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Author Topic:   Disadvantageous Mutations: Figures
Taq
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Message 11 of 93 (794472)
11-16-2016 12:09 PM
Reply to: Message 1 by Gregory Rogers
11-16-2016 5:33 AM


Gregory Roberts writes:
As I understand it, one of the key arguments of the Creationist school runs as follows:
1. The vast majority of mutations in evolutionary history are said to be disadvantageous. One debate I watched suggested that 80 to 90 percent were so.
Assuming that we are talking about eukaryotes with genome sizes above 500 million bases or so, then that is wrong. Most mutations are neutral (i.e. neither advantageous or disadvantageous).
Of the mutations that do significantly change fitness, I would agree that the majority are going to be disadvantageous. However, natural selection will remove these mutations from the population, so that isn't a problem. Rare beneficial mutations will be selected for and amplified in the population. This is why the rate of deleterious mutations can be greater than beneficial mutations and still lead to an overall increase in fitness or complexity.
Let's look at an example in a living population. There is a wild murine species called the rock pocket mouse. As it turns out, they come in two different colors, black and brown. The black mice came about through a random mutation that occurred in brown mice, and we find these mice in isolated basaltic outcroppings where their black fur allows them to hide in the black lava rocks. You can read the scientific paper here. This is one of the figures from the paper:
As you can see, the brown mice are well camouflaged in the brown desert, and the black mice are well camouflaged on the black lava rocks. The scientists also sequenced the DNA of the brown and black mice and they found that there was free interbreeding between black and brown mice. They also found that the allele for black fur was dominant, meaning that offspring only need one copy of the black allele in order to have black fur.
Here is the interesting thing. They didn't find any black mice in the brown colored desert that spanned the hundreds of miles between the black lava outcroppings. They also didn't find any (or very few) brown mice on the black lava rocks. Why? The obvious answer is natural selection in the form of predation.
This leads to another question. Is the mutant black allele beneficial or deleterious? The answer is that it is both. In the brown desert, the black allele is deleterious. On the black lava rocks, the black allele is very beneficial. So is the black allele a "failed" mutation?
When you speak about mutations, it is these sort of things that you have to keep in mind.
Rather, the first question I have in mind runs as follows: if a great many mutations fail (whatever the percentage of disadvantageous mutations, it is still, I presume, rather high, or at least it was at the beginning of evolutionary history), then would we not expect to find a high degree of examples of these failures in the fossil and skeletal records?
Do the vast majority of "failed" mutations show up in human skeletal remains? What differences would there be in a human skeleton from an indivudal who had hemophilia or diabetes? We would probably see achondroplasia like someone mentioned earlier, but how common is that in the human population?
We often only have 5 to 10 fossil specimens for any given fossil species. If you randomly picked 10 human beings from the entire population, what would be the probability that you would pick someone with a genetic disease which produces a physical difference in their skeleton? Probably pretty low, right?
Edited by Taq, : No reason given.
Edited by Taq, : No reason given.

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Taq
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Posts: 9972
Joined: 03-06-2009
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Message 25 of 93 (794618)
11-18-2016 11:03 AM
Reply to: Message 20 by AnswersInGenitals
11-17-2016 7:01 PM


Re: There are no disadvantageous mutations.
AiG writes:
No need to go digging in the muck and mire to discover the prevalence or effects of mutational failures. There are currently 130million humans born every year (goggle on ‘human birth rate’). According to The Physicians Committee for Responsible Medicine, there are ~150,000 babies born each year with serious birth defects (google on ‘birth defect rate). Most of these are due to gestational, not genetic mutational problems, (but does not include naturally aborted or still born fetuses). So we see that the rate of mutational defects that might show up in a fossil (or extant species) record is very small, less than 0.1%!
It is also worth adding that 25-50% of fertilized zygotes naturally terminate in the 1st month of pregnancy, usually without the mother ever knowing. Any fetuses carrying strongly deleterious mutations will not make it past this first month.

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Taq
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Posts: 9972
Joined: 03-06-2009
Member Rating: 5.5


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Message 29 of 93 (794822)
11-28-2016 10:43 AM
Reply to: Message 26 by Gregory Rogers
11-25-2016 10:33 AM


Gregory Roberts writes:
Why don’t I respond more? To be honest, science is not my strong suit, and much of the terminology is foreign to me; thus I persistently find myself reaching for google or Wikipedia, first of all to define such terms, and second to understand the science for which they are employed. I am compiling an ever-growing glossary of terms as we speak.
At this point I think we are all very curious as to what questions you may have. Is there any terminology we can help you with? Are there concepts you have questions about?

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Taq
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Message 31 of 93 (794827)
11-28-2016 5:03 PM
Reply to: Message 30 by Modulous
11-28-2016 3:39 PM


Re: Regarding the frequency of disadvantageous mutations
Modulous writes:
How many mutations are beneficial is determined by how 'fit' the population is to its environment. The more specially adapted it is, the easier it is for small perturbations to disrupt the adaptation. An example: Humans are built under the assumption that we'll have four limbs. It is possible to live with fewer, but even with communal assistance, the survival/birth rate is likely inhibited in the very long term. Trying to add more limbs is even worse. Our physiology is 'fine tuned' by evolution {or God if you insist} so any mutation that results in extra limbs is likely to cause problems elsewhere even if they are improbably useful limbs. Blood flow management, the nervous system, balance and so on are all likely to be impaired by the new structures.
Historical constraints are an interesting part of evolution. One of the features of evolution is that it tinkers with what is already there. What you don't see in a lineage of species is evolution stripping morphology down to the basics and then rebuilding it.
A good analogy is a building. When you start, it is relatively easy to change the foundation of the building to whatever you want. However, once you start building on top of the foundation you can't change the foundation anymore. Morphology is a lot like that. Things like 4 limbs formed the foundation of the tetrapod body plan. Even to this day we still have the same bone structures as the transitional tetrapods, such as Tiktaalik. For example, the forelimb of tetrapods, starting from the shoulder, have one bone, two bones, bunch of little bones, and phalanges. Everything from alligators, bats, and dolphins have this arrangement.

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Taq
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Posts: 9972
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Message 56 of 93 (798455)
02-02-2017 4:55 PM
Reply to: Message 50 by CRR
02-01-2017 7:07 AM


CRR writes:
That would be a naive way of thinking about it, but do you really dispute that the human genome contains more information than the E. coli genome? That I would find fascinating.
Does the human genome contain more information than the chimp, mouse, or chicken genome? The human genome is 3 billion bases, and the onion genome is 100 billion bases. Does the onion genome contain more genetic information?
However the whole idea of junk DNA has taken a hammering in recent years, but perhaps it does provide part of the answer.
The idea of junk DNA is as strong as ever, if not stronger. More an more data have demonstrated that only ~10% of the human genome is being conserved which is extremely strong evidence that up to 90% of the human genome has no sequence specific function.

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Taq
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Message 57 of 93 (798456)
02-02-2017 4:57 PM
Reply to: Message 54 by CRR
02-01-2017 11:13 PM


It used to be thought that 1 gene produced 1 protein, now we know that through alternative splicing one gene can produce thousands of proteins.
They could produce different proteins, but tons of evidence is demonstrating that they usually don't. Only in a minority of cases does alternative splicing result in an altered protein with any regularity.
Edited by Taq, : No reason given.

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Taq
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Posts: 9972
Joined: 03-06-2009
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Message 58 of 93 (798457)
02-02-2017 5:02 PM
Reply to: Message 50 by CRR
02-01-2017 7:07 AM


CRR writes:
That would be a naive way of thinking about it, but do you really dispute that the human genome contains more information than the E. coli genome? That I would find fascinating.
Using your philosophy of only focusing on features that are lost, a primitive bacteria evolving into a human would be a loss in information because humans would have lost the ability to do many things the bacteria were able to do, such as thrive in anaerobic environments and reproduce rapidly.
If evolution occurred exactly how scientists propose it, you would call each and every step a loss in information. A fish evolving into a tetrapod would be a loss in information because the fish loses its fins and loses the ability to swim. A reptile evolving into a placental mammal would be a loss in information because the animal no longer has scales nor the ability to lay eggs.
In fact, if we use your definition for a loss in information, the entire process would REQUIRE a loss of information in order to produce the biodiversity we see today. Such is the problem you run into when you try to define a gain in information such that evolution can't produce it.

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