مراقب 4
11-23-2010, 02:52 AM
هذا تعليق دوكنز على الفيديو، ردًّا على من يدعي أنّه مزيف، أو أنّ السؤال سطحي كما حدث حين وضعت الفيديو على صفحة الفيسبوك، فدوكنز يرى أنّ السؤال المطروح خلافي، وأن إجابات تطوريين من وزن جولد تكون بالنفي، ولكنه يجيب بنعم!
in september 1997, i allowed an australian film crew into my
house in oxford without realising that their purpose was
creationist propaganda. In the course of a suspiciously amateurish
interview, they issued a truculent challenge to me to "give an
example of a genetic mutation or an evolutionary process which
can be seen to increase the information in the genome." it is the
kind of question only a creationist would ask in that way, and it
was at this point i tumbled to the fact that i had been duped into
granting an interview to creationists - a thing i normally don't do,
for good reasons. In my anger i refused to discuss the question
further, and told them to stop the camera. However, i eventually
withdrew my peremptory termination of the interview as a whole.
This was solely because they pleaded with me that they had come
all the way from australia specifically in order to interview me.
Even if this was a considerable exaggeration, it seemed, on
reflection, ungenerous to tear up the legal release form and throw
them out. I therefore relented.
My generosity was rewarded in a fashion that anyone familiar
with fundamentalist tactics might have predicted. When i
eventually saw the film a year later 1, i found that it had been
edited to give the false impression that i was incapable of
answering the question about information content 2. In fairness,
this may not have been quite as intentionally deceitful as it
sounds. You have to understand that these people really believe
that their question cannot be answered! Pathetic as it sounds, their
entire journey from australia seems to have been a quest to film
an evolutionist failing to answer it.
With hindsight - given that i had been suckered into admitting
them into my house in the first place - it might have been wiser
simply to answer the question. But i like to be understood
whenever i open my mouth - i have a horror of blinding people
with science - and this was not a question that could be answered
in a soundbite. first you first have to explain the technical
meaning of "information". Then the relevance to evolution, too,
is complicated - not really difficult but it takes time. Rather than
engage now in further recriminations and disputes about exactly
what happened at the time of the interview (for, to be fair, i
should say that the australian producer's memory of events seems
to differ from mine), i shall try to redress the matter now in
constructive fashion by answering the original question, the
"information challenge", at adequate length - the sort of length
you can achieve in a proper article.
Information
the technical definition of "information" was introduced by the
american engineer claude shannon in 1948. An employee of the
bell telephone company, shannon was concerned to measure
information as an economic commodity. It is costly to send
messages along a telephone line. Much of what passes in a
message is not information: It is redundant. You could save
money by recoding the message to remove the redundancy.
Redundancy was a second technical term introduced by shannon,
as the inverse of information. Both definitions were mathematical,
but we can convey shannon's intuitive meaning in words.
Redundancy is any part of a message that is not informative,
either because the recipient already knows it (is not surprised by
it) or because it duplicates other parts of the message. In the
sentence "rover is a poodle dog", the word "dog" is redundant
because "poodle" already tells us that rover is a dog. An
economical telegram would omit it, thereby increasing the
informative proportion of the message. "arr jfk fri pm pls mt
ba cncrd flt" carries the same information as the much longer,
but more redundant, "i'll be arriving at john f kennedy airport on
friday evening; please meet the british airways concorde flight".
Obviously the brief, telegraphic message is cheaper to send
(although the recipient may have to work harder to decipher it -
redundancy has its virtues if we forget economics). Shannon
wanted to find a mathematical way to capture the idea that any
message could be broken into the information (which is worth
paying for), the redundancy (which can, with economic
advantage, be deleted from the message because, in effect, it can
be reconstructed by the recipient) and the noise (which is just
random rubbish).
"it rained in oxford every day this week" carries relatively little
information, because the receiver is not surprised by it. On the
other hand, "it rained in the sahara desert every day this week"
would be a message with high information content, well worth
paying extra to send. Shannon wanted to capture this sense of
information content as "surprise value". It is related to the other
sense - "that which is not duplicated in other parts of the message"
- because repetitions lose their power to surprise. Note that
shannon's definition of the quantity of information is independent
of whether it is true. The measure he came up with was ingenious
and intuitively satisfying. Let's estimate, he suggested, the
receiver's ignorance or uncertainty before receiving the message,
and then compare it with the receiver's remaining ignorance after
receiving the message. The quantity of ignorance-reduction is the
information content. Shannon's unit of information is the bit, short
for "binary digit". One bit is defined as the amount of information
needed to halve the receiver's prior uncertainty, however great
that prior uncertainty was (mathematical readers will notice that
the bit is, therefore, a logarithmic measure).
In practice, you first have to find a way of measuring the prior
uncertainty - that which is reduced by the information when it
comes. For particular kinds of simple message, this is easily done
in terms of probabilities. An expectant father watches the
caesarian birth of his child through a window into the operating
theatre. He can't see any details, so a nurse has agreed to hold up a
pink card if it is a girl, blue for a boy. How much information is
conveyed when, say, the nurse flourishes the pink card to the
delighted father? The answer is one bit - the prior uncertainty is
halved. The father knows that a baby of some kind has been born,
so his uncertainty amounts to just two possibilities - boy and girl -
and they are (for purposes of this discussion) equal. The pink card
halves the father's prior uncertainty from two possibilities to one
(girl). If there'd been no pink card but a doctor had walked out of
the operating theatre, shook the father's hand and said
"congratulations old chap, i'm delighted to be the first to tell you
that you have a daughter", the information conveyed by the 17
word message would still be only one bit.
Computer information
computer information is held in a sequence of noughts and ones.
There are only two possibilities, so each 0 or 1 can hold one bit.
The memory capacity of a computer, or the storage capacity of a
disc or tape, is often measured in bits, and this is the total number
of 0s or 1s that it can hold. For some purposes, more convenient
units of measurement are the byte (8 bits), the kilobyte (1000
bytes or 8000 bits), the megabyte (a million bytes or 8 million
bits) or the gigabyte (1000 million bytes or 8000 million bits).
Notice that these figures refer to the total available capacity. This
is the maximum quantity of information that the device is capable
of storing. The actual amount of information stored is something
else. The capacity of my hard disc happens to be 4.2 gigabytes. Of
this, about 1.4 gigabytes are actually being used to store data at
present. But even this is not the true information content of the
disc in shannon's sense. The true information content is smaller,
because the information could be more economically stored. You
can get some idea of the true information content by using one of
those ingenious compression programs like "stuffit". Stuffit looks
for redundancy in the sequence of 0s and 1s, and removes a hefty
proportion of it by recoding - stripping out internal predictability.
Maximum information content would be achieved (probably
never in practice) only if every 1 or 0 surprised us equally. Before
data is transmitted in bulk around the internet, it is routinely
compressed to reduce redundancy.
That's good economics. But on the other hand it is also a good
idea to keep some redundancy in messages, to help correct errors.
In a message that is totally free of redundancy, after there's been
an error there is no means of reconstructing what was intended.
Computer codes often incorporate deliberately redundant "parity
bits" to aid in error detection. Dna, too, has various errorcorrecting
procedures which depend upon redundancy. When i
come on to talk of genomes, i'll return to the three-way distinction
between total information capacity, information capacity actually
used, and true information content.
It was shannon's insight that information of any kind, no matter
what it means, no matter whether it is true or false, and no matter
by what physical medium it is carried, can be measured in bits,
and is translatable into any other medium of information. The
great biologist j b s haldane used shannon's theory to compute
the number of bits of information conveyed by a worker bee to her
hivemates when she "dances" the location of a food source (about
3 bits to tell about the direction of the food and another 3 bits for
the distance of the food). In the same units, i recently calculated
that i'd need to set aside 120 megabits of laptop computer memory
to store the triumphal opening chords of richard strauss's "also
sprach zarathustra" (the "2001" theme) which i wanted to play in
the middle of a lecture about evolution. Shannon's economics
enable you to calculate how much modem time it'll cost you to email
the complete text of a book to a publisher in another land.
Fifty years after shannon, the idea of information as a commodity,
as measurable and interconvertible as money or energy, has come
into its own.
Dna information
dna carries information in a very computer-like way, and we can
measure the genome's capacity in bits too, if we wish. Dna
doesn't use a binary code, but a quaternary one. Whereas the unit
of information in the computer is a 1 or a 0, the unit in dna can
be t, a, c or g. If i tell you that a particular location in a dna
sequence is a t, how much information is conveyed from me to
you? Begin by measuring the prior uncertainty. How many
possibilities are open before the message "t" arrives? Four. How
many possibilities remain after it has arrived? One. So you might
think the information transferred is four bits, but actually it is two.
Here's why (assuming that the four letters are equally probable,
like the four suits in a pack of cards). Remember that shannon's
metric is concerned with the most economical way of conveying
the message. Think of it as the number of yes/no questions that
you'd have to ask in order to narrow down to certainty, from an
initial uncertainty of four possibilities, assuming that you planned
your questions in the most economical way. "is the mystery letter
before d in the alphabet?" no. That narrows it down to t or g,
and now we need only one more question to clinch it. So, by this
method of measuring, each "letter" of the dna has an
information capacity of 2 bits.
Whenever prior uncertainty of recipient can be expressed as a
number of equiprobable alternatives n, the information content of
a message which narrows those alternatives down to one is log2n
(the power to which 2 must be raised in order to yield the number
of alternatives n). If you pick a card, any card, from a normal
pack, a statement of the identity of the card carries log252, or 5.7
bits of information. In other words, given a large number of
guessing games, it would take 5.7 yes/no questions on average to
guess the card, provided the questions are asked in the most
economical way. The first two questions might establish the suit.
(is it red? Is it a diamond?) the remaining three or four questions
would successively divide and conquer the suit (is it a 7 or higher?
Etc.), finally homing in on the chosen card. When the prior
uncertainty is some mixture of alternatives that are not
equiprobable, shannon's formula becomes a slightly more
elaborate weighted average, but it is essentially similar. By the
way, shannon's weighted average is the same formula as
physicists have used, since the nineteenth century, for entropy.
The point has interesting implications but i shall not pursue them
here.
Information and evolution
that's enough background on information theory. It is a theory
which has long held a fascination for me, and i have used it in
several of my research papers over the years. Let's now think how
we might use it to ask whether the information content of
genomes increases in evolution. First, recall the three way
distinction between total information capacity, the capacity that is
actually used, and the true information content when stored in the
most economical way possible. The total information capacity of
the human genome is measured in gigabits. That of the common
gut bacterium escherichia coli is measured in megabits. We, like
all other animals, are descended from an ancestor which, were it
available for our study today, we'd classify as a bacterium. So
perhaps, during the billions of years of evolution since that
ancestor lived, the information capacity of our genome has gone
up about three orders of magnitude (powers of ten) - about a
thousandfold. This is satisfyingly plausible and comforting to
human dignity. Should human dignity feel wounded, then, by the
fact that the crested newt, triturus cristatus, has a genome
capacity estimated at 40 gigabits, an order of magnitude larger
than the human genome? No, because, in any case, most of the
capacity of the genome of any animal is not used to store useful
information. There are many nonfunctional pseudogenes (see
below) and lots of repetitive nonsense, useful for forensic
detectives but not translated into protein in the living cells. The
crested newt has a bigger "hard disc" than we have, but since the
great bulk of both our hard discs is unused, we needn't feel
insulted. Related species of newt have much smaller genomes.
Why the creator should have played fast and loose with the
genome sizes of newts in such a capricious way is a problem that
creationists might like to ponder. From an evolutionary point of
view the explanation is simple (see the selfish gene pp 44-45 and
p 275 in the second edition).
Gene duplication
evidently the total information capacity of genomes is very
variable across the living kingdoms, and it must have changed
greatly in evolution, presumably in both directions. Losses of
genetic material are called deletions. New genes arise through
various kinds of duplication. This is well illustrated by
haemoglobin, the complex protein molecule that transports
oxygen in the blood.
Human adult haemoglobin is actually a composite of four protein
chains called globins, knotted around each other. Their detailed
sequences show that the four globin chains are closely related to
each other, but they are not identical. Two of them are called
alpha globins (each a chain of 141 amino acids), and two are beta
globins (each a chain of 146 amino acids). The genes coding for
the alpha globins are on chromosome 11; those coding for the beta
globins are on chromosome 16. On each of these chromosomes,
there is a cluster of globin genes in a row, interspersed with some
junk dna. The alpha cluster, on chromosome 11, contains seven
globin genes. Four of these are pseudogenes, versions of alpha
disabled by faults in their sequence and not translated into
proteins. Two are true alpha globins, used in the adult. The final
one is called zeta and is used only in embryos. Similarly the beta
cluster, on chromosome 16, has six genes, some of which are
disabled, and one of which is used only in the embryo. Adult
haemoglobin, as we've seen contains two alpha and two beta
chains.
Never mind all this complexity. Here's the fascinating point.
Careful letter-by-letter analysis shows that these different kinds of
globin genes are literally cousins of each other, literally members
of a family. But these distant cousins still coexist inside our own
genome, and that of all vertebrates. On a the scale of whole
organism, the vertebrates are our cousins too. The tree of
vertebrate evolution is the family tree we are all familiar with, its
branch-points representing speciation events - the splitting of
species into pairs of daughter species. But there is another family
tree occupying the same timescale, whose branches represent not
speciation events but gene duplication events within genomes.
The dozen or so different globins inside you are descended from
an ancient globin gene which, in a remote ancestor who lived
about half a billion years ago, duplicated, after which both copies
stayed in the genome. There were then two copies of it, in
different parts of the genome of all descendant animals. One copy
was destined to give rise to the alpha cluster (on what would
eventually become chromosome 11 in our genome), the other to
the beta cluster (on chromosome 16). As the aeons passed, there
were further duplications (and doubtless some deletions as well).
Around 400 million years ago the ancestral alpha gene duplicated
again, but this time the two copies remained near neighbours of
each other, in a cluster on the same chromosome. One of them
was destined to become the zeta of our embryos, the other became
the alpha globin genes of adult humans (other branches gave rise
to the nonfunctional pseudogenes i mentioned). It was a similar
story along the beta branch of the family, but with duplications at
other moments in geological history.
Now here's an equally fascinating point. Given that the split
between the alpha cluster and the beta cluster took place 500
million years ago, it will of course not be just our human genomes
that show the split - possess alpha genes in a different part of the
genome from beta genes. We should see the same within-genome
split if we look at any other mammals, at birds, reptiles,
amphibians and bony fish, for our common ancestor with all of
them lived less than 500 million years ago. Wherever it has been
investigated, this expectation has proved correct. Our greatest
hope of finding a vertebrate that does not share with us the ancient
alpha/beta split would be a jawless fish like a lamprey, for they
are our most remote cousins among surviving vertebrates; they are
the only surviving vertebrates whose common ancestor with the
rest of the vertebrates is sufficiently ancient that it could have
predated the alpha/beta split. Sure enough, these jawless fishes are
the only known vertebrates that lack the alpha/beta divide.
Gene duplication, within the genome, has a similar historic impact
to species duplication ("speciation") in phylogeny. It is
responsible for gene diversity, in the same way as speciation is
responsible for phyletic diversity. Beginning with a single
universal ancestor, the magnificent diversity of life has come
about through a series of branchings of new species, which
eventually gave rise to the major branches of the living kingdoms
and the hundreds of millions of separate species that have graced
the earth. A similar series of branchings, but this time within
genomes - gene duplications - has spawned the large and diverse
population of clusters of genes that constitutes the modern
genome.
The story of the globins is just one among many. Gene
duplications and deletions have occurred from time to time
throughout genomes. It is by these, and similar means, that
genome sizes can increase in evolution. But remember the
distinction between the total capacity of the whole genome, and
the capacity of the portion that is actually used. Recall that not all
the globin genes are actually used. Some of them, like theta in the
alpha cluster of globin genes, are pseudogenes, recognizably kin
to functional genes in the same genomes, but never actually
translated into the action language of protein. What is true of
globins is true of most other genes. Genomes are littered with
nonfunctional pseudogenes, faulty duplicates of functional genes
that do nothing, while their functional cousins (the word doesn't
even need scare quotes) get on with their business in a different
part of the same genome. And there's lots more dna that doesn't
even deserve the name pseudogene. It, too, is derived by
duplication, but not duplication of functional genes. It consists of
multiple copies of junk, "tandem repeats", and other nonsense
which may be useful for forensic detectives but which doesn't
seem to be used in the body itself.
Once again, creationists might spend some earnest time
speculating on why the creator should bother to litter genomes
with untranslated pseudogenes and junk tandem repeat dna.
Information in the genome
can we measure the information capacity of that portion of the
genome which is actually used? We can at least estimate it. In the
case of the human genome it is about 2% - considerably less than
the proportion of my hard disc that i have ever used since i bought
it. Presumably the equivalent figure for the crested newt is even
smaller, but i don't know if it has been measured. In any case, we
mustn't run away with a chauvinistic idea that the human genome
somehow ought to have the largest dna database because we are
so wonderful. The great evolutionary biologist george c williams
has pointed out that animals with complicated life cycles need to
code for the development of all stages in the life cycle, but they
only have one genome with which to do so. A butterfly's genome
has to hold the complete information needed for building a
caterpillar as well as a butterfly. A sheep liver fluke has six
distinct stages in its life cycle, each specialised for a different way
of life. We shouldn't feel too insulted if liver flukes turned out to
have bigger genomes than we have (actually they don't).
Remember, too, that even the total capacity of genome that is
actually used is still not the same thing as the true information
content in shannon's sense. The true information content is what's
left when the redundancy has been compressed out of the
message, by the theoretical equivalent of stuffit. There are even
some viruses which seem to use a kind of stuffit-like
compression. They make use of the fact that the rna (not dna
in these viruses, as it happens, but the principle is the same) code
is read in triplets. There is a "frame" which moves along the rna
sequence, reading off three letters at a time. Obviously, under
normal conditions, if the frame starts reading in the wrong place
(as in a so-called frame-shift mutation), it makes total nonsense:
The "triplets" that it reads are out of step with the meaningful ones.
But these splendid viruses actually exploit frame-shifted reading.
They get two messages for the price of one, by having a
completely different message embedded in the very same series of
letters when read frame-shifted. In principle you could even get
three messages for the price of one, but i don't know whether
there are any examples.
Information in the body
it is one thing to estimate the total information capacity of a
genome, and the amount of the genome that is actually used, but
it's harder to estimate its true information content in the shannon
sense. The best we can do is probably to forget about the genome
itself and look at its product, the "phenotype", the working body
of the animal or plant itself. In 1951, j w s pringle, who later
became my professor at oxford, suggested using a shannon-type
information measure to estimate "complexity". Pringle wanted to
express complexity mathematically in bits, but i have long found
the following verbal form helpful in explaining his idea to
students.
We have an intuitive sense that a lobster, say, is more complex
(more "advanced", some might even say more "highly evolved")
than another animal, perhaps a millipede. Can we measure
something in order to confirm or deny our intuition? Without
literally turning it into bits, we can make an approximate
estimation of the information contents of the two bodies as
follows. Imagine writing a book describing the lobster. Now write
another book describing the millipede down to the same level of
detail. Divide the word-count in one book by the word-count in
the other, and you have an approximate estimate of the relative
information content of lobster and millipede. It is important to
specify that both books describe their respective animals "down to
the same level of detail". Obviously if we describe the millipede
down to cellular detail, but stick to gross anatomical features in
the case of the lobster, the millipede would come out ahead.
But if we do the test fairly, i'll bet the lobster book would come
out longer than the millipede book. It's a simple plausibility
argument, as follows. Both animals are made up of segments -
modules of bodily architecture that are fundamentally similar to
each other, arranged fore-and-aft like the trucks of a train. The
millipede's segments are mostly identical to each other. The
lobster's segments, though following the same basic plan (each
with a nervous ganglion, a pair of appendages, and so on) are
mostly different from each other. The millipede book would
consist of one chapter describing a typical segment, followed by
the phrase "repeat n times" where n is the number of segments.
The lobster book would need a different chapter for each segment.
This isn't quite fair on the millipede, whose front and rear end
segments are a bit different from the rest. But i'd still bet that, if
anyone bothered to do the experiment, the estimate of lobster
information content would come out substantially greater than the
estimate of millipede information content.
It's not of direct evolutionary interest to compare a lobster with a
millipede in this way, because nobody thinks lobsters evolved
from millipedes. obviously no modern animal evolved from any
other modern animal. Instead, any pair of modern animals had a
last common ancestor which lived at some (in principle)
discoverable moment in geological history. Almost all of
evolution happened way back in the past, which makes it hard to
study details. But we can use the "length of book" thoughtexperiment
to agree upon what it would mean to ask the question
whether information content increases over evolution, if only we
had ancestral animals to look at.
the answer in practice is complicated and controversial, all bound
up with a vigorous debate over whether evolution is, in general,
progressive. I am one of those associated with a limited form of
yes answer. My colleague stephen jay gould tends towards a no
answer. i don't think anybody would deny that, by any method of
measuring - whether bodily information content, total information
capacity of genome, capacity of genome actually used, or true
("stuffit compressed") information content of genome - there has
been a broad overall trend towards increased information content
during the course of human evolution from our remote bacterial
ancestors. People might disagree, however, over two important
questions: First, whether such a trend is to be found in all, or a
majority of evolutionary lineages (for example parasite evolution
often shows a trend towards decreasing bodily complexity,
because parasites are better off being simple); second, whether,
even in lineages where there is a clear overall trend over the very
long term, it is bucked by so many reversals and re-reversals in
the shorter term as to undermine the very idea of progress. This is
not the place to resolve this interesting controversy. There are
distinguished biologists with good arguments on both sides.
Supporters of "intelligent design" guiding evolution, by the way,
should be deeply committed to the view that information content
increases during evolution. Even if the information comes from
god, perhaps especially if it does, it should surely increase, and
the increase should presumably show itself in the genome. Unless,
of course - for anything goes in such addle-brained theorising -
god works his evolutionary miracles by nongenetic means.
Perhaps the main lesson we should learn from pringle is that the
information content of a biological system is another name for its
complexity. Therefore the creationist challenge with which we
began is tantamount to the standard challenge to explain how
biological complexity can evolve from simpler antecedents, one
that i have devoted three books to answering (the blind
watchmaker, river out of eden, climbing mount improbable)
and i do not propose to repeat their contents here. The
"information challenge" turns out to be none other than our old
friend: "how could something as complex as an eye evolve?" it is
just dressed up in fancy mathematical language - perhaps in an
attempt to bamboozle. Or perhaps those who ask it have already
bamboozled themselves, and don't realise that it is the same old -
and thoroughly answered - question.
The genetic book of the dead
let me turn, finally, to another way of looking at whether the
information content of genomes increases in evolution. We now
switch from the broad sweep of evolutionary history to the
minutiae of natural selection. Natural selection itself, when you
think about it, is a narrowing down from a wide initial field of
possible alternatives, to the narrower field of the alternatives
actually chosen. Random genetic error (mutation), sexual
recombination and migratory mixing, all provide a wide field of
genetic variation: The available alternatives. Mutation is not an
increase in true information content, rather the reverse, for
mutation, in the shannon analogy, contributes to increasing the
prior uncertainty. But now we come to natural selection, which
reduces the "prior uncertainty" and therefore, in shannon's sense,
contributes information to the gene pool. In every generation,
natural selection removes the less successful genes from the gene
pool, so the remaining gene pool is a narrower subset. The
narrowing is nonrandom, in the direction of improvement, where
improvement is defined, in the darwinian way, as improvement in
fitness to survive and reproduce. Of course the total range of
variation is topped up again in every generation by new mutation
and other kinds of variation. But it still remains true that natural
selection is a narrowing down from an initially wider field of
possibilities, including mostly unsuccessful ones, to a narrower
field of successful ones. This is analogous to the definition of
information with which we began: Information is what enables the
narrowing down from prior uncertainty (the initial range of
possibilities) to later certainty (the "successful" choice among the
prior probabilities). According to this analogy, natural selection is
by definition a process whereby information is fed into the gene
pool of the next generation.
If natural selection feeds information into gene pools, what is the
information about? It is about how to survive. Strictly it is about
how to survive and reproduce, in the conditions that prevailed
when previous generations were alive. To the extent that present
day conditions are different from ancestral conditions, the
ancestral genetic advice will be wrong. In extreme cases, the
species may then go extinct. To the extent that conditions for the
present generation are not too different from conditions for past
generations, the information fed into present-day genomes from
past generations is helpful information. Information from the
ancestral past can be seen as a manual for surviving in the present:
A family bible of ancestral "advice" on how to survive today. We
need only a little poetic licence to say that the information fed into
modern genomes by natural selection is actually information
about ancient environments in which ancestors survived.
This idea of information fed from ancestral generations into
descendant gene pools is one of the themes of my new book,
unweaving the rainbow. It takes a whole chapter, "the genetic
book of the dead", to develop the notion, so i won't repeat it here
except to say two things. First, it is the whole gene pool of the
species as a whole, not the genome of any particular individual,
which is best seen as the recipient of the ancestral information
about how to survive. The genomes of particular individuals are
random samples of the current gene pool, randomised by sexual
recombination. Second, we are privileged to "intercept" the
information if we wish, and "read" an animal's body, or even its
genes, as a coded description of ancestral worlds. To quote from
unweaving the rainbow:
"and isn't it an arresting thought? We are digital archives of the
african pliocene, even of devonian seas; walking repositories of
wisdom out of the old days. You could spend a lifetime reading in this
ancient library and die unsated by the wonder of it."
1 the producers never deigned to send me a copy: I completely forgot
about it until an american colleague called it to my attention.
2 see barry williams (1998): Creationist deception exposed, the
skeptic 18, 3, pp 7-10, for an account of how my long pause (trying to
decide whether to throw them out) was made to look like hesitant
inability to answer the question, followed by an apparently evasive
answer to a completely different question.
Powered by vBulletin™ Version 4.2.1 Copyright © 2024 vBulletin Solutions, ENGAGS © 2010