Kindest Regards, gluadys!
I wanted to take a moment and let you know I am researching a response. I have gone through a lot of information, but I have a great deal more to go through yet to post a proper reply.
gluadys said:
The question is, given the processes used by evolution, why would you expect any other result? This goes back to understanding the branching nature of evolution. Once that is firmly in mind, this becomes a red herring question.
This had to do with fruit flies remaining fruit flies, meaning that they are still generally capable of "interbreeding." At some point, the "evolved" species is no longer fruit fly, at which point I would be satisfied the qualification of distinct speciation would have occurred. That is the basis of my comment, which I hope resolves the red herring.
Populations which do not inter-breed are effectively separate species.
Granted. Isolation, for example, can cause species to adapt. Some of the material I covered demonstrated where isolated "species" were artificially reintroduced and began hybridizing. This is not "true" or possible in all instances, but there are enough "exceptions" to give pause in consideration. I do not have my research in front of me to properly quote, but one example that stood out to me was that of the wild horse mating with the domestic horse, and producing viable offspring, even though the wild horse has two more genes than the domestic.
If you go to
www.talkorigins.org and type "speciation" into their search engine, you can bring up a document called "Observed Instances of Speciation" which gives more detail on fruit fly speciation and speciation in other organisms. Part of the document called "29+ Evidences for Macro-evolution also gives details of field and labratory instances of speciation."
I did go here, and I printed out some information, which I will go through when I can.
Actually, as Darwin correctly observed in the first chapter of Origin of Species, if you want to get a new species, hybridization is not the best way to go about it. Mendel's work confirmed this. The first generation may be quite uniform and have all the good qualities you want to combine. But when you mate the individuals in the first generation to produce the next, genetic sorting re-aligns the characteristics so that you get a variety of results. And eventually, without careful control of the stock, it tends to revert to its wild form.
I haven't read Darwin yet. Mental block, I'm sure. Perhaps one day. If I recall my high school biology class, Mendel was the monk who raised petunias to demonstrate genetic disposition (dominant and recessive genes). I also recall reading somewhere that he also fudged an awful lot of his data to make his point. My point being that "recessive" is not necessarily "submissive", perhaps just unexpressed individualization.
Controlled hybridization has produced many of the domesticated varieties we are familiar with. I cannot refute your comment, but selective breeding has served humanity well over the course of 4 to 5 thousand years of agriculture and animal husbandry. Left to their own devices, what you say about reversion is true. Yet, through selective breeding, as explained by the teacher in the aforementioned biology class using a mathematical model that I do not fully understand, he explained that a new "breed" could be created after something like 12 generations. Even after only 6 generations, the preferred genetic disposition was the dominant expression, provided the breeding stock was carefully selected and controlled. In effect, this is how the various breeds of dogs and cats were and are bred, as well until recently the majority of agricultural crops and livestock.
The more effective way to get new species is through allopatric speciation. Start with one species. Divide it into groups. Put each group into a different environment. Let it remain there for several generations until it is adapted to that environment. Chances are that when you compare them with each other and with the original, you will find you now have several different species, each with its own distinct characteristics.
Certainly. This is the mechanism used throughout nature. The example that immediately comes to mind is the blind cave fish. I don't know what stock it comes from, but the supposition is that after being trapped in a dark cave they lost the need for sight, so their eyes degenerated and now they no longer have the capacity to see. This is an adaptation, as presumably they have acquired other means to navigate (they do well enough in an aquarium). I do not know if they can mate with the parent stock.
It is true that hybridization sometimes gives a new species, but it is a rarer occurrence.
The example I looked at concerning a weed in England specifically pointed out a natural hybridization between two "native" or "naturalized" (related) species. Another example, controlled, crossed a radish with a cabbage (in Russia). The result was not worthwhile, producing the leaves of the radish with the root of the cabbage, but the two were distinct and unrelated species (or at the least not anywhere near closely related, radish is not in the brassica family).
While natural hybridization may not be the prevalent form, it does occur.
Actually, the fact that they freely cross-pollinate means they are NOT separate species, but varieties of the same species, just as terriers and poodles are varieties of one canine species: the domestic dog.
Another collection of information I looked at considered the development of the domestic dog from wild stock. After considering wolves, dingos, hyenas, coyotes and foxes, the research concluded that domestic dogs came from 4 distinct lines of the wolf, from different places in the world. The influence of the coyote and the others was dismissed by the conclusions. And the 4 lines of wolf are distinct, and at best only very distantly related. It was also concluded that fresh influx of "wild" blood from time to time came back into the domestic lineages. But, as far as I know, other than the problematics of size, all dogs are capable of interbreeding.
Actually, I think I have Vajradhara to thank for pointing me to the bulk of the information I have presented to this point.
As the taxonomy below shows, cabbage, broccoli, kale, kohlrabi and brussel sprouts are all varieties of Brassica oleracea a species of mustard. Each has been bred by human gardeners for its particular characteristics.
Brassica oleracea
Brassica oleracea var. acephala (kale)
Brassica oleracea var. alboglabra (Chinese kale)
Brassica oleracea var. botrytis (cauliflower)
Brassica oleracea var. capitata (cabbage)
Brassica oleracea var. gemmifera (brussel sprouts)
Brassica oleracea var. gongylodes (kohlrabi)
Brassica oleracea var. italica (asparagus broccoli)
Brassica oleracea var. medullosa (marrow-stem kale)
Brassica oleracea var. oleracea
Brassica oleracea var. ramosa (perennial kale)
You are correct, brassica is the scientific latin nomenclature. Cole is the colloquial nomenclature. I am not incorrect. Check the Old Farmer's Almanac or Organic Gardening or Mother Earth News.
Yes, good example both of the possibility of hybridization between closely related species, and of the limitations.
This dealt with sterility. And yes, it is a common problem with hybrids. Yet some of the research I looked at concluded that even among typically sterile offspring, it is quite common for an occasional virile offspring to occur. I concede that "occasional" is not conducive to natural selection, certainly not to abundant regeneration, but it does occur naturally. Adaptation and individualization.
Of course, biotechnology could not even be conceived without the fact of common descent.
All life shares genomic traits. Which is why deliberate genomic interference can occur in a laboratory setting. Which is why jellyfish can be deliberately mixed with rabbits, flounders with strawberries and tomatoes, bacillus (sp?) thurigensis with corn, and radishes with cabbages.
For sexually reproducing species, the definition of species is related to the ability to mate and reproduce. If Alba can mate and reproduce with other rabbits of her species, then Alba is not a new species.
That is why she is kept under wraps, to keep her from accidentally introducing the genomic manipulation into the natural system.
Adaptation is a consequence of natural selection. Adaptation does not generally occur all at once in a single generation. It takes place through the accumulation of successive variations by natural selection. A species which has become fully adapted to its environment may have become a different species than the one that first migrated into the same environment.
Some of the examples I looked at demonstrate this, like creatures stranded in an island environment, adapt to their surroundings (or perish, in which case we would not be discussing them). Some of them do change, very quickly, in the space of a very few generations, such as the English moths. This isn't hard to recognize when one sees the inherent differences in specific individuals. We would tend to look at moths as being moths (they all look the same to me...), but each individual has subtle differences. Like humans, short/tall, thin/stocky, fair skin/dark skin, fine hair/thick hair. Sorry for the shift in example, but I am not familiar with dissimilarities in moth populations. If a specific trait shows an advantage in survivability, that trait becomes more dominant in the gene pool of that species. Like changing color from light to dark in the case of the moths. There always were dark individuals, but they were the minority in the population prior to the industrial revolution. Against the soot that built up on everything, the light moths stood out and became better prey. The dark colored ones gained ascendency not through
change per se, but through a greater percentage of dark color being able to survive in the new environment. Adaptation, but both colors were already in existence in the population, before and after the transition stage.
Another consideration occurred to me, thinking of humans. The races are quickly becoming one. A poet and frequent guest speaker on PBS, Richard Rodriguez, pointed out a few months ago what he calls "the browning of America." As we become more racially tolerant and intermingled, we are becoming more the same. Yet I thought evolution was the divergence of populations? Perhaps an isolated circumstance, but considering it directly involves humanity, it is an exception worth great consideration. (LOL, evolution meets anthropology through philosophy!)
Adaptation, in and of itself requires a change in the distribution of gene alleles in the population. And that is the classic definition of evolution used today "A change in the distribution of alleles in a population that transcends generations."
Yes, but that distribution is throughout the species as a whole, at least in the case of the moths. The differing alleles were already distributed, as individualizations, throughout the population, in greater and lesser quantities.
When such changes also lead to speciation, that is unquestionably evolution.
Then why does a fruit fly remain a fruit fly? The herring has changed color. If it became a distinct "other", it would be an evident "species," but as long as it remains a fruit fly capable of interbreeding, it is merely an adaptation. Choosing not to interbreed given choice, might lead as you indicate, at which point I could humbly concede. Even in looking at the fruit fly info, the choice not to breed with the parent stock was not the indicator, it was a differentiation or individualization that was highlighted in a specific population. In limited populations, I seem to recall a reversion to interbreeding with the non-preferred species, although I will be hard pressed to find that in the info.
The balance of the conversation dealt with crocs and turtles, and I printed that material out just today and haven't had the oppportunity to go through it with any detail. The croc line, I did read, was the predecessor to and ancestor of one of the major lines of
dinosaurs, and yet managed to outlive an entire evolutionary branch? The mega-crocs died out, but the several species composing today's crocodiles, alligators and caimans, is largely unchanged since long before the dino-extinction, something like 120 million years ago. These are the creatures supposed to have made the transition from water to land, some of the original amphibians.
Thank you very much for your input. You have made me do my homework. I am still having trouble accepting the establishment doctrine concerning evolutionary theory, and there is much more that impinges on that mental outlook. Adaptation is a viable and recognized and demonstrated act of nature. Crossing the boundary from one species into another is not demonstrated to my satisfaction, at least not in the sense of not being able to interbreed.
