The following thoughts are probably not original, although I have never seen them put down in this way.
It is a fact that, in general, more complex organisms have more DNA that simpler ones. It is also a fact that more complex forms have more genes than simpler ones. Let's assume that these two facts are connected, as seems reasonable.
Let us also assume that there is some sort of connection between complexity and the numbers of different genes. Again, that seems fair.
Finally let us accept that complex forms have evolved from simpler ones. Not controversial, I hope.
Now let us ask what is the origin of the additional DNA that results in additional genes and increased complexity. Let's restrict ouselves to nuclear DNA. The additional DNA can only be the result of some sort of amplification process during the course of evolution.
Let us assume that this amplification applied equally across the whole genome. The result is, of course, that in the early stages of this process, there will exist multiple copies of identical genes. Let's call these gene families.
Now the progenitor organism managed along quite nicely with one (two if you like) copy of each gene, so its evolutionary descendent has many copies surplus to requirements.
It seems reasonable then to suggest that these "spare" copies are free to undergo any sort of change we care to imagine, without presenting themselves as a negative selection target. But these evolutionary "experiments" can be expected, from time to time, to confer selective advantage.
Moreover, it is known that gene families are capable of undergoing much more dramatic and sudden sequence alteration than are singletons. For example, single genes mostly suffer point mutaion, deletion or insertion. Gene families, on the other hand readily exchange blocks of sequence, and this is a relatively error-prone process.
So the suggestion is that a mechanism of this sort could quite easily result in sudden and dramatic evolutionary change with no evidence of intermediate forms
It is a fact that, in general, more complex organisms have more DNA that simpler ones. It is also a fact that more complex forms have more genes than simpler ones. Let's assume that these two facts are connected, as seems reasonable.
Let us also assume that there is some sort of connection between complexity and the numbers of different genes. Again, that seems fair.
Finally let us accept that complex forms have evolved from simpler ones. Not controversial, I hope.
Now let us ask what is the origin of the additional DNA that results in additional genes and increased complexity. Let's restrict ouselves to nuclear DNA. The additional DNA can only be the result of some sort of amplification process during the course of evolution.
Let us assume that this amplification applied equally across the whole genome. The result is, of course, that in the early stages of this process, there will exist multiple copies of identical genes. Let's call these gene families.
Now the progenitor organism managed along quite nicely with one (two if you like) copy of each gene, so its evolutionary descendent has many copies surplus to requirements.
It seems reasonable then to suggest that these "spare" copies are free to undergo any sort of change we care to imagine, without presenting themselves as a negative selection target. But these evolutionary "experiments" can be expected, from time to time, to confer selective advantage.
Moreover, it is known that gene families are capable of undergoing much more dramatic and sudden sequence alteration than are singletons. For example, single genes mostly suffer point mutaion, deletion or insertion. Gene families, on the other hand readily exchange blocks of sequence, and this is a relatively error-prone process.
So the suggestion is that a mechanism of this sort could quite easily result in sudden and dramatic evolutionary change with no evidence of intermediate forms
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