Richard Dawkins: Darwin and the (im)possible evolution of the eye (Revelation TV + NL/eng subs)


welcome to revelation TV studios
we are live. We didn’t intend to go live but we’re going to. That reminds
me really when I first went live eight years ago on revelation TVs first
broadcast – and my heart is pounding. Nevertheless it’s a very special day
for me and I’d like to warmly welcome our special guest Richard Dawkins.
Richard, Darwin seems to express that the
evolution of the eye was a hard case to explain says the the person who emailed
this into me Steve I think it was do you have any cases yourself where there is
uneasiness with this well that’s a famous quote from Darwin Darwin said
something like to suppose that the eye with all its intricate contrivance if he
goes on a great detail about how complicated and beautiful the eye is
could be could could come about as a result of evolution by natural selection
seems I freely confess absurd in the highest degree words to that effect that
quotation is very often given but it isn’t followed by what Darwin next said
which was to spend a good part of a chapter explaining exactly why actually
it is explicable and it’s a very it’s a it’s a in a way it’s a good rhetorical
technique to as it were offer something to your opponents before you then DISA
disillusion them it where it fails as if your opponents then take the offer and
then don’t quote what follows so the so the eye is actually very well explicable
by evolution and I’ve explained it in especially two of my books the blind
watchmaker and gliding large improbable but that wasn’t the question you asked
me you asked me the question is there anything that I find particularly
difficult no because that’s not the way science works we don’t say this is a
very difficult case therefore God must have done it therefore science can’t
explain it there for the supernatural must be wheeled in to explain it that
isn’t the way we work if science can’t explain
then we say all right then let’s go to work let’s see what we need to do what
new theories we need to bring into our science how we need to change our
science and that technique has always worked so far if there was something
that I was genuinely puzzled about then my response would not be oh it must be
supernatural my response would be then in that case we must roll our sleeves up
and go to work to try to understand it right well because to me this is apart
from the person who emailed us saying this is really and I put it at the top
of my list because it’s something that bothered me when I was growing up that I
thought how could we have evolved because the eye is so complex for
example we’ve got cameras in the studio here and they need camera operators to
pull focus and to be able to change shots and everything in the more
distance or close-up you get you have to change the the actual iris of the of the
camera perhaps even open it or close it a little bit so the that’s all done
instantaneously within from the within the brain the human brain and it’s so
complex that I thought yeah how could we have been bumping around without sight
for thousands or millions of years if we’ve evolved when really it needed to
be functioning from the word goal well yes all right I will answer that that
question certainly or absolutely right the eye is a most remarkable organ and
it does the same sorts of things that these television cameras do it does an
instant focusing it does instant stopping down with the iris diaphragm
it’s it’s got full color 3/3 color vision just like modern televisions have
and it is a remarkably beautiful it’s not totally flawless there are
interesting floors interesting imperfections which actually are
revealing nevertheless it does work very well and an engineer would give it
somewhat high marks for being well quote designed now you raise the question
doesn’t it all have to be working before it’ll work before it’ll it’s any any
good how could we bump along for millions of years with only half an eye
that’s a bit of a fallacy because actually
only a quarter of an eye only a hundredth of an eye is better than
nothing you can make a slowly climbing ramp of improvement from just the very
rudiments of vision just say being able to tell the difference between light and
shade nothing more than that right up to the perfection of human eye or the eye
of a hawk say and in order for evolution to explain that or all we need is that
there should be a ramp of improvement where every step a hundredth of an eye
two hundredths of an eye three hundreds of an eye etcetera fifty percent of an
eye fifty-one percent of an eye each step has got to be an improvement on the
one that went before and it’s easy to see why that would be
you start by being able to tell whether there’s a shadow whether it’s night or
day shadows useful that could be a predator moving overhead in the sea
night or day is obviously useful for all sorts of purposes then you could imagine
a cup instead of just having a flat sheet of light-sensitive cells it just
the edges turn up into a cup now the cup means that if there’s light
coming from that direction it hits that part of the eye it’s as light coming
from that direction it hits that part of the eye so already the animal can tell
the direction from which light is coming and the direction from which a shadow is
coming so we’ve haven’t got an image yet all we’ve got is the direction of light
now the cup can steadily and slowly over evolutionary time close over until you
end up with a little hole at the top and the little hole at the top the same
principles working all the way that light coming from that direction hits
that part of the retina and from that direction hits this part of the retina
but because there’s a hole it’s rather more precisely not exactly focused but
light from there hits there like from there hits there light from there hits
there because it’s got to get through the hole we’re moving towards a pinhole
camera now a pinhole camera if you make the hole small enough and remember we’re
having smooth gradient of closing up the hole
if you make the hole small enough then it makes a sharp focused image the
trouble with a pinhole camera is that the image is very dim because very
little light can get through the pinhole what you need is a lens because what a
lens does is gather light from different directions and focus it on a point
instead of how it having to go right through the middle of the hole it could
be gathered from a wider range of sources now a lens is not difficult to
arrange any old chunk of set of transparent gubbins will do the job
better than a pinhole so once again we’ve got a slow gradual improvement any
lump of gubbins transparent is better than nothing and then the lens simply
improves its shape gradually gradually gradually gradually has got to be
gradually every step has got to be a slight improvement over the previous one
you get a lens I just ask you the original yes and how long did this
process take well that’s very interesting I mean we’ve got hundreds of
millions of years to play with because that’s what geological time gives us and
then we’ve got maybe a billion years since the first eye since the first
focusing I appeared what about the child about trilobite s– have very beautiful
eyes very very clever I mean they’re just is amazing they have compound eyes
which is what modern insects and crustaceans have and it has in in the
fossil record is exactly the same today’s it was or in that sense it
didn’t evolve it had it was lenses by the bites doggone it but had the lens
mechanism which is trial about well trilobites have compound eyes which is a
very different principle and very interesting principle it’s it doesn’t
focus quite as sharp an image as our eyes do but it is a very beautiful thing
and trilobite do go back home hundreds of millions of years and for 500 million
years half a billion years it must have taken some time before trial of mites
came on the scene but even trilobite is a relatively recent compared to the
the earth which is four and a half billion years old
obviously of course as a creationist or believer in creation the book of Genesis
you know I would disagree with that but uh what would you disagree with with the
time I however think the world is then I would say that as because I’m a Bible
believer yes Christian that I believe that the book
of Genesis is an artifact the the record because Christ as well referred often to
the book of Genesis that in the beginning yes yes Adam and Eve and I
know that but before we get onto that because we can come back to that is that
there is an email that came in with regards to the I which I’d like to read
because it’s so it’s quite intelligently written in Richards book the greatest
show on earth and he gives the pages etc he claims the retina could not have been
designed as creationists say because the photoreceptors are at the back rather
than the front so it is back to front and it was a fact he said if it was
created it was the design of an idiot she’s just stopped there
recent research has shown that there are cells in the retina that guide light to
the photoreceptors and refocus it the scientists who did this research
described the light guiding cells in the retina structure with the words optimal
design for improving the sharpness of images and that’s from Physical Review
Letters etc etc will Richard admit he is wrong since he is not an expert on
optics and the researchers are well no I will not admit I rob this is a very
interesting case the the retina is back to front and the retina of the
vertebrate eye is back to front in the sense that the light-sensitive cells are
pointing away from the light now the light-sensitive cells are
connected to the brain via nerves and any sensible designer would have had the
nerves behind the light-sensitive cells which is in fact the way they are in
mollusks for example octopuses which have rather good eyes rather like ours
with the difference being that the light-sensitive cells point towards the
light and the wires connecting it to the brain lead backwards to the brain which
is the sensible way to do it now the vertebrate eye is back to from
so that the wires that connect the light-sensitive cells to the brain are
running along the front of the retina that means that the light has to
penetrate the this forest of wires nerves before it hits the
light-sensitive cells which are facing backwards now it’s very easy to see why
this happened it happened for historical reasons and doesn’t there’s no doubt
about that now it is of course true that humans for example and I mentioned Hawks
before see much better than octopuses so in spite of the fact that our eye has
this design flaw we have better eyes because natural selection comes along
afterwards and cleans up after the original mess that was made by this
fundamental design flaw natural selection came along afterwards and made
all sorts of little tit evasions which have the effect of giving us really
rather good vision and that happens again and again it’s very interesting
that you get a bungle to begin with and then rather than correct the bungle what
natural selection does is to come along and make little tit evasions little
tinkering x’ which sort of may make up for the further mistake and that’s a
very interesting and phenomenon like to go back to the timing yes of when do you
say that we reached our optimum where we’re at today how far back would you
have to go 10 oh I wouldn’t usually like optimum I mean like what I think was you
think we’re still evolving obviously where we’re at today what well what I
prefer to say is that natural select

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