Study Hints at How Genetic Mutations Led to Macroevolutionary Change

Scientific American ^ | Kate Wong

[realpatriot71]

EVOLUTION
Study Hints at How Genetic Mutations Led to Macroevolutionary Change

Image: Matthew Ronshaugen/UCSD

The fossil record contains numerous examples of dramatic evolutionary change in animals through time. Exactly how genetic alterations brought about these macroevolutionary changes, however, has proved difficult to ascertain. Now new research into the developmental biology of brine shrimp and fruit flies could throw light on the matter. According to a report published online today by the journal Nature, mutations in genes that guide embryonic development allowed insects to develop a radically different body plan from that of their crustacean-like ancestors some 400 million years ago.

The University of California, San Diego, team that conducted the research focused on so-called Hox genes, master switches that turn other genes on and off during the embryonic development of all animals, including humans. One of these Hox genes, known as Hbx, suppresses 100 percent of limb development in the thorax region of fruit flies, but only 15 percent in the brine shrimp Artemia (right). Modifications of Hbx, the investigators determined, would have allowed the many-limbed, crustacean-like ancient relatives of Artemia to lose their rear limbs, giving rise to the six-legged insects. "Before the evolution of insects, the Ubx protein didn't turn off genes required for leg formation," team member William McGinnis explains. "During the early evolution of insects, this gene and the protein it encoded changed so that they now turned off those genes required to make legs, essentially removing those legs from what would be the abdomen in insects."

In addition to shedding light on how major shifts in body design evolved, the new finding could help scientists better understand certain human diseases and deformities. "If you compare [Hbx] to many other related genes, you can see that they share certain regions in their sequences, which suggests that their function might be regulated like this gene," remarks lead study author Matthew Ronshaugen. "This may establish how, not only this gene, but relatives of this gene in many, many different organisms actually work." A number of these genes are involved in cancer and developmental abnormalities, he says, and "they may explain how some of these conditions came to be." ÑKate Wong

RELATED LINK:

"How Limbs Develop," by Robert D. Riddle and Clifford J. Tabin (Scientific American, February 1999), is available for purchase at the Scientific American Archive.

[realpatriot71]

Hmmmm? Thoughts?

[realpatriot71]

Ping!

[SlickWillard]

Image: Matthew Ronshaugen/UCSD

[Seeking the truth]

I wonder if them Hox genes are pronounced as below?

[throwthebumsout]

So, what they're trying to say is: a fly is a shrimp is a goat is a human - just switch the right Hox (hoax?) genes.

Yeah, right!

[Sabertooth]

I don't necessarliy have a problem with macroevolution per se. If it's proven or strongly indicated, I can live with that.

To be fair, this article doesn't claim that, only a hint.

Where I have a problem is the presumption of some that we have any real clue as to what might cause or drive macroevolution. It's there, I think, that we all need to concede that where the scientific evidence is concerned, "we really don't know" what causes speciation.

[WhatsItAllAbout]

You may be interested in this theard regarding the same subject: First Genetic Evidence Uncovered Of How Major Changes In Body Shapes Occurred During Early Animal Evolution

[ijcr]

Did this not occur in Thalidomide children?

[DaveyB]

The fossil record contains numerous examples of dramatic evolutionary change in animals…

WRONG! The fossil record contains many fully formed animals and not one proven transitional one.

God hating “scientists”, the high priests of the secular religion, must insist that these are evolutionary changes. There is no evidence of evolution in the fossil record. But they keep repeating the same mantra. All together now ..."600 billion years ...yada yada yada ..."

[realpatriot71]

We know that speciation is caused when a single species/group spilts and no longer mates. This can be caused by something as simple as river separating the two populations or one species does not recognize the "mating dance" of the other species. Now how changes occur at levels about genus, NO, we have no direct evidence of that ever happening, especially by mutation.

[realpatriot71]

No, what they're saying is the Hox gene allows for the expression of different genes that code for limb development. This could be one way that allowed for limb development or lack thereof. They have not said this is conclusive proof of macroevo, but rather this could be a mechanism.

[tallhappy]

We know that speciation is caused when a single species/group spilts and no longer mates. This can be caused by something as simple as river separating the two populations or one species does not recognize the "mating dance" of the other species.

How long is this supposed to take?

[Sabertooth]

We know that speciation is caused when a single species/group spilts and no longer mates.

While that's generally true, without getting into the particulars here, there are some problems with the mating/not mating definition of species. There are still some fuzzy areas around our definitions.

[stanz]

There is no evidence of evolution in the fossil record.

Archaeopteryx.
yada yada yada

[realpatriot71]

True. There is not real transitory fossil (at least in not my opinion). However, what is seen in the fossil record is that the least complex fossils are buried deeper than more complex species, with the most complex being at the top. I think to be intellectually honest, this is one of the toughest points for a creationist to explain.

[realpatriot71]

How long is this supposed to take?

In a case of California chipmunks, not more than a few generations. The different species can mate, but do not because the different groups have new matting rituals that the other species does not reognize. Speciation is really a definition of reproductive isolation in the wild.

[tallhappy]

Speciation is really a definition of reproductive isolation in the wild.

Where does this come from?

[realpatriot71]

Did this not occur in Thalidomide children?

I couldn't find any info in the mechanism at the genetic level for why Thalidomide children happened.

[RightWhale]

Just to be exoteric for a moment:
While I still don't "get" the controversy over evolution, I will add that there seems to be no verb form for the word speciation. There is specialize, derived from the French, to specify, to adapt, to concentrate on a specific profession. Perhaps we can use "specify" as the verb for speciation, but that would imply a conscious choice and we assume speciation and evolution are not the result of conscious decisions except by an effective deity.

[realpatriot71]

Where does this come from?

Repoductive isolation could be any number of things as I already said, anything from sexual organs are not compatible, to chromosome number not compatible, to a river or mountain that separates the two communities. This usually results in the two species being genetically different because of breeding only within the immediate group.

[tallhappy]

I will add that there seems to be no verb form for the word speciation

Speciate.

[tallhappy]

No. Where does the idea that species are defined by simply not breeding, not the inability to breed and produce offspring?

A thousand years ago people in Africa, Europe and America would have been different species.

[Registered]

Whew! Now that that's been figured out, explain the origin of symbiotic relationships?

[RightWhale]

Speciate is intransitive. I should have said transitive verb, implying an actor. Does something cause speciation? Can you cause speciation? Or does the organism just spontaneously speciate because it is speciation time?

[ThinkLikeWaterAndReeds]

Let us assume for a moment that macroevolution does exist. Let us also assume for a moment that the big bang theory is true. Hold on there you creationists, don't click the "post reply" button just yet. Prior to the big bang, there must have been something to go BANG, and there must have been some mighty force to ignite that something that went bang. Let us also assume that the creator of that something and the ignitor of that something was a force that some have come to know as a GOD. This creative power (a GOD in this example) could have devised a scheme that we refer to as macroevolution, as the mechanism that leads to the human. The point of evolution where the human emerged could have well been preordained. This still would be creation would it not?

[Registered]

Family portrait of my brine shrimp.

[twigs]

This usually results in the two species being genetically different because of breeding only within the immediate group.

For people who believe that man originated from one Adam, could this not explain the differences among people groups?

[realpatriot71]

A thousand years ago people in Africa, Europe and America would have been different species

This would be true if when these humans met they did not breed. Separate species when placed together will not breed with each other for various reasons as mentioned before. Humans, being rational, can choose not to breed, but we obviously can.

[tallhappy]

Where are you getting this revisionist definition?

[realpatriot71]

For people who believe that man originated from one Adam {and Eve}, could this not explain the differences among people groups?

Yes it can explain the differences.

[realpatriot71]

It's not revisionist. What is your problem with it?

[twigs]

Thank you. How long do you think such change as we see it today would take in man?

[cynicom]

If this is acceptable, it would seem that over millions of years there would have been more numerous and wider varying mutants.

[realpatriot71]

Yes that would be creation. However, the creation account mentioned in the Bible tells of a fully formed man, not an evolved men.

[tallhappy]

See:

Annu Rev Pharmacol Toxicol 2002;42:181-208 Molecular basis of environmentally induced birth defects. Finnell RH, Waes JG, Eudy JD, Rosenquist TH.

The molecular basis still isn't known.

[tallhappy]

It's not revisionist. What is your problem with it?

Revisionist or not, I'm asking where this is taught.

Who pioneered this view?

[realpatriot71]

LOL

I had forgotten that Sea Monkeys are brine shrimp. I always killed mine.

[realpatriot71]

Speciation of man. It's an interesting quetsion. I really think we're able to move about too easily for this ever to happen on Earth. The only was I can forsee and future speciation would be if man began colonizing the galaxy. I think the distances and time it would take to move about the galaxy could allow for speciation.

[realpatriot71]

I don't know about pioneering, but I learned this in my undergrad freshman biology class. I wouldn't think it would be taught any different anywhere else.

[twigs]

I'm sorry. I didn't make myself very clear. I wasn't talking about speciation. I was referring to the physical differences among different people groups. If everyone descended from an Adam and Eve, how long would it take, given the proper separation, for man to develop the physical differences we witness today.

[js1138]

Prior to the big bang, there must have been something to go BANG, and there must have been some mighty force to ignite that something that went bang.

This logic cannot be applied to first causes for the simple reason that you are merely pushing back the origins question. If God existed prior to the Big Bang, how did God originate?

The only honest answer is that no one knows. The same answer a scientist would give to the origin of existence.

[tallhappy]

When did you take intro bio?

[realpatriot71]

how long would it take, given the proper separation, for man to develop the physical differences we witness today.

I'll be honest. I don't know, but since I'm a believer in a recent creation I'd guess approximately 20,000-10,000 years.

[realpatriot71]

I had my first undergrad bio class 5 years ago

[ThinkLikeWaterAndReeds]

As a Taoist, I believe that there is a force in the universe, and beyond, that is incomprehensable and eternal and attempts to quantify it is nonsensical. Everything issues from it and everything returns to it. This is the only "leap of faith" required in my belief and excludes total randomness.

[twigs]

Have you read Bryan Sykes' The Seven Daughters of Eve: The Science That Reveals Our Genetic Ancestry? He argues that genetic mutations of mitachondrial DNA would trace most--I think around 95%--of Europeans back to seven women, the oldest of which would have been 35,000-40,000 years ago. That's from memory, so I'm not certain about the exact years he postulates. He also assumes that all these women were descended from an Eve. I found the book fascinating, but I could not evaluate it properly because I just don't know enough about genetics. I also believe in a more recent creation, but I can't always reconcile the differences I read between competing theories.

[colorado tanker]

Well said, but it's a little difficult for early 21st Century man to admit he doesn't know evrything.

[Quester]

Did this not occur in Thalidomide children?

The deformities of the thalidomide children were the result of thalidomide's ability to block the formation of new blood vessel systems in the body. The body's ability to form blood vessel systems is vital during fetal development, because arms, legs, etc. require the development of their own individual blood vessel systems to develop properly. You can think of the stunted or, apparently, missing, in some cases, limbs of the thalidomide children as body systems which were not supplied with the necessary nourishment for their normal development.

Interestingly, thalidomide, along with other drugs which, similarly, obstruct the development of new blood vessel systems, are proving to be quite beneficial in the area of the cancer treatment. The body's capability to develop new blood vessel systems is only really needed when new body structures are being developed, and is rarely in evidence in the human body apart from fetal development, menstruation, and cancer. In order for cancers to go from being pin-prick sized groups of abberantly multiplying cells to life-threatening masses, they need to grow, and, thus, need to develop their own blood vessel systems to supply themselves with the nourishment required for growth.

If blood vessel system development is obstructed, cancers cannot grow to life-threatening size, and, thus, can be controlled. Thalidomide and similarly acting drugs are currently being tested to determine their effectiveness in fighting cancer growth in humans. The most effective dosages and schedules of treatments are currently being worked out. To date, the results are mixed.