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Fri 27 Jul, 2007 01:50 pm
I'm having trouble forming this question... but here goes...
Do any animals today have living ancestors of a different species?
For example, Horses evolved from Eohippus. But Eohippus no longer exists. IF Eohippus did currently exist, then Horses would be examples of species which currently coexists with a different ancestral species.
Are there any species alive today which coexist with a different species which is considered ancestral to them.
I'm guessing that IF a "Living Fossil" species had a line which branched off from them ages ago, then the branch species might be an example of what I'm asking about.
Thanks,
Interesting Q. I'd start looking at reptiles first.
I'm guessing you could find some examples among domesticated animals -- the most obvious (the dog) being debatable about whether the dog and wolf are different species.
I don't know how you'd make the determination.
For example, there are about 100 species within the order Didelphimorphia (Western Hemisphere Opposums) but which one is the original? There are claims that the Virginia Oppossum is the original "living fossil" within the order but that is unproven thusfar.
I'd think it would be easier to find an example amongst the bacteria or Fungi than the animals.
patiodog wrote:I'm guessing you could find some examples among domesticated animals -- the most obvious (the dog) being debatable about whether the dog and wolf are different species.
I think dogs and wolves are still considered the same species.
Dogs and wolves can successfully interbreed, in that they produce sexually viable offspring. Given the relationship of man and wolf, it would be doubtful to say that wolves are sexually isolated.
How about the
coelacanth? I'm not going to bother to read all the link, but perhaps they have some living descendants.
Let me change the flavor of the question a bit...
Could it be that there is no species alive today, who's parent species still exists in a relatively unaltered form?
Chambered Nautili are a very ancient species, relatively unchanged for millions of years. Did no population of Chambered Nautili ever branch off to become a new species (which might be alive today)?
Sharks.... same question. Dragonflies... Did none of them ever produce descendent lines which formed a new species alive today?
aan organism that may have a chance to display its founder species may be one that was rafted away as continents broke up. (I cant think of any though) The ratite birds have an ancestral relationship to each other from their Pamgean origin. However, is there an "ancestral form"? Im not so sure.
There are a few species that have either remained dtatic or have been rediscovered after "going missing for a few tens of millions of years" These we call "lazarus species" not living fossils. They include the Coelecanth, the Dawn Redwood,Horshoe crab (limulus) mymmaromatid wasps (little tiny guys that are in the fossil record in Eocene amber) just one species of the wasps remains.
AS you can see, Im only able to cojure up those species that are fairly identical to their original ancestor. These species have, for whatever reasons, not undergone much morphological change. The horshoe crab has derived from a number of fossil forms that resemble(nut are not identical , to the living Limulus). In that respect, the derived species is not "its own ancestor"
Creationists will state that giant cockroaches and dragonflies of the PEnnsylvanian are just larger formsof present day insects and therefore do NOT evidence any evolution. However, the big ones are still dead and we have (over 250 million years) reatained similar body plans with some notable size differentiation.
I cant think of any case where the "common ancestor" of two or more descendant species still is hanging around.. In the case of LAzarus species we have an almost identical derived form freom its fossil ancestor. (Even though, in most cases like the Coelecanth, the original number of species of that genera were much larger (like about 7 or 8) . Now, what weve got left, even after a disappearance from the interim fossil record since the Cretaceous, is only 2 species of Coelecnth. The paleontologists have been able to ferret out a reason why there is an apparent absence in the dossil record for the Coelecanth. Its ancestral forms were specially adapted to an area of Gondwana that , when it broke up, was "on the trailing edges of two splitting continents. So the environments were not conducive to the Latemerias needs. It had, apparently, remained in a series of small deep water areas in and around the area between Madagascar and Afar , and in the Sunda deeps...
I hope someone can come up with some species worth discussingin light of your question ros. Im stumped. (and Ill go out on a limb to say that were gonna be hard pressed to find some)
The term ancestor and descendant are a little weird. I don't think that they are appropriate terms.
For example lets say that species A existed 10 thousand years ago.
Let's say now there exist species B and species C... both of which descended from species A.
Of B and C (the two species that exist now) how do you decide which is the ancestor and which is the descendant?
Are you really proposing that one of the two modern species won't have gone through any genetic changes... while the other has?
I think this is highly doubtful.
I don't think the question makes sense.
Setanta wrote:How about the
coelacanth? I'm not going to bother to read all the link, but perhaps they have some living descendants.
This might be right. I'll have to do a bit of reading.
The family tree diagram seems to show the Coelacanth as being 'in the line' for both lungfishes and land vertebrates. Which would mean that the Coelacanth is not just a living fossil, but also our living ancestor.
However, the diagram is not very detailed, it could be that the coelacanth merely has a common ancestor back in that line. I can't tell from the diagram yet.
Quote: Chambered Nautili are a very ancient species, relatively unchanged for millions of years. Did no population of Chambered Nautili ever branch off to become a new species
Chambered nautilii have displayed one of the most perfect sequences of "suture and chamber evolution" of any of the cephalopods. The nautiloids are found rom the CAmbrian through the present(with their "heyday" in the late paleozoic). We use the derived chamber and suture development to actually date the sediments in which we find the nautiloids. Theyre stratigraphic record is that good. Ammonoids branched off the NAutiloids but they died out in the early Paleocene. Nautiloids are good indicators of large open water bodies and sediment layers from large open water bodies. So we look for industrial minerals like Trona or K salts along margins where there are nautiloids finds. Simple detective tool.
farmerman wrote:I hope someone can come up with some species worth discussingin light of your question ros. Im stumped. (and Ill go out on a limb to say that were gonna be hard pressed to find some)
The Coelacanth is the closest thing I can think of so far. And maybe 'close enough' is 'good enough' to answer my question.
Mostly I was surprised when I began to realize just how rare it was for a founder species to coexist with a descendant species (or phylum or genus or whatever). I thought maybe I was missing something. And maybe I still am.
Life erases its ancestral trail as it develops. Those few species which have remained relatively unchanged over eons don't seem to produce offshoots very often either. So it's not just a matter of old forms surviving, it's also that they don't tend to create branches.
Is it purely coincidence that forms which survive a long time also don't produce new varieties? Or is the fact that they don't produce new varieties the very reason they survive so long.
Dont fall into a common misconception about Coelecanths there ros. The soft tissue analyses and DNA evidence has shown that these fish were from a group that divereged separately from the group of lobe finned fish that are most closely ancestral to tetrapods.
Go over to Dartmouth and , in the Library , they ahve the TREATISE ON PALEONTOLOGY. (Many volumes) You will find the complex relationship of the manyfossil species of LAtemeria and the 2 remaining .
Continental Drift is the primary reason we dont see these guys in Cenozoic sediments
Bollocks.
The reason we dont see these guys in Cenozoic sediments is that they had an IQ of 0.000001 and were ugly bastards to boot and thus, with feminine delicacy being what it is, were selected out.
Anybody with an IQ of 180 and the looks of Leo Vincey would have caused a frenzy to which continental drift, an inch or two a year, would have been a very minor difficulty. Tending, mathematically, to zero.
I would only say that the assertion-
Quote:The soft tissue analyses and DNA evidence has shown that these fish were from a group that divereged separately from the group of lobe finned fish that are most closely ancestral to tetrapods.
really is in need of the phrase " been said to have" in between the "has" and the "shown" in order to make even a modicum of sense intellectually.
As it stands it is merely another assertion which serves to reinforce our settled view that fm sticks to self flattery techniques like **** to a blanket.
farmerman wrote:Dont fall into a common misconception about Coelecanths there ros. The soft tissue analyses and DNA evidence has shown that these fish were from a group that divereged separately from the group of lobe finned fish that are most closely ancestral to tetrapods.
I never expected to find a species which was 'exactly' in the line of descent, but was more interested in the general aspect of the question.
I'm sure Coelacanths are somewhere off the line, but they are about as close to what I was looking for as anyone has suggested yet.
Do you think the 'living fossil' species are the way they are precisely because they didn't produce any offshoot species?
spendius wrote:Bollocks.
The reason we dont see these guys in Cenozoic sediments is that they had an IQ of 0.000001 and were ugly bastards to boot and thus, with feminine delicacy being what it is, were selected out.
Please don't pollute this thread.
Thank you.
This might be ignorant, but aren't birds descendents of dinosaurs, which are a lizard?
And birds and lizards co-exist today.
Is this what you're talking about?
Chai wrote:This might be ignorant, but aren't birds descendents of dinosaurs, which are a lizard?
And birds and lizards co-exist today.
Is this what you're talking about?
It's not ignorant, you're on the right track.
But I consider modern lizards to be too far distant from their ancestral kin to fit the type of ancestor I'm looking for.
Every living organism is a cousin to every other organism at some distant level. I was more looking for things which were along the same line of descent.
ros wrote-
Quote:Please don't pollute this thread.
I was simply making a point Darwin makes many times. If I used a more modern literary technique than you can cope with it does not represent the pollution of the thread. It represents the process which takes place from the anti-IDers point of view.
I can't understand what you're squawking about.
An article that hits on this very issue from CNN today:
Quote:Study: Dinosaurs coexisted with their ancestors
WASHINGTON (AP) -- Dinosaurs shared the Earth for millions of years with the species that were their ancestors, a new study concludes.
Dinosaurs arose in the Late Triassic, between 235 million and 200 million years ago, and came to dominate the planet in the Jurassic, 200 million to 120 million years ago.
Scientists had thought the dinosaurs rapidly replaced their ancestor species. Indeed, until 2003, when a creature called Silesaurus was discovered in Poland, no dinosaur precursors had been found from the Late Triassic.
Now, researchers report in the journal Science they have evidence from northern New Mexico that dinosaurs and their precursor species coexisted for tens of millions of years.
Matthew T. Carrano, curator of dinosauria at the Smithsonian's National Museum of Natural History, said there has been a long-standing debate over whether dinosaurs replaced earlier species gradually or suddenly.
"What they have is a snapshot of the transition, and it's clear there is a persistent environment with dinosaurs and these other older animals. So, at least in this place in the southwestern U.S., it was not abrupt," said Carrano, who was not part of the research team.
"Finding dinosaur precursors ... together with dinosaurs tells us something about the pace of changeover. If there was any competition between the precursors and dinosaurs, then it was a very prolonged competition," Randall Irmis, a graduate student at the University of California, Berkeley and co-author of the report, said in a statement.
The team reported finding 1,300 fossil specimens, including several complete bones, at Hayden Quarry at Ghost Ranch, an area made famous through the paintings of Georgia O'Keeffe.
There were no complete skeletons, and researchers are continuing to work at the site.
Their finds included bones from both early dinosaurs and dinosaur precursors as well as remains of crocodile ancestors, fish and amphibians, all dating between 220 million and 210 million years ago.
Included were leg bones of the carnivorous Chindesaurus bryansmalli, a close relative of the Coelophysis, a well-known Triassic dinosaur. They said both walked on two legs, reminiscent of the much later Velociraptor depicted in the film "Jurassic Park."
They also found remains of a Dromomeron romeri, a relative of the 235 million-year-old Argentinian middle Triassic precursor called Lagerpeton. Dromomeron was between three and five feet long, the authors concluded.
Another discovery was an unnamed, four-footed beaked grazer about three times the size of Dromomeron, they said.
The research was funded by the National Geographic Society, the Theodore Roosevelt Memorial Fund and the Jurassic Foundation.
http://www.cnn.com/2007/TECH/science/07/20/dino.ancestors.ap/index.html
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