Of course there are (and its “are” not is). In particular when one considers the limiting factor of time. Selective breeding has demonstrated plenty of limits on how far they can change a given set of stock.
Perhaps that relatively narrow range of difference is within the range of evolution as set up by God without any other divine input required. That is one possibility. But I don’t understand why you would think there would need to be a “reason” to expand general types into convergent types. Maybe its just fun. Like in Spore.
Agreed… time is a limiting factor on mutation. I wasn’t really thinking about the physics of mutation … but was thinking about what would be the theoretical limit for how much form and function is possible given infinite time.
What you are calling “fun” is what others would call “intentionally deceiving science”.
It would be so easy to have created what you call templates in a way that it would be impossible to detect any Nested Hierarchies of genetics. Each template would be constructed out of its own unique logic, with no “broken vitamin C” genes shared with branches of evolution that also exhibit converging evidence for Common Descent.
The only reason scientists propose Common Descent is because God has festooned so much of his creation with credible lines of Common Descent!
And in my model, there is a lot of common descent out there. But much of the evidence for “common descent” is also evidence for “common design” and its hard to tease out which is which. Rather than rise to that challenge I see a lot of hand-waiving which is of course unconvincing.
lets start with the fact that some species of bats were also lost this gene. do you agree? if so what is the problem to g et a convergent loss also between human and say a chimp?
Well, I think this article has it all … including a fairly reasonable defense against the idea that the pattern of Vitamin C loss indicates some kind of Divine intervention. Since I support God-Guided Evolution, I would agree there is Divine Intervention, but the kind that requires millions of years of Evolution, not a sudden fit of Special Creation, scattering vitamin C loss amongst the thousands of chromosomal matrices.
In the Wiki article link, we get background details:
". . . anthropoid primates, Cavia porcellus (guinea pigs), teleost fishes, most bats, and some Passeriform birds have all independently lost the ability to internally synthesize Vitamin C in either the kidney or the liver. In all of the cases where genomic analysis was done on an ascorbic acid auxotroph, the origin of the change was found to be a result of loss-of-function mutations in the gene that codes for L-Gulono-γ-lactone oxidase, the enzyme that catalyzes the last step of the ascorbic acid pathway outlined above.
[Footnote 126: Drouin G, Godin JR, Pagé B (August 2011). “The genetics of vitamin C loss in vertebrates”. Current Genomics. 12 (5): pages 371 – 378. doi:10.2174/138920211796429736. PMC 3145266 Freely accessible. PMID 22294879. http://www.eurekaselect.com/74669/article ]
GULO is the same enyzme used by virtually all vertebrates (when the gene works) to create vitamin C.
Below is some key text from the Bat study you provided here, @scd:
"Having successfully cloned bat GULO genes from 16 species, we carried out detailed evolutionary analyses. Our results show a range of forms of the GULO gene in bats. Combined with our earlier functional studies [14], we identify the following conditions:
pseudogenes that will have lost function, as seen in some Pteropus and hipposiderid species,
intact genes that functional studies showed loss of function in Vc synthesis (e.g. Pteropus vampyrus),
intact genes that maintain some ability to synthesize Vc (Rousettus leschenaultii and Hipposdieros armiger)."
“We found that strong purifying selection has shaped non-Pteropus bat pseudogenes, suggesting these bats are in early stages of loss in their ability to synthesize Vc. In the family Hipposideridae some species possess pseudogenes that show only small changes from the intact and functional genes of their close relatives. Together with the evidence for puryifying selection our results suggest that Vc function has been lost recently in hipposiderid species showing pseudogenized GULO.”
"Relaxed selection acting on Pteropus bat GULO suggests that bats in this genus lost the ability to synthesize Vc within the past 3 mya [25]. Thus we infer that pseudogenization of bat GULO evolved recently."
The writers think one of the key findings in the study is that not all bats have lost the ability to make GULO (and as is mentioned above, some bats don’t use GULO for their vitamin C needs). In their gradient of findings, they find groups of bat species appear to be gradually losing their ability to make GULO; some lineages can still produce it, while other (related) lineages cannot.
One explanation for this is that these Bat groups where there is a blend of GULO and Non-GULO capacity, may still live (or recently lived) in a an eco-niche which was high in Vitamin C naturally, and so genetic drift that is an equal-opportunity “hacker” of genetic function, would not feel pressures from Natural Selection. If there is a mutation which impedes Vitamin C production, but the creatures are getting plenty any way, it is a matter of chance (from the level of human perception) whether a lineage becomes predominantly non-GULO or not.
Now, what is also interesting in that article is this: "As GULO [Vitamin C gene] is present in all major vertebrate lineages except some bats (most of these being New World species) [8], anthropoid primates [12], [26], guinea pigs [11], some passerine birds [27], and some fishes [5], >> such loss-of-function is neither related to broad phylogenetic affiliations nor to diet [28]. << "Some researchers have even proposed that the loss of Vc synthesis is associated with higher speciation rates because of higher mutation rates [Footnote 29: ((Challem JJ (1997) Did the loss of endogenous ascorbate propel the evolution of Anthropoidea and Homo sapiens? Med Hypotheses 48: pages 387–392.
LINK = Redirecting )), [but, according to the authors, this… ] seems unlikely…"
So what we learn from this article is:
while most all vertebrates rely on the very same enzyme to produce vitamin C, different branches of vertebrate process C in different locations (kidneys vs. liver), involving genes in different locations, and with no pattern that relates the branches to each other - - because some branches lost the Vitamin C process dozens of years ago, while others appear to be in the middle of losing this function (i.e., the bats being studied, with incomplete differentiation between branches, starting as recently as 3 million years ago.
@scd, you have provided some more excellent data demonstrating that only common descent, natural selection and macro-speciation can explain the diversity of findings… despite the fact the findings all involve the same enzyme!
@swamidass, you will enjoy the surprising findings of the linked article @scd provided: “Recent Loss of Vitamin C Biosynthesis Ability in Bats”!
gbrooks. i think that you missed the main point here. the main point is that the same gene can be lost by convergent loss. therefore the fact that some species share the same pseudogene cant be use as evidence for a common descent.
Very wrong. You have to remember why the loss of functioning genes happens to begin with. If the gene is important, mutations that impair the gene (if that’s the only effect) are filtered out of the subsequent generations of offspring.
But if the gene in question is no longer effective, then its corruption is part of the “seemingly random” process of mutation. The odds of the same “very rare mutation” (adjacent to the same road map of other working genes) being reproduced in branches of produced from a common ancestral population are infinitesimally small.
So if, say, three species emerge from the original population with the broken gene - - each having the very same broken gene - - it’s because of common descent - - unless you think God really is intentionally trying to convince humanity of Evolution.
The only other choice is that God, in his employment of special creation, thought it would be amusing to insert a broken gene in exactly the same place of very similar chromosomal arrays, instead of giving each new branch of life it’s own unique genetic configuration, leaving out broken genes rather than creating false trails by inserting a useless and broken gene that first appeared in yet another special creation.
again: what is your main objection. first: according to special creation scenario this gene was active in the past and become a pseudogene. so its just a degeneration. secondly: if we can get the same gene loss several times by convergent loss then we cant claim that its impossible to get the same gee loss by convergent loss. simple logic.
There are many genes that are uniquely magnificent. They have been carried into many branches of the animal kingdom.
But there are two patterns for broken genes:
A) all the offspring lineages possess the broken gene of the common ancestral population.
vs.
B) non-connected branch populations having the same broken gene, because these branch populations no longer need the gene, and eventually any gene gets corrupted. If the gene has value, the corrupted gene gets washed out of the population. If the gene doesn’t, some offspring branches inherit the broken gene and some do not.
This latter option is what has been tested in the field with Bats. It is an indication that the gene was corrupted recently … and not inherited from some other branch that also suffered a corruption in the same gene … but many times in a different location (genes over time move around).
So, humans and chimps sharing a broken vitamin C gene becomes relevant… because all the other neighboring branches have functioning C genes.
But a few other non-primate branches have broken C genes… because it those other branches managed to survive without the C gene as well when it broke.
swamidass
(S. Joshua Swamidass)
Split this topic
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