Genetics and animals evolution. Dissemination 55th
About natural selection Charles Darwin points out that "the most simple organ that can be given the name eye has an optical nerve, surrounded by pigment cells and covered by translucid skin, but without lens nor any other refracting body" to say later that "we could descend one more degree and find clusters of pigment cells that seem to be vision organs without nerves… and serve only to distinguish light from darkness” and continue indicating “they are full of a gelatinous transparent substance, which protrudes forming a convex surface, like the cornea of superior animals” to finish indicating “we only have to place the naked extremity of the optic nerve – that in some inferior animals is deeply sunk in the body and in others near the surface- at the proper distance of the light concentration device and an image will form on it”.
As a culmination, Darwin takes a disquisition on whether these changes, moving from pre-eye to the primitive eye and from this one to a complex structure like arthropods or raptors eye, could be given simultaneously or gradually guided by natural selection and concludes that the most plausible way is the gradually influenced by natural selection.
Accepting in full Darwin’s opinion on the gradual evolution guided by natural selection, we can currently go one step further if we incorporate the necessary genetic basis of any modification.
Thus it is known that rhodopsin production (contained in the pigment cells referred to by Darwin) or the formation of the vitreous and aqueous humor of the eye that contains collagen, hyaluronic acid and proteins (transparent gelatinous substance cited by Darwin), or any part of vertebrated animals eyes develop in the ribosomes following the instructions contained in the messenger RNA formed in the nucleus from the chromosomal genetic code made of DNA.
Therefore it remains unexplained how it is iniciated, in animal cells, the synthesis of rhodopsin or vitreous humor collagen or protein MIP26, although we agree that natural selection will favor those who possess it.
At the moment there are three hypothesis: random mutations, the previous genetic code deployment by a mechanism of auto programming or the influence of certain substances from plant cells that are part of the animals feeding.
During the coming months in Veterinaria Digital we will provide information to be able to form a criteria on these hypothesis.