<br><br><div class="gmail_quote">2009/2/2 Steve Witham <span dir="ltr"><<a href="mailto:sw@tiac.net">sw@tiac.net</a>></span><br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
About charging into the valley of blindness, Jesus said, "If your right<br>
eye causes you to sin, pluck it out." But upon consideration he said,<br>
"First remove the plank from your own eye."<br>
<br>
Evolution seems to have crossed the gap between compound and<br>
single eyes in both directions. There's a fascinating variety of<br>
approaches including parabolic mirrors, corner reflectors,<br>
segment walls that retract under low light, and simple eyes wedged<br>
within compound eyes. The eye of some flying insects, including the<br>
bee, has a fovea--an area in the middle that gets better resolution<br>
using larger lenses.<br>
<br>
<a href="http://en.wikipedia.org/wiki/Compound_eye" target="_blank">http://en.wikipedia.org/wiki/Compound_eye</a><br>
<br>
I'm pretty sure the gene-activation signal for "form an eye here" is<br>
the same for humans, bees and octopi, erm,<br>
While marveling at your own eye<br>
give a thought to the octopi<br>
whose optical nerves<br>
straighten out all the curves<br>
that cause blind spots for you and for I.<br>
</blockquote><div><br>I thought mollusc and vertebrate eyes were a case of convergent evolution. From <a href="http://en.wikipedia.org/wiki/Evolution_of_the_eye">http://en.wikipedia.org/wiki/Evolution_of_the_eye</a><br>
<div style="margin-left: 40px;">The different forms of eye in, for example, vertebrates and mollusks are often cited as examples of <a style="outline-color: invert; outline-style: dotted; outline-width: 1px; outline-offset: 0pt;" href="http://en.wikipedia.org/wiki/Parallel_evolution" title="Parallel evolution">parallel evolution</a>.</div>
and<br><div style="margin-left: 40px;">At a cellular level, there appear to be two main "designs" of eyes, one possessed by the <a href="http://en.wikipedia.org/wiki/Protostomes" title="Protostomes" class="mw-redirect">protostomes</a> (molluscs, annelid worms and arthropods), the other by the deuterostomes (chordates and echinoderms)</div>
<br><br><br> </div><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><br>
MarkM says:<br>
>These have come up before on this list, and we've always concluded<br>
>(correctly IMO) that HCSs have no technical advantage over pure ocap systems<br>
>used with the Horton pattern. However, HCSs may provide the path through the<br>
>valley of blindness that allows us to reach the higher hill.<br>
<br>
By technical advantage you mean in terms of the kinds of effects you<br>
could achieve if starting from scratch. But, migration also has its<br>
technical problems. We need a capital-O notation for human effort.<br>
<br>
--Steve<br>
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</blockquote></div><br>