Claim 5 - The Eye is too complicated to have evolved
Many creationists quote outright the above 'fact' without ever actually
investigating the assumed principles behind the growth of the human eye.
The fact is that the human eye is an extraordinarily complex organ, but to
say therefore that it did not evolve is unscientific. One must prove that
it cannot have evolved, or else the argument is utterly invalid.
How does evolution claim the eye evolved?
Early primitive organisms were aware of their surroundings, just like
primitive organisms today, in very simple ways. Firstly they would be able
to sense physical contact, and they would be able to sense chemical
inbalances in the water surrounding them. Clearly an advantage would be
gained by any creature that could develop some sort of accurate sensory
apparatus with which it could analyse its surroundings.
From the first primitive organisms whose central nervous systems managed to
tune slightly more into the reception of light from certain slightly more
sensitive cells, these cells would them become more sensitive because they
gave the animal possessing them a slight advantage over his peers - he had a
slightly heightened sense of danger. These primitive cells would then
evolve into clusters of cells, and so on up to the eyes we see today. We
are not proposing that the eye suddenly appeared out of nowhere - we are
claiming that it evolved gradually over time from something much more
Is this plausible?
Many very tiny organisms today possess eyes. They are not an exclusive property
of mammals. For example, most insects possess eyes, some of which are extremely
tiny. The function of such eyes is significantly more primitive than those of a
human being, but they are still eyes. Study of the various types of life on
Earth tell us that the eye has evolved totally separately several dozen times,
suggesting that the process can't really be all that complex or unlikely.
Evolution tells us that large changes can occur over extremely long periods
of time, but in tiny steps. The change from a primate's eye to that of a
human isn't a very big step. The change from the eyes of common farmyard
animals aren't really all that different either. What about rodents? Well
they see too, though obviously with a lower resolution and sensitivity than
humans. Is it such a big claim to say that an eye the size of a rat's can
evolve into one the size of a chimpanzee's? Evolution shows us a way by
which that could happen. It might only be a very tiny change at a
The diameter of the human eye is approximately 2.4cm (1 inch). According to
page, the eyeball of a human being grows considerably over the course of
a human's life. We don't see that as being remarkable at all.
We could investigate the change in size required to grow a rat's eye up to
the size of a human's eye over a hundred million years, which is a typical
evolutionary timespan. A rat has an eyeball around 4mm in diameter. This is
a factor of 6 increase in size.
A little mathematics shows us that this change of a factor of 6 over 100
million years, assuming geometric growth, corresponds to an increase of
0.0018% in every thousand years. That's not really a remarkable change, is
it? If we assume linear growth then we need to increase the diameter of the
eye by 0.0002mm (200 nanometres) every thousand years. That's an increase
about 500 times thinner than the width of a human hair!
So we can easily evolve from a rodent's eye to a human's eye in a mere 100
million years, probably significantly less. Remember that we have much
longer than this to carry out our entire evolutionary sequence - perhaps
twenty or thirty times longer. Is it that much to claim that the eye can
develop from a primitive single receptor cell through a slightly more
complicated row or receptor cells, through a cluster of cells, right up to a
tiny spherical adornment and to the kind of eyes you see in tiny marine
animals, all the way up to that of a tiny land animal such as an insect, and
through to rodents and humans? I don't think so.
Remember - all we have to do is to prove that there is a series of small,
gradual changes that could lead from a primitive, light-sensitive cell right the
way up to the modern eye. We are not claiming that the eye sprang into being
Evolutionary timescales are really surprising, mainly because they are so
counterintuitive. You'd be amazed how long a billion years really is!
Human beings are used to thinking about things from human perspectives. A
human lives about 70-80 years on average, so we consider 100 years to be a
long time. In our everyday life, an hour is a long time. Any task which is
likely to take an hour to complete we might see as being lengthy. Those who
disagree should try doing the washing up at my house after one of my house
Many people use human arguments to try to disprove evolution, but they are
really not disproofs at all. In fact, they contain no logic or reasoning.
All they are is supposition. Supposition without factual backing is utterly
worthless. In order for an argument to be considered in the scientific
world it must be associated with logic and evidence. You can't simply claim
things and appeal to reason - you must provide evidence.
A billion years is a truly enormous time span. There are currently six
billion people alive on the Earth. Each one has, on average, 80,000 hairs
on their head. You could count all their hairs at a rate of 1 per second in
a mere 15 million years. In a billion years you would have the time to go
off and rest for a minute between each hair, or alternatively count the
hairs on every single human being 66 times! Just imagine what amazingly
complicated changes could occur in such a long time.
Richard Dawkins says the following;
"Thus the creationist's favourite question "What is the use of half an eye?"
Actually, this is a lightweight question, a doddle to answer. Half an eye is
just 1 per cent better than 49 per cent of an eye, which is already better
than 48 per cent, and the difference is significant."
In 1994, Dan-Eric Nilsson and Susanne Pelger presented the results of the
experiments that they had been running on the evolution of the eye. They
wrote computer simulations in order to analyse the rate at which such a
complicated optical organ could evolve from a simple initial condition. The
abstract of their paper contains the following description;
"Theoretical considerations of eye design allow us to find routes along which
the optical structures of eyes may have evolved. If selection constantly
favours an increase in the amount of detectable spatial information, a
light-sensitive patch will gradually turn into a focused lens eye through
continuous small improvements of design. An upper limit for the number of
generations required for the complete transformation can be calculated with
a minimum of assumptions. Even with a consistently pessimistic approach the
time required becomes amazingly short: only a few hundred thousand years."
Nilsson & Pelger used a few simplifying assumptions in order to carry
out this modelling technique. Whenever they were required to make any
important assumptions in terms of figures, timescales, rates etc. they
always chose the most pessimistic value. That is, the value which would
cause the estimated timescale for evolution to be the longest. Even through
this technique they discovered that the timescale was of the order of
400,000 years, assuming generations of one year each, i.e. for fish.
This experiment is available in "Nilsson, D.-E., and Pelger, S. 1994. A
pessimistic estimate of the time required for an eye to evolve. In Proc. Royal
Soc. London, vol. 256 of Series B, 53--58". It can be downloaded from the
Is this a fair representation? If not then drop me an email. Address below.
This page maintained by Colin Frayn.
Last Update : 22nd April, 2005