Bootstrap Framework 3.3.6

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Zdravo, živo!

Moderator: IriS

#436886
Na zahtev nekoliko forumaša, a posle nekog vremena (zbog moje lenjosti da kuckam), ovde u kratkim crtama izlažem ono što znam o medicinskim istraživanjima uzroka homoseksualnosti. Pokušao sam da ne tupim i ne objašnjavam previše, ve? da iznesem najka?e mogu?e šta znam o tome, te ako ima nešto nejasno, priupitajte.

GENETIKA

Velika studija objavljena 1993. u porodicama u kojima je zapažen statisti?ki velik broj homoseksualaca, bazirala se na izu?avanju porodi?nih stabala. Utvðeno je da je ve?i broj homoseksualaca dolazi sa maj?ine strane. Ova studija nije otkrila ni jedan poseban gen, ni grupu gena, ali je ukazala na to gde bismo ga mogli tražiti - na X hromozomu.

Jedno od uticajnijih istraživanja obavio je Hamer, na institutu za onokologiju u Vašingtonu. Hamer je kao uzorak koristio trideset i dva para homoseksualne bra?e. Pokazao je da ?ak dve tre?ine od parova dele jedan isti region na X hromozomu - Xq28 (napominjem da Xq28 nije gen, ve? ceo jedan deo hromozoma koji se sastoji od velikog broja gena). Jedna druga studija koja je objavljena nije potvrdila ove rezultate, te je hipoteza o X hromozomu gotovo u potpunosti napuštena. Od skora, ova se hipoteza polako vra?a u igru, jer postoje pretpostavke da genetika muške i ženske homosksualnosti nije ista, te da bi žene mogle biti "nosioci" grupe gena za mušku homoseksualnost.

Bailey i Pillard su 1991. godine utvrdili u?estalost homoseksualnosti kod monozigotnih (jednojaj?anih) blizanaca u ?ak 52%, kod dvojaj?anih 22%, i 11% za usvojenu bra?u homoseksualnih muškaraca. Nova studija je potvrdila ove rezultate sa neverovatnom podudarnoš?u.

Dosadašnja istraživanja u oblasti genetike pokazala su sa velikom verovatno?om da homoseksualnost jeste u velikoj meri stvar gena. Kako je ljudski genom pro?itan, i znamo da broji oko 30 000 gena, verovatno ?e pro?i još dosta vremena dok se ne utvrdi grupa gena (koja može da broji i do stotinu ili više) ne bude ta?no identifikovana. Genetika je, ipak, nauka u povoju. Da je u pitanju biološka a ne (isklju?ivo) psihohoška pojava, nedovsmisleno ukazuju anatomska istraživanja LeVaya i Gorskog. ?ak i da genetika sama nije pružila nikakve odgovore na ovo pitanje, da je homoseksualnost genetski uslovljena ukazuje i sama ?injenica da anatomske razlike postoje, i to razlike u delovima mozga koji se formiraju dosta rano u toku embriogeneze i koji su od velikog zna?aja za pravilno funkcionisanje jedinke, pa je uticaj spoljašnjih faktora minimalan, ako ne i nepostoje?i (ovde mislim prvenstveno da socijalne faktore).

ANATOMIJA

Prvo relevantnije istraživanje ljudske homoseksualnosti obavio je poznati neuroanatom Simon LeVay 1993 godine, ispitijuci mozgove homoseksualaca umrlih od side. LeVay je sa saradnicima pronašao razliku u jedru hipotalamusa poznatom pod imenom nucleus interstitialis tertius hypothalami (ili kra?e: INAH-3). Pokazao je da je ovo jedro TRI puta ve?e kod heteroseksualnih muškaraca nego kod homoseksualnih. Važno je napomenuti i to da jedra hipotalamusa spadaju u seksualno dimorfna jedra - pokazano je da su manja i do tri puta kod žena, nego kod muškaraca. Pored mozgova homoseksualaca, prou?avani su i mozgovi heteroseksualaca umrlih od AIDSa, kao i onih koji su umrli prirodnom smr?u. Istraživanje je uklju?ivalo i nekoliko ženskih mozgova, nepoznate seksualne orijentacije. Ukoliko je ovo istraživanje ta?no, implicira direktno da je seksualna orijentacija uroðena, i da na nju ni pojedinac ni društvo nemaju nikakvog uticaja. Uopštavaju?i, možemo kazati da su odreðene karakteristike mozga homoseksualca bliže karakteristikama heteroseksualnih žena nego heteroseksualnih muškaraca. (Bez obzira na to što se gej zajednica dosta protivila ovim istraživanjima ranih devedesetih, tvrde?i da mozgovi hetero i gej muškaraca nemaju nikakvih razlika, do danas je svako naredno istraživanje samo potvrdilo rezultate LeVaya i saradnika.) 1992. godine Gorsky sa saradnicima otkriva drugu veoma zna?ajnu razliku, u još jednom seksualno dimorfnom regionu, važnom delu mozga koji spaja puteve leve i desne hemisfere, u prednjoj moždanoj spojnici (comissura anterior). Utvðeno je da je ovaj region ve?i kod homoseksualnih muškaraca, što je analogno seksualnom dimorfizmu ove strukture - ovaj region je, takoðe, ve?i kod heteroseksualnih žena. Dick i Swaab istražuju?i na mozgovima transseksualaca utvðuju da je još jedan region hipotalamusa, stria terminalis, ve?a kod muškaraca nego kod transseksualaca. Stria terminalis je ujedno i seksualno dimorfni region u mozgu.

Glavna kritika ovih istraživanja, posebno prvog, temelji sa na koriš?enom materijalu - upotrebljivani su, izmeðu ostalih, mozgovi umrlih od AIDS-a. Meðutim, kako se i kontrolna grupa sastojala od heteroseksualaca obolelih od AIDS-a, uticaj bolesti na veli?inu ispitanih regiona, ?ak i da postoji, može se zanemariti. Byne je ponovo ispitao regione koje je ispitivao LeVay, ovaj put koriste?i mozgove umrlih prirodnom smr?u, i potvrdio istraživanja LeVaya, ?ime je svaka sumnja u ta?nost istraživanja i dobijenih podataka eliminisana.

2004. godine utvðena je biološka osnova homoseksualnosti kod ovce. Kako su svi osnovni genetski mehanizmi univerzalni za sva živa bi?a, pretpostavlja se da bi se na osnovu ovog istraživanja mogli dobiti važni rezultati i kod ?oveka. Ina?e, incidenca homoseksualnosti kod ovce je 8%, što je otprilike isti procenat kao i kod ?oveka. Utvrðeno je da postoji poseban region u hipotalamusu (!) ovce, nazvan oSDN - ovine sexually dimorphic nucleus, seksualno dimorfno jedro hipotalamusa (kao INAH-3 kod ?oveka) koji je ve?i kod heteroseksualnih ovaca, nego kod homoseksualnih. U pitanju je, dakle, analogna razlika onoj koju je LeVay pronašao kod ljudskog mozga. Nau?nici iz Portlanda, koji su ovo istraživanje zapo?eli, u saradnji sa geneti?arima sa UCLA-a, po?inju potragu za kompleksom gena koji kodira za razvoj ovog dela hipotalamusa.
By Simor
#436916
Originally posted by Ulix
2004. godine utvðena je biološka osnova homoseksualnosti kod ovce.
Istrazivao molekularni bilog Sven Bocklandt. Biolog je :mljac: .

Kao dodatak onome sto si napisao: citao sam da je, 2005. godine, istrazivac genoma u Cikagu izjavio da je pronasao ne jedan "gej gen", nego grupu gena, koji uticu na to da li ce muskarac biti homoseksualac.
By Ulix
#436928
Apsurdno je govoriti o jednom genu za homoseksualnost, iz prostog razloga sto je ljudski genom toliko mali da naprosto nije moguce imati po jedan gen za svaku osobinu; vecina zavisi od medjusobne interakcije gena. A sa druge strane, nelogicno je, jer je seksualno nesto suvise kompleksno da bi bilo kodirano od samo jednog gena.

Potrazicu to novo istrazivanje.
A potrazicu i sliku biologa. ;)
Korisnikov avatar
By zimizamizum
#436989
A Y-antigeni? Ajde ajde, daj malo o prenatalnim hormonima, nemoj da mi zeljni dobrih informacija o tome izvisimo... ;)

Inace, hvala na opisu. Dosta detalja o samim istrazivanjima mi je novo (uzorak i sl).
By Ulix
#437081
Originally posted by zimizamizum
A Y-antigeni? Ajde ajde, daj malo o prenatalnim hormonima, nemoj da mi zeljni dobrih informacija o tome izvisimo... ;)

Inace, hvala na opisu. Dosta detalja o samim istrazivanjima mi je novo (uzorak i sl).
'Ajde ukratko i o tome: statisticki je zabelezeno da su sanse za tridesetak posto vece da ce neko biti homoseksualac, ako ima stariju bracu; ovaj fenomen je prvo zabelezen u psihologiji, pa je neko vreme smatrano da je u pitanju odgoj, medjutim, vrseci studije na usvojenoj deci, pokazano je da je u pitanju ipak bioloski mehanizam; uzrok ovome su dogadjanja u materici za vreme prve trudnoce, ukoliko je dete musko. (Da napomenem samo da se sve ovo odnosi iskljucivo na musku homoseksualnost; kod zena slican mehanizam nije uocen.) Hipoteza je da sa svakim iznetim muskim detetom majka proizvodi sve veci broj HY antitela, na antigene koji se nalaze na povrsinama "muskih" celija, kod sisara. U pitanju je, dakle, imunska reakcija majke na celije ploda, sto u krajnjoj liniji moze da utice na razvoj mozga i proizvede one anatomske karakteristike o kojima sam gore pisao.

(Ovo nisam naveo u prvom postu zato sto je u pitanju hipoteza; koliko sam citao, postoje odredjeni dokazi, mada ne sasvim ubedljivi. Detaljnija naucna literatura na ovu temu mi nije, nazalost, dostupna. Zato ako neko od kolega sa foruma ima sta da doda na ovo, bio bih vrlo zahvalan.)
Korisnikov avatar
By unic0rn
#437085
Originally posted by Ulix
2004. godine utvðena je biološka osnova homoseksualnosti kod ovce. Kako su svi osnovni genetski mehanizmi univerzalni za sva živa bi?a, pretpostavlja se da bi se na osnovu ovog istraživanja mogli dobiti važni rezultati i kod ?oveka. Ina?e, incidenca homoseksualnosti kod ovce je 8%, što je otprilike isti procenat kao i kod ?oveka. Utvrðeno je da postoji poseban region u hipotalamusu (!) ovce, nazvan oSDN - ovine sexually dimorphic nucleus, seksualno dimorfno jedro hipotalamusa (kao INAH-3 kod ?oveka) koji je ve?i kod heteroseksualnih ovaca, nego kod homoseksualnih. U pitanju je, dakle, analogna razlika onoj koju je LeVay pronašao kod ljudskog mozga. Nau?nici iz Portlanda, koji su ovo istraživanje zapo?eli, u saradnji sa geneti?arima sa UCLA-a, po?inju potragu za kompleksom gena koji kodira za razvoj ovog dela hipotalamusa.
A uporedjivanje hipotalamusa [tj onih delova hipotalamusa] ovna i (hetero) ovce kao sto je radjeno kod ljudi?
By Ulix
#437086
Originally posted by unic0rn
A uporedjivanje hipotalamusa [tj onih delova hipotalamusa] ovna i (hetero) ovce kao sto je radjeno kod ljudi?
:yes:
Koliko znam - da.

@Simor: zao mi je ali nisam uspeo da nadjem sliku sa slatkim biologom (mozda bi onda tema privukla malo vise paznje :D ), ali sam nasao interesantan clanak o jednom njegovom istrazivanju: http://www.pedrotytgat.be/homoseksualiteit/ontstaan.htm
Korisnikov avatar
By kal zakath
#437119
Imajte samislost sa mnom, jer sam totalni laik na podro?ju genetike (saboravio i ono malo osnova koje smo u?ili u školi), pa ?e stoga ono što ?u napisati možda biti pogrešno ili nelogi?no.

Gledao sam jednu emisiju od BBC-ja (bila na nema?koj televiziji, što je još jedna od mogu?nosti za moje greške). U toj emisiji se tvrdi, da ne nasleðujemo samo "karakteristike" naših predaka, nego i njihova "iskustva". Naime kako sam ja shvatio, nisu svi geni koje nasleðujemo "aktivni". Postoje neki "šalteri" koji odreðene gene "uklju?uju" i "izklju?uju". Prvo su ustanovili, da greška na nekom kromosomu (ili se radilo o genu), izaziva dve razli?ite genetse bolesti u zavisnosti, dal je taj hromosom (ili gen), došao od majke ili od oca. Ako je došao od oca bila je valjda druga?ija kombinacija "šaltera" uklju?ena ili izklju?ena, nego kada je došao od majke. (mislim da se jedna od tih bolesti zove "ejdželmanov sindrom", drugu nisam zapamtio).

To jih je navelo na pitanje, kako ti geni "znaju " dali su došli od oca ili majke.

Onda su govorili o nekim istraživanjima (dva doktora jedan Englez i jedan Šveðanin), gde su ustanovili zavisnost izmeðu gladi i še?erne bolesti (ali potomaka oni koji su iskusili glad).

I na kraju su govorili o preživelima i koncentracionih logora i onih koji su doživjeli ili ?ak preživjeli 11.septembar. Naime djeca preživjelih logoraša su patila od nekih poreme?aja, z6a koje su mislili da su posledica toga što su kao djeca stalno slušala roditelje kako jim pri?aju o tome. E posle 11. septembra, su po?eli da vrše istraživanja na djeci onih majki koje su bile trudne kada se dogodio napad. Kada se doživi neka stresna situacija, aktiviraju se neki hormoni?, koji smanjuju taj stres. No djeca, koja su bila još neroðena u vreme napada, su roðena, sa istom koli?inom hormona?, koje su imale njihove majke, kao odgovor na tu situaciju.

Zna?i izveli su zaklju?ak, da se odreðene situacije, koje neko doživi, prenose kao genetski material na slede?e generacije.

(bilo je govora i o nekim eksperementima na miševima, gde su isprobavali variantu, da se možda ti "šalteri" gase, u tre?oj ili ?etvrtoj generaciji, no i dalje su bili upaljeni).


Valjda sam preneo otprilike ta?no.
By Simor
#437144
Na sajtu advocate.com sam nasao pregled istrazivanja na temu "born that way". Tekst je na engleskom, pa ako neko ne razume, izvinjavam se. Ima dosta od onoga sto je Ulix vec pisao, ali je napisano hronoloskim redosledom.

1899
Germany's pioneering researcher Magnus Hirschfeld writes that being gay or lesbian is biologically determined.

1991
A study of twins reveals that genes and biology are markers for homosexuality. Researchers find that 52% of identical twin brothers of gay men were also gay, compared with 22% of fraternal twins and just 11% of adoptive brothers.

1991
Simon LeVay, after studying the brains of dead gay and straight men, publishes a paper in Science arguing that homosexuality is biologically based. He later expands his ideas in the 1993 book The Sexual Brain.

1993
In a major study that spurs cultural battles, researchers say they have identified a gene pattern that determines male homosexuality. A National Cancer Institute geneticist suggests that a gay gene resides in the X chromosome, which men inherit from their mothers.

1995 & 2005
A 1995 NIH study focuses on male fruit flies that began mating with each other after their body chemistry was changed. In June 2005, scientists in Vienna report that a genetically altered female fruit fly attempted to mate with another female fruit fly instead of a male, suggesting sexual attraction is genetic.

1999
A University of Texas researcher finds that the tones produced by the inner ears of lesbians are weaker and not as numerous as those produced by straight women.

2000
Researchers find further evidence linking sexual orientation with birth order. Men with same-sex attraction seem more likely to be born later than straight brothers in families with multiple male children.

2003
Psychologists measure eye-blink reactions after subjecting gay and straight men and women to loud noises. The reactions of gay and straight members of each gender are found to be significantly different and linked to an area of the brain that determines sexuality. They conclude that a person's sexual orientation is determined before birth.

2004
The same genes that make men gay may also make their female relatives more fertile. Researchers find that the moms, sisters, and maternal aunts of gay men often have significantly more children than the mean-and many of their offspring are gay or lesbian as well.

2005
A genome researcher in Chicago says he has found a group of genes, not a single "gay gene," that strongly affect whether a man is homosexual. The University of Illinois at Chicago and the NIH scientists report having looked at the genes of 456 men, each of whom had at least two gay brothers, from 146 families. The finding that a variety of genes are common to most gay men echoes other recent gene research.
Korisnikov avatar
By Mr.Ja
#437194
:klap:
Ovo je bas interesantno...
Kada me ne bude mrzelo da citam do kraja, jos malo cu nahvalim ULIX-a kao osnivaca teme ;)
By Ulix
#437334
Pojasnjenja za kal zakath-a:
Originally posted by kal zakath
U toj emisiji se tvrdi, da ne nasleðujemo samo "karakteristike" naših predaka, nego i njihova "iskustva".
To je vise domen (para)psihologije nego genetike.
Naime kako sam ja shvatio, nisu svi geni koje nasleðujemo "aktivni". Postoje neki "šalteri" koji odreðene gene "uklju?uju" i "izklju?uju".
Jedan gen kodira za jedan protein (opsti slucaj sa par izuzetaka); ukljucuju se kada je potrebno sintetisati protein, u suprotnom nije aktivan. Postoje odredjene grupe gena koji su aktivni iskljucivo do rodjenja a po rodjenju se trajno inaktivisu (npr. geni koji kodiraju enzim telomerazu; aktiviraju se ponovo samo u kancerogenim celijama).
Prvo su ustanovili, da greška na nekom kromosomu (ili se radilo o genu), izaziva dve razli?ite genetse bolesti u zavisnosti, dal je taj hromosom (ili gen), došao od majke ili od oca. Ako je došao od oca bila je valjda druga?ija kombinacija "šaltera" uklju?ena ili izklju?ena, nego kada je došao od majke. (mislim da se jedna od tih bolesti zove "ejdželmanov sindrom", drugu nisam zapamtio).
U pitanju je mutacija na petnaestom hromozmu, i u zavisnosti da li je hromozom poreklom od oca ili majke mogu nastati dva razlicita sindroma: Angelmanov ili Prader-Vilijev. Ta se pojava naziva genetic imprinting i jako je retka. U vecini slucajeva nije vazno na cijem hromozomu se odigrava mutacija. Postoji isto tako zapazanje da majcini geni favorizuju razvoj nervnog sistema, dok ocevi favorizuju razvoj placente, sto ima znacaj u novijim teorijama evolucije (da banalizujem: majka ubija plod posto je on parazit i strano telo, dok ocevi geni plod brane).
To jih je navelo na pitanje, kako ti geni "znaju " dali su došli od oca ili majke.
Ovo stvarno ne znam kako jednostavno da objasnim. Ali znali su. Trust my word for it. :)
Zna?i izveli su zaklju?ak, da se odreðene situacije, koje neko doživi, prenose kao genetski material na slede?e generacije.
Mehanizmi ovoga zaista nisu poznati, iako su od sustinske vaznosti za evoluciju. I ne funkcionise iz generacije u generaciju, potrebno je mnogo vise vremena.
Korisnikov avatar
By jukie
#437382
Originally posted by Ulix
Pojasnjenja za kal zakath-a:
Originally posted by kal zakath
Naime kako sam ja shvatio, nisu svi geni koje nasleðujemo "aktivni". Postoje neki "šalteri" koji odreðene gene "uklju?uju" i "izklju?uju".
Jedan gen kodira za jedan protein (opsti slucaj sa par izuzetaka); ukljucuju se kada je potrebno sintetisati protein, u suprotnom nije aktivan. Postoje odredjene grupe gena koji su aktivni iskljucivo do rodjenja a po rodjenju se trajno inaktivisu (npr. geni koji kodiraju enzim telomerazu; aktiviraju se ponovo samo u kancerogenim celijama).
Ima raznih tih gena modulatora drugih gena... evo npr. školskog primera nasleðivanja boje dlake kod labrador retrivera...
gen B (kod labret) ima dva alela, B i b. B zna?i crna dlaka, b zna?i braon dlaka. Bb imaju crnu dlaku jer veliko dominantno B nadjacava malo recesivno b; zna?i stvara se dovoljno tamnijeg (crnog) oblika pigmenta da može da nadja?a smeði oblik.
gen E ima dva alela E i e. Ne mogu da se setim koja je osobina recesivna a koja dominantna, ali u svakom slu?aju jedan alel kaže "neka ostane boja koju odreðuje B gen, bilo da je crna ili braon" a drugi alel kaže "precrtaj B gen i ne gledaj ga kao da i ne postoji; neka se ne stvara taman pigment i neka ovaj pas bude žut".
By Gost
#437491
Originally posted by Ulix

ANATOMIJA
Važno je napomenuti i to da jedra hipotalamusa spadaju u seksualno dimorfna jedra - pokazano je da su manja i do tri puta kod žena, nego kod muškaraca.
Prvo odli?na tema, nastavi ako imaš još!
Ja se se?am da sam sa prof Filipovi?em
pri?ala o dimorfizmu. Elem znaš da se kao najve?a
razlika graðe mozga izmeðu muškaraca i žena navodi graða
Nc. septalis medialis-a (u hipotalamusu), i ?ovek je tada
navodio da se pretpostavlja da bi ovo jedro moglo
da ima ulogu u anatomskoj osnovi homoseksualnosti.
Korisnikov avatar
By zimizamizum
#437598
Originally posted by Ulix
Originally posted by zimizamizum
A Y-antigeni? Ajde ajde, daj malo o prenatalnim hormonima, nemoj da mi zeljni dobrih informacija o tome izvisimo... ;)

Inace, hvala na opisu. Dosta detalja o samim istrazivanjima mi je novo (uzorak i sl).
<snip>

(Ovo nisam naveo u prvom postu zato sto je u pitanju hipoteza; koliko sam citao, postoje odredjeni dokazi, mada ne sasvim ubedljivi. Detaljnija naucna literatura na ovu temu mi nije, nazalost, dostupna. Zato ako neko od kolega sa foruma ima sta da doda na ovo, bio bih vrlo zahvalan.)
E, ovo zaista MRRRZIM! Dakle napisem lep post, i, znajuci da sajt ume da zeza, lepo ga obelezim i uradim "copy". Cak proverim kopiju pejstovanjem u notepad. I, sta? Dok odem da, da prostis, piskiriskim, iskoci osigurac i komp se ugasi i....

Rekapitulacija:

Imam nekoliko izvora informacija vezanih za prenatalne hormone, ni jedan nije ni medicinski ni bogznakako cvrst sam po sebi, ali kad se uzmu zajedno mozda nisu za bacanje.

1) Tucic (Nikola) mi je predavao genetiku (za psihologe, limunada verziju), i on je naginjao ka tim Y-antigenima. U njega imam poverenja najvise zato sto sam se uverila da prati najsveziju literaturu: kad mi je predavao, udzbenik je tek bio nekih osam meseci star, a on bi povremeno rekao kako je u medjuvremenu otkriveno nesto novo... Imao je i razloge zasto ne bi trebalo imati previse poverenja ni u Hamera ni u LeVay-a, a ticalo se metodologije, ali ne umem vise da ponovim.

2) Jednom davno, nadjoh ja na polici stare brojeve Psychology Today. To je casopis za zainteresovane laike, kvalitetan ali bez detaljisanja oko istrazivackih metoda i nacina obrade i sl. U jednom broju iz ranih osamdesetih, bio je clanak o tipu koji je proucavao uticaj prenatalnih hormona kod ovaca. Uzeo je tridesetak nerodjenih zenskih jaganjaca, ubrizgao testosteron, i - voila! - dobio odrasle ovce koje su sve do jedne iskazivale lezbejske sklonosti! Da, da, i ja mislim da je previse cisto i uredno da bi tek tako bilo istinito... Ipak, bilo je napomenuto da kod ljudi postoje tri kriticna perioda za veliki uticaj hormona na mozak, i da se treci odvija nesto malo nakon rodjenja, sto daje prostor za uticaj sredine i bla bla.

3) U psihologiji su trenutno sve popularnija istrazivanja o musko-zenskim razlikama u mozdanom funkcionisanju, i prilicno je sigurno da prenatalni hormoni imaju izrazen uticaj na razna polno specificna ponasanja. Posebno se mnogo zna o uticaju testosterona.

A mozda se radi i o uticaju hladnog i distanciranog oca... ;)
Korisnikov avatar
By zimizamizum
#437603
Originally posted by Ulix
Pojasnjenja za kal zakath-a:
Originally posted by kal zakath
U toj emisiji se tvrdi, da ne nasleðujemo samo "karakteristike" naših predaka, nego i njihova "iskustva".
To je vise domen (para)psihologije nego genetike.
[/quote]

Moguce je da se radilo o ovome: i mozak je, kao i ostali delovi nasih tela, morao da sledi zakone evolucije. Niko vise (ko se time bavi) ne veruje da se radjamo kao tabula rasa, i da se sve da utisnuti kroz socijalne uticaje. U tom smislu, mozemo reci da nasledjujemo - genetski - jedan broj sklonosti ka razlicitim ponasanjima.

Primera radi, mnogo cemo se lakse uplasiti od zmije nego od automobila, iako realno u gradu skoro nikad ne nailazimo na zmije, a prakticno nikad u opasnim situacijama, dok smo se nagledali sudara automobila i svaki dan mozemo da procitamo u novinama o saobracajnim nesrecama. U tom slucaju, necemo reci da smo nasledili strah od zmija putem gena, ali jesmo nasledili sklonost da se lakse uplasimo od zmija nego od automobila.
Korisnikov avatar
By zimizamizum
#438418
Evo sumacije raznih istrazivanja koja je napravio jedan psiholog koji visi na jednoj grupi o seksualnosti koju i ja frekventujem. Nije bas o poreklu, ali su istrazivanja. Tip je inace odlican, prepun informacija.


Every epidemiology study I have seen has placed male homosexuality
between 2 and 4%, regardless of culture. It seems to be a robust
finding, and there is a ton of physiological and genetic data that
seems to show there sexual orientation is hardwired for men. DATA
DIGRESSION: You can make a focal lesion in the hypothalamus in most
male mammals and instantly change sexual orientation from het to homo.
Most studies point to prenatal hormonal exposure as the key variable,
and there is some theorizing that it is genetically adaptive to have
nonreporductive members of society supporting reproducing members (the
more siblings you have, the more likely you are to be gay; you have a
ten-fold increase in incidence from the first to the tenth kid, so it
is a big variable). There are numerous other physiological differences
between het and homo men: hypothalamus size, corpus collosum size,
number of fingerprint ridges, index finger length, lefthanded
incidence, inner ear structure, etc. There are no environmental
variables that affect sexual orientation, with the exception of
placental environment; you cannot change or induce sexual orientation
in men by treating them a certain way. In arousal studies using penile
tumescence you can determine male het vs homo orientation with
astounding accuracy. However, male bisexuals do not form a unique group
in any studies. About 2/3rds appear to be homo on arousal and
physiological differences, and the remainder appear to be het. Het or
homo orientation rarely changes across the lifespan, and most report
being aware of sexual orientation at or before puberty. All evidence
points to a biologically determined sexual orientation in men, with
bisexuality likely reflecting experimentation, curiosity, cultural
influences, or uncertainty.

In contrast, all female sexual orientations are highly variable and are
greatly affected by environmental variables. In most Western societies,
male homosexuals outnumber females 2-to-1 (1-2% incidence), but female
bisexuality waxes and wanes too quickly to compare. Moreover, there is
a near total absence of studies indicating where it comes from. There
are no physiological cues, no genetic or placental environment
variables. Developmental environment and current environment have a
huge impact. Men typically report sexual orientation discovery based
upon arousal (aroused by men = homosexual), whereas women typically
report discovery based upon non-arousal attraction (like comfort only
from women, etc. = lesbian). Arousal studies likewise have shown that
women do not show orientation-specific physiological arousal; lesbians
are aroused by male stimuli, heterosexual women are aroused by female
stimuli, etc. Women are also more likely to change sexual orientation
across the lifespan and 'discover' their orientation later in life.

One final difference to note. Male orientation predicts behavior very
well. For women, there is a lot of variation. The CDC report of 2002
showed that same-sex contact for men ages 18-44 was between 2.7 and
7.4%. For women it was between 13 and 15%. Homosexual and bisexual
orientation was 2.3 and 1.8% for men (more homo than bi), 1.3 and 2.8%
for women. Women are more likely to be of bi- orientation and much more
likely to be bi- in behavior.
Korisnikov avatar
By Zibro
#438424
sve velike istine i mudrosti su iznenadjujuce proste i uglavnom stanu u nekiliko recenica ....

cim se umesto konkretnog odgovora na konkretno pitanje susretnem sa gomilom teorija pretpostavki komplikovanih i nejasnih definicija tipa smuti pa prospi
izvedem jednostavan ali brilijantan zakljucak ....

ne zna se ! :njanjanja:
ili ako cemo biti malo fleksibilniji
niko sa sigurnoscu ne zna
Korisnikov avatar
By Mr Dee
#441969
Originally posted by zimizamizum

2) Jednom davno, nadjoh ja na polici stare brojeve Psychology Today. To je casopis za zainteresovane laike, kvalitetan ali bez detaljisanja oko istrazivackih metoda i nacina obrade i sl. U jednom broju iz ranih osamdesetih, bio je clanak o tipu koji je proucavao uticaj prenatalnih hormona kod ovaca. Uzeo je tridesetak nerodjenih zenskih jaganjaca, ubrizgao testosteron, i - voila! - dobio odrasle ovce koje su sve do jedne iskazivale lezbejske sklonosti! Da, da, i ja mislim da je previse cisto i uredno da bi tek tako bilo istinito... Ipak, bilo je napomenuto da kod ljudi postoje tri kriticna perioda za veliki uticaj hormona na mozak, i da se treci odvija nesto malo nakon rodjenja, sto daje prostor za uticaj sredine i bla bla.
zimi, je l' bi mogla ponovo da iskopas taj broj. :)




evo jednog interesantnog teksta koji nudi insight u opasnosti olakih interperetacije nekih dobijenih rezultata pri istrazivanjima uzroka homoseksualnosti. uzivajte.


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The Gay Gene?
by Jeffrey Satinover, M.D.

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Jeffrey B. Satinover, M.D. has practiced psychoanalysis for more than nineteen years, and psychiatry for more than ten. He is a former Fellow in Psychiatry and Child Psychiatry at Yale University, a past president of the C.G. Jung Foundation, and a former William James Lecturer in Psychology and Religion at Harvard University. He holds degrees from MIT, the University of Texas, and Harvard University. He is the author of Homosexuality and the Politics of Truth (Baker Books, 1996).
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In this age, in this country, public sentiment is everything. With it, nothing can fail; against it, nothing can succeed. Whoever molds public sentiment goes deeper than he who enacts statutes, or pronounces judicial decisions.
-Abraham Lincoln
On July 15, 1993, National Public Radio (NPR) made a dramatic announcement on stations across the country: Was a team of scientists at the National Institutes of Health on the trail of a gene that causes homosexuality? Their report would be published the next day in Science, one of the two most prestigious scientific research journals in the world.[1]
The discussion that followed explained for the listening public the implications of these findings for social attitudes toward homosexuality and for public policy concerning it. Science was on the verge of proving what many had long argued: that homosexuality is innate, genetic and therefore unchangeable-a normal and commonplace variant of human nature. In the light of these findings, surely only the bigoted or ignorant could condemn it in any way.

Shortly after the announcement, amidst a well-orchestrated blizzard of press discussions, there ensued the watershed legal battle over "Proposition 2" in Colorado. (This popularly enacted legislation precluded making sexual orientation the basis of "privileged class" minority status, a status conferred previously only on the basis of immutable factors such as race.)

Among the many crucial issues raised by the legislation was the question as to whether homosexuality was indeed normal, innate and unchangeable. One prominent researcher testified to the court, "I am 99.5% certain that homosexuality is genetic." But this personal opinion was widely misunderstood as "homosexuality is 99.5% genetic," implying that research had demonstrated this. Certainly, that was the message promulgated by NPR's report on the recent research, and by all the discussions that followed. In a few weeks, Newsweek would emblazon across its cover the phrase that would stick in the public mind as the final truth about homosexuality: "Gay Gene?"

Of course, just near the end of the NPR discussion, certain necessary caveats were fleetingly added. But only an expert knew what they meant- that the research actually showed nothing whatever in the way of what was being discussed. The vast majority of listeners would think that homosexuality had been all but conclusively proven to be "genetic." But the real question is whether or not there is such a "gay gene."

In fact, there is not, and the research being promoted as proving that there is provides no supporting evidence. How can this be? In order to understand what is really going on, one needs to understand some little- known features of the emerging study of behavioral genetics (much subtler than the genetics of simple, "Mendelian" traits such as eye color).

When it comes to questions of the genetics of any behavior-homosexuality included-all of the following statements are likely to be at least roughly true:


Such and such a behavior "is genetic";
There are no genes that produce the behavior;
The genes associated with the behavior are found on such and such a chromosome;
The behavior is significantly heritable;
The behavior is not inherited.
The scientific distinctions that make these seeming contradictions perfectly reasonable and consistent seem completely misunderstood by the media who report on them.
For example, in response to the "gay gene" research, the Wall Street Journal headlined their report (which appeared the next day), "Research Points Toward a Gay Gene."[2] A subheading of the Journal article stated, "Normal Variation"-leaving the casual reader with the impression that the research led to this conclusion. It did not, nor could it have. The subhead alluded to nothing more than the chief researcher's personal, unsubstantiated opinion that homosexuality, as he put it, "is a normal variant of human behavior." Even the New York Times, in its more moderate front-page article, "Report Suggests Homosexuality is Linked to Genes," noted that other researchers warned against over-interpreting the work, "or taking it to mean anything as simplistic as that the 'gay gene' had been found."

At end of the Wall Street Journal article, at the bottom of the last paragraph on the last page deep within the paper, a prominent geneticist was quoted for his reactions to the research. He observed that "the gene...may be involved in something other than sexual behavior. For example, it may be that the supposed gene is only 'associated' with homosexuality, rather than a 'cause' of it."

This rather cryptic comment would be most difficult to understand without the needed scientific background. Yet it is the most critical distinction in the entire article; indeed, it renders the findings almost entirely worthless. Why bury and fail to explain what it means? Perhaps the motives were innocent, but in fact, the belief that homosexuality is "biological" or "genetic" causes people to develop more positive attitudes toward it. They need not have the foggiest understanding of what "biological" or "genetic" really mean in order to change their view:


105 volunteer[s]... were exposed to one of three... conditions.... [T]he experimental group read a summary... emphasizing a biological component of homosexual orientation.... [O]ne control group read a summary... focusing on the absence of hormonal differences between homosexual and heterosexual men. [A]nother control group w[as] not exposed to either article.... As predicted, subjects in the experimental group had significantly lower[3] scores [more positive attitudes toward homosexuals] than subjects in the control groups.[4]
And:

Analysis indicated that subjects who believed that homosexuals are "born that way" held significantly more positive attitudes toward homosexuals than subjects who believed that homosexuals "choose to be that way" and/or "learn to be that way."[5]
What was actually going in the study the media was trumpeting? Dean Hamer and his colleagues had performed a kind of behavioral genetics study now becoming widespread-the so-called "linkage study." Researchers identify a behavioral trait that runs in a family and then look to see whether there is a chromosomal variant in the genetic material of that family, and if that variant is more frequent in the family members who have the trait.
To the uninitiated, a positive finding ("correlation" or "association" of a genetic structure with a behavioral trait) is taken to mean that the trait "is genetic"-that is, inherited.

In fact, it means absolutely nothing of the sort, and it should be emphasized that there is virtually no human trait without innumerable such correlations. We will see shortly just how this is can be so. The most important take-home messages will be these:

(1) All the research that has been done on homosexuality has been selectively trumpeted through the press in carefully crafted form in order to shape public opinion-hence public policy-in predictable ways. The research itself means almost nothing.

(2) The research projects that would truly mean something are scarcely being done because they would all explicitly or tacitly lead to but one end highly undesirable to activists: a method or methods for preventing homosexuality or changing it with ever-increasing efficacy; and to one conclusion: homosexuality per se is not inherited.

(3) Most of the research has been hastily and often sloppily done-but this point is a distraction. Even were it superb, the findings would still mean almost nothing.

(4) To whatever extent this research has been good enough to generate valid conclusions at all, these conclusions are precisely the opposite of what is claimed in the press.

Before we talk about specifics, here is what serious scientists think about the recent behavior-caused-by-genes research. From Science, 1994:


Time and time again, scientists have claimed that particular genes or chromosomal regions are associated with behavioral traits, only to withdraw their findings when they were not replicated. "Unfortunately," says Yale's [Dr. Joel] Gelernter, "it's hard to come up with many" findings linking specific genes to complex human behaviors that have been replicated. "...All were announced with great fanfare; all were greeted unskeptically in the popular press; all are now in disrepute."[6]
A scientist at Washington University School of Medicine calculated what would be required for such a replication. He:

...projected that if the trait [in question] was 50% heritable... detecting [just] one of [its] genes would require studying 175 families-that is, almost 2000 people.[7 ] Replicati[on] would require studying 781 families-another 8000 people.... [E]ach additional gene (for a polygenic trait), researchers would need... the whole business again. "Suddenly you're talking about tens of thousands of people and years of work and millions of dollars."[8]
Nothing even remotely close to this has been done with respect to homosexuality.
Using arguable-at-best methods, two American activists recently published studies showing that if one of a pair of identical twins is homosexual, the odds that the other one is, too, are less than 50% (the study examined a few dozens of pairs). On this basis, they argue that "homosexuality is genetic." British researchers generated comparable results in a similar study. Their conclusion? The surprisingly low odds that both twins were homosexual:


...confirmed that genetic factors are insufficient explanation for the development of sexual orientation.[9]
Two Columbia University researchers (who have published the most comprehensive research summary on the subject to date) note the unexpectedly:

... large proportion of monozygotic twins who [did not share] homosexuality despite sharing not only their genes but also their prenatal and familial environments.[10] The... [50% odds]... for homosexuality among the identical twins could be entirely accounted for by the increased similarity of their developmental experiences. In our opinion, the major finding of that study is that 48 percent of identical twins who were reared together [and where at least one was homosexual] were discordant for sexual orientation.[11]
Two other genetics researchers (one heads one of the largest genetics departments in the country, the other is at Harvard) comment:

... recent studies seeking a genetic basis for homosexuality suggest that... we may be in for a new molecular phrenology, rather than true scientific progress and insight into behavior.
While the authors interpreted their findings as evidence for a genetic basis for homosexuality, we think that the data in fact provide strong evidence for the influence of the environment.[12 ]
The author of the lead article on genes and behavior in a special issue of Science notes:

...the growing understanding that the interaction of genes and environment is much more complicated than the simple "violence genes" and "intelligence genes" touted in the popular press. Indeed, renewed appreciation of environmental factors is one of the chief effects of the increased belief in genetics' effects on behavior [my emphasis]. The same data that show the effects of genes also point to the enormous influence of non-genetic factors.[13]
The director of the Center for Developmental and Health Genetics at Pennsylvania State University comments:

Research into heritability is the best demonstration I know of the importance of the environment.
(Note the term "heritability;" we will be returning to it in detail as it lies at the heart of much confusion).
With regard to the work announced by NPR, genetics researchers from Yale, Columbia and Louisiana State Universities noted that:


Much of the discussion of this finding [of a purported gene locus for homosexuality] has focused on its social and political ramifications. [But] inconsistencies... suggest that this finding should be interpreted cautiously....
The results are not consistent with any genetic model....neither of these differences [between homosexuality in maternal versus paternal uncles or cousins] is statistically significant....small sample sizes make these data compatible with a range of... hypotheses.
[T]he... data... present no consistent support for the... results.[14]
By contrast to their public policy statements, the researchers responded carefully as follows:

We did not say that [the chromosome segment under study] "underlies" sexuality, only that it contributes to it in some families. Nor have we said that [it] represents a "major" gene, only that its influence is statistically detectable in the population that we studied.[15]
Ignoring possible flaws in the research, have the researchers actually pointed to this more modest claim with any degree of certainty? In fact, they have not-as they themselves acknowledge, but in language that will surely evade general understanding-and that will continue to be avoided by the press:

...the question of the appropriate significance level to apply to a non-Mendelian trait such as sexual orientation is problematic.[16]
English translation: "It is not possible to know what the findings mean, if anything, since sexual orientation cannot possibly be inherited the way eye-color is." Thus, to their fellow scientists, the researchers properly acknowledge what every serious researcher knows, but the public does not.

Complex behavioral traits are the product of multiple genetic and environmental antecedents, with 'environment' meaning not only the social environment but also such factors as the 'flux of hormones during development, whether you were lying on your right or left side in the womb and a whole parade of other things'...the relationships among genes and environment probably have a somewhat different effect on someone in Salt lake City than if that person were growing up in New York City.[17]
English translation: "You're more likely to become gay growing up in Manhattan than in Utah among Mormons and Christian fundamentalists, even if everything else is the same, including genes."
Unfortunately, anyone who is so disposed can readily offer the public partial truths which are seriously misleading. This is so only in part because of an easily led or poorly educated press. The major reason is really that the ideas being cooked beyond recognition once they leave the labs are inherently complex, even if originally formulated and presented properly. There are no "lite," sound-bite versions of behavioral genetics that are not fundamentally in error in one way or another.

Nonetheless, if one grasps at least some of the basics, in simple form, it will be possible to see exactly why the current research into homosexuality means so little-and will continue to mean little even should the quality of the research methods improve-so long as it remains driven by political, rather than scientific objectives.

There are really only two major principles that need to be carefully assimilated in order to see through public relations distortions to the actual meaning of recent research. They are as follows:


Heritable does not mean inherited.
Meaningful genetics research identifies and then focuses on traits that are directly inherited. One prominent genetics researcher (discussing a matter unrelated to homosexuality, but equally frustrated with the bad science reporting) flatly calls the question of heritability "trivial."
Heritable Does Not Mean Inherited
Heritability studies can be done on almost any human trait- physical, behavioral, emotional, etc.-and will show positive results. That is, almost every human characteristic you can think of is in significant measure heritable (thus discussing it is "trivial"). But few human behavioral traits are directly inherited the way simple physiological traits are (e.g., eye color). Inherited means "determined directly by genes," with little or no way of changing the trait by choice, or by preventing it, or by modifying the environment in which the trait has emerged (or is more likely to emerge).
Here is a simple hypothetical example, but it is 100% plausible. It tracks the kinds of studies that have been done with innumerable other traits, including homosexuality. (But only in the area of homosexuality has the meaning of such studies been so badly distorted).

Suppose that for political reasons you want to demonstrate that there is a "basketball gene" that "makes" people become basketball players ("BBPs"). (Please suspend your immediate, correct understanding that the idea is absurd.) To make your case you would use the same methods as with homosexuality. These methods fall into three categories, and represent important forms of preliminary research when investigating any trait: (1) twin studies; (2) brain dissections; (3) gene "linkage" studies.


Twin Studies
The basic idea in twin studies is to show that the more genetically similar are two people, the more likely it is that they will share the trait you are studying. So, you create a study set of pairs of people, divided into categories according to how genetically similar they are, as follows:

Pair Type Degree of Similarity
(% same genes)
Identical Twins 100%
Fraternal Twins 50%
Non-Twin Siblings 50%
Unrelated People <5%

The most similar are identical twins, the next most similar are fraternal twins (who are on average as different as non-twin brothers or sisters, but no more so), the least similar are unrelated people.

Then you identify those pairs of twins in which at least one is a BBP. It will not be difficult to show that if one such identical twin is a BBP, his brother (or her sister) more frequently will be, too, than would a non-identical twin or a non-twin sibling or a non-sibling. You would create groups of such different kinds of pairs to make the comparison in a large number of cases. (One set of identical twin pairs, one set of non-identical twin pairs, one set of non-twin siblings, and so on.)

From the "concordance rate" in each set (the percentage of pairs in each set in which either both are BBPs or both are not. Pairs in which one was and the other was not would be called "discordant for BBP") you would calculate a "heritability" rate. (Perhaps you have an armchair guess as to how many identical twin-pairs either both play or both do not play basketball. Probably a good deal more than half, the concordance rate for homosexuality in such twin-pairs.)

You respond to the reporter from Sports Illustrations that, "Our research demonstrates that BBP is very strongly heritable," and you would be right. But the article that comes out that month reads something slightly different, but completely wrong. "... Recent research shows that BBP is probably inherited. A number of outside researchers examined the work and found it substantially accurate and well- performed. They cautioned against arriving at hasty conclusions, however." No one notices the difference.


Brain Dissections
Second, your colleagues perform a series of autopsies on the brains of some dead people who appear to have been BBPs. (Old jerseys, high-top sneakers and Knicks ticket-stubs were found among their possessions, for example.) They do the same with a group of dead non-players (no sneakers, jerseys or tickets.) They report that, on average, "certain parts of the brain long thought to be involved with BBP are much larger in the group of BBPs than in the controls." Certain nationally renowned newspapers in the Northeast pick up on the story and editorialize, "It will be very difficult for anyone except poorly educated yokels who believe in Santa Claus, the Tooth-Fairy and God to argue that BBP is not inborn. For not only has it been proven to run in families, even the brains of basketball players are different."[18]
In a pretense of balance, some of these papers interview diehard believers in the old view-yokels who still think that one must decide to play basketball, and play it for a long time, before you really can be considered "a BBP." One of them is quoted as claiming that, "maybe if you do something long enough your brain changes as you get better at it, and that part of the brain gets bigger." (Remarkably enough, this surmise seems obvious to the old-time believer.) The reporter does not merely report the comment, however, he also hints that it is especially idiotic-typical of diehards and yokels-since everyone knows the brain does not change.

Of course, you yourself are well aware that among neuroscientists it is extremely old news that the brain indeed changes, quite dramatically, in just the way the old diehard guessed: those parts responsible for an activity get much bigger over time (and there are definitely parts that are more utilized in BBP). You will not lie about it if asked (since you will not be), but neither will you go out of your way to confirm the truth.


Gene "Linkage" Studies
Now for the coup de grâce. You find a couple of families of BBPs and compare them to some families of non-BBPs. You have a hunch that of innumerable genes of every imaginable sort likely to be "associated" or "linked" to BBP (you never use the word "causing" because you do not need to-no one knows the difference), there are some genes on, say, the X-Chromosome. After a few false starts, sure enough, you find what you are looking for: among the BBP families one particular chromosomal variant (cluster of genes) is more commonly found (though not always) than among the non-players.
Now, sympathizers at National People's Radio were long ago quietly informed of your research, since they want people to come around to certain beliefs, too. So, as soon as your work hits the press, they are on the air: "Researchers are hot on the trail of the 'Basketball Gene!' In an article to be published tomorrow in Sports Science... " Learned-sounding commentators pontificate in soft, accentless, perfectly articulated and faintly condescending tones about the enormous public policy implications of this superb piece of science-in-the-service-of- humankind. Two weeks later, there it is again, at a jaunty angle across the cover of the major national newsweekly: "Basketball Gene."

Now what is wrong with this scenario? It is simple: of course BBP is heritable ("has a non-zero heritability" to use the words of homosexuality researchers). That is because many physiological traits-muscle strength, speed, agility, reflex speed, height, etc.-are themselves directly inherited, and they make it more or less likely that one can, and will want to, and will successfully, and will therefore continue to want to, and will in fact continue to, play basketball. In short, because of intermediate inherited traits associated with BBP (none of which are BBP), it shows significant heritability. (The genetic association, of course, is in no way necessary or predetermined, and is highly culturally conditioned: there were no BBPs at all in, say, ancient Greece, yet the same genes were there.)

BBP also shows a strong biological representation in the brain, both at birth (e.g., nervous system factors contributing to reflex speed) and especially later (e.g., the parts of the cortex that are cultivated and become responsible for the movements of basketball, as in the huge increases in finger-related brain tissue among blind people who learn Braille).

And the specific genes that run in families that are responsible for height, athleticism, etc. can surely be found and they will be statistically linked to BBP. And if one identical twin decides to play basketball, the unusually strong emotional bond between such siblings will make it even more likely that his twin will, too. (The fact of their genetic identity, not their specific genes, are here influencing an outcome above and beyond the indirect contributions from any specific genes.)

The basic problem is this: BBP is "influenced" (made more or less an easy and enjoyable thing to do) by the presence or absence of other associated traits. For BBP we can readily guess what they are and so immediately see that the "genetic" component of BBP has nothing to do with the game itself but with these associated (facilitating) traits. What are these traits? Height, athleticism, bone structure, reflexes, muscle refresh rate, and so on. So evident are the specifics of this association that no serious researcher will waste his time looking into the genetics of BBP proper; he will concentrate on the obvious intermediate traits-height, athleticism and so on.

The same is true for homosexuality, except (a) the more important, intermediate traits with which it is associated are mostly unknown and suspected ones are harder to confirm, and (b) the research agenda is being distorted by the political requirement that no such associated traits be discovered and that homosexuality be falsely presented as directly inherited.


Meaningful Genetics Research Identifies and Focuses on Traits That Are Directly Inherited
Research into merely heritable traits is useful only in generating hypotheses about what the directly inherited traits might be. Here is what this means: Let us imagine that it was not immediately evident to us that the heritable aspects of BBP were intermediate traits such as height. A good researcher would not be at all tempted to conclude from the studies we described that BBP itself was inherited. He would conclude however that, indeed, there must be some inherited traits that facilitate BBP, and it would be these as-yet-unknown traits that were producing the "non-zero heritability" results. If he could identify the traits correctly, he would find that the heritability results, when he redirected his genetics research, would increase dramatically.
In other words, studying the genetics of BBP is really a crude way of unwittingly studying the genetics of height and athleticism, etc. If he selects his population on the basis of the indirect trait (BBP), when it is other traits that are really inherited, the researcher's results will be "fuzzed up" by the inevitable proportion of BBP's who lack these traits, or have them in lesser degree (e.g., a small number of shortish BBPs). But if he correctly identifies the traits in question, his next round of studies will "divide the herd" more efficiently, corralling his subjects not by BBP (or "sexual orientation"), but by height. Of course, there will be more BBPs among the tall subjects than among the short, but that is incidental. He will seek out other tall people who are not BBPs, and in his new study, the heritability factor (height) will be even more concentrated.

How might he guess at what the most important traits are, and then try to confirm his guess, so he could investigate the genetics of these traits? Very simply: he looks, does the best he can to name what he sees, and tries not to run afoul of the currently fashionable taboos enforced by the thought-police! He will probably have no trouble studying height, but he might run into difficulties should he suspect that athleticism (or even height) has a racial association. (More people of Nordic stock, being taller, become basketball players than do people of Appenzeller Swiss stock, being short. Perhaps other such groupings might occur to a researcher.)

In the case of homosexuality, the inherited traits that are more common among homosexuals (and that produce "non-zero heritability" in studies) might include such qualities as greater than average tendency to anxiety, shyness, sensitivity, intelligence, aesthetic abilities and so on. (Of course, these traits may themselves be further reducible to a variety of mutually influencing, associated genetic and non-genetic factors.) The brain changes that are more prevalent among homosexuals, the tendency of homosexuality to run in families (and to vary with degree of genetic similarity within families) and the presence of associated chromosomal markings are all certainly due to as yet unresearched and therefore not- yet-identified intermediate traits. There is no evidence that homosexuality itself is inherited.

Like height and BBP, these traits-intelligence, say, or anxiety-are surely widely distributed in the population at large and densely present therefore in groups that are properly selected to have them. If researchers had divided their populations by shyness or aesthetic sensibility, and ignored the homosexual/non-homosexual division, they might well have found even stronger chromosomal linkages as well as brain changes and twin concordance rates.


Conclusion
Here, then is a final summary, in the form of a dialogue.

Isn't homosexuality heritable?
Yes, significantly.
So it is inherited?
No, it is not.
I'm confused. Isn't there is a "genetic component" to homosexuality?
Yes, but "component" is just a loose way of indicating genetic associations and linkages. This will not make sense unless you understand what, and how little, "linkage" and "association" really means.
What about all the evidence that shows that homosexuality "is genetic"?
There is not any, and none of the research itself claims there is; only the press and, sadly, certain researchers do-when speaking in sound bites to the public.
But isn't homosexuality "biologically in the brain"?
Of course it is. So is just about everything else. I'll bet people who pray regularly have certain enlarged portions of their brains!
So doesn't that mean that homosexuality is "innate"?
No more than prayer is. The brain changes with use or nonuse as much as muscles do-a good deal more, in fact. We just do not usually see it happening.
But doesn't homosexuality run in families?
Yes.
So you get it from your parents, right?
You get viruses from your parents, too, and some bad habits. Not everything that is familial is innate or genetic.
But it just seems to make sense. From the people I know there's a type-it's got to be inherited-that runs in families and a lot of these people are gay, right?
That is what associated traits are-but what exactly is the associated trait-or traits-you are detecting? If there is one thing the research confirms, it is that it is not "gayness" itself. That is why these traits are sometimes in evidence at a very early age, long before sexuality is shaped.
So what are these traits?
An important question, indeed. Science is being seriously obstructed in its effort to answer that question. If we were allowed- encouraged-to answer it, we would soon develop better ideas on what homosexuality is and how to change, or better, prevent it. We would know who was at greater risk for becoming homosexual and what environments- family or societal-foster it. As one prominent gay activist researcher implied, all genetic things being equal, it is a whole lot easier to become "gay" in New York than in Utah. So who do you think would benefit most from that kind of research?
Well, what traits do you guess are "associated," as you put it, with homosexuality?
May I speculate, perhaps wildly? That is how scientific hypotheses are first generated. The important thing is not to avoid ideas that prove wrong, just not to cling to them if they do.
Okay, go ahead, speculate.
Intelligence, anxiety, sensitivity, aesthetic abilities, taste. You know, all the stereotypes.
But where do these traits come from? Aren't they inherited?
We do not know yet. Some may be. Or rather, we do not know how much is inherited, and which elements are direct and which merely further associated and linked with other yet more fundamental traits. But you are getting the picture. That is how the research ought to proceed. It is not necessarily that the traits that facilitate homosexuality are themselves bad; perhaps many are gifts. Athleticism is a generally good thing, and we think highly of people who satisfy their athletic impulses as, say, outstanding BBPs. Not so the fellow who merely becomes a thug.
Endnotes
[1]D. H. Hamer et al, "A Linkage Between DNA Markers on the X-chromosome and Male Sexual Orientation," Science (1993), 261, no. 5119, pp. 321-27.
[2]"Research Points Toward a Gay Gene," Wall Street Journal, 16 July 1993.

[3]A lower score on this scale means a less negative attitude toward homosexuality.

[4]Piskur and Degelman, "Attitudes Toward Homosexuals," Psychological Reports 71 (1992); my emphasis, pp. 1219-25 (part 2 of 3). See also K. E. Ernulf, "Cross-National Analysis."

[5]K. E. Ernulf, S. M. Innala, and F. L. Whitam, "Biological Explanation, Psychological Explanation, and Tolerance of Homosexuals: A Cross-National Analysis of Beliefs and Attitudes," Psychological Reports 65 (1989), pp. 1003-10 (1 of 3).

[6]Mann C. Genes and behavior. Science 264:1687 (1994).

[7]None of the studies of the genetics of homosexuality (all of which are initial; none are replicatory) have come even remotely close to studying this many subjects.

[8]Mann C. op. cit. p. 1688.

[9]King, M and McDonald, E. Homosexuals who are twins: a study of 46 probands. British Journal of Psychiatry 160:407-409 (1992)

[10]Byne W and Parsons B. Human sexual orientation: the biologic theories reappraised. Archives of General Psychiatry. 50, 3:230 (1993).

[11]Quoted by Horgan, J., Scientific American: Eugenics Revisited. June 1993, p. 123.

[12 ]Billings, P. and Beckwith, J. Technology Review, July, 1993. p. 60.

[13]Mann C. op. cit. pp. 1686-1689.

[14]Risch N., Squires-Wheeler E., and Bronya J.B.K., "Male Sexual Orientation and Genetic Evidence," Science 262 (1993), pp. 2063-65.

[15]Hamer DH et al. Response to Risch N et al. ibid. p. 2065

[16]Hamer DH et al. Response to Risch N et al. loc. cit.

[17]Mann C., op. cit. p. 1687.

[18]Readers may recall Simon LeVay's much touted discovery that the certain parts of the brains of (supposedly) homosexual men were larger than among (supposedly) heterosexual men. But even if the research is valid-its quality has been strongly criticized-the discovery of brain differences per se is on a par with the discovery that athletes have bigger muscles than non-athletes. For though a genetic tendency toward larger muscles may make it easier to-and therefore more likely that one will-become an athlete, becoming an athlete will certainly give one bigger muscles.

When this particular critique was raised, the press quickly took its accustomed potshot at the usual "poorly educated and easily led" religious groups for the suggestion's politically incorrect implications: "Some religious fundamentalists even suggested that homosexual activity somehow could have caused the structural differences [that LeVay claimed to have discovered."

But as the editor of Nature-an equally prestigious publication-wrote, commenting on the LeVay research: "Plainly, the neural correlates of genetically determined gender are plastic at a sufficiently early stage....Plastic structures in the hypothalamus allowing the consequences of early sexual arousal to be made permanent might suit those who claim an environmental origin to homosexuality well." This editor is not, to anyone's knowledge, a religious fundamentalist.


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izvor
Korisnikov avatar
By Mr Dee
#441971
i jos jedan:



Non-sex genes 'link to gay trait'

The scientists found regions on chromosomes 7, 8 and 10
Multiple genes - and not just the sex chromosomes - are important in sexual orientation, say US scientists.
A University of Illinois team, which has screened the entire human genome, say there is no one 'gay' gene.

Writing in the journal Human Genetics, they said environmental factors are also likely to be involved.

The findings add to the debate over whether sexual orientation is a matter of choice. Campaigners say equality is the more important issue.

Non-sex genes

Much of the past genetic research into male homosexuality had focused solely on the X chromosome, passed down to boys by their mother, according to lead researcher Dr Brian Mustanski.

His team looked at all 22 pairs of non-sex chromosomes of 456 individuals from 146 families with two or more gay brothers.

There is no one 'gay' gene.

Lead researcher Dr Brian Mustanski

They found several identical stretches of DNA that were shared among gay siblings on chromosomes other than the female X.

About 60% of these brothers shared identical DNA on three chromosomes - chromosome 7, 8 and 10.

Complex trait

If it were down to chance, only 50% of these stretches would be shared, said the authors.

The region found on chromosome 10 correlated with sexual orientation only when it was inherited from the mother.

The most important thing is that lesbian and gay men are treated equally.

Alan Wardle of Stonewall

Dr Mustanski said the next step would be to see if the findings could be confirmed by further studies, and to identify the particular genes within the newly discovered sequences that are linked to sexual orientation.

"Our study helps to establish that genes play an important role in determining whether a man is gay or heterosexual," he said, but added that other factors were also important.

"Sexual orientation is a complex trait. There is no one 'gay' gene.

"Our best guess is that multiple genes, potentially interacting with environmental influences, explain differences in sexual orientation."

Alan Wardle from the gay rights charity Stonewall said: "It's an interesting study that contributes further to the debate.

"Regardless of whether sexual orientation is determined by nature or nurture or both, the most important thing is that lesbians and gay men are treated equally and are allowed to live their life without discrimination."

izvor
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