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Evolution and Choice(Free will)

by sganesh88
Tags: evolution, freewill
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sganesh88
#1
Apr8-10, 09:22 PM
P: 288
This has been giving me head aches for the past so many days and it reflected in the "Random Evolution" thread too. But i think it deserves a new thread as googling for "evolution free will site:physicsforums.com" doesn't give satisfactory results.

So here is the question. Does the theory of evolution support conscious choice? By choice, i don't mean an illusion of choice. Is there an independent entity that exists without any kind of attachment to other parts of the body; that has the ability to make a choice? Or was Einstein right in saying that "Man can do what he wants but he cant want what he wants"-> meaning that this apparent choice is just an illusion. I read Sylas saying in the Random Evolution thread that evolution doesn't say anything about it. How could it not? If there's free will, it might very well change the way evolution works as it changes the trajectory of a organism every single moment. Genes would direct a way, freewill reviews this and either approves or rejects it-> millions of such yes-no decisions per minute. This new result approved by the freewill will have to be coded back to the genes. (An interesting example will be our initial lethargy to go to the gym. The freewill (if at all it exists) strongly rebukes this instinct and directs the body toward the gym. At a later point of time, the lethargic instinct ceases to be. Maybe a kind of pleasure develops too.)

Was this decision to rebuke and turn down the instinct, independent(freewill) or is it deterministic?


I hope i haven't violated any PF rules here.
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mgb_phys
#2
Apr8-10, 09:26 PM
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Quote Quote by sganesh88 View Post
So here is the question. Does the theory of evolution support conscious choice?
Yes, in fact for modern man it's the main evolutionary driver.
In another thread somebody asked if blondes would die out because the blonde gene is recessive.
But if gentlemen continue to prefer blondes, marry blondes and have lots of little blonde babies then that's evolution and for modern man it's a bigger effect than any vitamin D advantage having fair skin gives you in northern latitudes.
ThomasEdison
#3
Apr8-10, 10:45 PM
P: 107
Quote Quote by mgb_phys View Post
Yes, in fact for modern man it's the main evolutionary driver.
In another thread somebody asked if blondes would die out because the blonde gene is recessive.
But if gentlemen continue to prefer blondes, marry blondes and have lots of little blonde babies then that's evolution and for modern man it's a bigger effect than any vitamin D advantage having fair skin gives you in northern latitudes.
Many men might be prefering dyed blondes.

apeiron
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Apr8-10, 11:39 PM
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Evolution and Choice(Free will)

Quote Quote by mgb_phys View Post
Yes, in fact for modern man it's the main evolutionary driver.
I think that is a bit too quick an answer.

Social intelligence is an evolutionary driver in a social animal like the hominids (and apes generally).

Tool-use, division of labour, general planning capabilities would also be clear evolutionary drivers.

But not "freewill". At least not biological evolution. Yes, a case can be made for social or cultural evolution.

The notion of freewill arose in ancient Greek philosophy along with the idea of individualism and democracy more generally.

It was a social idea, but ironically the idea was to put the individual and his/her smart choice making in an abstract rather than social context. You acted not because everyone around you told you so (as happens in "primitive" societies even today), but because you were taken to be an autonomous choice-maker acting within an abstract backdrop of emotions and principles.

So you were motivated by loyalty or bravery. Or you succumbed to greed or lust. You acted according to justice and fairness. Or else you freely chose not to.

It is all really a big social game of pretend. But it was also a very powerful way to teach people to think. It unleashed a lot of individual creativity.

Of course, this game of the "unshackled individual unbeholden to anything except true feeling and philosophical principle" has its downsides. A lot of people these days use it to rationalise some rather anti-social behaviour.

It also has the unfortunate effect of sparking endless hand-wringing debate about whether we are really as free as we think. The debates made worse by roping in the determinism of Newtonian physics and the "personal relationship with god" trick played so neatly by proselytizing religions.

Taking the OP example of going to the gym, all that happens is that we live complex lives and have a variety of choices with a variety of paybacks over a variety of timescales.

The body does have an evolved motivation not to waste energy. So wanting to sit around is natural enough. Hunter/gatherers never felt they had to take up jogging.

Modern man knows the health problems caused by an unnaturally sedentary lifestyle and can imagine the consequences. But the consequences are far off, so do not feel urgent in the way that a hungry belly feels for a hunter/gatherer. In making reasoned trade-offs, it is easy to say I'll go to the gym tomorrow (and work out twice as hard, promise).

This is just evidence that we are socially liberated individuals free to make choices, as opposed to freely (ie: undeterminedly) making choices.

On the other hand, people join gym classes, employ personal trainers, tell other people about their plans to get fit, and make use of many other social reinforcers of their behaviour.

Being told what to do (especially in a contextual peer pressure fashion) is actually still quite a powerful determiner of our actions - because we indeed evolved as such social creatures.

It is easier to see how we evolved to conform then how we evolved to be individually free and self-actualising or whatever.
sganesh88
#5
Apr9-10, 06:49 AM
P: 288
An unpublished note by Darwin himself
“the general delusion about free will [is] obvious,” and that one ought to punish criminals “solely to deter others”—not because they did something blameworthy.4 “This view should teach one profound humility,” wrote Darwin, “one deserves no credit for anything… nor ought one to blame others.” Darwin denied that such a fatalistic view would harm society because he thought that ordinary people would never be “fully convinced of its truth,” and the enlightened few who did embrace it could be trusted.
- a discovery.org article "Is evolution compatible with Free will"

EDIT:
oh I gather the site belongs to a conservatist christian group. Anyway i hope they wouldnt have made up Darwin's note.
Jon Richfield
#6
Apr9-10, 07:18 AM
P: 258
There are more concerns here than I see anyone addressing, and more than I can address at present. Also more than I can find cogent answers for!

BUT:
Consider two kinds of evolutionary selective adaptation:
1: Natural selection
2: Teleological selection (something like what is often called "artificial selection")

These two entail and require different answers.

Now, think of what you mean by "will".
And what you mean by "free".
And what you mean by "free will" (watch it! You can't just concatenate the previous two to get a useful answer!)

Write down your answers and store them somewhere you wont be able to tear them up.

Now, get hold of a copy of a book called "The Mind's I" by D. Hofstadter and D. Dennett. Read it and make sense of it. It is a terrific book, readable, but if you read it quickly and think you understand it, you may be right.
Just may be.
Clear and non-technical and friendly it certainly is, but it is a hard read; not to be tackled when you don't have a lot of time to spare. It is full of ideas, challenging ideas, ideas that raise questions, and there are no crib sheets, no worked examples in the appendix.

Then try the questions again and compare the results with what you had written and stored.

If you are not up to all this, best steer clear. Strong meat for weak teeth or full mouths!

You have been warned.

Cheers,

Jon
Mkorr
#7
Apr11-10, 02:09 PM
P: 51
Another book that presents the compatibilist account of human freedom (an account that is fully compatible with evolution and determinism) is "Freedom Evolves" by Daniel Dennett. In this view, freedom is the ability to predict the outcomes of conscious actions on inanimate objects and act to avoid certain consequences. This perspective actually presupposes determinism, since this form of freedom needs the (statistical) predictability of the natural world.
Jon Richfield
#8
Apr11-10, 02:20 PM
P: 258
Quote Quote by Mkorr View Post
Another book that presents the compatibilist account of human freedom (an account that is fully compatible with evolution and determinism) is "Freedom Evolves" by Daniel Dennett. In this view, freedom is the ability to predict the outcomes of conscious actions on inanimate objects and act to avoid certain consequences. This perspective actually presupposes determinism, since this form of freedom needs the (statistical) predictability of the natural world.
Yeesss.... I have a high opinion of Dennett. I seem to have heard of that book. I must see whether I can find it. Did it leave you with any clear impression of the field and its implications?


Thanks MK,

Jon
sganesh88
#9
Apr12-10, 02:37 AM
P: 288
In this view, freedom is the ability to predict the outcomes of conscious actions on inanimate objects and act to avoid certain consequences
A computer program can train a system to learn from history. That doesn't mean the system has freewill does it?
Jon Richfield
#10
Apr12-10, 04:25 AM
P: 258
Quote Quote by sganesh88 View Post
A computer program can train a system to learn from history. That doesn't mean the system has freewill does it?
Quite right. I had been wondering whether to point that out. You don't even need a computer; think of of a simpler program-controlled device, like a break-back mousetrap. It sits there quietly thinking to itself: "Mmmmmoussse... mmmmoussse... MOUSE! SNAPPP!!!" Millions of times a second it decided when not to snap, and finally snapped shut in milliseconds when the mouse came along. (Ooops! Was that a finger? Oh well, never mind, the finger will have to do till the mouse comes along! You can tell that is what it thinks because it doesn't let go.)

You don't like my scenario? How do you prove that the trap doesn't have consciousness and free will?

How do you know I don't?

Cheers,

Jon
sganesh88
#11
Apr12-10, 06:36 AM
P: 288
How do you prove that the trap doesn't have consciousness and free will?
The accumulation of my past experiences suggests that. I have left my specks in the terrace a million times and everytime i go up to find it, i see it faithfully waiting for me at exactly the same location. So is the case with other objects.
Frame Dragger
#12
Apr12-10, 07:31 AM
P: 1,540
Maybe a better question for the OP is: "free will" is generally a religious concept; "free will vs. predestination", or one for Quantum Physics (in a more general sense), so why couch evolution in these terms?

Wow, I get to post this twice in one morning....

http://hd.media.mit.edu/01.29.09_naturemag_secsig.pdf

Quote Quote by Nature 2009
Moreover, he says, the literature is full of
experiments showing that conscious explanations
for our behaviour are often just rationalizations
invented after the fact. He cites the
example of a patient whose corpus callosum
had been severed as a treatment for epilepsy,
making it impossible for one side of the brain
to communicate with the other. Gazzaniga and
his colleagues presented the word ‘walk’ to the
patient’s left visual field, which corresponds to
the right side of the brain. When the patient
stood up and began walking, they asked him
why; the right side of the patient’s brain had
been shown to lack the ability to process language.
His left brain, which never received the
walk command, but which handles language
processing, quickly invented a logical explanation:
“I wanted to go get a Coke.”
The conclusions drawn from such anecdotes and studies, as well as the apparant "concert" vs. "module" nature of higher reasoning, which free will could be considered the apex of, are unclear. That said, it would seem that "free will" is not cut-and-dry, taking mysticism out of the equation. Of course, as a whole that person DID make a choice, it was just not properly narrated, so to speak. Why is it a shock that a collection of cells, each of which would be considered an organism on its own, should provide a clear "macro vs. micro" line anymore than QM just STOPS and the macroscopic worls "emerges"? When our brains act in a concerted manner, we percieve normal consciousness. Just deprive someone of company and sleep, and you'll see how fragile that is.

@apeiron: The concept of free will has been around for a lot longer than Greece; for instance much Cuneform is concerned with legalisms regarding choices made by an individual. There are many more examples... although free will and "liberty and freedom" are very different. Your point about Solopism and the like is well taken, but that may be an issue of ability to cope with underlying illness or dysfunction. We can't "fix" people with APD (sociopaths), and when they become dangerous, we can't let them be free, even though it's clear to science at this point, that they are not CAPABLE of much or any impulse control or empathy. It really isn't hard to imagine a society in which such people are "corrected" through (whatever brand) of psychcosurgery... if not here in the USA, somewhere. I suspect we'll both be alive to see some of it too.

Of course, to me that smacks of killing person A, and replacing them with B, albeit in the same body. Now, if we're talking about a rapist, pedophile, etc Paraphilias, then I can see the people actually WANTING to be "fixed". However, how do you "fix" someone who is schizophrenic, while retaining who they are? This is the kind of thing that could be simple treatment OR the equivalent of murder/lobotomy. When it comes to people taking responsibilty, it's one thing to recognize the source of pro or anti -social behaviours... it's another to recognize the necessity to keep an organized and fucntional society. Then again, people who believe that a god ordains all actions still want people in jail, executed, burned at the stake (now and in the past). Clearly people don't want to consider the notion until something other than jail or execution is an option. After all, what kind of people are we, if in fact they DON'T have as much lattitude in their thinking or behaviour... and we still killl them or put them in prison? We'd be both helpless to do otherwise, AND we'd feel terrible. Cognitive dissonance arises, sides are taken... yadda yadda.


@sganesh88: That's really convincing evidence, but not PROOF. see: "Solopism" for one view, although it's not whine I ascribe to.
Jon Richfield
#13
Apr12-10, 09:12 AM
P: 258
Quote Quote by sganesh88 View Post
How do you prove that the trap doesn't have consciousness and free will?
The accumulation of my past experiences suggests that. I have left my specks in the terrace a million times and everytime i go up to find it, i see it faithfully waiting for me at exactly the same location. So is the case with other objects.
"Other objects...?" Like moons and mice and morons and marrons, like stones and scones and scratches and screw-pines, like cars and cardamoms and computers and cabbages and kings? You could use similar arguments for every one of those. Which of them are sentient and which have wills, whims and wonts?
No one has yet so much as scratched the surface of such existentialist questions; certainly your criterion doesn't help much for crystals, scallions, scallops, scarabs, shadows, or geometric lathes.
Your mousetrap with its wontful spring and willful trigger will sit silently hating mice for lifetimes of increasing malice, till it will gleefully smash a heedless finger in lieu. Surely that is evidence enough of sentient spite?

As FD said, your supporting evidence might be persuasive, but as proof, it is about as cogent as saying that something is or is not sentient because you say it is. Those who said to the wood, "Awake", to the dumb stone, "Arise, it shall teach!" and those who replied: "Behold, it is laid over with gold and silver, and there is no breath at all in the midst of it;" they had just as strong a case for or against as anything that you have said. The proof works both ways.

That mousetrap could lie doggo for as long as your specs, and still surprise your careless toe. "But in contrast, my faithful specs would not do that to me," you protest? Just wait till you tread on them in the dark, then let's hear you say it again while binding up the bleeding!

The so-called inanimate objects hate people who insult and contemn them so viciously; it is too late to repent, to beg forgiveness; as soon as you relax your vigilance, they will STRIKE!!! Shin and finger, eye and ear, digestion and dermis, all will suffer in their season!

What better proof could anyone ask? The converse of Turing's test is as compelling as its obverse!

Jon (wooden of head and cotton of heart, as you now begin to realise, surely?)
Mkorr
#14
Apr12-10, 12:13 PM
P: 51
Quote Quote by sganesh88 View Post
A computer program can train a system to learn from history. That doesn't mean the system has freewill does it?
From the compatibilist perspective, freedom is not an all-or-nothing property, but gradual, increasing as the predictability and ability to act to avoid unwanted consequences of the system increases. So that system would have some amount of freedom (albeit very, very limited), if it could make predictions and act to avoid negative outcomes. So learning from history is a necessary, but not sufficient premise from this perspective.

From the compatibilist perspective, humans obviously are not free in the libertarian sense of the term, but Dennett argues that it can accommodate all the varieties of freedom wanted. He further argues that we do not really want libertarian freedom anyways, because that would mean, according to Dennett, that our actions where not determined by who we are, what we know about the world or our moral character, which would be a horrible nightmare.

Quote Quote by Jon Richfield
Yeesss.... I have a high opinion of Dennett. I seem to have heard of that book. I must see whether I can find it. Did it leave you with any clear impression of the field and its implications?
I got the impression that the compatibilist account is really the only one of the three major views on freedom (compatibilism, hard determinism and libertarian freedom) that is compatible with both evolution, determinism of the macroscopic physical world and some form of moral responsibility. Hard determinism is by definition incompatible with moral responsibility, libertarian freedom is by definition incompatible with the brain/mind as an evolutionary product. Maybe compatibilism is the best of two worlds, so to speak.

The book also had some very interesting criticism of the methodology and theoretical assumptions of Benjamin Libet experiment(s), a largely disinterested discussion of libertarian freedom as well as a very general criticism of Cartesian materialism. Granted, Freedom Evolves is a popular account, but I thought that it covered the topic well. It also connects to some of his earlier works, especially Consciousness Explained and Elbow Room.
apeiron
#15
Apr12-10, 03:23 PM
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Quote Quote by Frame Dragger View Post
@apeiron: The concept of free will has been around for a lot longer than Greece; for instance much Cuneform is concerned with legalisms regarding choices made by an individual. There are many more examples...
Really? The Summerians expressed freewill as a philosophical concept?

The idea of the individual as standing apart from society and convention came into strong focus in philosophical debate with Socrates. But perhaps you can cite a philosopher who was as influential from some earlier time or culture.

If you merely mean that all earlier complex societies, with their ranks of kings, nobles, scribes, freemen and slaves, would have created an awareness of relative social freedoms and rights, then of course I could not disagree. But where was it a metaphysical issue?

BTW, "concert vs module" - the distributed vs modular debate is best viewed in terms of scalefree networks and other powerlaw models of plasticity~stability.

The tendency to clump (look like a module) would be in exact equilibrium with the tendency to spread (look distributed) if the brain operates along dissipative structure or scalefree connectivity principles. Plasticity~stability would be self-simlar or fractal over all scales.

One illustration of this principle is the fact that the human brain scaled up in powerlaw fashion during evolution (so a fact relevant to this thread too). Some researchers argue, for example, that the prefrontal lobes are not out-sized in humans, merely that the whole brain was scaled up in (scalefree) proportion and as the highest level, most plastic, region, the prefrontal had to be larger to maintain the general equilibrium balance.

This would argue that we are not special because of enlarged prefrontal lobes, but just because we have overall, in proportion, larger brains.

There are many other findings along these lines, including the exaggeration of lateralisation in humans, and the greater size of foveal representation in the visual cortex.
Frame Dragger
#16
Apr12-10, 04:14 PM
P: 1,540
Quote Quote by apeiron View Post
Really? The Summerians expressed freewill as a philosophical concept?
Yes. All people were not equal, as a great number of laws seem to concern the disposition of slaves, but their laws (again, The Code of Hammurabi), and reflect consequence meant to deter individuals from making false accusations. We could argue all day, no doubt, but it's hard to imagine that the concept of individual free will was not considered.

Of course, maybe a better question is whether a lack of evidence that is as proximal and understandable as Greek Philosophy, means that societies didn't consider free will. What makes you believe that the assumption wasn't that people were free from total external (metaphysical) control? The popularity of many concepts, and the amount of data recorded by the Greeks and then Romans (not to mention the Roman "adoption" of much that was Greek) makes for a very accurate historical picture. That is more unusual than not.

Quote Quote by apeiron View Post
The idea of the individual as standing apart from society and convention came into strong focus in philosophical debate with Socrates. But perhaps you can cite a philosopher who was as influential from some earlier time or culture.
Ahhh, so now it has to be "free will as discussed by philosphers", and recorded in history in a way that few things are, explicitly at least. It IS clear that the Sumerian->Akkadian (etc) pantheon was very similar to the Greek pantheon (no shock there), and both were very... human in terms of their natures. There is some question as to whether figures mentioned in Cuneform inscriptions were believed to be gods, god kings, or just exactly what. So, yes, one must infer based on the evidence at hand.

If you merely mean that all earlier complex societies, with their ranks of kings, nobles, scribes, freemen and slaves, would have created an awareness of relative social freedoms and rights, then of course I could not disagree. But where was it a metaphysical issue?
I suppose that you could believe that at that time, people didn't consider those matters, but I don't believe that. The sheer number of laws regarding escaped slaves, or people who harbored them reflect a keen sense of individual responsibility.

Quote Quote by apeiron View Post
BTW, "concert vs module" - the distributed vs modular debate is best viewed in terms of scalefree networks and other powerlaw models of plasticity~stability.
That is one view, especially if you're deeply into bioinformatics.

Quote Quote by apeiron View Post
The tendency to clump (look like a module) would be in exact equilibrium with the tendency to spread (look distributed) if the brain operates along dissipative structure or scalefree connectivity principles. Plasticity~stability would be self-simlar or fractal over all scales.
You've been reading Dr. Wiley I presume, and no, I'm not going to disagree. Still, there are a lot of if's there... too many for anything but academic theory, or someone who is trying to advance the science of (brain) imaging, especially in terms of how to interpret and filter information. It's that kind of thinking that led to evidence, rather than just suspicions about a constantly "on" network that does more than just "hum".

Quote Quote by apeiron View Post
One illustration of this principle is the fact that the human brain scaled up in powerlaw fashion during evolution (so a fact relevant to this thread too). Some researchers argue, for example, that the prefrontal lobes are not out-sized in humans, merely that the whole brain was scaled up in (scalefree) proportion and as the highest level, most plastic, region, the prefrontal had to be larger to maintain the general equilibrium balance.
Yes, a very basic debate that is unlikely to be settled soon, and of which I am aware.

Quote Quote by apeiron View Post
This would argue that we are not special because of enlarged prefrontal lobes, but just because we have overall, in proportion, larger brains.
That seems not to be the case, but then brain size is notoriously misleading. I recommend a bit of research into the Corvidae Family (of birds, not a family of people). Some researchers also are discovering structures which act much like our frontal/pre-frontal lobes, in birds.

Quote Quote by apeiron View Post
There are many other findings along these lines, including the exaggeration of lateralisation in humans, and the greater size of foveal representation in the visual cortex.
Yes, but then we evolved with sight as our primary sense, and there is absolutely no concseus regarding the rest. All interesing, all around for a long time. I'm not sure why you're telling me this.

EDIT: I'm not even going to attempt correct my spelling anymore... *throws up hands and starts swearing*... I've become completely dependant on spellcheck for so many years. ARRGH! (Aries Rising Record Group Holdings)
apeiron
#17
Apr12-10, 05:24 PM
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Quote Quote by Frame Dragger View Post
We could argue all day, no doubt, but it's hard to imagine that the concept of individual free will was not considered.
That is precisely the point. We could argue all day if we rely on appeals to what we can imagine might be the case in some ancient culture.

Am I wrong that the dialogues of Socrates are a critical text handed down to us that document some actual philosophical stance? Even today, we are influenced by tales like Socrates drinking the hemlock. But I cannot detect any trace of Summerian belief in the modern social construction of freewill.

You just seem to be trying to score points against me here (as usual). You pick on a small part of what I say and try to correct me, while failing apparently to understand the overall argument.

Freewill is a social construction. That Western cultural construction has living roots in Greek and Roman philosophy. We still use the same arguments, the same tales. The issue here is not whether the Summerians might have had intellectual priority here somehow, but the origins of the western mythology of freewill as an innate psychological faculty.

(Though, yes. it would be historically interesting if you could indeed present the texts that show the Summerians exactly foreshadowed the later arguments of atomists, Socrates, etc.)

Quote Quote by Frame Dragger View Post
You've been reading Dr. Wiley I presume,
Who is he. The name does not immediately ring any bells. The idea of scalefree neural organisation is in fact pretty widespread in neuroscience.

Quote Quote by Frame Dragger View Post
That seems not to be the case, but then brain size is notoriously misleading. I recommend a bit of research into the Corvidae Family (of birds, not a family of people). Some researchers also are discovering structures which act much like our frontal/pre-frontal lobes, in birds.
OK, for the last time, quit patronising me. Surely you have learnt by now that anytime you think I should do a "bit of research", I am in fact already intimately familiar with that area.

I haven't got my files with me now, but later I will post a Lancet Neurology column I wrote on exactly this - how bird brains compare to mammals as an example of convergent evolution.

How many times must you discover that I in fact have done my homework before I open my mouth?
apeiron
#18
Apr13-10, 02:28 AM
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As promised, what real research on bird brains looks like.......

Do birds seem a little bit alien to you? It’s those beady expressionless eyes, the sudden darting movements, a stop/start sort of mind. No question that a parrot or raven is as smart as a monkey or dog, but surely their brains are wired up differently somehow?

This is the lay impression. And the avian experts agree. Yet exactly how the brains of birds differ is causing great ructions at the moment. Avian neuroscientists have finally put one century old view about its architecture to rest. But still they can’t quite decide the story that ought to replace it!

The layout of the lower brain of birds and mammals is of course much the same -
brainstem, cerebellum, midbrain and thalamus. However the cortical lobes look very different. There is no six-layer sheet of cortex wrapped around a mass of white matter connections. Instead the avian telencephalon seems a dense mass of nuclei. This led early neuroanatomists – who believed that birds ranked lower on the evolutionary scale and were thus largely instinctual in nature – to conclude that their cortical lobes were merely elaborated basal ganglia. And so all the higher bits of a bird’s brain got labelled as striatal this or striatal that. Even a strip of undoubted cortex on the dorsal surface was named hyperstriatum as if it wasn’t quite up to its mammalian counterpart.

Within ornithological circles, it was soon realised birds weren’t basal ganglia-brained. Only the most ventral nuclei were actual striatal structures. But by then the terminology had stuck, generating vast and continuing confusion. Even in 1998, a Journal of Neuroscience paper mistakenly compared the neostriatal control of grooming “syntax” in rats to the neostriatum song memory area in birds - bird neostriatum being more properly equivalent to temporal cortex.

Last year researchers finally agreed to a complete overhaul of the neuroanatomical nomenclature. Largely this was done by replacing each striatal reference with a pallidial one. So now, for example, the neostriatum is the nidopallium. But the experts remain divided on the deeper question of how to view the actual organisation of the bird brain.

One camp take the startling view that birds have a six-layer cortex like mammals after all – it’s just that the layers are split up into processing blobs! So layer four, the cortical “input” layer, is rolled up as a central nuclei known as the entopallium (formerly the ectostriatum). This then feeds into an adjacent lump, our friend the neostriatum or rather nidopallium, which serves the processing functions of cortical layers two and three. The nidopallium then feeds into what used to be thought of as the bird’s equivalent of the amygdala, the arcopalluium. This handles the chores of mammalian cortex layers five and six.

This way of looking at the connectivity of the avian brain suggests that birds and mammals have taken different anatomical routes but arrived at a remarkably similar processing architectures. However recent evidence based on homeobox genes questions the cortical layer hypothesis. Instead it seems the bird’s higher brain is the result of a massive expansion of that mysterious region, the claustrum.

The accepted story on mammals is that they branched from the reptile line about 300 million years ago as small nocturnal grubbers. So the part of the brain that ballooned was the dorsal cortex, an associative area linking the olfactory bulb to the hippocampus – the right sort of brain architecture for “filling in” the what and where of smells. Visual and auditory input then got diverted from midbrain to cortical areas to allow the same associative processing of the confusing noises and degraded images of the night-time jungle.

Birds on the other hand didn’t diverge from the dinosaurs until 100 million years later, so plenty of time to follow a different neurodevelopmental track. And birds were daylight fliers who just needed sharp eyes and snappy reflexes. Hence birds stuck mainly to a “collicular” style of sensory processing, expanding their midbrain optic tectum. The cortical expansion that did take place happened along an embryonic amygdala-claustrum axis.

Now the idea that birds may have a more “encephalised” amygdala is a bit of a poser for those who say birds aren’t emotional. But perhaps it does fit with the idea they are more instinctual – snap decision makers rather than associative ponderers. However a claustral origin for their cortical regions has left neuro-ornithologists floundering. What does it even do in humans except perhaps some kind of cross-modal sensory integration? Oh well, still more questions than answers then. But it does show that there must be surprising number of different ways for evolutionary tinkering to construct a brain.


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