Evolution of the Brain

In a discusion with a psychiatrist recently, he informed me that there had been some debate by neuroscientists about mental illnesses, such as schizophrenia, being an evolutionary leap. Unfortunately, he was unable to cite the source of this research. I was wondering if anyone else knows of this research and can both comment on it, and also provide references.

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Lucy

Thread moved here from the Proposed New Topics forum.Hi Limpid,Welcome to EvCForum. Although your topic doesn't have direct relevance to the basic context of this forum (evolution vs. creationism), we do have a number of scientists available who may be able to answer your question.In order to make your stay here more pleasant and productive, I hope you'll take a moment to peruse the links in my signature below, especially the forum guidelines.Again, welcome to EvC and thanks for adding to our diversity.Edited by AdminQuetzal, : No reason given.

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Hi Limpid,Let me reiterate what my evil twin AdminQuetzal said and welcome you to EvCForum.One of the things that might help generate a better response to your question is to elaborate a bit on what your psychiatrist friend meant by "evolutionary leap". Many of us, myself included, feel that the term is misleading, to say the least. IMO, there were seven major transitions during the course of evolutionary time (the number varies on who you ask), that could at a stretch be considered "leaps" - although even here they were very slooooooow leaps lasting millions or even hundreds of millions of years. If you can define what you (or your friend) mean by it, maybe we can come up with a decent answer that places the problem in context.

I'll try and find some of the science referring to how schizophrenia may be maintained in the human population but it goes something like this...Schizophrenia has been shown to have possible genetic causes (twin studies), a related condition is schizotypy. Schizotypy is also common within families of schizophrenics (i.e. may be genetic), it is a condition that falls short of psychosis but does show mild elements of schizophrenia such as unusual experiences etc. Why does schizophrenia maintain itself in the population if it is genetic? It certainly isn't conducive to reproduction.Many creative types are known to suffer from similar unusual experiences and have been shown to have higher than normal levels of schizotypy and other psychiatric disorders. There is also evidence that these creative types are very successful at gaining sexual partners So, putting 2+2 together, the hypothesis suggests that schizotypy is a result of genes that enable a trait of creativity (language skills etc), this trait is maintained by sexual selection. The downside of the genes underlying this trait is, in some circumstances, the possbility of developing schizophrenia. See it a trait scale ranging from the extreme of no schizotypal behaviour to the other extreme of severe schizophrenia, with schizotypy being somewhere in between.There was a study not so long back supporting this hypothesis. It's fairly tentative at the moment though. A good article is in a Royal Society journal, I'll hunt it down when I get a chance.I'll add articles by edit as I find them...http://www.psy.vanderbilt.edu/...tions/Folley_Park_NIROT.pdf 404 File Not Found :: New Mexico's Flagship University | The University of New Mexico http://www.staff.ncl.ac.uk/daniel.nettle/jrp.pdfhttp://www.staff.ncl.ac.uk/...%20clegg%20proceedings%20b.pdfEdited by melatonin, : add links

One article I stumbled across that may provide an overview of research efforts is Evolutionary Perspectives on Schizophrenia from the Feb. 2003 Canadian Journal of Psychiatry:Page not found - Canadian Psychiatric Association - Association des psychiatres du CanadaApparently this is an area of active research which has produced several competing hypotheses.Edited by anglagard, : reduce alliteration

Thank you all very much for your responses. I can't exactly state what the psychiatrist meant, however, I do understand the evolutionary "leaps" are very, very long in the scheme of evolution. Unless you are a white or grey moth living in London, where the white ones, being noticeable, were "taken out" by preditors very quickly. I am fascinated with the evolution of the brain. Unfortunately, due to university studies I selected, I was unable to study this. Also, I would think that it has not had a long resonance in scientific fields. One other thing that I found out - also fascinating - is that we have a residual reptilian part of the brain. Could anyone kindly enlighten me on these sort of evolution. I am a complete novice, starting from scratch, so no matter how basic the information I receive, it will be welcome. Thank you again.

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Lucy

Could this be a reference to the notion of the bicameral mind?

Dr Adequate, Thank you very much for this information, which is very interesting in itself and poses a lot of questions. This is only a guess, but I think that the psychiatrist was perhaps referring to the creative and original ideas that such people demonstrate. Might I suggest that this would not only apply in the arts, but even include those in purely scientific fields. One has an extraordinarily original hypothesis and then seeks to establish it through research.

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Lucy

When a neuroscientist/psychologist talks about the reptilian region of the brain they are referring to the evolutionary ancient structures such as the limbic system/brainstem. This includes areas that are related to emotion, motivation, and instinct.If we take anxiety and fear as an example. Fear is an adaptive response to environmental threat, it results in the hormonal cascade of 'fight or flight' (or freeze as well actually). This process can occur very rapidly, it is generally automatic, involuntary, and unconscious. The mechanisms involved in fear are limbic systems and evolutionary ancient. On perceiving a threat, two neural pathways are activated; (i) the subcortical limbic system (as described above, rapid, instinctive, and coarse); (ii) a neocortical higher cognitive pathway (slow and accurate). The subcortical process will prime a human to attention and enable a rapid response, the slower higher corticial processing will assess the threat in more detail, if the threat is false, the higher cortical processes will dampen the subcortical fear activity.In anxiety disorders the higher processes are unable to control the subcortical activity and essentially these instinctive processes 'highjack' processing resulting in abnormal levels of limbic activity when faced with fairly innocuous stimuli - fearfulness, sweating, heart-racing (a fight or flight response) etc.So, the 'reptilian' brain is an old region of the brain that has since seen newer cortical layers added on top (neocortex). However, the lower processes are still adaptive but can be problematic in some individuals.The above is quite simplistic though. There is clearly evolutionary development of the brain as we climb up the evolutionary 'ladder'.ABE: and Macleans triune ideas (the basis of the reptilian idea) are not so well respected now. The modern notion of the limbic system has grown to include more cortical areas (orbitofrontal) and the brainstem areas are not fear response (fear is also limbic). It very simplistic and quite wrong.Edited by melatonin, : No reason given.Edited by melatonin, : added stuffEdited by melatonin, : must sleep...

I've done a bit of googling round, and I think I understand the situation now. The argument goes like this.From the point of view of natural selection, schizophrenia is bad news. Until the recent development of effective drugs, it was very bad news indeed.And it certainly has a strong genetic component, although other factors must be involved, since schizophrenia can strike just one of a pair of identical twins.Moreover, it usually strikes young in life: it used to be known as dementia praecox --- "the madness of teenagers" --- for that reason.So for these reasons, natural selection ought to scrub it out of the gene pool.But it hasn't. The incidence of schizophrenia is at a startlingly high rate for an illness with a genetic basis.Now we know of other genetic illnesses which fit this pattern. The textbox example is sickle-cell anemia, and in that case the riddle is resolved as follows: if you have one sickle-cell allele, this protects you from malaria; two, and you get sickle cell anemia.So it has been hypothesised that schizophrenia should have a similar genetic basis: that the alleles which cause schizophrenia should be good for you unless you have too many of them, in which case you develop schizophrenia.Since schizophrenia is a mental illness, it seems a safe bet that these alleles, in the right quantity, should enhance one's mental abilities.Some people have suggested that the specific mental ability enhanced is creativity. I've looked at some of the arguments and don't find them really compelling. (I don't mean to imply that this hypothesis is wrong, just that I have yet to be convinced of it.)Some hard answers should come as a fruit of the revolution in practical genetics. Come back in ... ooh, call it twenty years ... and I'll tell you all about the genetic basis of schizophrenia.Edited by Dr Adequate, : Edited for spelling.

One problem is that the gene neuregulin-1 seems to play a part. Unfortunately it also plays a part in a whole host of other processes that are not related. So it is very possible that it can well be genetic, yet can strike just one of a pair of identical twins.

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Aslan is not a Tame Lion

You may have it the wrong way around.Consider that the human brain development is likely a result of fisherian feedback sexual selection, and ask yourself what feature is being selected in this manner:

• Sheer brain size?
• Intelligence?
• Creativity?

For these to be a selection 'short-hand' they have to signal increased fitness. Sheer brain size does not meet this criteria, and the evidence is the range is size of the brain and it's failure to correlate with intelligence quotients (IQ) - note creativity is harder to measure?.The other question on which applies is which are seen as "sexy" or "attractive" -- artists, singers (rock band?), dancers - or - mathematicians, scientists, etc.Mating song and dance, creative body adornment to attract mates ...There are also correlations noted between schizophrenia and creativity, as there are for schizophrenia and intelligence (and between intelligence and creativity), the jury is out on what real relationship is involved, yes?But consider that intelligence doesn't have to be related to creativity -- a computer can be intelligent but I've yet to see much spontaneous creativity from them.If what is being selected for is creativity and what comes along for the ride is intelligence, then it makes sense that the intelligence correlates to the creativity.Enjoy.

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RebelAAmericanOZen[Deist
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Probably genetic susceptibility but {environmental\chemical\developmental\etc} triggersThe question is whether the twins that are not schiz show beneficial characteristics -- artistic\creative\intelligence\etc. -- as well as other siblings (more likely to carry one copy than normal population if the schizs carry two?)

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we are limited in our ability to understand
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RebelAAmericanOZen[Deist
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to share.

An associated problem is that schizophrenia is most certainly not a homogenous condition, there are various forms and we definitely see a distinction between positive (delusions etc) and negative (avolition etc) symptoms.

To be FAIR AND BALANCED, I should point out that there is an alternative theory as to the causes of schizophrenia, and that we'd devote equal time to discussing this theory if we weren't all a bunch of God-hating bigots.