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.”
Safe, convenient, and free of the need for explanation.
Doesn't get any better than that for the tough questions.
What is your explanation?
I understand your point. You're saying that if complexity implies a designer, why doesn't the designer of the complexity have a designer?
And I'm saying, maybe he does, if as you say he's necessarily "complex" (although I'd like to know how you know).
But the real issue is the link between complexity and design. Is the kind of complexity we find in life evidence (not necessarily proof) of design or not? And you're the guy who's dodging that issue, buddy. Capisci?
It all comes down to "faith" in your uncaused cause, and my uncaused cause doesn't it. Of course in science there is no such thing is there? Funny that science bases the beginning on something that inherently makes this law moot.
*YAWN!* Think about it: free markets are "spontaneous" only in the sense that they have no central planner. They are however directed by numerous intelligent individuals acting by design predicated on their own self-interest.
But if you really think you can compare them to spontaneous evolution from pond scum, why go right ahead....
And in saying "maybe he does", you create a cosmic hall of mirrors of infinite scope and proportion.
An endless string of continuously designing designers, each with a great complexity than his creation.
Welcome... to the Twighlight Zone.
But it is logical. Indeed science should explore the mysteries of creation, or a begininnig, and theologians should by no means attempt to hide behind what can't be known. A God of the Gaps so to speak. That kind of theology is based on ignorance and will never stand.
Because unless you acknowledge a designer
why bother?
I find "big bang" suggestions every bit as disatisfying as I find infinite strings of intelligent creators.
Neither rings true to me.
But I am content to say "right now, I just don't know".
OK... for the sake of argument, your designer is acknowledged.
Now where did he come from?
And you being the "one who knows", know that there is no answer to that question. That's being confrontational.
Scientists have no interest in proving a designer. They flee from the very notion. But the very laws they unearth prove otherwise.
The philosophy of logic has no problems with something being self existant. It has tremendous problems with something coming form nothing. (say for example a universe) not that logic matters when discussing science.
An endless string of continuously designing designers, each with a great complexity than his creation.
Nonsense. You've simply tried to set a logical trap and then fashion a reductio ad absurdum from it. Your vapid little exercise doesn't demonstrate that complexity is no evidence of design. You've proved nothing, except that you're unwilling to confront that issue. Go back to your pond.
He has always been. We are only relegated to time here on earth. But you knew that already....
I can see that the inability to answer the question has made you a bit testy.
Perhaps we'll speak again when you're in a better mood.
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