CTB wrote:
CTB wrote:
Notwithstanding the fact that Wilson was not without critcs (the likes of Steven Jay Gould amongst them) to the theories you quote, you are making a huge leap in flawed logic here; if we are indeed in a naturally-occurring mass-extinction event, how can it possibly be due to human activity?
Comrade Shampanyov wrote:
Loss of habitat.
What's that got to do with climate change though? That's the point of the thread afterall.
I've never said that the current mass extinction event is due to climate change. I have said that we will lose more species as a result of climate change. And as long as humanity is appropriating the Earth's landmass for itself, new species won't be able to evolve to replace the lost species, simply because those habitats are being converted to human use.
CTB wrote:
The fossil record implies accelerated speciation could be a result of dynamic climatic conditions, so pairing habitat loss with climate change seems a flawed argument to me; that's the point I'm trying to make.
I agree about accelerated speciation , except that we're interfering with the process now. For example, how likely is it that, if the habitat existed-- a big if, considering that species are dieing off because we're appropriating their habitat-- we would "allow" a species like the sabre-tooth tiger to evolve in, say, London, or New York? Not very likely.
That problem-- ot wanting certain species in the first place-- aside, the real problem is lack of habitat. We're converting habitat to human use, and that is why species are dieing off, and if the habitat no longer exists, then there is no niche for newly evolved species to fill. Thus, because there is no niche to fill, new species won't evolve.
Well, new species of cockroach and rat might, but that's hardly a consolation for the loss of all of the other species
CTB wrote:
No argument whatsoever that humans have had a huge impact on habitat loss, (and to a lesser degree, the creation of habitats too - check out your local landfill for a species-rich habitat).
The Holocene Mass-extinction Theory which apparently explains the current extinctions and the extinction of the Megafauna puts a bit of a downer on the idea that human activity is responsible for the 'current' extinction event - not a lot of petrochemical usage in the Pleistocene that I was aware of.
Comrade Shampanyov wrote:
I'm relying on memory here, but I believe that the two main factors driving the Pleistocene megafauna extinctions were climate change and human hunting.
Very contentious area of research, with many theories. However, would you consider the possibility that the same climate change you cite here as contributing to the megafaunal extinction is part of the current climatic phenomena?
I think it's background noise that's been completely drowned out by human activity.
CTB wrote:
But what is the source of this genetic variation? No dispute at all that natural selection of the best fit drives evolution, but the genetic variation responsible for it is initiated by mutations, which isn't exactly a "highly overstated importance". Since Wiki has been cited before, you'll find this summary fairly sound: "Most biologists believe that adaptation occurs through the accumulation of many mutations of small effect. However, macromutation is an alternative process for adaptation that involves a single, very large-scale mutation." (this is a quote from here)
Comrade Shampanyov wrote:
As I understand it, variation is the result of genetic recombination. Sex for the rest of you lot. We're carrying around a lot of information within our genes, some of which is expressed physically, because those alleles are dominant, and some of which is passed on to the next generation, perhaps to appear as a physical expression if the next genetic recombination works out that way. If genetic variation is expressed in Boatraceface through an extraordinarily large cock that splits his foreskin, and in other Redcar males with varying cock sizes--some extraordinarily small, some extraordinarily average-- and if that extraordinarily large cock gives Boatraceface some survival advantage, he will pass that trait on to his offspring, and if that gives them a survival advantage, they will pass that trait on to their offspring. Eventually, all male inhabitants of Redcar will have extraordinarily large cocks.
I'm really reluctant to continue with the analogy of Boaty's cock here, but what you are describing is the inheritance and expression of genes already in existence in the genepool. The point I'm getting at is that mutations add new characteristics to this genepool spontaneously that are not an effect of recombination of exiting characteristics. For example a mutation that is expressed as, say, males having two cocks (stay with me here). If this 2-knob characteristic is expressed and turns out to be a survival advantage (can't think of one just yet, would make post-pub weeing a nightmare), then they will pass that trait on to their offspring, etc.
No dispute over the process itself, though.
OK, fair enough point.
But I think in the larger scheme of things, it's the variation all of us carry within us that drives most of natural selection. For example, getting away from cocks and going back to red beaks/yellow beaks, within a population of birds there may be a range of alleles that allow for beak color ranging from pale yellow to bright red. Most birds in that population will have medium yellow beaks. Some will have slightly paler yellow beaks, and some will have slightly more orange beaks. That's the variation in phenotypes (the physical expression of the genes.). But a bird with a yellow beak may have recessive genes for a pale yellow beak, while another bird with a yellow beak may have recessive genes for an orange beak. Occasionally, offspring will be born with those phenotypes (pale yellow beak, orange beak.). If the orange beak confers some sort of advantage to those offspring, possibly as a result of changing environmental conditions, then that bird's offspring will be more likely to survive to reproduce, and the alleles for orange beak will be passed on to another generation. If orange beak continues to be an advantage, over time, more and more of the population will have the orange beak phenotype.
As I understand it, that is a far more common mechanism for evolution than mutation, which more often than not is unsuccessful.
CTB wrote:
I was just trying to demonstrate what I regards as the overimportance placed on human 'non-natural' activity. Humans are after all just another form of life endemic to the earth, so by definition our activities, for better or worse, can never be regarded as unnatural.
Comrade Shampanyov wrote:
It's still an unnecessary-- and preventable-- occurrence. The difference between the previous 5 extinction events and this one is that for the first time, mass extinction is occurring through the activities of one of Earth's species.
Once again, depends on how much credence you put in the mass extinction theory. I think of it more as yes, we are able to recognise that it is a preventable occurence, but is it an innate characteristic of humans to do anything to prevent it? This is getting more philosophical than scientific, but it's still interesting to discuss.
Well, according to the Gaia hypothesis, the Earth functions as an organism (this may have analogy to some Asian religions that focus on the "one-ness" of all things.). So on the one hand, one could say that humans altering the climate is a natural process. And if it's a harmful process, Gaia will respond in ways to counter that. Perhaps in ways that snuff out the human species. or perhaps, the "green" counter to the threat of climate change is also a part of nature-- Gaia's response.
As long as we're getting philosophical.... :)