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Author Topic:   Extent of Mutational Capability
Taq
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Posts: 9970
Joined: 03-06-2009
Member Rating: 5.6


Message 114 of 279 (793316)
10-25-2016 3:16 PM
Reply to: Message 108 by Tangle
10-25-2016 10:45 AM


Re: Clades
Tangle writes:
This is where it gets messy, Neanderthals are now - along with at least 4 other human forms mostly classed as sub-species of Homo sapiens. They can't be species as they interbred.
Since speciation is not a binary event we can expect limited interbreeding during speciation for many populations. Whether we decide to call them separate species or subspecies does nothing to change the reality. The map is not the territory, as the old saying goes. What we do have is genetically distinct populations that did occasionally interbreed. What produced genetically distinct populations was a lack of free interbreeding between the populations, also known as speciation.

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 Message 108 by Tangle, posted 10-25-2016 10:45 AM Tangle has replied

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 Message 115 by Tangle, posted 10-25-2016 4:05 PM Taq has replied

  
Taq
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Posts: 9970
Joined: 03-06-2009
Member Rating: 5.6


(1)
Message 117 of 279 (793322)
10-25-2016 4:53 PM
Reply to: Message 115 by Tangle
10-25-2016 4:05 PM


Re: Clades
Tangle writes:
I wonder how distinct?
"Neanderthal genetic differences to humans must therefore be interpreted within the context of human diversity."
The question I often ask in return is how do they know that 5% of the modern human genome is made up of Neanderthal DNA? How do they tell the difference between Neanderthal DNA and modern human DNA? The answer is pretty simple. It's different.
Not only is it different now, it was different then. I can't seem to find it now, but if memory serves they found an ancient (25,000 years old?) modern human fossil and were able to extract mitochondrial DNA. The mtDNA from the ancient modern human closely matched that of living modern humans. Neanderthal mtDNA does not.
Fossil Hominids: mitochondrial DNA
green is modern human v. modern human, red is modern human v. Neanderthal, blue is modern human v. chimp
[these are values for living modern humans and Neanderthals]
I think it is also worth mentioning that these Neanderthals were identified by morphology. If this were just a case of a diverse modern human population, then why the correlation between the very different mtDNA and the very different morphology? The best answer, IMHO, is that they were separate species.
Edited by Taq, : No reason given.
Edited by Taq, : No reason given.

This message is a reply to:
 Message 115 by Tangle, posted 10-25-2016 4:05 PM Tangle has replied

Replies to this message:
 Message 118 by Pressie, posted 10-26-2016 6:04 AM Taq has not replied
 Message 119 by Tangle, posted 10-26-2016 6:19 AM Taq has replied

  
Taq
Member
Posts: 9970
Joined: 03-06-2009
Member Rating: 5.6


Message 120 of 279 (793350)
10-26-2016 10:46 AM
Reply to: Message 119 by Tangle
10-26-2016 6:19 AM


Re: Clades
Tangle writes:
But at that level, the term 'species' doesn't really mean much.
Of course it still means something. It means that limited interbreeding is producing statistically significant genetic divergence which can be objectively measured.
A great dane and a shitzu could reasonably be called morphologically different species and I doubt they could breed naturally...... but we have them as the same species.
Maybe we shouldn't treat them as separate species.
Sapiens and Neanderthal's lived together and sucessfully mated - for thousands of years. It looks like Neadethals could speak - they certainly used tools, drew art, had clothing and ornaments. I suspect if they were living with us now, we'd call them human - in the general usage of that word and science might not even classify them as a subspecies. But who knows, it's all pretty interesting though.
1. If there was free interbreeding then they would fall into the range of variation for modern humans. They don't.
2. They were recognized as not being anatomically modern humans when we first found them. Time isn't going to change that.

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 Message 119 by Tangle, posted 10-26-2016 6:19 AM Tangle has replied

Replies to this message:
 Message 121 by Tangle, posted 10-26-2016 11:17 AM Taq has replied
 Message 127 by caffeine, posted 10-27-2016 5:44 PM Taq has not replied

  
Taq
Member
Posts: 9970
Joined: 03-06-2009
Member Rating: 5.6


(1)
Message 144 of 279 (793514)
10-31-2016 5:01 PM
Reply to: Message 121 by Tangle
10-26-2016 11:17 AM


Re: Clades
Tangle writes:
I'm not at all convinced. You say 'limited interbreeding', it's not at all clear that that was the case, and in anycase what does it mean?
The genetic divergence between the populations does make it clear, IMHO.
As to what limited interbreeding means, it means that breeding within the populations was much more common than interbreeding between the populations. What matters is the effect it has on the genomes of each population. What doesn't matter is the human need to force things into comfortable categories.
What I (and, presumably, scientists studying the subject) am interested in is HOW did we end up with two populations with divergent DNA. From what I can see, the best explanation is limited interbreeding which led to different mutations accumulating in each population. At this point, you can call it whatever you want. You can call it Marklaration, for all I care. Most would call that speciation, but we can ditch these terms if they don't work.
Were they actually that different and over what timescale? Are they more different than I am from say an Australian aboriginal?
The difference between two Neanderthals appears to be the same as the distance between you and Australian aboriginals (assuming you are of European descent). However, the distance between you and a Neanderthal is much more than that between you and an Ozzie aboriginal.
They were identified from pieces of bone. The DNA tells us more and so does archaeology. Science now classifies them as a subspecies rather than a seperate species. I think the truth is somewhere in between and I find the whole idea fascinating as it's so recent.
Tomayto, tomahto. A rose by any other name . . . take your pick of idioms. Like I said before, it is foolish to think that there is some sharp demarcation between subspecies and species. You might as well be asking for a consensus, down to the mm, of when someone goes from being short to tall. The line is always going to be arbitrary. What matters is the data, and the explanations we can find for it.
Like you, I also find it very interesting. Like many scientists, I would be horridly excited to find out if everything we know is wrong, that sweet moment when horror over being wrong is mixed with the wonder of new information. Such is science . . .

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Taq
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Posts: 9970
Joined: 03-06-2009
Member Rating: 5.6


(1)
Message 155 of 279 (793541)
11-01-2016 10:57 AM
Reply to: Message 145 by CRR
10-31-2016 9:15 PM


CRR writes:
The Wright brothers intelligently designed the Kitty Hawk. An intelligent design team designed the A380.
A daddy airplane and a mommy airplane do not get together and make baby airplanes. It is this difference between life and airplanes that makes the analogy meaningless.

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 Message 145 by CRR, posted 10-31-2016 9:15 PM CRR has not replied

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Taq
Member
Posts: 9970
Joined: 03-06-2009
Member Rating: 5.6


(4)
Message 217 of 279 (794619)
11-18-2016 11:12 AM
Reply to: Message 216 by Dr Adequate
11-18-2016 10:46 AM


Dr Adequate writes:
And CRR, while he may be a creationist, is at least trying to be right. There's been some work and thought put it there, and while he is mistaken his mistakes have on occasion been subtle.
To be fair, the mistake that CRR seems to be making is a common one, the Sharpshooter Fallacy. This is where you calculate the probability of a specific event happening after it has happened.
A good analogy is a deck of cards. If you shuffle the deck and then lay out all 52 cards one at a time, the probability of getting those specific cards in that specific order is 52!, which is a rather large number. However, the very act of shuffling and dealing cards guarantees that a highly improbable event will occur.
The same applies for evolution. Once you have imperfect replicators competing for limited resources the guaranteed outcome is evolution. The product of that evolutionary process is going to be nearly infinitely improbable. However, once the process of evolution starts you are guaranteed an extremely improbable outcome because something will evolve. As Stephen Jay Gould said on many occasions, if we rewound the tape of evolution and started it again we wouldn't expect the same outcomes. If we went back to the Cambrian, there is no reason that we would expect to see humans, or even primates, hundreds of millions of years later. We would expect to see different types of species.
The trick that creationists try to play is pretending that the outcome we see is the only possible outcome. That is where their math goes awry. It is like calculating the odds of our 52 card hand, pretending that the order of cards we see was somehow predestined or the only one that could occur. This is the Sharpshooter Fallacy, where you draw the bulls eye around the bullet hole, pretending that the shooter was aiming for the bulls eye from the start.

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 Message 216 by Dr Adequate, posted 11-18-2016 10:46 AM Dr Adequate has not replied

Replies to this message:
 Message 218 by NoNukes, posted 11-23-2016 11:51 PM Taq has not replied
 Message 221 by CRR, posted 01-21-2017 9:46 PM Taq has not replied

  
Taq
Member
Posts: 9970
Joined: 03-06-2009
Member Rating: 5.6


Message 257 of 279 (798913)
02-06-2017 12:45 PM


Probabilities
The statistical models within population genetics "aren't my bag", so I thought I would pose a few questions to see if my limited understanding is correct.
Let's say that the mean probability of winning the Powerball lottery is about 1 in 150 million. We already know that the vast majority of winners did not buy 150 million tickets before they won. In fact, most winners probably bought less that 500 tickets in their life time, some much fewer. When you get enough people buying tickets you can have very rare or highly improbably things happen well away from the mean.
Would this also apply to the fixation of alleles? Each human is born 50 mutations. In a population of just 1 million, that is 50 million mutations in a single generation. With that many mutations isn't it possible for many of those mutations to reach fixation in a much shorter time frame than the mean fixation rate?
Edited by Taq, : No reason given.
Edited by Taq, : No reason given.

Replies to this message:
 Message 260 by Dr Adequate, posted 02-06-2017 9:42 PM Taq has not replied
 Message 261 by caffeine, posted 02-07-2017 3:24 PM Taq has replied

  
Taq
Member
Posts: 9970
Joined: 03-06-2009
Member Rating: 5.6


Message 262 of 279 (799142)
02-07-2017 5:38 PM
Reply to: Message 261 by caffeine
02-07-2017 3:24 PM


Re: Probabilities
caffeine writes:
While some would go to fixation quicker than the mean, wouldn't a larger population mean it's harder for any mutation to go to fixation? A mutation is much more likely to be fixed (or lost) in a small population than a large one, isn't it? Am I missing something obvious?
That's a good point as well. If the probability of an allele reaching fixation is 1/n, where n is the population size, then a large population would decrease the probability of any single allele reaching fixation. I believe this is why population bottlenecks can fix many neutral alleles in a short amount of time.

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 Message 261 by caffeine, posted 02-07-2017 3:24 PM caffeine has not replied

  
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