Posted on 03/11/2019 2:51:56 PM PDT by Sopater
Then why is Evolution's a Fact being promoted in this thread?
hopeful monsters?
That’s because Nature says ‘abracadabra’ and you didn’t.
No, but if it's important to you, I can be.
My first source, going back about 15 years, on how to deal with these questions was Eugenie Scott.
ml/nj: "So teach me: Do you believe new species evolve over many generations or does speciation happen from one generation to the next?"
Ha!, which came first, the chicken or the egg? ;-)
The answer is: words like "species", "genus", "family", etc., are all artificial constructs and matters of definition.
With the recent advent of DNA analyses some critters have been redefined as more or less closely related than previously believed.
The critters themselves never changed, not one bit, but suddenly we see them in a different light.
Today the rough dividing line is genus -- within a genus breeds, sub-species & species can at least sometimes interbreed.
But between two genera species cannot naturally interbreed, so that is a hard & fast line of division.
But everything else is pretty much a matter of definitions & interpretations.
When exactly does a different population become a "breed" (or race)?
When are different breeds considered separate sub-species?
How does a sub-species become a different species?
It's all definitions & interpretations.
Well known examples include Indian & African elephants -- cannot interbreed so are classified as separate genera.
Polar Bears & Brown Bears were thought to also be separate genera until it was discovered they do interbreed in nature, occasionally, so now they are just separate species in the same genus.
Bottom line: setting aside cross-breeding, no mother ever gave birth to a different species, but a common ancestor, say, a million generations ago, might well give rise to several different species.
Is that the answer you hoped for?
Lots of words to answer a simple question.
All species have characteristic chromosome numbers. For us humans it's 23 pairs. Sometimes humans are born with the wrong number of pairs (usually 24) but none of those ever have produced a grandchild, SFAIK. Apes have 24 pairs. So tell me: how did we go from 22 or 24 or whatever pairs to 23 pairs except from mother to child?
[You may consult Eugene Scott, whoever he is or was.]
ML/NJ
"Is that the answer you hoped for?
It's as good as Joe's!"
The DNA evidence suggests splitting or combing of chromosomes does happen, on occasion.
How, why or what consequences, we don’t know, but do expect a natural explanation will be found, eventually.
That’s what science does.
In the mean time “God of the gaps” theology can easily say, “God did it”.
I prefer to think that whatever natural explanation may present itself, God is both ultimately and directly responsible.
You disagree?
In the mean time “God of the gaps” theology can easily say, “God did it”. I prefer to think that whatever natural explanation may present itself, God is both ultimately and directly responsible.
You disagree?
I prefer to say, "I don't know," when I don't know. Others seem to like to pretend.
As for you splitting and/or combining chromosomes, we don't see any grandchildren of any animals with any chromosomial abnormalities, handwaving notwithstanding.
ML/NJ
Do you agree?
This thread has DEvolved from It is written in stone; to Well, GOD could do it if HE wanted to.
"I don't know" is the understood answer to many specific questions, but does not mean we know nothing about the subject, and what we do know may be worth rehearsing -- if only to restrict further arguments from ignorance.
ml/nj: "As for you splitting and/or combining chromosomes, we don't see any grandchildren of any animals with any chromosomial abnormalities, handwaving notwithstanding."
"Handwaving" describes your statement here.
Here's how one article addresses it:
But researchers have long noted fused chromosomes in both animals and humans.
As Miller points out, a 2013 Chinese report described a 25-year-old male, otherwise completely healthy, with only 22 pairs of chromosomes instead of 23, the result of a fusion of chromosome pairs 14 and 15.
Similarly, a Spanish study described a case in which both parents of a family had by chance carried a fusion between chromosome pairs 13 and 14.
Three of their six children inherited the same fused chromosome pairs.
In short, none of these objections stand up to scrutiny.
Fusion happened, and humans and chimpanzees share a common biological ancestor."
The de novo mutation that produced chromosome 2 took place by means of a Robertson translocation.
Robertsonian translocation occasionally occur today in the human population, although they are seldom noticed.
The reason that they are unnoticed is because they don’t significantly affect the phenotype.
Robertsonian translocations don’t even produce a significant reproduction barrier.
One reason Robertsonian translocations don’t have a significant effect is that the Robertsonian translocation preserves the centromeres.
The chromosomes in the germline cell ‘recognize’ each other by their centromeres.
So as long as the centromeres are conserved, meiosis is no big deal...
"...Let me qualify what I just said though.
The Robertsonian translocation that caused the fusion of chromosome 2 probably caused an extremely small hybridization barrier that would be virtually unnoticeable in the first few generations after the de novo mutation.
The fusion of chromosome 2 would cause an extremely small hybridization barrier.
It would not be anywhere as big as the famous case of mules and hinnys.
Horses and donkeys have incompatible chromosomes due to a couple of de novo mutations that occurred a long time ago.
The apes with fused chromosome 2 would have been nearly as fertile as the apes without this mutation.
There would be a slight increase in the frequency of Down’s syndrome in crossings between apes with the fusion and without the fusion.
It would hardly be noticed in humans, let alone apes.
However, this small increase in risk could have caused a separation of ‘species’ over many, many generations.
People with a Robertsonian translocation crossing with people without the transplocation may have a slightly increased possibility of having offspring with trisomy 21.
Trisomy 21 causes Down’s syndrome, which in protohumans would have been fatal.
The increase in susceptibility is slight, but there probably is one."
How strong is the chromosome fusion idea?
Well, the first article above refers to it as the "fusion hypothesis", saying:
Not from me.
I've always said God did it, even if the physical evidence He left suggests natural processes.
First, Eugenie Scott is sometimes mentioned by Creationists as a, ah, boogie-person for her strong defense of science against their attacks on it.
Second, here is another discussion of your specific question.
This writer from 2013 is more pessimistic about the probabilities of successful reproduction among fused-chromosome offspring than is the 2017 writer in my post #172 above -- link here.
But he does lay out a realistic scenario in which such events could happen.
Color me unimpressed. You're wasting your time.
Maybe these chromosomes weren't fused at all? Otherwise you would have to explain why three of the six children had normal chromosomes (which is the implication here).
ML/NJ
Sorry, in the interest of brevity (which I've already grossly abused) in post #174 I provided you only a link, not quotes from it, but that does explain at least some of what you say:
From 2013, a less optimistic view of reproductive problems related to chromosome fusing:
The observation that such an event is very unlikely is, in fact, a significant genetic clue that the human species almost went extinct at one point!
Here's what happened: Specifically, the 12th and 13th chromosomes of the ancestors of modern humans (the same chromosomes in apes today except humans) fused to become the 2nd chromosome in modern humans.
A chromosomal fusion in one particular individual doesn't necessarily impact health, but it may reduce their fertility.
About a million years ago, an ancient human (let's say a male) was born with a fused 12th and 13th chromosome.
Thus, he had 47 chromosomes, with three of them being 12, 13, and a 12+13 fusion.
During meiosis, there are three equally likely ways to partition those three chromosomes into two groups:
Of course, under normal circumstances, natural selection eventually weeds these odd-chromosomed humans out of the population due to their reduced fertility.
However, if a 47-chromosome man mates with a 47-chromosome woman (with the same two chromosomes fused), then 1/36 of their children could viably have 46 chromosomes.
Furthermore, now that these children have an even number of chromosomes, the fertility issues no longer exist if these descendants continue to mate with others with 46 chromosomes.
The chances of two people with the exact same fusion mating is extremely small... unless they are closely related.
And that's almost certainly what happened about a million years ago:
For some still unknown reason (possibly climate change, disease, famine, etc), the world human population was reduced to only a few thousand individuals (or perhaps even just a few hundred) scattered around Africa.
Thus, there was much inbreeding in these small isolated groups, creating genetic bottlenecks where rare genes or genetic features (such as having fused 12-13 chromosomes) could become widespread."
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