My alternative is inspired by Grasse’s concept of « mother form » organisms, that is primitive, non-specialized ancestral groups that holds the “blueprint” for major biological lineages. These « mother forms » are characterized by high morphological plasticity and act as the creative origin from which a vast array of specialized species eventually radiates. IOW, “mother forms” are stable blueprints that carry the essential information needed to deploy new, complex structures when the right internal or external conditions are met. Most importantly, these « mother forms » would somehow be protected from GE, much like stem cells, which may also be less prone to mutations.
Not familiar with this concept. Where was it published? How would you test it, and has anyone tried to?
Many, many questions arise. Now, if there were “mother forms”, wouldn’t we be able to see them and recognize them? Wouldn’t they be spitting out new species regularly, and wouldn’t their genomes show up as ancestral to all their descendant species? (On a tree this would result in a zero-length branch for the mother form and a star phylogeny among all its descendants.) Why has no such species been found out of all those studied? And why are so many known species present in the fossil record, lasting for millions of years in most cases? Finally, how would mother forms be protected from GE? (For that matter, what makes you think that stem cells have a lower mutation rate than other somatic cells?)
3 Likes
So we are meant to speculate:
-
That these "mother form"s exist? (Where?)
-
That they have DNA?
-
That they reproduce (where?) (or are they immortal)?
-
Per your final sentence, that for some completely unexplained, yet also ludicrously convenient ‘reason’ they, out of all living things, are not subject to GE?
-
But by some inexplicable contradiction to (4), they are meant to simultaneously be the progenitors of variant (i.e. mutated) forms that are subject to GE.
It would seem that we should only see "mother form"s – as, by (4), they are incapable of mutating into something else (and particularly something imperfect). That all we see is these ‘something elses’ would seem to demonstrate that this hypothesis is ludicrously internally inconsistent.
This would in fact seem to be a perfect exemplar of the absurdity at the heart of all Creationist theorising.
3 Likes
@Giltil,
While I suspect this idea isn’t going to work out, I appreciate that Grasse has attempted to write down a plausible alternative. It’s the right way to go about presenting ideas. Thanks for sharing.
1 Like
Would someone do the courtesy of providing a citation?
I hadn’t heard of him either.
From Wiki:
He was an expert on termites who rejected Neo-Darwinism and was a proponent of Neo-Lamarckism.
2 Likes
He seems to have been sufficiently obscure that I had to provide Google with a lengthy quote from @Giltil before it could tell me what this was all about.
According to the article, and particularly the Dobzhansky review it references, it seems that Grassé’s theory had some major holes in it:
Biologist Theodosius Dobzhansky wrote in a review that Grassé’s belief that evolution is directed by some unknown mechanism does not explain anything.
I’m seeing little evidence that his theory was considered viable even in his own day, let alone that it outlived him.
I’m also seeing little evidence that he provided a clear enough definition of what he considered to be “mother forms” (some, ill-defined, or maybe even undefined, subset of stable body plans, it would seem). This would seem to render his theory ‘not even wrong’.
The citation below is from Grasse’s book titled « Evolution of Living Organisms »
“The derivation of one type of organization from another never occurs through the intermediary of specialized types. Major evolution has proceeded from archaic form to archaic form — forms which, by their organizational plan, do indeed belong to a well-defined systematic unit, yet retain a structure of a general type… They are the mothers from which spring the phylums that realize a certain morphological type, or idiomorphon, by surrendering to specialization… Creative evolution takes its source in the mother forms; in their absence, new types of organization never appear ».
Well, it happens that I had this notion. Looking further, the situation is probably not as clear cut as I thought. However, it does seem that stem cells have a higher ability to repair their DNA than their more differentiated counterparts. Moreover, I found the reference below that seems to support the idea that ES cells have a lower mutation rate than somatic cells.
A lower rate of a couple of rare mutation types. Nothing to do with the sort of mutations we commonly discuss here, and presumably nothing to do with what you intended.
3 Likes
Do you have the least notion what that quote meant, what these “mother forms” might be, how to recognize them in the fossil record, and/or whether they are still around? Based on that quote, which given the ellipses you must have found in a secondary source, they seem to be the ancestors of phyla. But do all members of a phylum spring directly from the mother form, or what? How does this help you if the mother forms disappeared millions of years ago after doing their work?
1 Like
And here’s another. Burn!:
https://academic.oup.com/sysbio/article-abstract/27/4/487/1735057?redirectedFrom=fulltext
1 Like
Well, the authors report a reduction in intragenic mutations in ES cells relative to MEF cells both at the Aprt and Hprt locus, and they suggest that this may be associated with mismatch repair activity. Why do you assert that this has nothing to do with the sort of mutations commonly discussed here?
See 89 and 126
They’re talking about mitotic recombination and multilocus deletions leading to loss of heterozygosity.
3 Likes
Neither presents a clear hypothesis. I’ve asked you several questions in attempts to clarify, which you have ignored. @RonSewell tried again and you just pointed to the previous unclear claims. Do better, please.
1 Like
I have so many questions.
Do you have any actual evidence for this hypothesis of yours? How would you even test it? What should the data look like if there was an ancestral “mother form” organism with a lower mutation rate?
Which species are related through this “mother form” ancestor? What was it’s actual mutation rate? “Lower” admits quite a range. How much are we talking here? For how long did the “mother form” persist and spawn new branches? Why did the mechanism ensuring low mutation rates not persist in the descendants?
Has anyone ever found a fossil of this “mother form” organism, and how would we recognize that a fossil is actually such a thing?
2 Likes
We might cut Gil a little slack on this one, as it wasn’t his idea. There is already plenty of existing criticism of Grasse’s work, and at a glance “Lamarckism” seems to sum that up very well.
2 Likes
But was it Grasse’s idea? Or is Gil appealing to a seriously garbled version of something Grasse hinted at? It’s not clear what Grasse meant or what Gil meant, and the one who’s here and not dead isn’t explaining himself.
2 Likes
Not exclusively. They are also pointing to intragenic mutations. Here are some relevant passages:
- Cells lacking APRT activity fell into two classes when the Aprt locus was analyzed by PCR. Class I cells, which constituted approximately 80% of the APRT-deficient clones, lacked the wild-type allele (Fig. 3a). Class II cells retained the Aprt allele and had presumably sustained an intragenic Aprt mutation.
- The reduction in intragenic mutation in ES cells, observed both at Aprt and Hprt, may also be associated with mismatch repair activity. This observation would be consistent with elevated levels of point mutations that occur in mice lacking MLH1 or PMS2 (32).