Thanks again, George. Along with Pope St. John Paul II, I believe in evolution–the descent of species–as a fact. However, I don’t credit the neo-Darwinian model for how evolution occurs as a sufficient explanation. Intelligent Design is interesting, but is more an epistemological or philosophical proposition than a scientific one, because it can’t be tested empirically. God does enter into my view of how everything, including life came about. This is why I find the notion behind Darwin’s Radio interesting: God sending a signal of some sort for sudden, “punctuated” (as Jay Gould would term it) speciation changes to occur.
hi dr bob. what you mean by “-the descent of species–as a fact”?
you are talking about speciation?
Yep, what I mean is that there is a commonality in DNA, protein composition, that parallels the commonality in morphology. Are DNA is very similar to other hominid species, still similar (but less so) to other primates, and… down to fish, mollusca and other genera and orders where there is some similarity, but much less, as depicted in the phylogenetic tree, indicating descent from some common ancestor.
ok. here is some interesting point: some similar species (morphological) are actually very far from each other. dolphin and shark are more similar to each other then dolphin and bat. so does it disprove the evolution prediction? not at all. so the fact that similarity usually agree with genetics actually tell us nothing about evolution but a simple logic. more then this- we now know that there is no an hierarchy in the phylogenetic tree:
so again- evolution isnt a fact but a belief.
I’m surprised to hear that the dolphin and bat DNA’s are less similar than dolphin and shark. The phylogenetic trees I’ve seen put the shark very far down the trunk.
I’ll check out the link you gave to see what they say.
im not talking about the dna level but morphologic. the dolphin and the bat are mammals. so shark is less similar in the dna level but more similar morphologically to dolphin then to bat. so its not always true that similarity in the dna level mean similarity in morphologically.
I’m not sure where you want to go with all this,i dsccccc. Looking at the link very superficially it seems that they are trying to discredit the phylogenetic tree. I haven’t had a chance to check the references given in the footnotes of the linked article. However it is certainly the case that RNA provides a more straight-forward way of tracing descent than DNA, since it’s passed down through the female line. I’m not sure how this works with lower orders, but I’d guess it’s the same. So in principle, I would be skeptical of claims from comparisons of DNA rather than RNA about the validity of the phylogenetic tree.
And you’re quite correct, there isn’t a one-to-one correspondence with morphology and genetics–I was being sloppy in my usage.
Hominid evolution in the Rift valley of Africa was unusually rapid, with many changes occurring over the past million years. (See Dennis Venema’s articles here on Biologos on human evolution). Rick Potts at the Smithsonian has postulated that a series of severe and dramatic climate changes from hot and humid to cold and dry that took place during that time in that place might have put enormous selection pressure on all the creatures living there, including hominids. We dont have fossils for all of the prehuman types, some may have had very small populations, and many might have not lasted very long. As Leo and George stated, the general mechanism of evolution, including isolation was absolutely true for hominins. The Neanderthals also orginally came from Africa but migrated out much earlier, and evolved distinctly from Sapiens.
You complaints about neo Darwinism are justified, and there is some (but not yet a huge amount) of evidence that some alternative mechanisms to the slow accumulation of point mutations in structural genes, might have happened to help drive rapid human evolution. One example is retrotransposition. Human have far more retrotransposons than other primates, and these elements can produce gene amplifications and other potentially dramatic large scale effects.
But it should also be said that a point mutation in the PAX6 gene that allowed for language (by changing the shape of the larynx, for example) would be highly advantageous. There are in fact good mathematical models that show that any mutation with a very strong selective advantage (such as those for white skin in Northern regions, or the ability to drink milk) can spread through a population in a matter of a few thousand years. For something as important and valuable as language, there is no reason why such a mutation would not become fixed within a fairly short time span.
Thank you for a very enlightening comment, particularly the information about hominid changes in South Africa.
With respective to selective advantage for a language gene–would this be advantageous? I can think of scenarios, allowing for cooperation in hunting, etc., but how would it start–with two, three, …n, words? The origin of language I think is more of a mystery than that of homo sapiens, I believe.
And you consider this plausible?
Beagle Lady, perhaps I’m overly sensitive, but I don’t find the tone of your comments to fall in the realm of “gracious discourse”, so this is the last comment of yours to which I will reply. With respect to Bear’s mechanism of a second fetus for his story, It’s science-fiction, Beagle Lady. So, if you want to regard it as one regards time travel as a device in science-fiction, that is an option. And 60 years ago, who would have thought black holes, the Higgs boson, DNA, RNA, retroviruses, etc. plausible? And, if you want to look at biology critically, who nowadays would find embryology itself plausible?
ok. but it only one problem out of many in the evolution theory. so again- we dont have any scientific evidence for evolution.
I don’t think I was being ungracious. And we understand today about human reproduction.
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