If life is ribozyme-based, it could be arising every day in the present and quickly killed off by ribonuclease.
No, not coherently.
I read some interesting modeling/simulation work that suggests that a population of cells with different, simpler codes that nevertheless exchange genetic material horizonally can converge on a similar code as a result.
Aggarwal N, Bandhu AV, Sengupta S. Finite population analysis of the effect of
horizontal gene transfer on the origin of an universal and optimal genetic code.
Phys Biol. 2016 May 27;13(3):036007. doi: 10.1088/1478-3975/13/3/036007
Froese T, Campos JI, Fujishima K, Kiga D, Virgo N. Horizontal transfer of code
fragments between protocells can explain the origins of the genetic code without
vertical descent. Sci Rep. 2018 Feb 23;8(1):3532. doi: 10.1038/s41598-018-21973-y
Yes, that is what I was thinking of, though I had not seen those papers yet. Great finds.
Interesting. Must be very small genomes. And how different could those codes be? If they had no particular resemblance I can’t see how it would be possible. And why would the initial codes resemble each other?
I had the same thoughts. There must be some similarities between these different codes in order for any exchanged material to be translatable in the receiving organism.
I also think there are reasons to think this can’t be much of an explanation for the universal conservation of the translation system. If one can make a case for exchange of tRNA+aaRS(as they do in those papers), that implies they already have similar ribosomes (which have to be able to interact with that tRNA), otherwise how could the actual catalyst of peptide formation accept tRNAs from an organism that supposedly have a different origin? Did it evolve a similar ribosome convergently?
I think the case for the universality of the genetic code being evidence for common descent goes beyond “merely” the fact that the same amino acids map to the same codons in all known life, when we also look at the molecules that effectuate translation, they clearly exhibit tree structure in the sequences that encode them, implying all these components derive from a common ancestor. It seems absurd to think two or more different origins of life converged on a similar method of translation. That implies a level of determinism in protocellular evolution we just have no evidence to suspect.
They certainly have to be similar at the anticodon and amino acid ends, and presumably have a similar distance between those ends.
i dont think so. specially when we are talking about skeleton and not about living creatures. when we are talking about living creatures- any kid can tell if its a monkey or human.
Well, there’s a strong argument.
you cant distinguish between human and a monkey?
Humans are monkeys. That much is clear from your genome and fossils of your closer relatives. You can’t get away from that just because the connection is in the past.
if you believe in a common descent. but if you dont believe in a common descent then he is not. so its depend in what you believe or in your definition.
No. Bible-affirming Christian Karl Linnaeus didn’t “believe in a common descent”—he lived long before Darwin and didn’t think in such terms—but he classified humans right alongside the few apes known to Europeans at the time.
Linnaeus classified orangutans and chimpanzees in the genus Homo, while calling humans Homo sapiens. Linnaeus also placed the genus Homo in the Primate family, which included the lemurs’ genus.
The classification was not a matter of “what you believe” but one of morphology and careful study. I share much of Linnaeus’ Biblical theology and have no problems acknowledging the close similarities between humans and other primates.
I’m curious, @scd, do you also object to classifying humans as mammals? How about vertebrates? How about primates? Or is there something specifically objectionable about some of the taxonomic classifications but not others?
The facts don’t actually depend on what you believe. Some beliefs are true, others false. Humans are monkeys: that’s true. Separate creation: that’s false. All the evidence shows that.
Both sides are asserting that the facts support their position. How does this get resolved?
To state the obvious once again:
English language words like monkey and ape have definitions which vary depending upon a scientific context versus a more casual usage among the average English speaker who is not a scientist.
If shown a photo of a typical human, the average person surveyed on the street would never say “That’s a monkey” or “That’s an ape”—or even “That’s a primate.” Yet, in the context of a natural history museum in the Hall of Mammals, the same photo might appear with those of related animals under the caption, “The Primate Family.”
One side is ignoring most of the facts.
It’s the same side that falsely claims, “Both sides are looking at the same facts.” Ring any bells?
A good start is to recognize the confusion which comes with equivocation fallacies. We must also recognize the differences between denotations (strict definitions) and connotations (idea or even emotions suggested by words beyond their primary meaning.) I would suspect that when @scd objects to classifying humans in the same taxonomic classification as apes or monkeys, he may be concerned that humans not be considered “mere apes” or “mere monkeys” as if the Bible doesn’t assign special spiritual characteristics to humans.
Karl Linnaeus believed that humans were specially endowed by God with unique characteristics (including the Imago Dei) but he didn’t consider this to be in any sort of conflict with recognizing the many shared features which placed all primates in the same family.
What are the set of facts that you believe is most troubling for the theory that humans and chimps share a common ancestor? What are the set of facts that you think are the strongest support of this hypothesis?
I don’t find any of those facts troubling. (Obviously, many other evangelicals find the theory extremely troubling—but you asked specifically for my own viewpoint on this.)