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TelMiles
In: London
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How come much of "evolution" happens in a negative sense? Things don't evolve something they need, they evolve without something they don't need.
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Against all Gods.
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DPCrisp
In: Bedfordshire
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Looks like 7 out of 8 conditions are negatives, but they are of 3 kinds.
You can either need trait/gene/something X, or not need X.
You can either need not to have X, or not need not to have X.
You can either have X or not have X.
That makes 8 combinations, only one of which is all positive: need and have X is a normal state of affairs.
Other normal states of affairs are
don't need and don't have,
need not to have and don't have,
don't need not to have and don't have.
A couple of states mean you may be prepared to meet the opportunity to do something new:
don't need but have,
don't need not to have but have.
And a couple of states kill you off:
need but don't have,
need not to have but have.
Most of these states are "negative", but most of them are at least sustainable. A few doors close and a few open, but mostly it's rolling stones... I mean... status quo.
We talk about selection pressure, but what about a selection vacuum?
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TelMiles
In: London
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A further thought, has anything evolved recently, ie since we started recording such things, and if they have, have they evolved positively?
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Against all Gods.
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Mick Harper
Site Admin
In: London
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The one always quoted is the dark moths that appeared in Birmingham when the Industrial Revolution made the buildings they were on dark. But of course nobody can show this is evolution since presumably the dark moths already existed in the general moth population. In other words, evolution's never been observed either in the real world or in the palaeontological world (still no common ancestors...).
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Most textbooks fail to mention, however, that the peppered moth story began to unravel in the 1960s, when biologists noticed that dark moths were unexpectedly plentiful in some unpolluted locations. When anti-pollution legislation led to cleaner air in the 1970s, light-colored moths made a comeback; but, contrary to theory, the comeback occurred without corresponding changes in tree trunks. Then, in the 1980s, biologists realized that peppered moths almost never rest on tree trunks (as Kettlewell wrongly supposed when he initially released the moths onto tree trunks, creating atypical conditions). Instead, these night-flying insects probably spend their days hiding underneath horizontal branches high up in the trees, where they can't be seen.
In 1998, University of Chicago evolutionary biologist Jerry Coyne wrote: "From time to time, evolutionists re-examine a classic experimental study and find, to their horror, that it is flawed or downright wrong." According to Coyne, the fact that peppered moths rarely rest on tree trunks "alone invalidates Kettlewell's release-and-recapture experiments, as moths were released by placing them directly onto tree trunks." Coyne concluded that this "prize horse in our stable of examples" of natural selection "is in bad shape, and, while not yet ready for the glue factory, needs serious attention" (Nature, Nov. 5, 1998) |
http://www.arn.org/docs2/news/pepperedmyth111702.htm
Unravelling in the 60's? I think this is still taught in high school.
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Ishmael
In: Toronto
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| EndlesslyRocking wrote: | | Unravelling in the 60's? I think this is still taught in high school. |
It most certainly is.
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Hatty
Site Admin
In: Berkshire
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| According to Coyne, the fact that peppered moths rarely rest on tree trunks "alone invalidates Kettlewell's release-and-recapture experiments, as moths were released by placing them directly onto tree trunks." |
This is passing strange or is it a typical example of how scientists "prove" a hypothesis? The logical way to proceed would be to place the critters in a neutral environment, then monitor their progress and record their chosen habitat. And repeat the experiment with other moths. Are there other examples of evolutionary theory being re-examined, like them finches?
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Hatty
Site Admin
In: Berkshire
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Apparently we've been evolving in a random fashion but traits which are advantageous are passed on to succeeding generations; why is it that traits that are disadvantageous 'skip' a generation only to reappear, sometimes in only one of the offspring?
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Ishmael
In: Toronto
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| Hatty wrote: | | Apparently we've been evolving in a random fashion but traits which are advantageous are passed on to succeeding generations; why is it that traits that are disadvantageous 'skip' a generation only to reappear, sometimes in only one of the offspring? |
Dawkins is one who argues that genes seek to preserve themselves (The Selfish Gene). If so, then "disadvantageous" genes are no less desirous of self-preservation than those that bestow advantages. A gene is a gene is a gene.
Some time ago it occured to me that the best way for a gene to preserve itself is to not express itself at all. So called "junk" DNA represents the very height of evolution.
Genes that fail to manifest as characteristics are preserved against selective pressures. These unexpressed genes survive so long as the heavy-lifting DNA, which assumes responsibility for designing the host organism, performs adequately. The Genes that have no impact on the shape of their carrier can never be selected out. They are immortal so long as the species survives.
Perhaps when the organism is failing -- when it is in danger of extinction (and thus eliminating the history of silent DNA its lineage has accumulated) -- the "junk" activates. Perhaps it activates rather randomly. Perhaps there is a pecking order of seniority among the hidden genes in which the last one to go dark is the first required to express itself. Every gene gets tried until some alteration has been made in the host that insures the survival of the rest of the DNA strain -- both silent and expressed.
Genes that express themselves are evolutionary failures -- not successes. Every gene aims to turn itself off and achieve the nirvana of "junk" status. Expressed genes have proven unable to do so. Every single one of our manifest characteristics has proven absolutely essential to the continued existence of the species. Every time one of these essentials tries to go dark, the species comes under survival stress.
If human beings are breeding-out intelligence, I'm not worried. I am confident that the DNA strands that control smarts will be quick enough to turn themselves off and thus survive intact until the next time they are needed.
To answer your question specifically, genes that skip generations are likely those that are in between dark and light status. They are attempting to go dark and either will do so eventually unless some selective pressure is preventing their shut-down.
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Mick Harper
Site Admin
In: London
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The blessed Dawkins is presently regaling British television audiences with the wonders of evolutionism. This week he got into fearful strife because (as it happens) he subscribes to two contradictory paradigms: Darwinian Evolution and Liberalism. So he spent most of the hour trying to convince us that Survival of the Fittest didn't apply to humans even though he used up the remainder of the programme insisting (for the benefit of his other audience, the Christian fundamentalists) that human beings were just animals and subject to everything animals are.
Thanks to The Dawk I am now pretty much persuaded to Social Darwinism even though I am not a Darwinist!
Foreigners can watch the programme on BBC-i.
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Ishmael
In: Toronto
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Denying natural selection is tantamount to denying the weather. But though wind may shape the tree, no one would be so foolish as to assign it responsibility for the tree's very growth.
No one except Dawkins.
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Hatty
Site Admin
In: Berkshire
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| ...genes that skip generations are likely those that are in between dark and light status. They are attempting to go dark and either will do so eventually unless some selective pressure is preventing their shut-down. |
An ingenious explanation, Ishmael! It's a risky strategy in the case of colour-blindness for example, when only one of the offspring is affected, especially as the gene is almost invariably carried by women but seems to pay off. It could presumably be bred out by only letting the unaffected child father offspring. I wonder if there's a reason why this particular gene hardly ever affects women even though they're the carriers and whether this is a common occurrence. Sneakier and sneakier.
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DPCrisp
In: Bedfordshire
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| Apparently we've been evolving in a random fashion but traits which are advantageous are passed on to succeeding generations; why is it that traits that are disadvantageous 'skip' a generation only to reappear, sometimes in only one of the offspring? |
Did you see the thing about haemophilia in the royal families?
Recessive genes, probabilities and sheer luck are one thing, but what confused me was that they said a third of all cases of haemophilia are new, not inherited. Does that mean it's an incredibly commonly occurring mutation?
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DPCrisp
In: Bedfordshire
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| Some time ago it occured to me that the best way for a gene to preserve itself is to not express itself at all. So called "junk" DNA represents the very height of evolution. |
Hmm. Good point.
| Every gene aims to turn itself off and achieve the nirvana of "junk" status. |
If genes are selfish, yes...
| Every single one of our manifest characteristics has proven absolutely essential to the continued existence of the species. |
Well, you won't find any evolutionists saying that.
| I am confident that the DNA strands that control smarts will be quick enough to turn themselves off and thus survive intact until the next time they are needed. |
You think individual genes (whatever they are) are definite enough on their own to "control smarts", etc.?
What if it's like a light bulb put away as a spare: when you put it in another room, it illuminates something quite different. Or a drop of oil that, in different situations, can make things slippery, make things stick, do nothing at all...
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Mick Harper
Site Admin
In: London
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| Denying natural selection is tantamount to denying the weather |
No, no. Denying evolution is tantamount to denying the weather. The method by which evolution occurs is at question. I for one don't believe in natural selection, leastways not by genetic mutation and then individual advantage.
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