Neandertalilainen ei ajatellut kielellisesti, kuten nykyihminen?

 

• http://aamulehdenblogit.ning.com/profiles/blogs/neandertalilainen-ei-ajatellut-kielellisesti-kuten-nykyihminen
• Kirjoittanut Spammiro Botti (13. maaliskuu 2013, 18:00)

.. ainakaan samoilla aivojen osilla kuin ihminen, jota ovat näköaivokuoren perua.

Uudet tulokset neandertalailaisen aivoista viittavat siihen, erityisesti ns. Marty Serenon teorian valossa, että tiedonkäsittely neandertalin ihmisen aivoilla olisi muistuttanut enemmän simpanssin vastaavaa kuin nykyihmisen. Suunnattoman laaja osa simpanssin aivokuoresta kuuluu ainakin puissa elävillä simpansseilla näköaivokuoreen. Ihmisllä noista osista on muodostunut paitsi ihmisen paljon pienempi näköaivokuori (vaikka ihminen näkee paljon paremmin) myös kaikki kielellistä informaatiota käsittelevät osat, jotka ihmisellä muodostavat pääosan isojen aivojen kuoresta. Tähän viittaa myös neandertalilasen ja simpanssi huomattavasti suuremmat silmät ihmiseen nähden. Tässä artikkelissa on nyt asia vain nähty nurinkurisesti.

Neandertalilaisella kuitenkin oli ollut sialiinimutaatio, joka lisää ehdol-listumisaineen myeliinin määrää aivoissa moninkertaisesti, kun sen sijaa simpanssilla ”liian” myeliinisoitumisen estävä sialiini on tallella.

http://www.pnas.org/content/107/suppl.2/8939.full.pdf

Neanderthalin ihmisen sukupuuton syy selvisi – liian suuret silmät

” Tutkijoiden mukaan neanderthalin ihmisen silmät kehittyivät niin suuriksi, että näköhavaintojen käsittely vei liian paljon aivokapasiteet- tia. Tämä esti esimerkiksi ryhmätyötaitojen kehittymisen.

Neanderthalin ihmisten kalloja tutkineet tiedemiehet ovat mahdollisesti selvittäneet syyn sille, miksi neanderthalilainen kuoli sukupuuttoon ja nykyihminen, Homo sapiens, selvisi.

Tutkijat ovat todenneet, että neanderthalin ihmisellä oli selvästi nykyihmistä suuremmat silmät. Tästä seurasi, että neanderthalilainen joutui käyttämään suuren osan aivokapasiteetistaan näköaistimusten käsittelyyn, jolloin muu intellektuaalinen kehitys kärsi.

Neanderthalin ihminen eli noin 250 000 vuoden ajan, mutta katosi jääkauden aikaan noin 28 000 vuotta sitten. Neanderthalilaiset elivät jonkin aikaa rinta rinnan myös nykyihmisen kanssa Afrikassa.

Neanderthalin ihminen kuitenkin siirtyi Eurooppaan, missä se joutui sopeutumaan pitkiin öihin ja pilvisiin päiviin. Sopeutuessaan neanderthalilainen kehitti suuret, vahvat silmät ja aivojen takaosan, joka kykeni prosessoimaan suuren määrän näköhavaintoja.

Neanderthalin ihmisen silmäkuopat olivat keskimäärin kuusi millimetriä suuremmat kuin nykyihmisen. Tutkijoiden mukaan ero on merkittävä.

Homo sapiens puolestaan pysyi aurinkoisessa Afrikassa, eikä tarvinnut lisätehoa silmiinsä. Sensijaan nykyihmisen aivojen otsalohko alkoi kehittyä.

Ihmisen ajattelu keskittyy otsalohkoon. Sen kehitys merkitsi sitä, että nykyihminen sai eräitä erittäin tärkeitä ominaisuuksia. Kognitiivisten taitojen paraneminen auttoi ihmistä muodostamaan ryhmiä, toimimaan yhteistyössä ja kehittämään taitojaan.

Kun jääkausi vaikeutti olosuhteita, nykyihminen sai ratkaisevaa etua taidoistaan. Hän pystyi luottamaan kumppaneihinsa, välittämään informaatiota toisilleen ja reagoimaan nopeasti tapahtumiin.

Arkeologit ovat löytäneet vahvistusta tälle teorialle. Homo sapiensin hallusta on mm. löydetty neuloja, he siis kykenivät ompelemaan itselleen vaatteita, jotka olivat oiva apu jääkauden asukkaille.

Tutkimus on julkaistu Preceedings of the Royal Society B Journal -tiedelehdessä ja siitä uutisoi BBC.
Lisää aiheesta

BBC: Neanderthal large eyes ’caused their demise’ ”

Marty Serenon mukaan ihmisen kielellisrakenteista informaatiota prosessoivat alueet ovat muodostuneet näköaivokuoren alueista kielellisen uudelleenjärjestämisen tuloksena.

http://discovermagazine.com/1996/jun/abrainthattalks785#.UUCSs1exeUY

”  FROM THE JUNE 1996 ISSUE

A Brain That Talks

Our brains are much like those of our primate cousins, so where did we get our uniquely human gift of speech? One human says we simply rewired brain structures devoted to a different, more general primate specialty – vision.

I always had this weird idea that I had to know lots of different things, says a faintly uncomfortable Marty Sereno. He shifts in his chair, turning his back to a Post-it-fringed computer screen and a table so deep in open journals that it looks like the cross-bedded planes of a geologic formation. Sereno is sitting in his office at the University of Califor- nia at San Diego, where drawn miniblinds shut out the distracting southern California sunshine. When you’re trying to do interdisciplinary stuff, he continues, it’s no good putting two specialists together in a room, because they can’t talk to each other. You’ve got to pretend you’re in the other field; you have to go and live with the natives. It has to be all in one head.

To understate the case considerably, the 40-year-old Sereno has a lot of things in one head. There is his primary research interest, of course, which is the neurological architecture of vision in primates and rodents. Then there are the new techniques in brain imaging that he has helped pioneer, and the computer programs he and his collabora- tors have conceived to display the results. There is, as well, a wealth of information on subjects as various as linguistics, communication systems in animals, philosophy, and modern jazz (he’s an avid guitarist).

And then there is his unconventional theory about brain evolution and the origins of human language, which has been simmering on a back burner of his mind since graduate school. The theory appears flamboyantly interdiscip- linary and complex. But Sereno merely shrugs at that characterization. Some things just have a lot of parts, he says. Not an impossible number, but enough that ten won’t do. Sometimes it just has to be a hundred.

Reduced to almost haiku proportions, Sereno’s idea is this: language ability arose in the human brain not through the development of a new, uniquely human language organ, as most accounts have it, but by a relatively minor rewiring of a neural system that was already there. And that neural wiring belonged largely to the visual system, a part of the brain that recent research–including Sereno’s own–has shown to be almost unimaginably complex.

These are statements slightly less heretical than those an earlier Martin nailed to the door of Wittenberg Castle Church, but not by much. Language is often regarded as a cognitive boundary, one of the last things that separate us from our primate cousins. But if Sereno is right, and language rode into our brains on the coattails, so to speak, of vision, we humans are once again a little less special than we thought.

For the moment, the evidence Sereno produces to support his theory is largely circumstantial; he cites chiefly the path taken by the brain in the course of its evolution. Roughly 500 million years ago, when the first vertebrates appeared, a small lump at the rear of the brain stem expanded to become the cerebellum. At the same time, a pair of small, primitive structures surrounding the brain stem and cerebellum expanded into the two hemispheres of the cerebrum. Finally, between 200 and 300 million years ago, the six-layered cerebral cortex appeared in mammals as a blanket of nerve cells covering the cerebrum. In humans, this eighth-of-an- inch-thick layer is folded in intricate wrinkles, and the rear two-thirds of it is divided into areas corresponding to the senses, or what neuroscientists call modalities: hearing, touch, vision, and so on.

As Sereno points out, we know that in the other, nonhuman higher primates, the visual processing system takes up half the cortex. It is not known precisely how much of the human brain is given over to vision – the kinds of invasive experiments traditionally needed to determine that can only be done in animals, not people. But Sereno thinks it likely that new techniques in brain scanning will reveal that we, too, have that much visual cortex in our brains. And he thinks that natural selection could well have jury-rigged those preexisting structures to perform some new functions. What could be more logical, he asks, than running the new train of language on the old tracks of vision? We ought to pay more attention to the things animals do that might have been built upon for language, he says. Look – the system is definitely souped up in us. People can do a lot more stuff than monkeys can. But the basic hardware is not that different.

According to the prevailing notion of how the human brain is organized, language is centered in a couple of areas on the left side of the brain that are named for the nineteenth – century scientists who discovered them. One, called Broca’s area, sits just below the temple; it is involved in language production. The other, Wernicke’s area, is just behind the ear and seems to control language comprehension.

Broca’s and Wernicke’s areas are certainly involved with language, says Sereno; his quarrel is with the idea that language is confined there. In his view, localizing a higher-order function such as language to two quarter-size patches of cortex smacks of a prescientific mind-set. It’s sort of like a holdover from the phrenologists, he says, referring to proponents of the eighteenth-century notion that such individual traits as musical ability or a tendency toward violence could be detected from bumps on the skull. Sereno thinks instead that language centers might be scattered all over the brain, largely in the mosaic of cortical areas devoted to visual processing but also in parts devoted to motor coordination and auditory perception.

Most scenarios of language evolution tend to sidestep the knotty issue of what might have gone on in the human brain to make language possible. Since the researchers who are interested in language evolution tend to be linguists and anthropologists, not neuroscientists, they focus on questions such as when language evolved or what its early phases might have been like. But Sereno brings a much broader perspective to the table.

… ”