Changing Chromosome Numbers

[Powell]

If we have 46 chromosomes and other primates have 48 chromosomes then there must have been a point during our evolutionary path that two chromosomes fused together to form one chromosome (from what i've read it is apparently chromosome 2). If this is true then the fusion of these 2 chromosomes must have been a random mutation according to darwinian evolution. However if this new mutant hominid had any offspring with any of the other hominids around it that still had the 'normal' chromosome number then it's children would be infertile (as in the cases of mules were the horse has 64 chromosomes and the donkey has 62 chromosomes giving an offspring of 63 chromosomes that does not pair properly and cannot divide) So if the children where infertile then there is no way this mutation would suceed. The only way this could happen is if a large number of the hominidsall mutated within the same generation and were all in the same geological area and decided to mate with each other. The path of human evolution was very rapid in evolutionary terms and I think the odds of this random mutation happening lots of times within the space of about 20 years very slim indeed.

 

So my Questions are:

 

1. How do to chromosomes fuse together?

2. What is the evolutionary advantage of having less chromosomes

3. how did any offspring of the new mutant hominid born without being infertile.

[Wormwood]

It is an interesting question no doubt. There are other evolutionary characteristics which suggest a different mechanism than we traditionally observe. HGT is a good example, or the explanation of endosymbiosis. The only answer that is consistent with these anomalies IMO is rapid evolution. Certainly, anyone can see that a given organism will make numerous minor adjustments through the mechanisms we have identified, but what we have identified doesn't even begin to explain something like the Cambrian explosion. Watching bacteria acquire different alleles doesn't explain such rapid diversification/speciation, or something like sexual reproduction; but a rapid evolutionary response to extreme environmental stimuli would be consistent with any of these. There has to be some sort of stimuli that shuts down the natural defenses against genetic mutation (self correction processes) but also moves in the same general direction across different organisms of the same species.

 

Again, think about sexual reproduction. If one organism developed this trait, it would not be very useful. It would require multiple organisms of the same species to develop this "random mutation" at the same time.

[bored_teen]

no, 4 chromosomes would fuse. if we have two less, and two fuses into one, we'd need 4 (2 pairs) to fuse.

 

so what'd happen if instead of a 2 chromosome difference, there was a 4 chromosome difference? it would be fertile, right?