>>How does complexity come about?
> >>Complexity increases by variations, some of which themselves
> >produce even more-complex variations.
Susan:
>> what Chris talks about above has been observed to occur and isn't
>>controversial.
Me:
>What observations do you have in mind? (I hope you are not confusing
>observation with inference).
Susan replies:
>this is from the much-maligned talk.origins website:
>"[An] obvious increase in information can occur when a gene duplicates
>and the two copies undergo independent mutations leading to two genes with
>somewhat different functions.
I agree that this can happen and probably has happened. But is this
really the mechanism behind the origin of so many new genes? I
am quite familiar with this textbook model, enough so to realize
that it is not very robust in that it simply ignores the obstacles
to the duplication-functional divergence proposals and merely assumes
they were overcome. Thus, it's not a question of whether this
can occur. It's a question of whether this was really the driving
mechanism.
>Gene duplication, mutation and selection are all known to occur
>due to natural biochemical processes in a variety of organisms studied
>in the laboratory.
What variety of organisms has this been observed in? What genes
and what functions is this author talking about?
>Many gene families are known with members that encode proteins
>having related structure and related but distinct function. Each family can
>be explained by multiple gene duplications followed by random
>mutation and differentiation of the functions of the individual gene
>copies.
This is an inference, not an observation. That something can be
explained in light of this model is hardly surprising given that
the model is so vague. What is almost always missing from
these explanations is independent evidence that the model
correctly interprets the data. Typically what you have is this:
Two genes are found that are similar. Similarity is interpreted
to mean genetic relatedness. The differences are interpreted
to arise from divergence after duplication. The mutations
and differentiation of functions, along with the selective
advantages associated with them, are unknown and simply
exist in the realm of vague imagination. None of this means
the model-explanations are incorrect, but I think it important
to realize we are dealing with explanation that may sound
more rigorous than they really are.
>Clearly the expansion from a single primordial gene to a large
>family of genes with distinct functions represents an increase
>in genetic information."
I would tend to agree, however, with two caveats. First,
increasing the amount of genetic information does not
necessarily correlate with an increase in organismal complexity.
Secondly, as far as I know, such expansions are all
inferences and not observations.
Chris also replied to my request with the following:
>For just two examples: the increase in genes of yeast forced to live for
>many generations in a low-sugar environment, the increase in genes in
>bacteria forced to live in an environment that's too warm for them, etc.
Without references for these claims, I can not reasonably discuss
them or their significance. Perhaps Chris can supply those
references. Furthermore, while he is at it, I note that he gives
the impression there are many such examples (since these are
just two and the list is followed with "etc."). Given that
Chris seems knowledgeable about this area and probably has
a longer list of obervations in mind, perhaps he can also pick
the five most impressive examples of these observed examples
of increasing complexity.
Mike