02 Feb '09 09:53>1 edit
It has been traditionally thought by evolutionists that eyes between at least some of the main animal groups had evolved independently from each other and more than once.
The bases for this assumption was simply because it is hard to imagine how the eye of, say a fruit fly with its compound eye and, say, the human eye could have a common ancestral eye because the eyes are just so totally different in structure.
But, recently, a gene called the pax-6 gene has been discovered that is responsible for both the development of the fruit fly eye and the human eye!
http://www.pbs.org/wgbh/evolution/library/04/4/text_pop/l_044_01.html
(There are almost certainly another thread about this (somewhere) because many of you must already heard of this but I think it is interesting enough to make this new thread about it here)
Not only that -it has been found in virtually all the main animal groups with eyes! -and in each one, it is responsible for either part or all of eye development.
For this to have come about by chance can be calculated to be less than one in a trillion! -therefore, we can assume this is no coincidence and that virtually all animals that have eyes share one common ancestor which had eyes that must have been a very very simple animal with two very very simple eyes -just like some very simple primitive worms that are alive today with such eyes.
The consequences of this discovery are obvious; the eye didn’t evolve independently many times over but, surprisingly given the vast range and seemingly incompatible designs of various eyes, evolved just once!
The pax-6 gene has evolved to change its function in eyes many times so that, for example, it is responsible for just the development of just the iris of the eye in humans while it is responsible for the development of the whole of the compound eye in fruit flies. In some causes, multiple copies of the pax-6 gene has evolved in an animal with each one responsible for the development of a different aspect to the animal's eye (haven’t been able to find a link about this but I have heard of it from somewhere -I don’t remember where).
The bases for this assumption was simply because it is hard to imagine how the eye of, say a fruit fly with its compound eye and, say, the human eye could have a common ancestral eye because the eyes are just so totally different in structure.
But, recently, a gene called the pax-6 gene has been discovered that is responsible for both the development of the fruit fly eye and the human eye!
http://www.pbs.org/wgbh/evolution/library/04/4/text_pop/l_044_01.html
(There are almost certainly another thread about this (somewhere) because many of you must already heard of this but I think it is interesting enough to make this new thread about it here)
Not only that -it has been found in virtually all the main animal groups with eyes! -and in each one, it is responsible for either part or all of eye development.
For this to have come about by chance can be calculated to be less than one in a trillion! -therefore, we can assume this is no coincidence and that virtually all animals that have eyes share one common ancestor which had eyes that must have been a very very simple animal with two very very simple eyes -just like some very simple primitive worms that are alive today with such eyes.
The consequences of this discovery are obvious; the eye didn’t evolve independently many times over but, surprisingly given the vast range and seemingly incompatible designs of various eyes, evolved just once!
The pax-6 gene has evolved to change its function in eyes many times so that, for example, it is responsible for just the development of just the iris of the eye in humans while it is responsible for the development of the whole of the compound eye in fruit flies. In some causes, multiple copies of the pax-6 gene has evolved in an animal with each one responsible for the development of a different aspect to the animal's eye (haven’t been able to find a link about this but I have heard of it from somewhere -I don’t remember where).