Detlev Arendt (left), Florian Raible and Peer Bork.
(Photo Credit: Marietta Schupp, Photolab, EMBL
Heidelberg)
Posted on 11/27/2005 7:11:52 AM PST by Pharmboy
Species evolve at very different rates, and the evolutionary line that produced humans seems to be among the slowest. The result, according to a new study by scientists at the European Molecular Biology Laboratory [EMBL], is that our species has retained characteristics of a very ancient ancestor that have been lost in more quickly-evolving animals. This overturns a commonly-held view of the nature of genes in the first animals. The work appears in the current issue of the journal Science.
Detlev Arendt (left), Florian Raible and Peer Bork.
(Photo Credit: Marietta Schupp, Photolab, EMBL
Heidelberg)
Genes hold the recipes for proteins. The genes of animals usually contain extra bits of DNA sequence, called introns – information which has to be removed as cells create new molecules. The number of introns in genes, however, varies greatly among animals. While humans have many introns in their genes, common animal models such as flies have fewer. From an evolutionary perspective, it was long assumed that the simpler fly genes would be more ancient. The current study reveals the opposite: early animals already had a lot of introns, and quickly-evolving species like insects have lost most of them.
To discover what early animals were like, scientists usually compare their descendents. This is difficult when comparing distantly-related animals such as humans and flies. In these cases, it helps to look at living organisms that have preserved many features of their ancestors. Detlev Arendt's group is doing this with a small marine worm called Platynereis dumerlii. "Similar animals are already found in the earliest fossils from the Cambrium, about 600 million years ago," Arendt explains, "arguing that Platynereis could be something like a 'living fossil'." This makes it an ideal model for evolutionary comparisons to find out what the common ancestors of humans, flies and worms were like."
Until quite recently, such comparisons could only be made by looking at physical characteristics such as the structure of bones, teeth, or tissues. But DNA sequencing now permits scientists to make comparisons of the genetic code and read evolutionary history from it. An international consortium involving researchers from EMBL, the UK, France and the United States has now sequenced a part of the Platynereis genome. "The fraction of Platynereis genes we have been able to look at tells a very clear story," says researcher Florian Raible, who performed most of the computer analyses. "The worm’s genes are very similar to human genes. That's a much different picture than we've seen from the quickly-evolving species that have been studied so far."
Raible is member of both Arendt's group and a second EMBL lab, that of Peer Bork, whose specialty is analyzing genomes by computer. "Human genes are typically more complex than those of flies," explains Bork. "Classicallystudied species like flies have far fewer introns, so many scientists have believed that genes have become more complex over the course of evolution. There have already been speculations that this may not be true, but proof was missing. Now we have direct evidence that genes were already quite complex in the first animals, and many invertebrates have reduced part of this complexity."
Not only are the introns there – the team also discovered that their positions within genes have been preserved over the last half a billion years." This gives us two independent measurements that tell the same story," Raible explains. "Most introns are very old, and they haven't changed very much in slowly-evolving branches of life, such as vertebrates or annelid worms. This makes vertebrates into something like 'living fossils' in their own right."
The discovery that Platynereis also represents a slowlyevolving branch of animal life has important implications for the study of humans. "We've already learned an incredible amount about humans from studies of the fly," Arendt says. "The marine worm might well give us an even better look at important conserved processes. Another thing that this has shown us is that evolution is not always about gain; the loss of complexity can equally be an important player in evolution."
Source article: Vertebrate-type intron-rich genes in the marine annelid Platynereis dumerilii F. Raible, K. Tessmar-Raible, K. Osoegawa, P. Wincker, C. Jubin, G. Balavoine, D. Ferrier, V. Benes, P. de Jong, J. Weissenbach, P. Bork and D. Arendt. Science, 25 November 2005
XenuDidit placemark
Suppose one has three populations, a, b, and c. A sample is drawn from each and an estimate of the mean is calculated. Depending on the results, one might be unable to determine if mean(a) differs from mean(b), or that mean(b) differs from mean(c). However, it might be evident that mean(a) differs from mean(c).
The same logic could be (and is) applied to different animals. When is a difference a difference? It depends on the one establishing the criteria I suppose. Is a short-tailed hawk different than a red-tailed hawk. Is a fox different than a coyote? Is a salt-water striper different than a fresh-water white bass? Is a white cat different than a black cat? Is a beagle different than a basset hound? It depends on the sensitivity of the criteria and the reason for grouping I suppose. At one extreme, every animal is unique, so you have complete granularity. At the other, you have a complete continuum and the famous quote by the head of PETA is true.
If, for the purposes of discussion, someone suggests that demarcation can occur other than the current ones for species that might be useful, I don't think that is a difficult concept, nor worthy of the scorn you were handing out. It isn't as if it were without precedent. We do it every day.
When you have formulated your alternate taxonomy come back and show the world of biological science how it explains everything so much better than the conventional one. I wish you joy of your Nobel Prize that will be richly deserved if you can show that the whole of biology has been barking up the wrong tree for the past 150 years.
Remarkable. You completely disregard (or fail to comprehend) my point, and still manage to be insulting and condescending. Just as well, I suppose, as that appears to be the real goal of your posts anyway.
A poster suggested that there may be logical groupings of plants and animals that might be beneficial for a different model. You said it couldn't be, that no such alternatives could be developed. I suggested that if biologists are that hung up on the problem, maybe they could get help from other fields. Did I recommend a grouping methodology? No. I only suggested that such would be reasonable and possible. The rest is your fantasy.
For that to be true "a poster" would have to explain what problems the phylogenetic taxonomy is giving biologists. No-one has so far done that, other to express a desire that there should be some classification that corresponds to the belief that evolution is true.
You said it couldn't be, that no such alternatives could be developed.
I don't recall saying that, but let's continue, because my memory isn't always flawless, and I can't be ar$ed to re-read the thread.
I suggested that if biologists are that hung up on the problem....
Biologists aren't hung up on the problem at all. They already have a taxonomy that seems to work excellently. That a concept of unbridgeable "Kinds" doesn't exist in it is a problem for certain creationists, not biologists. That is the biggest issue here, that you appear to be trying to solve... what problem exactly? Using.... what methodology exactly?
, maybe they could get help from other fields. Did I recommend a grouping methodology?
No you didn't. That would have been helpful, but apparently you want me to formulate your hypothesis for you.
No. I only suggested that such would be reasonable and possible. The rest is your fantasy.
And I repeat in the absence of significant flaws in the current biological taxonomy your suggestion will become interesting only after someone has done it, and shown that the new taxonomy explains biology better than the old one. I wish you luck.
No-one has so far done that, other to express a desire that there should be some classification that corresponds to the belief that evolution isn't true.
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Hox genes are very similar for arachnids and vertebrates implying that they have changed little during the past 500 million years.
From Wikipedia: Hox genes are a group of related genes that specify the anterior-posterior axis and segment identity of metazoan organisms during early embryonic development. These genes are critical for the proper number and placement of embryonic segment structures (such as legs, antennae, and eyes).
I’m suspicious of science articles when the researchers include an unnecessary picture of themselves.
Some politicians even today have human like genes,
or so they claim.
Yeah, well, what about FReepers who include unnecessary pictures of Zahi “Zowie” Hawass?!? Huh?!? Huh?!?
;’)
Ahem, that's, that's just un....
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