Posted on 12/18/2001 5:07:16 PM PST by Map Kernow
LONG-LOST relatives of the human race have been traced for the first time. They live at the bottom of puddles. A family of humble microbes has been found to carry a special signalling gene that was previously known only in the animal kingdom. The discovery suggests that the single-celled creatures represent a vital staging post in evolution and that all animal life on Earth descended from something very like them.
The survivor from our ancient ancestors is the collar flagellate or choanoflagellate — a microscopic organism that uses a sperm-like tail to swim through shallow water, grazing on bacteria that lodge in its feeding “collars”.
Its remarkable evolutionary legacy, which stretches back at least 600 million years, has been identified by researchers in the US. Today 150 species of collar flagellates exist around the world, but evolution also gave rise to a more complex lineage that eventually led to the animal kingdom.
“They are the closest nonanimal organism to animals,” said Sean Carroll, Professor of Genetics at the University of Wisconsin-Madison, who led the research. “They are to animals what chimps are to humans, and by studying some of their genetic characteristics, we can begin to make some strong inferences.”
In the study, published today in the Proceedings of the National Academy of Sciences, Professor Carroll and his colleague Nicole King analysed proteins from a species of collar flagellate called Monosiga brevicollis. They located a type of signalling gene, receptor tyrosine kinase (RTK), which sends messages to other genes telling them to become active or making them dormant. It is almost identical to similar version found in animals as diverse as humans and sponges.
The findings support strongly the idea that many genes that animals use today were already in place and available on the eve of animal evolution, but changed in function with the step forward to multicellular organisms with distinct body plans and systems of organs.
The microbes, which measure five thousandths of a millimetre in diameter, are protazoans — simple organisms that were once regarded as animals but are now generally considered to be part of a separate kingdom, the single-celled protists.
Scientists consider the moment at which multi-celled animals, or metazoa, evolved from the protozoans to be one of the turning points in the history of life on Earth. The process is thought to have taken place about 600 million years ago.
“The question is, who were the ancestors of animals and what genetic tools did they pass down to the original animals,” Professor Carroll said. The evolution of the metazoa from the protozoans is one of the milestones in the history of life. To build a multicellular organism compatible with a multicellular lifestyle is something that is very difficult. It takes a lot of genetic machinery to do that, and you have to ask the question, did it all arise when the animals came along, or was some of it in place earlier? “We’re starting to get a glimpse of the genetic tool kit we have in common. In choanoflagellates, we’ve found genes that previously were believed only to exist in animals. It’s a confirmation of the idea that the genes come first, before their exploitation by organisms.”
The study concludes: “We have discovered in M. brevicollis the first RTK, to our knowledge, identified outside the metazoa. The architecture . . . resembles that of RTKs in sponges and humans and suggests the ability to receive and transduce signals. Thus, choanoflagellates express genes involved in animal development that are not found in other eukaryotes (complex organisms), and that may be linked to the origin of the metazoa.”
ID is certainly a possibility, but as Patrick Henry points out in #189, why go there if there is no evidence pointing in that direction? When the evidence points that way science will assuredly follow.
Behe and Dembski go there because they have no evidence. Runnin’ scared, they are.
And again I say that to many the laws and the order is evidence. But after reading the last few posts on this thread I think I'll run scared. It's going downhill fast....
Well.
Homochirality of life is not likely a matter of chance. There is plenty of evidence which suggests that multiple influences from catalysts, substrates, parity violating weak forces, gamma rays, stability of complexes and so forth influence the energetic advantage of one isomer or enantiomer over another. Just because sugar forms a racemic mixture in your particular reaction doesn't mean that all reactions result in racemic mixtures.
There are myriad sucy revealing glimpses from the world of science. If you put them all together, what picture does this "mind" present? Anything approaching current evolutionary theory?
To what degree is it "not likely."
That is good "organic chemistry humor":-)LOL!You should consider that for some text book. cheers
My head is swimming with terms from my undergraduate organic chemistry classes! I must say you sound very cerebral, pedantic, and a regular erudite. I hope to never have to argue some point with you. :o)
Even in the various theories to which you refer, a quantum world is still not absolutely nothing, but a necessary set of physical conditions. Things cannot happen where there is total nothingness because by definition there are no things in total nothingness. A quantum vacuum is not nothing, and fluctuations in a quantum vacuum do not constitute an exception to the principle that whatever begins to exist has a cause. The universe still has to have a source, and appealing to arbitrary necessity by saying that it just happens to exist is not a reasonable or satisfying explanation.
Isn't that the whole point of science anyway; namely, looking for rational reasons for things? Our scientific knowledge about the physical universe is based on our understanding of cause and effect, and it is therefore reasonable to assume that the universe itself has a cause, and so is contingent.
Cordially,
He is mearly a sesquipedalian. If he were to defenestrate the big words we might be able to have a conversation.
Given a set of conditions with an outcome favorable to L, even with a small advantage, it would eventually rule out R. So, I think it's very possible that ancient conditions were such that both L and R existed, but that one gained an advantage, not by pure chance, but because conditions favored one over the other. Conditions elsewhere in the universe may well tip the advantage to the mirror compounds.
The fact that conditions favored one over the other..
Was that not determined by chance?
I don't pretend to have anything useful to say about the how it is that the universe is instead of isn't. But this initial state of affairs, for example, is not the immediate reason you turn one way to go to work in the morning instead of the other way. Nor is it the reason for the homochirality of life.
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