Darwin re-visited

[CraigD]

Homosexuals do not pass on their genes.

This is a logical conclusion only if one assumes that all homosexuals never have heterosexual sex. This assumption is not supported by my experience – Of the roughly 20 males I personally know who have acknowledged to me that they are homosexual, 4 of them have fathered at least 1 child. I only know 10 women who have acknowledged to me that they are homosexual, 4 of whom have born at least one child.

 

I’ve discussed the details of parenthood with only a few homosexuals, most of them male. Several had children while in heterosexual relationships, before “coming out” and adopting a nearly or fully homosexual life style. One had a child as the result of a single sexual encounter with a female friend. A male homosexual couple and a female homosexual couple I know had child by way of a complicated agreement. None had children via artificial inseminated “surrogacy”, though I understand that this is sometimes done.

 

None of the children of homosexuals who I know are, to my knowledge, homosexuals.

 

It appears to me that, while homosexuality may reduce the probability of passing on one’s genes, it doesn’t reduce it to nearly zero. Conversely, being heterosexual doesn’t increase the probability to nearly 100%.

[Michaelangelica]

 

None of the children of homosexuals who I know are, to my knowledge, homosexuals.

 

It appears to me that, while homosexuality may reduce the probability of passing on one’s genes, it doesn’t reduce it to nearly zero. Conversely, being heterosexual doesn’t increase the probability to nearly 100%.

 

OK You win:)

You can have homosexual behaviour.

It is a matter for conjecture if it is an inherited trait anyway(I am not fond of socio-psycho-biology either)

 

What about the very promiscuous bacteria? (most of this planet's life)

How do they choose which bits of another's geonome to appropriate?

The "Natural Selection" model just does not work here.

 

Why do some species (in all senses of the word) decide to die?

[Michaelangelica]

This article has helped me understand that there is more at work than "Natural Selection". which is the point I started to make.

Darwin alone does not account for the 20C events or expansions of biological knowledge.

http://www.talkorigins.org/faqs/faq-intro-to-biology.html

My problem is fitting what I know into that one model

(I am still not convinced we have all the answers especially with bacteria)

But this goes some way to helping. Especially the anthropomorphizing of the word "selection"

When selection is spoken of as a force, it often seems that it is has a mind of its own; or as if it was nature personified.

This most often occurs when biologists are waxing poetic about selection. This has no place in scientific discussions of evolution.

Selection is not a guided or cognizant entity; it is simply an effect.

 

A related pitfall in discussing selection is anthropomorphizing on behalf of living things.

Often conscious motives are seemingly imputed to organisms, or even genes, when discussing evolution.

This happens most frequently when discussing animal behavior. Animals are often said to perform some behavior because selection will favor it.

This could more accurately worded as "animals that, due to their genetic composition, perform this behavior tend to be favored by natural selection relative to those who, due to their genetic composition, don't."

Such wording is cumbersome.

To avoid this, biologists often anthropomorphize. This is unfortunate because it often makes evolutionary arguments sound silly.

Keep in mind this is only for convenience of expression.

 

The phrase "survival of the fittest" is often used synonymously with natural selection. The phrase is both incomplete and misleading.

For one thing, survival is only one component of selection -- and perhaps one of the less important ones in many populations.

For example, in polygynous species, a number of males survive to reproductive age, but only a few ever mate.

Males may differ little in their ability to survive, but greatly in their ability to attract mates -- the difference in reproductive success stems mainly from the latter consideration.

Also, the word fit is often confused with physically fit.

Fitness, in an evolutionary sense, is the average reproductive output of a class of genetic variants in a gene pool. Fit does not necessarily mean biggest, fastest or strongest.

 

the genetics of these populations is consistant with drift models.

 

Thus, it is wrong to consider natural selection as the ONLY mechanism of evolution and it is also wrong to claim that natural selection is the predominant mechanism. This point is made in many genetics and evolution textbooks, for example;

 

"In any population, some proportion of loci are fixed at a selectively unfavorable allele because the intensity of selection is insufficient to overcome the random drift to fixation.

Very great skepticism should be maintained toward naive theories about evolution that assume that populations always or nearly always reach an optimal constitution under selection.

The existence of multiple adaptive peaks and the random fixation of less fit alleles are integral features of the evolutionary process.

Natural selection cannot be relied on to produce the best of all possible worlds." (Suzuki, D.T., Griffiths, A.J.F., Miller, J.H. and Lewontin, R.C. in An Introduction to Genetic Analysis 4th ed., W.H. Freeman, New York 1989)

 

And:

 

"One of the most important and controversial issues in population genetics is concerned with the relative importance of genetic drift and natural selection in determining evolutionary change.

The key question at stake is whether the immense genetic variety which is observable in populations of all species is inconsequential to survival and reproduction (ie. is neutral), in which case drift will be the main determinant, or whether most gene substitutions do affect fitness, in which case natural selection is the main driving force.

The arguments over this issue have been intense during the past half- century and are little nearer resolution though some would say that the drift case has become progressively stronger.

Drift by its very nature cannot be positively demonstrated. To do this it would be necessary to show that selection has definitely NOT operated, which is impossible.

Much indirect evidence has been obtained, however, which purports to favour the drift position. Firstly, and in many ways most persuasively is the molecular and biochemical evidence..." (Harrison, G.A., Tanner, J.M., Pilbeam, D.R. and Baker, P.T. in Human Biology 3rd ed. Oxford University Press 1988 pp 214-215)

 

The book by Harrison et al. is quite interesting because it goes on for several pages discussing the controversy.

The authors point out that it is very difficult to find clear evidence of selection in humans (the sickle cell allele is a notable exception).

In fact, it is difficult to find good evidence for selection in most organisms - most of the arguments are after the fact

[CraigD]

As promised some days ago, this thread is to be the new home for a line of inquiry originally started in 6721, which, though interesting and popular, had drifted too far from the original thread’s subject.

[CraigD]

What about the very promiscuous bacteria? (most of this planet's life)

How do they choose which bits of another's geonome to appropriate?

The "Natural Selection" model just does not work here.

Organisms like bacteria do appear to confound our usual definitions of “species”, “offspring”, and “individual”.

 

They don’t reproduce sexually, but, as Michaelangelica notes, swap DNA nearly or perhaps even more effectively than organisms that do. Some have suggested that bacterial exchanges of DNA is more analogous to a sort of “spoken language” than the kind of gene-swapping we and other animals perform via reproduction.

 

The distinction between a bacterial species and individual is vague. Since they reproduce clonally, the descendent of a dead ancestor bacterium is arguably the same individual. Alternately, since they incorporate genes from other individuals, the same bacterium is arguably no more the same individual after the exchange than a child of a sexually reproducing organism is the same individual as either of its parents. The analogy of “bacterial DNA exchange = sexual reproduction”, however, is inexact, as a recipient bacterium gains relatively much less genetic information from the donor than the nearly 50% that a sexually reproduced child gains from either parent.

 

When Darwin wrote “The Origin of Species” from about 1840 to 1859, I don’t think he anticipated how unlike the beasts, birds, bugs, and plants he was able to study were organisms like bacteria. Nonetheless, bacteria appear to compete for resources – to “fight for survivial” - as or more intensely than other organisms, so the “survivial of the fittest” idea, though an imprecise one, appears to apply as well to them as to the organisms with which Darwin was familiar.

Why do some species (in all senses of the word) decide to die?

:( I’m unable to think of an example of an entire species “deciding to die.” Can you expand on this idea, Michaelangelica?

[sebbysteiny]

What about the very promiscuous bacteria? (most of this planet's life)

How do they choose which bits of another's geonome to appropriate?

The "Natural Selection" model just does not work here.

 

So the argument is this. 'There is one part of evolution I don't fully understand. Therefore Natural Selection, and not my own knowledge, must be at fault.' No offence, but I think you should trust the most challenged and as yet undefeated theory of evolution more than even your expertise and intelligence.

[Michaelangelica]

Organisms like bacteria do appear to confound our usual definitions of “species”, “offspring”, and “individual”.

 

They don’t reproduce sexually, but, as Michaelangelica notes, swap DNA nearly or perhaps even more effectively than organisms that do.

Thanks for your comments on bacteria. they certainly don't fit the Natural Selection Hypothesis.

Please don't mis-understand me. i am not throwing Natural Selection out with the bathwater. It obviously has its place. what I am arguing is that it is not the only game in town given what we now know and our 20C experiences.

Bacteria, at 80% of the world's life, really have to be explained.

It is extraordinary, and quite wondrous, that the can swap genetic material at will (It almost approaches the incomprehensibility of Quantum Physics)

 

Some explanation as requested:-

In 1926, people in Europe and America began to come down with a strange sleeping sickness which became known as Encephalitis lethargica. Victims would go to sleep and not wake up. In ten years the disease kills some five million people then quietly went away

The 1918 bird/swine flu killed untold millions (Estimates vary from 20-100 million). It appeared in Madrid, Bombay and Philadelphia all in the same week (!?!) then it disappeared.

(my thanks to Bill Bryson)

The point is that some viral and bacteria epidemics (at least among humans -God knows what is happening with the rest of life on the planet) DIE.

This is not good "Survival of the Fittest" How does Darwin explain Death, extinction?

[Kayra]

Thanks for your comments on bacteria. they certainly don't fit the Natural Selection Hypothesis.

 

Not what he said I think.

 

When Darwin wrote “The Origin of Species” from about 1840 to 1859, I don’t think he anticipated how unlike the beasts, birds, bugs, and plants he was able to study were organisms like bacteria. Nonetheless, bacteria appear to compete for resources – to “fight for survival” - as or more intensely than other organisms, so the “survival of the fittest” idea, though an imprecise one, appears to apply as well to them as to the organisms with which Darwin was familiar

 

 

Some explanation as requested:-

In 1926, people in Europe and America began to come down with a strange sleeping sickness which became known as Encephalitis lethargica. Victims would go to sleep and not wake up. In ten years the disease kills some five million people then quietly went away

The 1918 bird/swine flu killed untold millions (Estimates vary from 20-100 million). It appeared in Madrid, Bombay and Philadelphia all in the same week (!?!) then it disappeared.

(my thanks to Bill Bryson)

The point is that some viral and bacteria epidemics (at least among humans -God knows what is happening with the rest of life on the planet) DIE.

This is not good "Survival of the Fittest" How does Darwin explain Death, extinction?

 

One way to explain it is like this.

These particular diseases were likely to virulent for their own good. They killed people to fast.

 

This single factor in their genetic makeup proved to be a considerable weakness. One which, given time, they would have evolved a solution to. Alas, they did not have the time, or perhaps the luck, to evolve a less virulent form of themselves before a combination of:

• lack of hosts (less social contact)
  
• existing hosts exposed and immune
  
• man quickly isolating sick people
  
• And I am certain a variety of other things as well.
  

Left the organisms without susceptible hosts to infect.

 

Survival of the fittest. They did end up killing themselves, but not because of evolution, but rather lack of timely evolution.

[Eclogite]

This is not good "Survival of the Fittest" How does Darwin explain Death, extinction?

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. Look at it like this:

 

Fitness = Life

Unfitness = Death

 

 

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. Thus, epigenetics, while not constituting a wholesale return to Lamarckian ideas definitely puts a new twist on the role of the environment.

[Michaelangelica]

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

.

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

.

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."

[Kayra]

Perhaps this will help.

 

Evolution has 2 critical repeated steps at the very basis of the process.

 

Step one. Create diversity in a population

Step Two. Remove from that population that which is not fit.

[ughaibu]

Evolution isn't about individual species, it's about the interactions of ecosystems.

[Kayra]

Evolution isn't about individual species, it's about the interactions of ecosystems.

 

Hmm.

 

I am afraid I would ahve to take issue with that statement.

Evolution is all abou the individual species. Interactions within an ecosystem is an expected side effect of this.

[ughaibu]

Take a population, split it into half a dozen sub-populations and put each in a different ecological environment. The basic statement of Darwinian evolution is that the characteristics of these sub-populations will diverge. They will also have an impact on the other organisms in the ecosystems into which they are introduced.

[Kayra]

Yep. Very true.

 

But life forms will always act (or try to act) in what they see as their own best interests.

 

The interaction of the individual species inevitably and eventually creates an ecosystem simply because this is usually the best thing for the individual species.

 

Groups of life forms evolve together in an ecosystem (and hence the ecosystem evolves) only because each life form seeks its own best means of procreation.

 

The evolution of an ecosystem is a side effect of the evolution of a life form.

[ughaibu]

I would say the two are interdependent, with neither having a precedent role or being an effect of the other. If an individual member of an ecosystem is transplanted elsewhere, both the remaining system and the transplanted species will adapt to meet the new conditions.

[Kayra]

Oh dear.. I smell a chicken or the egg conundrum. :)

 

All I can think of is that life can exist without an ecology, but an ecology can not exists without life.

 

This really should give life the precedence :hihi: