Re: Ping Rumple

Rumpelstiltskin wrote:
On Sun, 20 Sep 2009 18:18:50 -0700, Islander <nospam@xxxxxxxxxxx>
wrote:

Rumpelstiltskin wrote:
On Sat, 19 Sep 2009 18:46:48 -0700, Islander <nospam@xxxxxxxxxxx>
wrote:

Rumpelstiltskin wrote:
On Sat, 19 Sep 2009 12:47:11 -0700, Rita <Rita@xxxxxxxxxxx> wrote:

In a post in reply to Emily about eugenics -- improving the
gene pool -- I cited Darwin and natural selection:

Another argument against is that
eugenic policies could also lead to loss of genetic diversity, in
which case a culturally accepted improvement of the gene pool could
very likely, as evidenced in numerous instances in isolated island
populations (e.g. the Dodo, Raphus cucullatus, of Mauritius) result in
extinction due to increased vulnerability to disease, reduced ability
to adapt to environmental change and other factors both known and
unknown. A long-term species-wide eugenics plan might lead to a
scenario similar to this because the elimination of traits deemed
undesirable would reduce genetic diversity by definition.
The cheetah is in danger because there's so little diversity in its DNA. There's a lot of concern about
the lack of genetic diversity in, for example, commercial wheat, since a plague organism could rapidly devastate all the grain since all would be equally affected, and there would be no varieties that might have greater resistance and thereby provide a basis for a grain more resistant to that plague.

A "Eugenics plan" sounds very dangerous to me,
though life is dangerous anyway, for individuals and for whole species. We humans don't know what we're doing. As is well known, trying to protect children against everything produces adults who are not hardened to weather subsequent viral and
bacterial attacks in adulthood. As to mankind's
wisdom and expertise, Voltaire noted that "The course of rivers to the sea is not so swift as the course of man into error", and Burns of course wrote:

Now mousie, thou are no thy lane
In finding forethought might be vain.
The best-laid plans o' mice and men
Gang aft agley,
And leave us nought but grief and pain
For promised joy.

Humans had a bottleneck, it's now thought - about 150,000 years ago. Homo sapiens is about 200,000 years old. The modern theory (opposed to Darwin's gradualism) is that Homo sapiens arose as a result of rapid speciation ("punctuated equilibrium") and hasn't changed much since. According to the site below, humanity might have been down to just 2000 people at that time. If we'd gone extinct, we
wouldn't have evolved again. Perhaps something
from another hominid line would have mutated into
a large-brained species like ourselves, or perhaps
something else would, or perhaps it wouldn't happen at all for the foreseeable future.

I don't think that you can claim with any degree of certainty that any species that becomes extinct might not appear again if the evolutionary environment favors it. In the DNA study of biological evolution, it has been shown that the tree of life is, in fact, not a tree but a network of reconvergent branches. Specific DNA traits appear, disappear, and reappear again over time.

It's not certain, only 99.999999999999999% certain,
about as certain as I am that there is no god. That's just the odds of the DNA. Any animal that goes extinct is done for, except for human intervention. We might get the dodo and the quagga back, just because we have the DNA and might be able to clone it, in the manner of "Jurassic Park". Even if we only had the complete DNA map, we might be able to recreate an extinct animal, but there is the complication, of unknown severity, that the development of an animal is not just the product of its DNA, but also of the environment of the placenta. And very recently, "epigenetics" has been suggested. I hope "epigenetics" does have a future, and isn't just a chimera, because it would be interesting to have Lamarckian components of evolution resurrected.



I certainly do not mean to imply that we should dismiss extinction because the species "might" reappear. As you point out, the chances of that are pretty remote for anything more complex than a few cells. On the other hand, given enough time...


That assumes that there's one optimum, but there isn't. We humans certainly are not perfection, nor is any other complex animal. We're so far from optimum that there are trillions upon trillions of arrangements that would work
just as well, and trillions of arrangements that could work
even better if natural selection could jump a wide valley
that in practice would be impossible without a "designer".
For example, centaurs might be a good idea - four legs
would be handy - four arms IMV much better - but we
can't jump the mountain up which we climbed by way of small handholds that random variation could
reasonably stumble upon, across a valley or hopeless
monsters over to a mountain with successfully hopeful monsters that have four arms. Wouldn't it be
handy for birds to have arms? But they don't. The first fish to crawl onto land had four fin structures so we vertebrates get four legs, two arms and two legs,
or two legs and two wings. We can subtract from that four little by little, as with snakes and whales,
extra limbs arising spontaneously would be tough.

Dawkins' "Climbing Mount Improbable" goes into
that. One can look at humans, their eyes, their hands, and ask "how could this arise without the intervention of a god?" The cliff face to get to humans seems so high. But if you go around the back of the mountain, you'll find there is at least one way to get up to pinnacles which, seen only
from the viewpoint where the top of the cliff can
be seen easily, seems impossible to get to. Dawkins goes into the eye particularly, since it's so often used to "prove" the existence of gods because "what use is half an eye?" Dawkins shows creatures still around on the earth today that show a path, from light-sensitive cells useful for telling if it's day or night, to larger patches that can make out blurry large shapes, to indented patches that provide some focussing, to pinholes that will increase the focussing like a pinhole camera, as in the chambered nautilus, to pinholes with a drop of dew to act as a lens, then a colloid, then a colloid with a stiff outer surface, and so forth.
Little by little, you do get to the eye by little bits,
each of which does offer advantage. The eye
has evolved separately several times, so there's
not just one way to climb that particular cliff. We humans have the pathway for channeling the
information to the brain on top of the retina, rather stupidly blocking part of the light. That's just the way it worked out in vertebrates. Once fixed, there's too far of a valley to jump to get to the more practical idea of having the transmission cells underneath the retina where they don't block the light. Squids and Octopi evolved eyes separately though, and they did stumble across
the more sensible way, with the transmission cells below the retina instead.

Perhaps some viruses are "perfect" in the sense that the possibilities are so small in number that there is one structure that can be called optimum from a given viewpoint, and they're simple enough that there's a chance they might get there twice before the universe ends.
Humans aren't going to get four arms though,
no matter how useful it would be, before the universe ends, without starting from six-finned
fishes and working back up from there, but with the added disadvantage of having to deal with an "arms race" along the way with creatures that developed from four-finned fish and have by now attained enormous advantages in other ways.

We humans are like gods now though in that
we can foresee and implement design, instead of just bumbling along stupidly as natural selection does because it has no brain. Zaphod Beeblebrox got an extra arm and an extra head attached to himself in "The Hitchhiker's guide to the Galaxy", thus getting across a wasteland between the mountain we're born on, across a
Death Valley toward a shining peak we can see
far away in the distance, which would be too far to get to without dying in the valley even if we started out in the right direction toward that shining peak, unless we had godlike vision
and capability such as humans have: the only time in Earth's five-billion year history that any
creature has climbed so high. But the climb
up was only to a peak that could be attained naturally, not somehow a leap up to a peak that has no handholds to get to the summit. That is,
until and unless a creature evolves with the capacity to see the peak, and develop the advanced climbing gear necessary to get up it. We can only naturally climb mountains that have such handholds as allow them to be crawled up, the way Natural Selection does.
The mountain on which on which humans now
find themselves on was necessarily one of those mountains with handholds all the way up.
The climb may have been tricky sometimes, but never impossible.

IIRC, Dawkins describes macro-mutations as a way for evolution to move from one hill to another.

The analogy of hill climbing is a useful way to think about evolution, but if one needs to be completely accurate, one must also consider that the hill can change over time due to external influences. For example, when a bacteria becomes immune to an anti-bacterial agent it is because that agent was introduced into the bacteria's particular hill and the bacteria evolved in an altogether different way.

I think that we have discussed hill climbing before. I first became aware of it as a software programming technique.

Epigenetics sounds interesting. First I heard of it. Hmmm. Cells behaving in ways that are not in their "program." An external effect?


I only heard of it lately. What I gather about it is that
the operation of genes is controlled by proteins around
the DNA molecules, hence the "epi-". These proteins
do get inherited, as the contention goes, but unlike genes whose pattern is for the most part cast in stone,
they're affected by what goes on in an animals lifetime.
Identical twins start out with the same genes and always have the same genes, but the overlaying proteins that regulate the genes change and differ.

Here's the Wikipedia article on epigenetics. Note
the "structural inheritance" and "evolution" sections
which hint at the highly speculative but very intriguing possibility of Lamarckian inheritance. This idea may go nowhere, or it may open our eyes to a whole new Wonderland:
http://en.wikipedia.org/wiki/Epigenetics



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