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Chemo-Affinity Hypothesis

Arthur Brash | January 10, 2010 | 13:22

Ingenious experiments have shown that nerve cells, when they grow out from the spinal cord, or from the brain, find their way to their end organ not by following any kind of overall plan but by chemical attraction, rather as a dog sniffs around to find a bitch in season. An early classic experiment by the Nobel-Prize-winning embryologist Roger Sperry illustrates the principle perfectly.

Sperry and a colleague took a tadpole and removed a tiny square of skin from the back. They removed another square, the same size, from the belly. They then regrafted the two squares, but each in the other’s place: the belly skin was grafted on the back, and the back skin on the belly.

When the tadpole grew up into a frog, the result was rather pretty, as experiments in embryology often are: there was a neat postage stamp of white belly skin in the middle of the dark, mottled back, and another neat postage stamp of dark mottled skin in the middle of the white belly. And now for the point of the story. Normally, if you tickle a frog on its back with a bristle, the frog will wipe the place with a foot, as if deterring an irritating fly. But when Sperry tickled his experimental frog on the white ‘postage stamp’ on its back, it wiped its belly! And when Sperry tickled it on the dark postage stamp on its belly, the frog wiped its back.

What happens in normal embryonic development, according to Sperry’s interpretation, is that axons (long ‘wires’, each one a narrow, tubular extension of a single nerve cell) grow questingly, out from the spinal cord, sniffing like a dog for belly skin. Other axons grow out from the spinal cord, sniffing like a dog for belly skin. And normally this gives the right result: tickles on the back feel as though they are on the back, while tickles on the belly feel as though they are on the belly. But in Sperry’s experimental frog, some of the nerve cells sniffing out belly skin found the postage stamp of belly skin grafted on the back, presumably because it smelled right. And vice versa.

People who believe in some sort of tabula rasa theory – whereby we are all born with a blank sheet for a mind, and fill it in by experience – must be surprised at Sperry’s result. They would expect that frogs would learn from experience to feel their way around their own skin, associating the right sensations with the right places on the skin. Instead, it seems that each nerve cell in the spinal cord is labelled, say, a belly nerve cell or a back nerve cell, even before it makes contact with the appropriate skin. It will later find its designated target pixel of skin, wherever it may be. If a fly were to crawl up the length of its back, Sperry’s frog would presumably experience the illusion that the fly suddenly leaped from the back to belly, crawled a little further, then instantaneously leaped on the back again.

Experiments like this led Sperry to formulate his ‘chemo-affinity’ hypothesis, according to which the nervous system wires itself up not by following an overall blueprint but by each individual axon seeking out end organs with which it has a particular chemical affinity.


Excerpt: The Greatest Show on Earth: The Evidence for Evolution. ISBN: 978-1-4165-9478-9
Copyright 2009 by Richard Dawkins
Reprinted without permission.
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Anti-theism, Delicious Literature, General
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Time to think a spell

Arthur Brash | November 14, 2009 | 18:37
Looking at the shelves at the polish store can have a negative effect on my psyche – religious books, conservative magazines and papers, Christian tokens in many forms lie about in all corners.
 
I can’t help but wonder how I’ll fit in when I come face to face with it in Poland – the country where I was born, the country that had trouble becoming part of the EU due to its seemingly non-existent separation of church and state. If freedom is the space between church and state, Poland will feel very confined.
 
How does one look in the face of the people from which a recent Pope was chosen, and who see Mother Theresa as a wonderful human being? (In fairness, much of the civilised world still sees Mother Theresa as some sort of saint.) Atheists – yet alone anti-theists – appear to be as rare in Poland as human decency and scientific inquiry is in organised religions.
 
I don’t mind being a heathen in the eyes of the religious, I find it a kind of compliment on the same level that being a “good christian boy” is an insult. It’s the sheer number of the ignorant that concerns me. There is after all power in numbers.
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Africa

Arthur Brash | October 2, 2009 | 11:37

 
There is a story, which is fairly well known, about when the missionaries came to Africa. They had the Bible and we, the natives, had the land.
They said “Let us pray,” and we dutifully shut our eyes.
When we opened them, why, they now had the land and we had the Bible.
 
Desmond M. Tutu

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Glenn Beck, Have a Bag of Pretzels!

Arthur Brash | August 18, 2009 | 13:21

What do WalMart, BestBuy, Procter & Gamble, and Travelocity have in common? Come to think of it, too much – forget I asked. But there is one thing I’d like for them and their likes to continue doing, and that’s pulling advertising money out from propaganda aired on FoxNews. (If this dream turns reality, FoxNews as a whole will go off air and the stupefied Under 50IQ Paranoiacs-R-Us will be left to wonder the streets, thus increasing their chances of getting killed by a speeding vehicle.)

Reports suggest that the list of companies requesting their advertisements not be part of Glenn Beck’s Duckspeak has now reached 20. (Source: The Huffington Post)

Even God is pleased; using angels’ blood He signed a self-imposed Cease to Kill Kittens, normally executed by the Almighty at a 1:1 ratio for each act of human masturbation. (Since the Reforms of ‘79, acts of ape and chimp masturbation do not result in kitten executions. Ever since, humans have tried and failed to work out a similar deal with God, leaving many to feel shame and guilt over simply being human.)

The cease is valid on all days a new company pulls its advertising from FoxNews, a gesture which outraged the Mice Consortium, but to which the K9 Units responded with an enthusiastic wag of the tail.

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Anti-theism, Aspirations, Political Perspective, Soap Box
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Ask an Atheist – 5 Questions

Arthur Brash | May 11, 2009 | 21:36

1. What in your opinion is the biggest misconception about atheism?
Atheism is probably the most useless word – it says absolutely nothing. Understand that, and you just might grasp your neighbourhood atheist.

Atheism is a negation of theism. It tells you absolutely nothing about what I believe. Yet time and time again, theists lump atheists together under one umbrella of “the belief in non belief.” It’s absurd.

There is no belief in the non-belief of something. You make a case for an invisible god in the room, and somehow think that me not going along with the idea is a whole new belief system? Then you’re misusing the word belief. You’re rendering it useless to the point where it does not help identify any group in a meaningful way. You’re doing what religion does best – mudding the water. Making everything so blurry, no one knows the facts, and each is left to proclaim their own “truth.”

2. Do you think there is extra-terrestrial or extra-universal intelligence?
Yes. Has it visited us on earth? No, probably not. Basis? Drake Equation. I suggest you look into it when you get a chance.

3. What in your opinion is the poorest argument for religion and why?
Religion has no good arguments, not a single one. But if I could rid the planet of just one, I’d like for everyone to recognise that religions do not make us moral beings. When you read Deutronomy 22 and are told to stone the woman who’s not a virgin on her wedding night, you find no other direct counter verse. You are deciding which verses follow. The moral compass is inside you, but religion is trying to convince you that it was it that gave you this gift. Like hell it did. Pun intended.

4. What would would be your perfect society? Secular? non religious? Anarchic? Why?
Just as there probably is no god, there is nothing that is perfect. For some people the idea of mortality and secularism is hell, and I don’t think I’d find myself enjoying life in a secular society full of stressed out fellow men. I mean you can get the best job position in the world, but if everyone around you is going to pieces, you’re not likely to enjoy your work.

Forget one encompassing solution for everyone. Each to their own, without fear of persecution and imposed creeds. I’d personally be one miserable creature if evidence for god began surfacing. What I enjoy of my life I enjoy because it will end, “and nothing shall be left of me or my ego.” Nothing that is limitless has ever found any value in the hearts of men.

5. If when you die you find god, how would you justify yourself to him?
I will adopt Rick Moen’s Strategy: “In the unlikely event of losing Pascal’s Wager, I intend to saunter into Judgement Day with a bookshelf full of grievances, a flaming sword of my own devising, and a serious attitude problem.”

If despite being blessed with a brain I am told by god that I was to ignore everything it tells me, he is no king of mine. “To his credit, man has for thousands of years worked to fix the botched job god has done.” I don’t know who said that, but I have a feeling we’d see eye to eye.

If there is a god, the only sensible thing to do is to picket his gates – have him give some credit where it is due. No more free-riding. Give us a pat on the back and some perks for putting up with shit like cancer, violence, suffering, and the god damned Conservative, right wing politics.

Amen.

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