I have some questions about evolution.
1. Random Mutation. Is it really random?
"To determine how the bacteria had gained their tails, Dr. Xavier and his colleagues sequenced the DNA of 24 lines of hyperswarmers. In 24 out of 24 cases, they discovered that they have gained a mutation in the same gene, called FleN."
http://www.nytimes.com/2013/08/15/scien … .html?_r=0
How could a random mutation occur repeatedly, in the same gene? Every single time.
2.Convergent Evolution, how can it be explained?
How do you explain things like marsupial dogs, flying squirrels, and saber toothed cats? How can the just "happen" to look just like their placental counterparts?
3. How do you explain the Cambrian Explosion?
How do you explain that all of the phyla showed up suddenly, at the very beginning? Darwinian theory suggests there should be a bottom-up progression, and instead we have a top-down progression in evolution.
Given that a gamma ray that produced a specific mutation came from another galaxy, it's hard to call it anything but random. Now, which mutations are kept is most definitely NOT random; few mutations that do not result in increased reproduction are kept. Some (blue eyes, maybe), but not many.
Convergent evolution; give a specific need or environment it would seem that the things inhabiting that environment or needing that ability would look similar.
Top down evolution? Are you saying that higher animals all devolved into lower, simpler forms in the Cambrian explosion? That DOES happen - whales went back to the sea - but is fairly rare. A changing environment might produce such a result.
"Given that a gamma ray that produced a specific mutation came from another galaxy, it's hard to call it anything but random. Now, which mutations are kept is most definitely NOT random; few mutations that do not result in increased reproduction are kept. Some (blue eyes, maybe), but not many."
Then how could the same mutation "randomly" occur 24 times in a row, according to the article? I've seen other studies with the same type of result as well. So this isn't an isolated or unique incident.
"Top down evolution? Are you saying that higher animals all devolved into lower, simpler forms in the Cambrian explosion? That DOES happen - whales went back to the sea - but is fairly rare. A changing environment might produce such a result."
No, I mean that Darwin would expect more diversity in the beginning. The "tree" is upside-down.
First, I doubt that the same mutation occurred. That would require identical strings of DNA in different species, and that isn't going to happen.
But the same mutation can certainly occur in the same species (although rare) - there are, after all, a limited number of options to the DNA that will produce any change at all. And, given that that limit is very high, I flatly refuse to believe that the same mutation occurred 24 times in a row to sequential generations.
?? Darwin said that all species came from a preceding one. How does that make the early species higher in number than later ones? I'm confused.
Well, that's what the article said about the mutations.
About the Cambrian explosion, I am talking about how there were only a few thousand species, yet ALL of the phyla were represented, right from the beginning. There should have been much more diversity at the beginning, leading to different phyla later on, in a progressive manner. I mean, more diversity in one phyla before a new one comes along. Instead, the all just seem to pop into existence all at the same time.
Either I am not understanding you, or you are not following the article. Or it was written by the apologetic crowd trying to disprove evolution with false data. Similar mutations occur all the time; identical mutations over 24 successive generations do not.
But the Cambrian explosion lasted 20 million years! It didn't pop up overnight at all, although it was an example of rapid evolution. Species developing to fill empty niches, and doing so quite rapidly, but still taking millions of years to do so.
I will see if I can find more on the subject of the article. Perhaps I am misreading it, but I don't think so. It seemed pretty straight forward, and wasn't from any creation site or anything.
The Cambrian had all the phyla, with no precursors to the body plans. There was very little variation. Lots of different types of trilobites etc, but basically the same.
The phyla were very complicated right from the beginning. The trilobite eye was one of the most advanced eyes ever.
It LOOKS like they just "poofed" into existence. But of course they didn't, and genetic evidence shows that one phyla evolved into another.
I'm just saying evolution doesn't look Darwinian for the most part. Something else is going on. It's an exciting mystery.
Did you read the article? I reread it, and my conclusions are still the same. I'm not sure how you got something different from it.
Somehow I missed the link, but have read it now.
And I misunderstood; it was not 24 successive generations that all produced the same mutation; it was that the same mutation developed over many generations, and did so several times. There is a vast difference.
In the second case, it is likely that the change was already latent in the genetic structure, and it did not require an outside influence to develop. Just normal evolution of an existing species that can come from other sources already present. Perhaps an incorrect gene replication for example - something that is frequent. Perhaps a chemical in the petri dish that allowed bacteria with multiple tails to grow. Maybe even the frequency of the light impinging on the organisms.
"24 out of 24 cases" led me to think they were in a row, but perhaps I misinterpreted that. Your arguments are rational. More to think about.
The cases were probably in a row, but each case contained many, many generations. Bacteria reproduce rather rapidly, after all, and there were no indications just how many generations it took to produce the changes.
That they had the SAME change doesn't indicate randomness to me. There still had to be the same genetic mutation at some point in all the cases.
Yes, there did. And somewhere in 500 or whatever generations the environment favored that mutation, whether from chemicals, gene replication or whatever. Or, maybe, just a tendency towards that change that was already built in but never developed because the environment did not favor it until put into a petri dish with no other competition.
Here's another one showing how mutations aren't so random:
"In the new study, published online today in Public Library of Science Biology5, Doebeli and colleague Matthew Herron, also at UBC, went back to the frozen samples from three of their test tubes and sequenced 17 gene samples from various stages of the experiment. The DNA showed that in some cases identical mutations appeared independently in all three test tubes: despite the random nature of mutations, the same changes in the environment favoured the same genetic solutions."
http://www.nature.com/news/predictable- … ns-1.12459
"There are about 4.5 million nucleotides in the E. coli genome," he said. "Finding in four cases that the exact same change had happened independently in different populations was intriguing."
Read more at: http://phys.org/news/2013-02-evolution.html#jCp
It seems to me that the same mutation will reoccur. Random means random, the same thing can happen repeatedly because each event is independent. Random chance does not know that it ever happened before.
That said, I imagine some sequences are more fragile than others. Some changes do happen more often than others when you bombard your drosophilla or whatever with a mutagen.
That seems to go against common sense. Random means anything is likely to happen, not the same random change over and over again. How is that logical/ Probability wise it is possible. You CAN toss a coin and get all heads for a hundred tosses, but it's not likely to happen.
Octopii evolved rods and lenses in their eyes independently of invertabrates. How likely is this, for two entirely different lines to evolve the same exact eye parts, and just where they need to be(the eye)? It seems pretty lucky to me that they would evolve the exact parts they need, in the exact spot, useful for sight.
"The eyes of octopuses and squids are a wonder to scientists and evolutionary biologists, because they are similar to the eyes of vertebrates and yet they have been shown to have evolved independently. Both eyes have evolved lenses and similar muscle structures"
No one knows, of course, exactly how it happened. But, consider that if there were 1,000 trials, and the best one succeeds, won't it be the best one in more than one species? There is also the question of just how possible other forms of vision are: given that reception of light is advantageous, just how many methods are physically possible, which one is best and which ones are possible given the genetic and physical structure of the organism?
Same for the location: if eyes (including nerves and the associated brain activity) are on the bottom of the animal rather than a useful location, would evolution select for them? Or "discard" the animal that is putting effort into something it can't use? This seems like asking why people haven't developed fins on their feet - contra-survival items don't make it in the long run.
Saying there were 1000 trials is just guesswork, and NOT a proven fact.
What is a proven fact is that the helpful mutations happened, independently, multiple times. That shows, to me, that sight is an inevitable part of the organic world.
"That shows, to me, that sight is an inevitable part of the organic world."
And yet we know that to be false; there are many animals (complex ones) without sight at all.
Diversity is also an inevitable part of the organic world. We need all different types of organisms to make the world work.
--face it, omnipresent, omniscient and omnipotent Mighty Triple O is involved behind the scenes.
by cooldad 7 years ago
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