The premise of Parker’s book is that the evolution of the
eye, long thought to be a very weak link in the evolutionary chain, because of
the length of time that it would take, could in fact have happened in about
500,000 years. Which is, in evolutionary terms, just the blink of an eye. He
says this happened at the beginning of the Cambrian Epoch, which would have
been approximately 543 million years ago.
Well, actually, according to Parker there’s no approximate about it. Dating of fossils
is so exact that he says it took place exactly then, give or take a million
years. This corresponded with what scientists call the Cambrian Explosion,
which was a rapid increase in the number of species in a short amount of time
(evolutionary speaking). Other things taking place at that time, in addition to
species suddenly having eyes, is the sudden appearance of hard body parts and
eyes. All the phyla we know now are found in fossils know to be after the
explosion, but not in fossils known to be before the explosion. Parker says
this happened precisely 543 million
years ago. It was the sudden evolution of eyes, he says, that caused the need
for animals to evolve hard body parts, which in turn gave rise to the explosion
in the number of species, all because eyes changed the whole relation of prey
and predator.
The book goes on, in great detail, to state what happened at that time, as
determined from the fossil record. Finally, toward the end, Parker gives us his
view on the why: “Why it happened is
the puzzle this book sets out to solve.”
Those who doubt evolution say this explosion would
correspond to certain parts of the Creation account in the book of Genesis.
Parker and his peers would reject this (though see his book The
Genesis Enigma for a lengthy discussion of the Genesis account of
creation), saying that God, if He really exists, had no part in any creation of
all things animal, vegetable, or mineral. Everything had to happen by natural
causes.
On page 224, Parker begins his discussion on the rapid
evolution of the eye. First a patch of light-sensitive skin occurs, for
whatever reason. Mathematical modeling done has shown that, from that small patch
of light-sensitive skin, 364,000 generations would be needed for a fully
developed eye to evolve if the rate of evolution were just “0.005 percent from
one generation to the next.” He then says this is pessimistically slow, and
that a much faster rate of evolution is likely. Based on the life span of the
species living 544 million years ago, those generations would pass in about a
half million years. The 0.005 percent change per generation was based on a
light-sensitive patch of skin changing in length, width, or protein density by
1 percent for each generation.
But, what I don’t get is why
evolution should happen at 0.005 percent from generation to generation. Does evolution
happen from “adaption”—that is, the slow process of survival of the fittest then
breeding offspring who are even more fit—or does it happen by “mutation”—the
sudden, unexplained occurrence of a change in the animal that just happens to
be fitter than a non-mutated offspring?
Say that a larger animal is fitter than a smaller animal,
because it will win a fight between the two. Or it will have more success in
predation, and thus will live longer and breed more often, and it’s offspring
will be more likely to be like it than like those smaller/weaker members of the
species at the opposite side of the bell curve. In any species I suppose no two
critters are exactly alike. There will be a range of sizes, for example, with
some kind of distribution around a mean or average. Those few of the species
who are a standard deviation or more above the mean will have greater success
at predation and living and breeding. After some generations of this, the mean
will change; it will be larger/stronger/fitter. But the species preyed upon
will be adapting too, and will have a new mean after those generations and be
fitter to fight off the predation of the other animals.
Now, the animals in question don’t will this to happen, as I understand evolutionary theory. The stimulus
to adapt must come from external pressures, not internal causes. They don’t
say, “Our species has to grow larger and stronger or we won’t survive. Let me
produce larger and stronger offspring.” It takes place through natural
selection based on success and failure of the various members of the species. Over
a long period of time the specie changes or, as evolutionists believe, a whole new
species develops.
This idea that evolutionary change by adaption should take
place in nice 0.005 percent steps seems to me to be ridiculous. It assumes that
at each change the species is fitter than it was before the change. Parker says
that is obviously true, but it’s not obvious for me.
So, while I enjoyed this book and took in a lot of
information, I am not persuaded by the conclusions, which are:- The eye evolved precisely 544 million years ago
- The eye evolved in a period of 500 thousand years in a series of tiny steps, with each step producing a species mean that was fitter than the one before
- That the impetus for this natural process was probably a rapid increase in the intensity of sunlight
2 comments:
I may have to read the book.
It's a good book, though I wouldn't put it on my essential reading list.
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