Science Forums 2

[Michaelangelica]

Originally Posted by Eclogite

Death is the mechanism by which natural selection works on the individual. Extinction if the mechanism by which natural selection works on the species, or higher taxonomic group.

I sense this is a major stumbling block for you, but I am not quite sure why. It should be the keystone of the concept, yet you are seeing it as a negative.

Diversity is good for the survival of any species
Agreed?
Why does "Natural Selection" work against diversity?

Look at it like this:

Fitness = Life
Unfitness = Death

Again my problem is with the circular nature of the argument.
a good model should be able to PREDICT. Natural selection just conveniently "explains" everything after the event[/QUOTE].[/QUOTE]
I don't like the words "fit" and unfit" as they imply a value judgement. No such judgement, choice or selection is being consciously made.

On a second point, evolution is not seen today as being purely the result of natural selection. Genetic drift and factors such as gene flow, or genetic recombination of various sorts, are also clearly understood to play an important role. These aspects are fundamental to the modern synthesis of Darwinism.
In addition, other factors are slowly being recognised as playing a role. Recent research has demonstrated that speciation through hybridisation is much more common than originally thought. The potential for environmental factors to effect the expression of genes in offspring has been recognised

.[/QUOTE][/QUOTE]
Thanks for this. When I started this barney I was not aware that there had been "tweeks' in the system.
I feel 'it' needs these, and probably many more, especially to explain bacterial "evolution"
Non religious sane info on "tweeking' Darwin is hard to find among the religious hysteria however I did find this article which was of interest:-

the challenge to evolutionary thinking in recent decades from advocates of Intelligent Design and creationism have impelled many scientists to band together in defense of Darwin's ideas, shoving alternative theories to the background.

It seems the attack from the fundamentalist right has stymied the evolution of evolutionary theory (pardon the pun)


This following is an obvious overstatement to attract attention, but perhaps that is necessary

Darwin was wrong, and his modern-day adherents perpetuate his mistakes.

That sounds like the opening salvo of an advocate for Intelligent Design or some other religiously driven critique of the theory of evolution.

But it actually summarizes the ideas of Jeffrey Schwartz, a noted anthropologist at the University of Pittsburgh and one of a growing group of critics of standard Darwinian theory.

Here are his criticisms of two aspects of Darwin's theory.
http://www.post-gazette.com/pg/06149/694046-85.stm

In criticizing Darwin, Dr. Schwartz does not dispute his theory that humans, animals and plants evolved from other species.
In fact, one of his books, "The Red Ape," argues that orangutans, not chimpanzees, are the closest evolutionary relatives of human beings.

He does take issue with two key parts of traditional Darwinian thinking, though -- gradualism and adaptation.

Gradualism holds that new species evolve from their ancestors through tiny, incremental changes.
Adaptation says those changes come in response to shifting conditions in the environment.

"We have abundant evidence," Darwin wrote in one of his books, "of the constant occurrence under nature of slight individual differences of the most diversified kinds; and we are thus led to conclude that species have generally originated by the natural selection of extremely slight differences."

Dr. Schwartz said he has two problems with that view.

First, if evolution were gradual, there should be a record of continuous changes in prehistoric fossils, but there are many gaps between species in the fossil record.

Darwin said it was simply bad fortune that those intermediate fossils were missing. Scientific creationists have used the fossil gaps to argue that God created species separately, as described in the Book of Genesis.

But there is another possibility, Dr. Schwartz said. There isn't a huge number of missing transitional fossils because they were never there in the first place. Instead, new species emerged suddenly due to genetic alterations that created sharp differences with their predecessors.

Another problem with gradualism, he argued, is that it suggests that complex structures, such as a vertebrate's eyes or a mammal's mammary glands, had thousands of slightly different precursors in earlier creatures. That defies logic, he said. Modern evolutionary thinkers like Niles Eldredge and the late Stephen Jay Gould dealt with the fossil gaps by coming up with the theory of "punctuated equilibrium." Creatures evolved pretty much the way Darwin had described, they said, but not at a steady pace. Sometimes there would be fallow periods; sometimes there would be profligate explosions of new species.

That concept still embraced the idea of adaptation, though, Dr. Schwartz said -- that changes in environmental conditions drive "natural selection" by favoring the survival of species best suited to those conditions.

He has an alternative view.

Dr. Schwartz contends that new organisms are probably generated by random changes in developmental genes, and that any new features they have will remain in existence as long as they don't hurt the creatures' chances of survival.

"Basically," he said, "if a feature doesn't kill you, you'll continue to have it."

Rather than the environment causing species to change by favoring one type of creature over another, he said, it's just as likely that a creature produced by random evolution can survive in different environments.

His favorite example is the mongoose lemur, found on Madagascar and the Comoros Islands off the coast of Africa. On Madagascar, these lemurs are active in the day, eat fruits and leaves and travel around on the ground. In the Comoros, they are active at night, stay in trees, and feed by hanging upside down from their hind feet to suck nectar out of flowers.

"This kind of shift is actually quite common," he said. "These lemurs have the same teeth, the same feet, the same eyes, but if the environment changes, they change their activity and their diet, not their anatomy."