How Evolution Can Allow for Trivial Developmental Leaps

Evolution News & Views ^ | July 29, 2009 | Casey Luskin

[GodGunsGuts]

How Evolution Can Allow for Trivial Developmental Leaps

Some evolutionary-development researchers must be taking cues from the PR team that overhyped “Ida.” A recent article on ScienceDaily was titled, “How Evolution Can Allow For Large Developmental Leaps,” but the article documents nothing of the kind. It begins by discussing a long-recognized problem in evolution: “when it comes to traits like the number of wings on an insect, or limbs on a primate, there is no middle ground. How are these sorts of large evolutionary leaps made?” I appreciate the author’s acknowledgment that functional intermediate forms can be a problem for Darwinian evolution. I then expected the article to discuss how “large evolutionary leaps” might occur, but instead, it went on to discuss research that showed trivial biological changes in bacteria.

When the going gets tough, many bacteria will hunker down and produce spores that can house and protect a bacterium’s genetic material until the environment returns to a favorable state. The ScienceDaily article reported that certain bacterial mutations may cause bacteria to produce one spore, two spores, or just die, with those traits appearing in differing proportions in bacterial populations depending on the particular mutation. Biologists were already well aware that many bacteria produce multiple spores, and at best the research shows how bacteria might produce more of something they already produce.

So what about evolving different numbers of insect legs or primate limbs? Somehow the researchers forgot to address that topic. If you’re looking for “large evolutionary leaps,” you won’t find any here — just bacteria that can make one spore, two spores, or die. But as Jonathan Wells showed in Icons of Evolution, it overtaxes Darwinian processes simply to produce an extra set of non-functional useless wings on fruit flies, to say nothing of producing an extra set of wings that are functional. And how about the evolutionary origin of wings or legs in the first place? It would seem that for now, the Darwinian solution to these kinds of problems exists only in the over-exaggerated titles of press releases.

[GodGunsGuts]

Ping!

[grumpa]

http://www.faithfacts.org/evolution-or-creation/origins-and-silly-putty

[grumpa]

http://www.faithfacts.org/evolution-or-creation/origins-and-silly-putty

[BigEdLB]

The thoery of big leaps - supposedly uses a similar mechanism as Down’s Syndrome - Extra chromosomes and genes, but where is not detrimental...

[GodGunsGuts]

Looks like a great website. Thanks for passing it along!

All the best—GGG

[FormerRep]

I read the original article. The criticism written by the author of your post is valid. The title establishes expectations not met in the body of the publication.

[Alamo-Girl]

Thanks for the ping!

[Ira_Louvin]

“Biologists were already well aware that many bacteria produce multiple spores, and at best the research shows how bacteria might produce more of something they already produce.”

Too bad that is not what the article states…………

What the scientists looked at was a “mutant in which the sporulation process was altered,” Eldar explains. “Usually, these cells talk with each other, with the small spore telling the large mother cell, ‘I’m here, and I’m doing OK.’ In the wild-type cell, this chatter is loud; in the mutant, it’s just a whisper, and the mother can’t always hear.”

When this whispering sort of mutation occurs, the researchers discovered, there are four possible outcomes:

· The bacterium sporulates normally, like the wild type.

· The bacterium makes two copies of its chromosome instead of one, so that there are three chromosomes but creates only a single spore. In this case, the mother cell retains two of the chromosomes and gives the spore one.

· The bacterium makes only one copy of its chromosome, but creates two spores instead of one. In this case, each spore will have a chromosome, and the mother cell will have none. (This is a lethal mutation; neither the mother nor its spores will survive.)

· The bacterium makes two copies of its chromosome instead of one, so that there are three chromosomes. It then creates two spores. In this case, the mother and each of the twin spores will have a single chromosome.

This last possibility, notes Eldar, is something that had never been seen before in B. subtilis. But that doesn’t mean this twinning behavior doesn’t have its advantages. “In some environments, it might be better for the cell,” he says. “We know that because there are other species whose wild types do the same thing that our mutant was doing only once in a while.”

The scientists soon realized that this variability was their way in to understanding how evolution makes the leap from one to another phenotype. “You can’t switch from 1 to 1.1 spores,” Eldar points out. “But it’s easy to find a mutation that simply changes the frequency of the behavior. If 10 percent of the population makes 2 spores and the rest makes 1, that works. It solves the need for a quantum jump between 1 and 2 spores.”

Once they had seen this rare behavior in a small minority of the bacteria, the researchers took the process one step further, tweaking other players in the sporulation system. For instance, they looked at what would happen if, in addition to dampening the communication between mother and spore—making the mother think she hadn’t yet successfully produced a spore—you also increased the volume of the signals that tell the mother to replicate its chromosome.

Perhaps not surprisingly, they found that these sorts of changes increase the percentage of B. subtilis individuals that decide to produce two spores rather than one. In fact, by combining mutations, Eldar says, they were able to up the percentage of bacteria that create twin spores from about 1 percent (in singly mutated bacteria) to as high as 40 percent (in multiply mutated bacteria).

“When you have only a single mutation, twinning shows very low penetrance,” Eldar says. “But when you add more and more mutations, you can build up the penetrance to very high levels.”

We showed that some mutations cause a low frequency of twin spores to develop in the same cell, rather than a single spore per cell, as occurs normally,” Elowitz says. “The relative frequency of this form could be tuned up to high levels by other mutations.”

This study provides a concrete example of a particular scenario to explain developmental evolution. “It illustrates a somewhat unfamiliar mode in which developmental evolution might work,” Elowitz adds. “Qualitative changes from one form to another can proceed through changes in the relative frequencies—or penetrance—of those forms.

It’s interesting that noise—these random fluctuations of proteins in the cell—is critical for this to work,” he continues. “Noise is not just a nuisance in this system; it’s a key part of the process that allows genetically identical cells to do very different things.”

In addition, Elowitz notes, the work shows that “bacterial development can be a good system to enable further study of these general issues in developmental evolution.”

http://www.sciencedaily.com/releases/2009/07/090720163716.htm

When you do not have the facts on your side I guess using a straw man is the next best thing…

I guess the 9th commandment only applies some of the time?

[count-your-change]

In summary of the article, a mutation in the wild-type cell weakens the message between mother cell and spore so that the mother cell produces two spores, each with its own chromosome OR

one spore with one chromosome or somewhere in between these two outcomes.

So what conclusions are to be drawn from this other than mutations affect spore production of a bacterium?

The last possibility hadn't been seen in one particular bacterium but had in wild types.

The bacterium either makes one spore or two. And?

[Ira_Louvin]

You seem to have overlooked this part:

“Perhaps not surprisingly, they found that these sorts of changes increase the percentage of B. subtilis individuals that decide to produce two spores rather than one. In fact, by combining mutations, Eldar says, they were able to up the percentage of bacteria that create twin spores from about 1 percent (in singly mutated bacteria) to as high as 40 percent (in multiply mutated bacteria).

“When you have only a single mutation, twinning shows very low penetrance,” Eldar says. “But when you add more and more mutations, you can build up the penetrance to very high levels.”

We showed that some mutations cause a low frequency of twin spores to develop in the same cell, rather than a single spore per cell, as occurs normally,” Elowitz says. “The relative frequency of this form could be tuned up to high levels by other mutations.”

This study provides a concrete example of a particular scenario to explain developmental evolution. “It illustrates a somewhat unfamiliar mode in which developmental evolution might work,” Elowitz adds. “Qualitative changes from one form to another can proceed through changes in the relative frequencies—or penetrance—of those forms.

It’s interesting that noise—these random fluctuations of proteins in the cell—is critical for this to work,” he continues. “Noise is not just a nuisance in this system; it’s a key part of the process that allows genetically identical cells to do very different things.”

In addition, Elowitz notes, the work shows that “bacterial development can be a good system to enable further study of these general issues in developmental evolution”

Your answer was right there in front of you.

[count-your-change]

Whatever the frequency of the two spore production it is still more of the same, spore production so I didn't overlook that at all.

““When you have only a single mutation, twinning shows very low penetrance,” Eldar says. “But when you add more and more mutations, you can build up the penetrance to very high levels.”

More mutations, more twinning. More of the same.

The conclusion offered is that going from production of one spore to two is evolutionary development but development into what is left out. Stripped of the fluff one sentence would tell the story: Mutations cause a bacterium to produce two spores instead of one with varying results.

From the Nature abstract comes the fluff of supposed potential:

“These results suggest a potential pathway for developmental evolution between monosporulation and twin sporulation through states of intermediate twin penetrance.” A little bit of meat and a whole lot of water for a mighty thin soup.

[Ira_Louvin]

“But when you add more and more mutations, you can build up the penetrance to very high levels.”

“Qualitative changes from one form to another can proceed through changes in the relative frequencies—or penetrance—of those forms.

The more mutations the greater the chance for evolutionary change, the answer is right there in front of you.

[count-your-change]

“The more mutations the greater the chance for evolutionary change, the answer is right there in front of you.”

Hype and fluff not supported by what was described as actually happening in either the article or the abstract.

And this is gibberish:

““Qualitative changes from one form to another can proceed through changes in the relative frequencies—or penetrance—of those forms.”

Change from one form to another proceeds from frequency of the changed forms? HUH???