700,000,000 years ago one single act of origination started us down
the road to having vision. That it appears unique is interesting
unless there is a reason it is hard. I would prefer easy and
multiple originations and a sorting out.
It is still a long time ago and reminds us of the antiquity of our
core biological toolkit inheritance.
Everything began as a cellular application with huge variation
possible. Recall that natural selection works wonderfully at the
cellular level. It is much more doubtful thereafter. Then the
organism is unconsciously able to modify his offspring and we get an
evolution of successful choices instead.
New study sheds
light on how and when vision evolved
by Staff Writers
Bristol UK (SPX) Oct 31, 2012
The study, which used
computer modelling to provide a detailed picture of how and when
opsins evolved, sheds light on the origin of sight in animals,
including humans. The evolutionary origins of vision remain hotly
debated, partly due to inconsistent reports of phylogenetic
relationships among the earliest opsin-possessing animals.
Dr Davide Pisani of
Bristol's School of Earth Sciences and colleagues at NUI Maynooth
performed a computational analysis to test every hypothesis of opsin
evolution proposed to date.
The analysis
incorporated all available genomic information from all relevant
animal lineages, including a newly sequenced group of sponges
(Oscarella carmela) and the Cnidarians, a group of animals thought to
have possessed the world's earliest eyes.
Using this
information, the researchers developed a timeline with an opsin
ancestor common to all groups appearing some 700 million years ago.
This opsin was considered 'blind' yet underwent key genetic changes
over the span of 11 million years that conveyed the ability to detect
light.
Dr Pisani said: "The
great relevance of our study is that we traced the earliest origin
of vision and we found that it originated only once in
animals. This is an astonishing discovery because it implies that
our study uncovered, in consequence, how and when vision evolved in
humans."
Paper: 'Metazoan opsin
evolution reveals a simple route to animal vision' by Roberto Fueda,
Sinead C. Hamilton, James O. McInerney, and Davide Pisani in PNAS.
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