Text 494, 139 rader
Skriven 2004-10-24 22:24:00 av Michael Ragland (1:278/230)
Ärende: Re: The uncertainty of ev
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Included here is a definition of the "extrernal transition phase" by
Professor Stephen Hawking

http://www.hawking.org.uk/lectures/life.html



This has meant that we have entered a new phase of evolution. At first,
evolution proceeded by natural selection, from random mutations. This
Darwinian phase, lasted about three and a half billion years, and
produced us, beings who developed language, to exchange information. But
in the last ten thousand years or so, we have been in what might be
called, an external transmission phase. In this, the internal record of
information, handed down to succeeding generations in DNA, has not
changed significantly. But the external record, in books, and other long
lasting forms of storage, has grown enormously. Some people would use
the term, evolution, only for the internally transmitted genetic
material, and would object to it being applied to information handed
down externally. But I think that is too narrow a view. 

We are more than just our genes. We may be no stronger, or inherently
more intelligent, than our cave man ancestors. But what distinguishes us
from them, is the knowledge that we have accumulated over the last ten
thousand years, and particularly, over the last three hundred. I think
it is legitimate to take a broader view, and include externally
transmitted information, as well as DNA, in the evolution of the human
race. 

The time scale for evolution, in the external transmission period, is
the time scale for accumulation of information. This used to be
hundreds, or even thousands, of years. But now this time scale has
shrunk to about 50 years, or less. On the other hand, the brains with
which we process this information have evolved only on the Darwinian
time scale, of hundreds of thousands of years. This is beginning to
cause problems. In the 18th century, there was said to be a man who had
read every book written. But nowadays, if you read one book a day, it
would take you about 15,000 years to read through the books in a
national Library. By which time, many more books would have been
written. 

This has meant that no one person can be the master of more than a small
corner of human knowledge. People have to specialise, in narrower and
narrower fields. This is likely to be a major limitation in the future.
We certainly can not continue, for long, with the exponential rate of
growth of knowledge that we have had in the last three hundred years. An
even greater limitation and danger for future generations, is that we
still have the instincts, and in particular, the aggressive impulses,
that we had in cave man days. Aggression, in the form of subjugating or
killing other men, and taking their women and food, has had definite
survival advantage, up to the present time. But now it could destroy the
entire human race, and much of the rest of life on Earth. A nuclear war,
is still the most immediate danger, but there are others, such as the
release of a genetically engineered virus. Or the green house effect
becoming unstable. 

There is no time, to wait for Darwinian evolution, to make us more
intelligent, and better natured. But we are now entering a new phase, of
what might be called, self designed evolution, in which we will be able
to change and improve our DNA. There is a project now on, to map the
entire sequence of human DNA. It will cost a few billion dollars, but
that is chicken feed, for a project of this importance. 

Once we have read the book of life, we will start writing in
corrections. At first, these changes will be confined to the repair of
genetic defects, like cystic fibrosis, and muscular dystrophy. These are
controlled by single genes, and so are fairly easy to identify, and
correct. Other qualities, such as intelligence, are probably controlled
by a large number of genes. It will be much more difficult to find them,
and work out the relations between them. Nevertheless, I am sure that
during the next century, people will discover how to modify both
intelligence, and instincts like aggression. 

Laws will be passed, against genetic engineering with humans. But some
people won't be able to resist the temptation, to improve human
characteristics, such as size of memory, resistance to disease, and
length of life. Once such super humans appear, there are going to be
major political problems, with the unimproved humans, who won't be able
to compete. Presumably, they will die out, or become unimportant.
Instead, there will be a race of self-designing beings, who are
improving themselves at an ever-increasing rate. 

If this race manages to redesign itself, to reduce or eliminate the risk
of self-destruction, it will probably spread out, and colonise other
planets and stars. However, long distance space travel, will be
difficult for chemically based life forms, like DNA. The natural
lifetime for such beings is short, compared to the travel time.
According to the theory of relativity, nothing can travel faster than
light. So the round trip to the nearest star would take at least 8
years, and to the centre of the galaxy, about a hundred thousand years.
In science fiction, they overcome this difficulty, by space warps, or
travel through extra dimensions. But I don't think these will ever be
possible, no matter how intelligent life becomes. In the theory of
relativity, if one can travel faster than light, one can also travel
back in time. This would lead to problems with people going back, and
changing the past. One would also expect to have seen large numbers of
tourists from the future, curious to look at our quaint, old-fashioned
ways. 

It might be possible to use genetic engineering, to make DNA based life
survive indefinitely, or at least for a hundred thousand years. But an
easier way, which is almost within our capabilities already, would be to
send machines. These could be designed to last long enough for
interstellar travel. When they arrived at a new star, they could land on
a suitable planet, and mine material to produce more machines, which
could be sent on to yet more stars. These machines would be a new form
of life, based on mechanical and electronic components, rather than
macromolecules. They could eventually replace DNA based life, just as
DNA may have replaced an earlier form of life. 
This mechanical life could also be self-designing. Thus it seems that
the external transmission period of evolution, will have been just a
very short interlude, between the Darwinian phase, and a biological, or
mechanical, self design phase. This is shown on this next diagram, which
is not to scale, because there's no way one can show a period of ten
thousand years, on the same scale as billions of years. How long the
self-design phase will last is open to question. It may be unstable, and
life may destroy itself, or get into a dead end. If it does not, it
should be able to survive the death of the Sun, in about 5 billion
years, by moving to planets around other stars. Most stars will have
burnt out in another 15 billion years or so, and the universe will be
approaching a state of complete disorder, according to the Second Law of 

Thermodynamics. But Freeman Dyson has shown that, despite this, life
could adapt to the ever-decreasing supply of ordered energy, and
therefore could, in principle, continue forever.

"It's uncertain whether intelligence has any long term survival value.
Bacteria do quite well with it."

Stephen Hawking
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