fundamentally different codes, the codes must have arisen independently or diverved since LUCA.
You have it backwards. The single genetic code shows that thereās one tree of life. Itās what we expect if thereās only one tree. āEvolutionā doesnāt predict that there will only be one. But evolution could not account for any scenario.
No, the second hypothesis is not reasonable. There is no mechanism for wholesale transformation of the genetic code. How could an organism survive it? Such few changes as we observe are in rare codons in small genomes, and thatās for a reason.
Universal common ancestry + specific auxiliary hypotheses predicted a universal genetic code. As variants of the standard genetic code were found, those auxiliary hypotheses were modified to allow for the prediction of a near-univeral genetic code. Had fundamentally different genetic codes been found, those auxiliary hypotheses could have been modified further.
[Edited to add:]
Are you making an anti-evolutionary argument? Remember, āevolution is cleverer than you are.ā (Orgelās second rule)
Objection: calls for speculation. Not every hypothesis is credible and not every hypothesis can be entertained. In such a case, the more credible hypothesis would be independent origins.
A single tree is a special case that requires vertical inheritance and a near absence of horizontal genetic transfer between divergent species. This happens to be the case for eukaryotes.
The reason evolution predicts this pattern is that there is no genetic communication between lineages. Different lineages will accumulate different mutations. This produces a pattern of shared features from common descent and lineage specific adaptations, otherwise known as a nested hierarchy.
Languages are a good analogy. You can find quite a few similarities between the Romance languages (e.g. French, Spanish, Italian). Those similarities were inherited from their shared language, which is Latin. However, there are also differences, and those differences arose independently in each language. In fact, you can even organize the Romance languages into a tree:
Why notā¦ canāt two or more trees of life evolve on the same planetā¦ Evolution doesnāt place any restrictions on how many genetic codes there can be.
If it turned out that there were two distinct types of Genetic codeā¦ the theory of evolution will not be falsified.
There could have been multiple trees, but the evidence demonstrates that there wasnāt.
Universal Common Descent would be falsified. The theory of evolution doesnāt state how life had to change in the past, it merely uses the evidence to determine how life did change. The theory is a description, not a proscription.
This makes my point. Which is that evolution perse does not predict a single tree of life.
Another interesting point is that , if tomorrow, human beings succeeded in making a life form from scratchā¦ it would also look like it shares a common ancestor with natural organismsā¦ because of being DNA based.
So there is atleast one case, where an organism can share the genetic code without sharing a common ancestor.
Evolution does not predict that there is only a single tree. However, it does predict what evidence we should see if eukaryotes share a common ancestor. It just so happens that the evidence is consistent with eukaryotes sharing a common ancestor.
In the same way, DNA fingerprinting does not predict that DNA at the crime scene will match the DNA of the suspect. Does this mean DNA fingerprinting is not a reliable scientific tool?
This is my initial pointā¦ and I am glad you agree.
I find this statement curious. Why are you stopping at eukaryotes. Why not say there is a tree from prokaryotes to eukaryotes and so on.
By the way, how do you know eukaryotes did not āevolveā several times from prokaryotes?
Letās drop the analogiesā¦ itās a waste of timeā¦ I could just claim the proofs for common ancestry are like lie detectors or even worse just a set of circumstantial evidence and not like DNA fingerprinting.
If we are talking about a strict tree structure, then it doesnāt apply in a strict sense to all life. Due to horizontal genetic transfer, life as a whole resembles a root ball with many different lines of intersecting inheritance.
The evidence is consistent with a common ancestor for all eukaryotes.
The analogies were trying to help you understand how evidence works.
Actually, itās very interesting that eukaryotes evolved exactly once from prokaryotes in about 4.0 billion years of lifeā¦
Talk about winning the lotteryā¦ itās wierd that things that happen regularly and something that has happened only once in billions of years are both evidence for āevolutionāā¦ I think the problem is that evolution is the only game in town.
Why is that weird? Why would you expect the same organism to evolve independently many times?
The same classā¦ I.e eukaryotesā¦
Why not? Eukaryotes have had the most timeā¦ and there are a huge number of prokaryotes.
Why only once?
For the same reason that I would not expect the English language to independently emerge on a separate planet that had never come in contact with humans.
Itās not a separate planet. Same planet, same ancestors (prokaryotes).
Whenever you get stuck, you try to answer with some kind of analogyā¦ why not try answers likeā¦ I donāt know why.
