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.

[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.