Evolutionary biologist have finally determined the origins of eyesight. This is very significant for it displaces an assumption that eyesight originated over a span of several eons during the course of animal evolution. Latest interpretative findings tell that this assumption is wrong.
Davide Pisani and colleagues from the National University of Ireland have traced the ancestry of three kinds of ‘opsin’, a protein that animals use, in combination with a pigment detecting light. By comparing the genome sequences of sponges, jellyfish and numerous other animals they tracked the origin of ‘opsins’ back to the common ancestor of all animals except sponges.
What did they find?
They found that placozoa, a flat shapeless cell about 755 million years ago duplicated a gene to change one copy making ‘opsin’. This puts us during the Cambrian Eon. Placozoa today only have that one kind of ‘opsin’, they lack the ability to create an amino acid change at position 296 that makes light detection possible. Dr. Pisani concludes that the last opsin common ancestor, dubbed LOCA had no vision. However, whatever evolved immediately after Placozoa, whether it be an insect or jellyfish, was capable of detecting light.
Dr. Pisani was able to map out the historical evolution of this light detection via ‘opsin’ during two historical periods both in the Cambrian Epoch between 711-700 Million years ago giving us three kinds of light sensing optics that humans have. That vision was an evolutionary innovation is new to biologists, many thought the differences between the compound eye of an insect and the camera like lens of the human eye just to disparaging to think of a common link historically.
What links the differences between the two is Pax6, a gene hinting at a common origin. Dr. Pisani found the Pax gene in jellyfish, hinting of a possible origin sequence there. What we must insist on is the long historical development toward the camera like lens eye of humans, for the genetic duplications that led to ‘opsin molecules’ evolving into camera lens eyes was not quick.
The first lensed eye that fossilized belongs to a trilobite which dominated the Cambrian oceans about 500 million years ago. Dr. Andrew Parker from Oxford has argued that newly perfected eyes can be explained from the impact of sudden hard-bodied animals that happened during the Cambrian ‘explosion’. What predators hunting by sight for the first time, prey needed protection and mobility. An ‘arms race’ led to a plethora of new hard body designs. Sound familiar?
A synoptic vision of life is possible with the discovery of LOCA’s ancestor, LUCA. This genome sequence may be duplicated in the laboratory and dubbed Eve, nevertheless, with the arrival of gene mapping evolutionary biologists can discover and map out the historical changes that constitute their discipline. The first to do this was Dr. Francis Crick who deciphered the genetic code of bacteria, animals and yeast cells seeing that they were all converging on the same universal cipher concluded that sometime in the Cambrian Epoch all life on Earth had a common ancestor.
Watch for Eve, if only for the cynical gnomes to win a Nobel! Or as Dr. Richard Feynman said “That Damned Nobel.” God Bless the man, he knew a crank when he heard one!