(urth) Mystery of Ascia

[Gerry Quinn]

From: "Lee Berman" <severiansola at hotmail.com>
> Gerry Quinn wrote (21-01-2011 20:10):
>>> It would be foolish to take a law such as Dollo's as an absolute in any
>>> case - but it is a pretty solid general prediction if the conventional
>>> theory of evolution is valid.
>
>>Antonio Pedro Marques:
>>Not really, since our species is not known for being dependent on 
>>biological
>>adapation to the environment in the same way the others are.
>
> There is something to what Antonio says but not only because humans use 
> cultural flexibility to
> adapt to our environments. It is also because our species is so young. As 
> young as 50,000 years
> old but no more than 1 million years old depending on how you want to 
> define things. Either way,
> not long enough for significant evolutionary change to take place, on the 
> level that Dollo's Law
> requires.

Nonsense.  Dollo's Law will apply in any situation where selection is 
sufficient to reduce the presence of certain genes to a very small 
proportion of the population.  It will also apply to a degree when new genes 
become essentially omnipresent in a population, or at least when new genes 
start to interact significantly with other genes to the extent that they 
cannot simply be discarded.

This can and does occur on a timescale that is quite short compared to human 
evolutionary history.

I gave an obvious example: a tribe of Swedes, relocated to sub-Saharan 
Africa, will never become identical to the local people there (or more 
precisely, to their ancestors there, if we assume for simplicity that they 
started there and moved as a tribe to Sweden), even though they will adapt 
to the local climate in ways which will probably be similar to a degree. 
The Swedes have gained and lost genes over time, and the original pattern of 
genes and corresponding traits will never be replaced.  They may turn black, 
but they will never be the same *shade* of black.  This is precisely Dollo's 
Law in action.

Dollo may have formulated it in terms of large structural changes, but it 
applies on a smaller scale too.


> Anyway, Dollo's Law, while insightful, is pretty damn archaic. It was 
> formulated before Mendelian
> genetics was widely understood. And even 5HoC was written before a couple 
> revolutions in modern
> understanding of genetics occurred. So Gene Wolfe didn't understand that 
> most shorter term evolution
> (like in the tens of millions of years) occurs by a shutting off of 
> certain genes, not their
> loss from the gene pool.

Gravity was discovered before more modern understandings of it were 
developed.  Does that mean we should throw away the concept?

> This is one of the reason our genome is mostly composed of "junk DNA". 
> Codes for stuff that doesn't
> do anything. But the genes are often still there, and sometimes they get 
> accidentally turned on as we
> see when those rare children are born with a tail or covered in a furry 
> pelt.


The mechanism of shutting off is completely irrelevant. If a gene is shut 
off over many generations it is because another gene has changed, or been 
lost, or gained.

If humans develop tails or fur, they will be different from the tails and 
fur of our ancestors.

- Gerry Quinn