Quote:
Originally Posted by raveneye
Well this is a bit misleading. . . . If we're anthropomorphizing a plant (implying here that it doesn't want to pass on potentially destructive genes) I think we should at least limit that sentiment to the plant's interests. The plant doesn't "care" if it contains a gene that might harm somebody that's going to eat it. Or, to put it more officially, there is no selective advantage for a plant to evolve mating avoidance with another individual containing genes that are detrimental to potential herbivores. There certainly is selection to avoid mating with individuals containing genes that might reduce the fitness of that particular plant, yes. How effective that selection is in practice (ie "reinforcement") is one of the big disputes right now in plant evolutionary biology. But there is nothing in nature that "tries" to prevent dangerous genes from being passed on, until those genes actually exert an effect in an individual that reduces its personal fitness. If harming a herbivore doesn't reduce a plant's fitness, then there's nothing to prevent that plant's descendents from obtaining such a gene from a mate.
Actually plants hybridize all over the place. About half of all plant species evolved through hybridization followed by polyploidy. In fact if you draw an evolutionary "tree" of most plant groups, it looks more like a net than a tree. Many plant genera are cross compatible.
But nevertheless, the fact that there are genetic barriers to hybridization is really not pertinent to the question of whether new anti-herbivore or human toxicity can evolve in a plant species "naturally"; such barriers never evolved to prevent evolution of anti-mammal toxicity. And further, there is tremendous variation within widespread species in secondary chemical defenses; any particular plant could gain many new toxicities by mating widely enough even staying within its taxonomic species.
The popular view seems to be: the more genetically distant two parents are, the more "dangerous" it is (to humans) to mix their genes. I really know of no biological evidence that could be used to support this view. I don't see any reason to believe that a natural cross of two individuals within a species is any less likely to produce a new kind of toxicity to humans than inserting a single gene from another species, no matter how distant. In fact, the natural cross is far more likely to produce an individual radically different from its parents (since 10s of thousands of genes are being mixed in random combinations) than the transfer of a single gene.
I think there is a lot of fear of the unknown packaged into this popular view.
I also say, full speed ahead on all these technologies.
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You are arguing against a strawman, perhaps because you laced your assumption about what I was talking about into your response. I never made any statement regarding herbivores' safety in my initial statement.
I simply stated that when plants hybridize there are a number of natural barriers to prevent incompatible partners from mating. Those barriers can be circumvented in the lab. While two plants mating (and they certainly do mate, I'm not and never did attribute human traits and motivations to their crossbreeding tendencies) may produce a highly toxic result, that is neither here nor there in relation to my argument. I wasn't saying that artificial breeding programs will necessarily produce harm to humans and my opposition to eating genetically manipulated foods does not rest on that sentiment.
What I wrote was that comparing lab manipulation with natural crossbreeding is specious. Any kinds of natural checks that might otherwise prevent something from occurring can be circumvented in the lab. We don't necessarily know the results of our actions until we have decoded the DNA. Genetically manipulated food is not "safe" to humans or the environemtn, it's status is "unknown." For all the people who profess to operate in some scientific capacity on this board, you ought to reconsider your strong stance against those of us who argue more research ought to be conducted on the implications of manipulating genetic structures without knowing the results of one's actions before proclaiming "full steam ahead."
EDIT: I want to clarify something in regards to your claim that I was anthropomorphizing plants. You read me as writing that plants won't produce something toxic to herbivores in the wild. I actually meant that plants won't hybridize into something that can not reproduce. That is, they will not produce offspring that are harmful to the species itself. In the lab, those checks can be circumvented and we can produce wheat, for example, that can breed with other plants and render entire crops sterile. Evolution is for the most part a lenghty process wherein the organism develops and reproduces within the context around it. The lab, unless it mimics the context, renders those kinds of natural limitations on what might come out of a given set of parents inconsequential--in effect leapfrogging one or more steps that might have otherwise prevented the intended organism from coming about.
Oh yeah, and I voted for "absolutely, show me where to fund it."
as I stated already, I am all for research and deciphering what is going on in these black boxes. Implementing policy without knowing what the ramifications are is where I draw the line.