Tuesday, September 8, 2009 | Reason : Evolution and Biology | print version

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Molecular Decay Of Enamel-specific Gene In Toothless Mammals Supports Theory Of Evolution

by ScienceDaily

Thanks to rod-the-farmer for the link.
http://www.sciencedaily.com/releases/2009/09/090904071650.htm

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Biologists at the University of California, Riverside report new evidence for evolutionary change recorded in both the fossil record and the genomes (or genetic blueprints) of living organisms, providing fresh support for Charles Darwin's theory of evolution.

The researchers were able to correlate the progressive loss of enamel in the fossil record with a simultaneous molecular decay of a gene, called the enamelin gene, that is involved in enamel formation in mammals.

Enamel is the hardest substance in the vertebrate body, and most mammals have teeth capped with it.

Examples exist, however, of mammals without mineralized teeth (e.g., baleen whales, anteaters, pangolins) and of mammals with teeth that lack enamel (e.g., sloths, aardvarks, and pygmy sperm whales). Further, the fossil record documents when enamel was lost in these lineages.

"The fossil record is almost entirely limited to hard tissues such as bones and teeth," said Mark Springer, a professor of biology, who led the study. "Given this limitation, there are very few opportunities to examine the co-evolution of genes in the genome of living organisms and morphological features preserved in the fossil record."

In 2007, Springer, along with Robert Meredith and John Gatesy in the Department of Biology at UC Riverside, initiated a study of enamelless mammals in which the researchers focused on the enamelin gene. They predicted that these species would have copies of the gene that codes for the tooth-specific enamelin protein, but this gene would show evidence of molecular decay in these species.

"Mammals without enamel are descended from ancestral forms that had teeth with enamel," Springer said. "We predicted that enamel-specific genes such as enamelin would show evidence in living organisms of molecular decay because these genes are vestigial and no longer necessary for survival."
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http://www.sciencedaily.com/releases/2009/09/090904071650.htm

Posted: Tuesday, September 8, 2009 | Permalink

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1. Comment #413401 by fossil-fish on September 8, 2009 at 7:05 pm

That is such a neat and simple argument to follow. Would love to hear the counter to it.

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2. Comment #413420 by Harvatos on September 8, 2009 at 8:14 pm

That is such a neat and simple argument to follow. Would love to hear the counter to it.

God act in mysterious (read inconherent) ways...

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3. Comment #413423 by steveroot on September 8, 2009 at 8:17 pm

Fascinating. None of this was known when I was in dental school in the late 1980s. As for the counter-argument, of course it is the bullet-proof "goddidit". ;-)
Steve

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4. Comment #413437 by Nails on September 8, 2009 at 9:28 pm

I wonder whether deactivating the gene drove the evolution of filter-feeding, of whether early whales beagn adapting towards this and lst the enamalin gene along the way?

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5. Comment #413449 by Moq on September 8, 2009 at 9:48 pm

So the discovery supports theory of evolution.

Who knew? (Apart from most reasonably informed people.)

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6. Comment #413450 by AdamMil on September 8, 2009 at 9:58 pm

I wonder whether deactivating the gene drove the evolution of filter-feeding, of whether early whales beagn adapting towards this and lst the enamalin gene along the way?

I think the latter. If the deactivation of the gene caused hardship for the animal, it would be unlikely to spread through the gene pool, but if enamel was no longer necessary, there'd be no selection pressure against its deactivation.

It reminds me of the deactivation of the gene that allows us to synthesize vitamin C. The theory goes that since we were able to procure ourselves a steady supply of vitamin C in our diet, there was no longer selection pressure against the mutation of that gene.

Although on second thought, I can imagine the former happening too, if first they developed an eating style that no longer required enamel, and then later evolved filter-feeding...

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7. Comment #413460 by Opisthokont on September 8, 2009 at 10:42 pm

providing fresh support for Charles Darwin's theory of evolution

This is simply irresponsible journalism. Yes, it does provide support, but so do thousands of other papers published each year. And this is indeed fascinating research, worthy of public attention -- but because it tells an interesting story in and of itself. Support for Darwin's theory (and the theory has gone so far beyond Darwin that any responsible journalist would stop calling it that already) is simply not an important part of the story. Then again, perhaps this journalist probably still thinks that evolution is a scientifically controversial subject....

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8. Comment #413468 by padster1976 on September 8, 2009 at 11:19 pm

Well fancy that!

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9. Comment #413491 by -dr- on September 9, 2009 at 1:08 am

7. Comment #413460 by Opisthokont on September 8, 2009 at 10:42 pm

Then again, perhaps this journalist… still thinks that evolution is a scientifically controversial subject...

It does have that flavor, doesn’t it? – odd for a science website. When they write about a new discovery in astrophysics, I doubt they describe it as “fresh support for gravity.”

David in Toronto

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10. Comment #413507 by Crazycharlie on September 9, 2009 at 1:59 am

I've been fascinated by whale and cetacean evolution since I was a child. I was about 8 or 9 years old when I saw diagrams of many different whale skeletons. I was absolutely amazed that some of the skeletons had vestigial hind legs. Right then I made the connection that whales or at least whale ancestors had walked on land! Incredible! Baleen whales with "tooth-specific genes" is another fascinating piece of the puzzle in whale evolution.--Comment#413460 Opisthokont, It seems to me as if many journalists are almost reluctant to give the impression that they completely agree with evolution and Darwin.--- "...providing fresh support Charles Darwin's theory of evolution." --As if Darwin's theory needed support!

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11. Comment #413541 by Barry Pearson on September 9, 2009 at 6:27 am

#413420 by Harvatos:
God act in mysterious ... ways...

Chuckle!

An aside - why do people who make such a claim still feel entitled to describe God's position on a whole range of matters?

Shouldn't someone who makes such a claim then just shut up about God's intentions and desires, because they are mysterious (and "beyond human understanding")?

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12. Comment #413542 by Roy_H on September 9, 2009 at 6:44 am

Which just goes to show you , creationist's arguments don't have teeth!

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13. Comment #413543 by Barry Pearson on September 9, 2009 at 6:45 am

#413491 by -dr-:
When they write about a new discovery in astrophysics, I doubt they describe it as “fresh support for gravity.”

Hm! I think they may well say "fresh support for Einstein's theory of general relativity".

Evolution is a fact. Gravity is a fact. "Natural Selection" is overwhelming confirmed, and won't be superceded although it will be refined and supplemented. "General Relativity" is problematic, even though it gives good results in most cases, and a theory of quantum gravity will spring some surprises.

"Evolution" nowadays tends to be shorthand for "Evolution by Natural Selection". (It wasn't pre-Darwin). "Gravity" isn't really shorthand for anything.

I too regret the need to reinforce that "Evolution by Natural Selection" has overwhelming evidence and it keeps coming in. But surely the need is there. After all, a certain well known person has just published a book on this topic! So it is hardly fair to blame a journalist for drawing attention to this.

What I appear to be saying is that Evolution is actually on a firmer footing than Gravity!

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14. Comment #413545 by mordacious1 on September 9, 2009 at 7:05 am

3. Comment #413423 by steveroot

From article:

Despite the absence of teeth, modern baleen whales retain copies of tooth-specific genes, such as enamelin, in their genomes; these unnecessary genes, which were inherited from toothed ancestors, show evidence of mutational decay.

So they didn't teach you about dealing with mutational decay? Flossing doesn't help?

Actually, I just came on line to calm down after watching Tony Blair on "Letterman" explaining why it was important to attack Iraq after 9/11. Can't the Brits keep that mook in their own country? We need to send GW to the UK to give some speeches, as payback.

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15. Comment #413571 by Bernard Hurley on September 9, 2009 at 11:00 am

Personally I think, in the present climate, it is worth saying that the discovery supports the theory of evolution. Virtually every new discovery in the biological sciences supports, in the sense of providing new evidence for, the theory of evolution, and the few that do not are still consistent with it. We are used to this, but the evolution deniers are not. It is worth rubbing their noses in it at every possible opportunity.

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16. Comment #413582 by Muetze on September 9, 2009 at 12:10 pm

Evidence for evolution? Great Scott!

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17. Comment #413685 by Border Collie on September 9, 2009 at 11:09 pm

How on Earth would we know that this supports Darwin's theory of evolution if a journalist didn't tell us? I mean, I sit around in neutral all the time just waiting for a journalist to define reality for me and explain the obvious.

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18. Comment #413879 by Gnuatheist on September 10, 2009 at 5:14 pm

"Man falls to his death providing fresh support for the Theory of Gravity!"

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19. Comment #414119 by steveroot on September 11, 2009 at 10:09 pm

14. Comment #413545 by mordacious1 on September 9, 2009 at 7:05 am
avatar3. Comment #413423 by steveroot

So they didn't teach you about dealing with mutational decay? Flossing doesn't help?

Nope. Dentistry is a "cash and caries" business. ;-)

Maybe some fluoride would keep those genes in line. :-O
Steve

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