Well's may have done a PhD in developmental biology but I think it is generous to still call him a developmental biologist. He had 2 publications from his PhD research in 1996 and 97 and has only published one thing since, a purely speculative paper about a role for polar ejection forces generated by centrioles in causing cancer which was published in 2005. So it is over a decade since Well's had any published research in the field of developmental biology.
Wells writes:
"When an egg's genes are removed and replaced by those of another type of animal, development follows the pattern of the original egg until the embryo dies from the lack of the right proteins"
Well's is essentially correct here. There are certainly exceptions amongst closely related species, such as the many ongoing experiments to regenerate extinct or threatened species by SCNT into related species, but most highly divergent species will not develop to term in such a case. I certainly don't think that the cat-rabbit experiments you discussed gave rise to full term cat clones.
This is because the oocyte is nothing like identical in many different species. If you compare a human oocyte to a
Xenopus you will find they are 1/10th the size and of strikingly different composition with the
Xenopus oocyte containing large quantities of yolk proteins for the embryo to feed on.
Wells writes:
"Biologists have found that mutations in developmental genes often lead to death or deformity, but they never produce changes that benefit the organism..."
Well this is a disingenuous argument. By far the vast majority of mutational experiments in developmental biology are done with the explicit purpose of breaking genes to such an extent that they cause death or deformity. This is done because death and deformity are nice readily apparent things which can be easily identified and scored. So most mutational studies are crudely designed to make large severe damaging mutations with ionising radiation or potent mutagenic chemicals.
These experiments are done to elucidate the normal course of devlopment, that is why they are developmental biology experiments. When it comes to looking for beneficial mutations in an experimental setting evolutionary biologists will normally tend to look at microorganisms with generation times measured in hours or days rather than multicellular organisms with generation times in weeks or months.
The only way to identify beneficial mutations is by following the success of various mutations in a population and observing which ones confer improved reproductive success. Obviously this takes several generations to properly establish as you need to exclude the effect of random factors causing genetic drift.
So Well's is technically correct that this hasn't been seen experimentally but neglects to mention that no one is actually doing such experiments to generate beneficial mutations in specifically developmental genes. He assumes such mutations do not exist, but he has no evidence for it. There are examples of beneficial mutations in a number of other types of genes such as metabolic genes allowing for insecticide resistance.
Wells writes:
"DNA mutations never alter the endpoint of embryonic development: they can't even change the species"
Clearly this argument is confused, the various deformities Well's previously mentioned are examples of DNA mutations altering the developmental endpoint. If he means thta we don't see frogs giving birth to cats, well that is evolution as only a creationist could understand it.
He is certainly wrong about changes in DNA not giving rise to new species, although as a creationist his definition of species may be highly idiosyncratic. There are numerous examples from
Drosophila of cases where the genetic basis of reproductive isolation, arguably an efffective definiton of distinct species, has been clearly identified.
The genes
Nup160 and
Nup96 which produce proteins involved in the nuclear pore complex have both been shown to cause hybrid incomaptibilites between
D. simulans and
D. melanogaster (
Presgraves et al., 2003;
Tang and Presgraves, 2009).
Anopther such paper on the same species is (
Brideau et al., 2006) which is interesting as it again describes hybrid incompatibility between
D. simulans and
D. melanogaster. In fact the experiments done in the
Nup160/
Nup96 papers were performed on hybrids which had had the incompatibility caused by the appropriately named
Lethal hybrid rescue gene rescued, protecting the hybrid males from their usual fate of death.
So these experiments identified 4 distinct genes with specific mutations combinations of which could produce reproductive isolation but which indivdually did not, therefore allowing the existence of hybrid populations as intermediates between the two distinct species.
He goes on about microtubule arrays and membrane patterns in the egg, and how those arrays are created by mysterious organelles called centrosomes which are inherited independently of an organism's DNA.
Why does he think these are mysterious? This is one of those words like complex which creationists think will magically make their argument for them despite being completely worthless in scientifc terms. Membranes aren't produced by centrosomes, I think either you or Well's misunderstood something. Or does membrane patterns refer to membrane associated feature like the cilia or transmembrane proteins?
In any case as Mr. Jack points out it is incorrent to say these are independent of DNA. They are not all synthesised
de novo in the new zygote after fertilisation but they were dependent on a number of proteins coded by DNA for their creation. Obviously this is an example of 'irreducible complexity' in the trivial sense that without one element the other could not exist in its current state, it is considerably harder to show that it is 'irrecudibly complex' in the sense that such a system could not evolve from functional intermediates, indeed cell division in the absence of a centrosome has been shown to occur and indeed the full development of adult flies (
Megraw et al., 2001).
Basically he's bringing this up to show that this can't be explained by our current theory of evolution.
This may be why, but it doesn't do that. It certainly shows that DNA is not the be all and end all of development, or evolution, but then no develop mental biologist has held that view for about the last 30 years. Epigenetic factors are readily accepted as a key component in development, indeed one of the major problems with intraspecies, let alone cross species, SCNT is the presence of epigenetic markers which make the DNA distinct from that in a newly fertilised zygote.
If you can't get from one species of animal to another by replacing or mutating its DNA, then the Darwinian explanation is finished.
This seems reasonable, but it also happens to be demonstrable that you can do this in some cases, i.e. the
Drosophila species I mentioned previously.
Also, since all cells have the same DNA, and yet cells differentiate themselves into different types during development, something outside of the cell's DNA has to be in play
Absolutely, but in a lot of cases it is simply the products of that cells DNA. The whole way development produces thgese different cell types is not through magical effects of mysterious organelles like the centrosome but through the complex interaction of the whole embryonic environment with the genome.
To act as if this is all a complete mystery is simply to ignore all of the devlopmental research of the last 30-40 years which has been an ongoing process elucidating exactly how differentiation and diversification occur.
TTFN,
WK
I actually had a discussion unregistered on polonium halos here before. Just thought I'd add more information lol than "yeah haha" lol
™ Version 4.2
