[extropy-chat] Looking for examples of naturally evolved X-ray vision?

[Damien Broderick]

At 10:37 PM 1/17/2006 +0100, Alfio Puglisi wrote:

> > Now, five billion years later,
>
>more like five hundred millions years later. Dry land wasn't highly
>priced in the real estate market before then.

An interesting book on this topic is: Parker, Andrew In the Blink of an 
Eye: The Cause of the Most Dramatic Event in the History of Life, London: 
The Free Press, 2003.

Here's a chunk from my own book FEROCIOUS MINDS:
......................................................................

It is slightly shocking that for nearly four billion years our planet’s 
most complicated creatures were bacteria, algae, single-celled primitive 
creatures: bland, living on sunlight like plants but unable to see by its 
illumination. For most of the tenure of life on earth, long before insects 
and dinosaurs and rats and us, the light was on­but nobody interesting was 
at home. Life changed and diversified, but at an excruciatingly slow pace. 
A little more than half a billion years ago, everything accelerated, in an 
extraordinary burst of evolutionary inventiveness. That surge in novelty, 
when complicated life galloped into existence, is known as the Cambrian 
explosion.
           We don't have much instinct for these sorts of numbers. Yes, 
half a billion years is a tremendous span, equivalent to ten million 
pre-industrial human lifetimes strung out one after the other, and for all 
our antiquity humans have only been here for a thousand generations. If an 
average lifespan today represents the history of life on the planet, a 
human would be a very strange monster indeed. For the first 68 years or so, 
you would remain a single celled embryo, patient and mindless in your 
mother's womb. Abruptly, in a single month, you would start developing in 
earnest. Clumsy speech and dexterity would be delayed until the closing 
days of your 80th year, and true intelligence would not blossom until the 
final few hours.
           Self-preening, we stress that final burst into brilliant 
intellect, and disregard a tormenting question: why the extreme delay at 
the starting line? How is it that almost nothing happened for the first 
seven-eighths of life's history? What kept the brakes locked down on 
evolution, and what released them at long last, permitting an explosive 
flowering from just four basic kinds of very ancient inner and outer body 
design into 10 times as many, giving rise to everything we see and much 
that is already extinct, like the dinosaurs?
           The Cambrian explosion took place between about 543 and 538 
million years ago. Into those five million years were crammed all this 
rococo fabrication of complex life's ground rules. Why so fast, and why so 
long to get started? It would be neat and satisfying to resolve both 
questions with one answer. Zoologist Andrew Parker, a Royal Society 
research fellow at Oxford University, deemed by the Times one of the three 
most important young scientists in the world, took an interesting shot at 
the task seven years ago. His popular account is readily accessible to 
non-scientists. Possibly too accessible, since he leaves out any pointers 
to other research, except for some names mentioned in passing, which makes 
it hard to follow up claims hotly contested by other experts. Still, his 
book is richly crowded with altogether fascinating details, the very stuff 
of polymathy: how our planet was frozen for hundreds of millions of years 
under kilometers of ice, stopping life in its tracks; why the working 
insides of animals vary more than their defensive shells; exactly what 
causes the shimmering opalescence and iridescence of a pearl or a beetle's 
wing.
           For Parker, the key to the Cambrian event was the long delay 
before vision evolved. For vast stretches of time, creatures navigated and 
sought prey (or evaded the hungry) using touch, smell, taste, magnetic 
sensing: intimate and blurred. The world lay in fog. Then light-sensitive 
patches on the skin evolved with striking swiftness into true eyes, 
conscripting from other purposes the nerve wiring needed to turn images 
into a map of the world. Parker calls the epoch when sight came into useful 
focus the `Light Switch'. Once its switch was thrown, you could see others 
across a crowded room (or pool, or paddock) and they could see you. Under 
that spur, that naked transparency, natural selection was ruthless and 
quick, testing and conserving a vast number of sighted creatures such as 
trilobites, Parker's favorite candidate for the first eyed animal. It seems 
he is wrong, though, since trilobites (as Cambridge zoologist Simon Conway 
Morris argues) appeared as the Cambrian explosion was subsiding, not 
igniting. Well, details, details. Parker's key idea is fresh and fertile 
and fun.
           In the luminous shallows of Australia’s Great Barrier Reef, he 
ran into a dark brown cloud of cuttlefish ink. As it cleared, he faced 
thirty of the animals, forming `an exact arc around me, tentacles to face, 
eye to eye. Their brown bodies instantaneously bleached as I moved toward 
them... [then] displayed a wave of color changes. Brown and white 
synchronized undulations... suddenly a `loud' red...a calming green as I 
retreated... their eyes remained silver, like mirrors' (4). This is 
deliciously vivid, exactly capturing how crucial the sense of sight has 
become since the first clear-lensed eye opened half a billion years ago.[1]
           Even if eyes were the crucial breakthrough to explosive 
diversity, why did they take so long to arrive? My guess, reading toward 
the end of this detective story, was that air or water had perhaps long 
been murky, and cleared with a change in the environment. Either that, or 
the great slow orbit of the solar system into the dusty arms of the galaxy 
and out again might have modified the intensity of the Sun's light. Parker 
tries all these notions, and more, but fails to find a totally satisfying 
culprit. Still, his theory insists that there must be one, and so provokes 
a new and exciting scientific quest.


[1] In his efforts to be lucid as well as engaging, Parker does sometimes 
slip into unintended comedy. `Chemical detectors,' he explains carefully, 
`detect chemicals' (282).