I was surprised to read in this paper @Rumraket shared with me that the scientists seem to deny a UCA.
Nearly all macroscopic life is multicellular. As Leo Buss emphasized in The Evolution of Individuality , the very existence of integrated multicellular organisms is an outcome of evolutionary processes, not a starting condition1. It seems, in fact, to be a common outcome: multicellular organisms have evolved from unicellular ancestors dozens of times2,3,4. Animals, land plants, fungi, red algae, brown algae, several groups of green algae, cellular and acrasid slime molds, and colonial ciliates, among others, each descend from a different unicellular ancestor4,5.
There are many common ancestors on the tree of life. We have a common ancestor we share with chimps. Then another one that both chimps and us share with gorillas, and then yet another one that chimps, gorillas, and humans share with orangutans. And so on.
The answer depends on the scope of “universal”.
Humans and the great apes. There is a consensus on this, the “common descent of man.” There is just so much positive evidence for this it is hard to envision what could demonstrate it was false.
All life on earth right now. For the most part, there is a consensus on UCD, This is not dogma, however, and it would be a big deal, very exciting, if someone could identify a new tree of life here on earth.
All life on earth , including life in the past. I don’t know for sure on this one, and think it might be an open question.
All life in the solar system. This is an open question on several levels. First off, is there life on other planets in our solar system? If there is, was it seeded from the Earth (or did it seed life on Earth) or was it a new tree of life? Once again, it would a big and exciting finding if we found a new tree of life. Technically, it would demonstrate UCD was false.
All life in the universe. This is an open question on a more focused level, reducing down to "is there life in other planetary system or galaxies? If yes, it would be a new tree of life. Of course, that’s assuming that technology that allows travels movement across the galaxy is impossible. THat also means that if SETI is successful, UCD would technically be false.
You have misunderstood what that’s saying. Each multicellular line is descended from a different unicellular ancestor, but those ancestors are all descended from the same common eukaryote ancestor. A common ancestor of all life is a bit more tricky because of all the horizontal transfer that was going on back then.
I know that is the view. Sigh. I’m annoyed because my question was quite specific and you’re not responding to that.
The similarity of the genomes and the math you like to cite? Am I missing something else?
mtDNA and y-chromosome mutation rates can demonstrate it is false, which is why creationists continue to focus on that. So I’m not sure why you still can’t envision it yet, when it’s obvious it could demonstrate it…and that is what they’re running around claiming all the time. It should be obvious to everyone.
This is what I was asking.
Interesting how you make this claim about HGT in the past as if it was fact. But thanks for the explanation.
Definitely. This is one of the big questions, and everyone would love to find life that unambiguously derives from a different origin. There are so many open questions on early evolution, the origin of homochirality, the possibility of different types of genetic polymers, alternative translation systems and genetic codes.
Well LUCA has an asterix on “universal,” meaning it would be (according to the consensus) the universal ancestor of "all life that we currently know of on the Earth. "
That is an intrinsically interesting entity, even if it isn’t truly universal in the end.
You thought what was consensus? Not sure what you’re confused about. The reason I mentioned those things is because finding organisms that derive from a different origin could help understand to what extend those things are basically contingent outcome of chance circumstances in early evolution, or are likely to evolve convergently again and again even if life originated elsewhere and/or under different circumstances. How predictable is the process of life’s origin, and how predictable is it’s early evolution?
Yes, you are missing quite a lot. I’m just presenting one example of evidence there is qutie a bit.
Now, you are right that I can envision “conterfactual” evidence that could disprove the common descent of man. However, I cannot imagine evidence consistent with what we already know that could disprove it.
Only counterfactually. The evidence as we find it only increases our confidence in common descent.
Even then, even if Jeanson’s calculations were correct (they are not), it would not be evidence against common descent. It would be, rather, evidence of something very strange going on in the molecular clock. It would be odd, because humans and chimps would be far closer to one another genetically than the molecular clock would predict. That’s exactly the opposite of what YECs have been arguing elsewhere, that humans and chimps are too far apart for evolution (not too close!).
I still don’t know exactly what you mean by passive aggressive and why what I’d call slight sarcasm is “passive aggressive,” as that was my intention, but yes I could have said: “That is conjecture; we cannot know how much HGT was going on, if any.” That would be a nicer way to state it.
Do you even know what HGT is? Questioning whether HGT happened billions of years ago or even thousands of years ago (in a YEC framework) is akin to asking if the sun shined billions or thousands of years ago because we were not there to observe it.
Wow. Are you really repeating the “Were you there?” meme? That is hard-core YEC. When you are reduced to the level of Ken Ham, it’s time to quit.
I am still missing something?
It happens.