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Chromosone Fusion


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#1 jason777

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Posted 30 March 2010 - 02:59 AM

It is quite clear that the human version of chromosome 2 has in fact suffered a fusion event sometime in the past. Telomeres, for example, are usually found only at the ends of chromosomes - not in the middle. However, within the middle of chromosome 2 there is a pretelomeric sequence, a telomeric sequence, an inverted telomeric sequence and an inverted pretelomeric sequence - in that order. There are also remnants of an extra centromere as well as similar banding patterns with the equivalent chromosomes (2p and 2q) of apes

How can I possibly even suggest such an argument? - against the vast majority of mainstream scientists? Well, for one thing, chromosomal fusions happen to be fairly common - even within the same species. In fact, there are humans alive today that have chromosomal fusions - and surprise surprise, they're still human! - morphologically and functionally indistinguishable from other modern humans. Another example can be found with horses. Hybrids of the wild horse have 33 pairs while the domesticated horse has 32 chromosomal pairs. Also, domestic dogs and wolves of the genus canis have 78 chromosomes while foxes have a varied number from 38-78 chromosomes. Yet another example is the house mouse Mus Musculis, which has 40 chromosomes, while a population of mice form the Italian Alps was found to have only 22 chromosomes ( Link )

So, the different chromosomal numbers between humans and apes doesn't necessarily indicate common ancestry. It is not evidence for when the event took place, nor is it evidence for the ancestry prior to that event. It could just as easily mean that similar creatures with independent ancestries originally had the same chromosome number and general banding patterns - a number that was later altered by fusion mutations in the human population during a population bottleneck. Given another dramatic population bottleneck in the future, such a transmissible fusion could easily happen again - in either apes or humans . . . or any other creature for that matter. That's what's clearly predictable here. Even those who believe in intelligent design (ID) understand that not all genetic features require the input of intelligence. The simple fusion of two chromosomes, without any significant functional gain or loss, is easy to explain via random mindless processes and is actually fairly common. No big deal. Not very surprising or shocking - not even from an ID perspective. In fact, evolutionists would make exactly the same argument for the common ancestry of humans and apes without the fusion of chromosome 2. This fusion event really adds nothing to the argument. It simply presents no additional explanatory or predictive power to the argument for common descent beyond the simple observation that similarities suggest a common origin of some kind...

In other words, those evolutionists who present this argument do not provide any evidence that the human ancestor who originally had 48 chromosomes (as apes do), was actually any more closely "related" to apes, functionally or morphologically, than are modern humans. It isn't the fact that apes have 48 chromosomes that make them look and act and function like apes rather than humans. If it were that simple, evolutionists would actually have a very good argument. The problem for Darwinists is that it isn't nearly that simple - not even close. This chromosomal number difference produces no obvious functional differences between apes and humans in and of itself - none at all. Therefore, it is not a stretch to assume that any 48 chromosome ancestor of modern humans might have also had a chromosomal scheme similar to that of apes, regardless of whether or not that individual was "related" to apes via common descent. Claiming that banding pattern similarities is evidence of common ancestry with apes simply invokes the “similarity = common descent” argument, and thus begs the question.

While it is quite reasonable that strong similarities, such as exist between humans and apes, do in fact indicate a common origin, that common origin is not necessarily based on common descent via slow genetic modifications selected by mindless nature over time from some shared common ancestor. Given the highly functionally complex differences between the two species which are being discovered more and more in recent years (especially in non-coding regions of the genome) it seems far more likely that the common origin of these differences, as well as the similarities, was based in deliberate highly intelligent design. The only event(s) that clearly do not require the input of high-level outside intelligence are events like random chromosomal fusions or other forms of random mutations which are very unlikely to produce any functional benefit beyond very low levels of functional complexity.

Again, it is entirely possible, quite likely in fact, that our human ancestors underwent a chromosomal fusion event during a population bottleneck in fairly recent history (i.e., within the past several thousand years at most), easily explaining the fusion of chromosome 2. This concept is supported by an article published in a 2003 issue of Nature by Rohde et. al. where the authors make the following argument:



"These analyses suggest that the genealogies of all living humans overlap in remarkable ways in the recent past. In particular, the MRCA [most recent common ancestor] of all present-day humans lived just a few thousand years ago [~3,000] in these models. Moreover, among all individuals living more than just a few thousand years earlier than the MRCA, each present-day human has exactly the same set of genealogical ancestors."




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Posted 30 March 2010 - 01:25 PM

Yes, but where is the lack of variation that would indicate a bottleneck??? A chromosomal fusion cannot, by itself, reduce variation.

#3 Cata

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Posted 30 March 2010 - 04:31 PM

The chromosomal fusion indicates that all humans today had the same ancestor up to a certain point.
According to this, the MRCA lived a few thousand years ago.

Lack of variation?
I do not get exactly what you mean, but if I remember correctly humans have very similar genes to each other, more than a 99.9 percent similarity among each other.
A fusion would not reduce variation, but a bottleneck will.

#4 Hawkins

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Posted 30 March 2010 - 07:49 PM

I think that first it needs to be addressed that whethre a fused chromosom and a split chromosom will distinguishingly identifies humans from the great apes.

Second is how possible it is for a split rather than a fusion. Say if fusion and split can't uniquely identify humans from apes, it doesn't matter if chromosom 2 is fused or splited, humans will still be humans and apes will still be apes.

Third, if the fusion/split actually distinguishes humans from apes, then we may need to address humans and apes are more alike in the past or now. If humans and apes are more alike in the past, it shows that either human chromosom 2 is 'more fused' in the past or more 'splited' in the past in order to be more assemble to the apes.

Either way, if humans and apes in the past are more alike to each other, where will be the position of other homoerectus such as the neanderthals. That is, the neanderthals' chromosom 2 may well be half fused or half splited such that they may be able to interbreed with other homoerectus or even apes.

Finally, if the homoerectus between man and ape can interbreed with both, ANYTHING will be possible. ;)

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Posted 30 March 2010 - 10:48 PM

The chromosomal fusion indicates that all humans today had the same ancestor up to a certain point.
According to this, the MRCA lived a few thousand years ago.

Lack of variation?
I do not get exactly what you mean, but if I remember correctly humans have very similar genes to each other, more than a 99.9 percent similarity among each other.
A fusion would not reduce variation, but a bottleneck will.

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It's the variation of alleles. For example, eye color and hair color are examples of variation.

A more applicable example would be blood type. I'm sure you know that blood type is the most important factor to consider when in blood transfusions, organ transplants, etc. Cheetahs lack this variation. You can take the skin of any cheetah and graft onto another cheetah and it won't be rejected.

Humans have too much variation for a recent genetic bottleneck. This is why inbreeding is such a big deal in populations.

Think about it like this. Let's say a generation is 30 years, and you wanted to go back to the time of Jesus, so say 60 generations. Since you have two parents, and each of their parents have two parents your family tree would grow exponentially at a rate of 2^number of generations. So 60 generations ago would be 2^60 which is over 1 quintillion human beings, or more than have ever lived. If two cousins 5 times removed had kids this collapses part of the tree.

The point of all that is that the most recent common ancestor doesn't mean the first, the only, or the beginning. Other humans today would also be descendants of the other humans living at the time of the MRCA, but would also be connected to the MRCA's lineage. There would be humans before the MRCA and common ancestors before the MRCA as well.

#6 Cata

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Posted 01 April 2010 - 05:46 PM

Humans have too much variation for a recent genetic bottleneck.  This is why inbreeding is such a big deal in populations. 


How do you claim to know this when you are only looking at humans today?
Do you know how much time is needed for a certain amount of variation, or are you just assuming so from your evolutionary presumptions?

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Posted 04 April 2010 - 03:26 PM

How do you claim to know this when you are only looking at humans today?
Do you know how much time is needed for a certain amount of variation, or are you just assuming so from your evolutionary presumptions?

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Because a lack of variation has been observed in living animals. I think I mentioned cheetahs to you.

#8 jason777

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Posted 04 April 2010 - 09:30 PM

Because a lack of variation has been observed in living animals. I think I mentioned cheetahs to you.


How many cheetahs are alive today? Surely not 4.5 billion. Some estimates are ~10,000, so we can easily establish why cheetah variation is less than humans. In fact, according to evolution, cheetahs have been around many millions of years and that should give them more variation than humans. It would'nt be very likely that only two individuals survived an extinction event and prevented the past range of variation to be passed on. It's not a problem for creation because the bible says that only one breeding pair was taken aboard the ark.

Humans live all around the world and have produced .1% variation because of it. Cheetahs only have two populations on the same continent, which would'nt prevent them from breeding together today. Human population growth is also exponential and not linear, so that also accounts for a kick start in human genetic variation.

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#9 skeptic

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Posted 06 April 2010 - 05:28 AM

I think that first it needs to be addressed that whethre a fused chromosom and a split chromosom will distinguishingly identifies humans from the great apes.

Second is how possible it is for a split rather than a fusion. Say if fusion and split can't uniquely identify humans from apes, it doesn't matter if chromosom 2 is fused or splited, humans will still be humans and apes will still be apes.

Third, if the fusion/split actually distinguishes humans from apes, then we may need to address humans and apes are more alike in the past or now. If humans and apes are more alike in the past, it shows that either human chromosom 2 is 'more fused' in the past or more 'splited' in the past in order to be more assemble to the apes.

Either way, if humans and apes in the past are more alike to each other, where will be the position of other homoerectus such as the neanderthals. That is, the neanderthals' chromosom 2 may well be half fused or half splited such that they may be able to interbreed with other homoerectus or even apes.

Finally, if the homoerectus between man and ape can interbreed with both, ANYTHING will be possible.  :lol:

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At first, the fused chromosome is not what makes us human apart from the other apes. It´s just one of several differences, so you are right it doesn´t matter for the distinction to be a human or an ape.

We can distinguish a split from a fusion event in chromosomes because of the location of the telomeres in the middle of the fused chromosome. We are therefore quite sure there was a fusion event at some point in our history. A chromosome fusion or other deformations could be a problem at reproduction but don´t have to, so the individual with the fused chromosome could normally reproduce with other "non-fused" individuals. It´s remarkable but actually just like other "normal" mutations. With genetic drift this trait could get fixed in the population over time. There is no such thing as "half splitted" or "half fused".
Normally you need a bottleneck event to get a trait fixed fast by genetic drift. Without bottleneck it takes more generations.

Again, it is entirely possible, quite likely in fact, that our human ancestors underwent a chromosomal fusion event during a population bottleneck in fairly recent history (i.e., within the past several thousand years at most), easily explaining the fusion of chromosome 2. This concept is supported by an article published in a 2003 issue of Nature by Rohde et. al. where the authors make the following argument:

"These analyses suggest that the genealogies of all living humans overlap in remarkable ways in the recent past. In particular, the MRCA [most recent common ancestor] of all present-day humans lived just a few thousand years ago [~3,000] in these models. Moreover, among all individuals living more than just a few thousand years earlier than the MRCA, each present-day human has exactly the same set of genealogical ancestors."


He doesn´t talk about a bottleneck, he talks about an most recent common ancestor. Big difference, they don´t have to relate to each other.
The world population of humans 1000 years ago and earlier might have been around a million individuals. Every living human has two parents. They also have each two parents and so on. Depending on the mobility of the people you need at least 20 generations (about 400 years) to be statistically related to the whole population of all humans. Depending on the mobility model the actual period is around 3000 years. That doesn´t mean at that time there was only one couple alive or something like that, just that all descendants from all people alive at that time are related to some extend.




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