Stevo2 wrote:crayon851:
You're sitting on the fence. It really is black or white. But the black or white is like oranges or apples. They're different. I've posted long ago, and won't add here tonight. I'll come back soon. But I'm still impressed that this thread is still going, that's great. Keep it going until I come back.
Stevo
Only the issue of which should be taught in schools is black and white. The rest is really shades of grey, seeing you cannot prove or disprove crayon851's hypothesis.
good stuff Pauligirl. I was caught by the recent fossil lines that were found in Canada . Remember the interbreeding is in a natural population and I still stand by (although I have no evidence to support it so it fits right in this thread) that the interbreeding controls are more subtle, having to do with estrus cycles and whatever mating rituals occur. The morphological changes that are occuring are in the feet (hair obviously cause polar bear fur strands are hollow) and dentition/
This gets back to one of your earlier posta re evolution via genetic variance in the foundation species.
The Discovery Institutes William Dembski has said that his organization (well not his personallybut hes as much a spokesman as theyve got) He says that UK and Germany are targets for their infiltration.
We've been infiltrated before.We just chew 'em up and excrete the useless parts.
uh spendi cf satts post above.
farmerman wrote:This sorta sums up a good fossil record that uses climatological change as another adaptive engine
Quote:Somewhere during the mid-Pleistocene period (roughly 100,000 to 250,000 years ago), a number of brown (same as grizzly) bears (Ursos arctos) probably became isolated by glaciers. many probably perished on the ice; however, they apparently did not all disappear. Some survived due to the fact that "organisms vary" (Steve Gould's terminology and logic is used here), that is, every litter of grizzly's has a variation in coat thickness, coat color etc. which imparted a slight evolutionary advantage to some indivials of each litter. These successful individuals underwent an apparent rapid (rapid, probably because of the small population, and extreme selection pressure) series of evolutionary changes in order to survive (note they were not necessarily "better" in any absolute sense, or on any absolute "bear" scale of perfection - they were simply more in keeping with their new environment than their siblings). Today, polar bears are adapted to their harsh northern environment.
Hecht (in Chaline, 1983) describes polar bear evolution: the first "polar bear", Ursus maritimus tyrannus, was essentially a brown bear subspecies, with brown bear dimensions and brown bear teeth. Over the next 20,000 years, body size reduced and the skull elongated. As late as 10,000 years ago, polar bears still had a high frequency of brown-bear-type molars. Only recently have they developed polar-bear-type teeth.
Adaptation, is it , or is it not factored into the ID.Creationist mind? Im gonna go out on a limb here and say no.
Not sure what you're trying to incinerate with this comment.
But isn't it possible that both brown bears and polar bears have been around for the same period of time and that so-called intermediates are simply the results of interbreeding which they could and still can do? Possibly in warmer centuries the brown bears tend to travel much farther north and the polars much far south.........
real life wrote:farmerman wrote:Adaptation, is it , or is it not factored into the ID.Creationist mind? Im gonna go out on a limb here and say no.
Not sure what you're trying to incinerate with this comment.
I find the implications of that insinuation quite inflamatory.
You better watch our RL, I think FM is trying to burn that limb right out from under ya
Given the style and substance of the argument rl so far has displayed, neither rl nor argument would likely notice the limb fall away; support is not a foundational requisite for either.
Oh, and as for polar bear/brown bear interbreeding - while zoologic experiments may have determined viable, fertile offspring result, in the wild, the polar bear is cognizant of only 3 categories of thing; polar bears, non-food items, and food. Anything not a polar bear falls into one of the other two kingdoms, and only that empirically determined to be not food falls into the non-food kingdom - and even then, experiment-on-encounter often is employed to verify the categorization.
timberlandko wrote:Oh, and as for polar bear/brown bear interbreeding - while zoologic experiments may have determined viable, fertile offspring result, in the wild, the polar bear is cognizant of only 3 categories of thing; polar bears, non-food items, and food. Anything not a polar bear falls into one of the other two kingdoms, and only that empirically determined to be not food falls into the non-food kingdom - and even then, experiment-on-encounter often is employed to verify the categorization.
Are you citing any type of hard information that shows polars and browns will not mate in the wild? Or are you just basing this on your conjecture?
I can't speak for timber, but if it is conjecture: what is your refutation, real life?
Well, I tellya, rl, I'm no degreed naturalist, but I am an avid amature naturalist, and an avid hunter, and I've hunted and taken both Ursus Arctos (Arctic Brown Bear) and Ursus Maritimus (Polar Bear). I sorta make it a point to study up some on any critter I intend to hunt, to learn about their attributes and habits. I've found that to be particularly good practice when the focus of attention happens to be a very large critter, and even moreso if the critter happens also to be a carnivore.
Polar Bear females typically enter their annual 2-to3-week estrus in late winter, early spring - March/April, mostly, naturally defining the mating season. Arctic Brown Bears typically mate much later in the year, from around mid-to-late May to around early-to-mid July. Both species are solitary hunters, apart from females with young, and are extremely territorial, hardly likely to tolerate the presence of another of their own kind not of their clan, let alone another bear period regardless of gender or sub species, in their accustomed hunting range; fellowship and level-playing-field competition is not either bear's thing, by any means. The likelyhood of natural hybridization is slim at best, and I know of no such instance.
May I recommend to you:
Walker's Mammals of the World: Nowak, R, ed (2 Vols)
The Johns Hopkins University Press, Baltimore MD (6th edition June 1, 1999)
ISBN: 0801857899
The Smithsonian Book of North American Mammals: Wilson, D. and Ruff, S., eds
Smithsonian Books, Washington DC (1999)
ISBN: 1560988452
Mammals of North America: Kays, R. and Wilson, D., eds
Princeton University Press, Princeton NJ (2002)
ISBN: 0691070121
Wild Mammals of North America: Feldhammer, G., Thompson, C., and Chapman, J, eds
The Johns Hopkins University Press, Baltimore MD (2cd edition, October 2003)
ISBN: 0801874165
The Mammals of Canada: Boden, J. and Boden, E., eds
Toronto University Press, Toronto CA (1999)
ISBN 0802021379
All 5 works are considered scholarly, authoritative standards in the field, should be available through any major bookseller or library system, and all contraindicate the notion of natural hybridism occurring between Ursus Arctos and Ursus Maritimus, while interestingly each references experimental hybridization conducted under clinical conditions as matter of zoologic research.
timberlandko wrote:The likelyhood of natural hybridization is slim at best,
Well, apparently we would both have to come to the conclusion that even if this is true today (by no means an established proposition) , it wasn't necessarily true in the past.
If you take the position that one evolved from the other then there would have had to have been considerable interbreeding for a number of generations, unless you want to postulate that it all took place in one swell foop.
timberlandko wrote:and I know of no such instance.
Quite likely there are a lot of things that you aren't aware of.
No doubt one of the contributory factors to any lack of interbreeding these days would be a relative lack of contact. Makes it kinda tough, ya know. Long distance relationships never work out so well.....
Timber, thanks, that sounds like a reasonable answer to the speciation question that ros made. The speciation isolation mechanism most unbreachable appears to be estrus cycle.
rl saysQuote: If you take the position that one evolved from the other then there would have had to have been considerable interbreeding for a number of generations, unless you want to postulate that it all took place in one swell foop.
I suppose you could say that "interbreeding" occurs between the foundation species until a mating barrier occurs. The genetic diversity that conferred the first environmental advantages probably were passed down through successive variation as the geographic isolation made itself evident( the glaciation retreated). The morphological differences between polar bears and barrne ground grizzlies and brownies are still occuring as you can see from thelinks.The geologic facts that support the evolution of the polar bear have to do with a rapidly changing environment and where the polar bears v brownies are seen today.The gradual "sabretoothness" of present day polar bears and sharper grasping molars are a very recent feature and dont appear of brownies, grizzlies , blackies , cinnaminnies, or other N arboreal bears, just U maritimies
real life wrote:timberlandko wrote:The likelyhood of natural hybridization is slim at best,
Well, apparently we would both have to come to the conclusion that even if this is true today (by no means an established proposition) , it wasn't necessarily true in the past.
If you take the position that one evolved from the other then there would have had to have been considerable interbreeding for a number of generations, unless you want to postulate that it all took place in one swell foop.
Ignorant, unthinking poppycock. An isolated population is an isolated population, distinct and separated - generally by geologic, climatologic, and/or or other environmental barriers - from populations of like kind. The members of an isolated population breed with one another, not with representatives of the population(s) from which they are isolated. Thats the point of "
isolated" - non-contact with others not in like manner and location separated into a distinct, isolated population - the concept is quite simple, really not even requiring much depth of thought to grasp. Apparently, more depth of thought, however, than achieveable by some.
Prattling on, continuing in the vein of rhetorical self-immolation, rl wrote: timberlandko wrote:and I know of no such instance.
Quite likely there are a lot of things that you aren't aware of.
Given that there is much of which any individual is unaware, phrasing the obervation as was done must be construed an attempt at sarcasm. Should such be the case, the attempt failed; sarcasm must have a point.
Wrapping to a typically self-defeating conclusion, rl wrote:No doubt one of the contributory factors to any lack of interbreeding these days would be a relative lack of contact. Makes it kinda tough, ya know. Long distance relationships never work out so well.....
Indeed. As referenced above, that is the deal with isolated populations.
In the website I provided on brown bears this little tidbit appeared;
Quote:Subspecies
There are few recognized subspecies of brown bear, despite their incredible diversity. Only two subspecies of brown bear are recognized: Ursus arctos horribilis, which includes all brown bears except those living on the Alaskan islands of Kodiak, Shuyak and Afognak, which are recognized as the subspecies Ursus arctos middendorffi. Some researchers recognize other subspecies, such as the European brown bear (U. a. arctos), the Hokkaido brown bear (U. a. yesoensis) in Japan, the Siberian bear (U. a. beringianus), the red bear (U. a. isabellinus) of northern India and the Himalayas, the Manchurian bear (U. a. manchuricus), the horse bear (U. a. pruinosus) of Tibet, Sichuan and western China, the Baja bear (U. a. californicus), and the Mexican bear (U. a. nelsoni) which became extinct in the 1920's. The Syrian bear (U. a. syriacus), which ranged from Asia Minor to Iran, became extinct in 1932. Here is a listing of other mentioned subspecies of brown bear. Due to their incredibly wide range, it is likely there are many more subspecies than are currently recognized.
Now if a subspecies were isolated long enough could it not become, over time, a species of its own? Once the isolation takes place the inbreeding between two subspecies would come to an end.
Thats pretty much what happens, xingu, though its not a matter of breeding between or among sub species; the isolated population becomes a sub species.
isolation need not mean physical separation in all cases. Ring species are those that are proximally located and spread out so that each small modifcationIincluding behavioral) becomes a cumulative isolating mechanism for end members .In small populations genetic drift accounts for much of the acquisition of end member status.
