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'In Studies of Virtual Twins, Nature Wins Again'

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By chuckles (Fri Sep 05, 2008 at 03:40:09 PM EST) (all tags)

By [Dr. Nancy L. Segal's] definition, virtual twins are unrelated children born within nine months of each other who enter a family, through birth or adoption, in the first year of life. Since 1991, Dr. Segal has been studying 137 such sets of siblings, whose average age difference is three months.

As scientific subjects, virtual twins provide a rich pool of material for researchers tackling the nature-versus-nurture question. In Dr. Segal’s studies, as in so many involving biological twins, it seems that nature is winning.

Raised together essentially from birth, or at least since infancy, virtual twins may be genetic strangers, but they share an environment from an early point in life.

...

Several major twin studies over the last 20 years, particularly those following twins raised by different families, have provided what scientists say is clear evidence that genetics play a greater role than environment in intelligence and a range of personality traits. Dr. Segal’s research, believed to be the first to examine virtual twins as a subset of the twin population, has bolstered the prevailing view through another lens.

...

Dr. Segal has found that identical twins were the most alike in their thinking, fraternal twins somewhat less so, and virtual twins strikingly different. When it comes to intelligence, for example, her research has found that only 25 percent of the differences between twins — virtual, fraternal or identical — can be accounted for by their environment, 75 percent by genetics.

So... if the NY Times is willing to admit today that intelligence is primarily genetic, how long until they admit that humans belong to geographically distributed genetic clusters for which the word "race" is a reasonable shorthand? How long until they admit that most neurological traits have genetic bases, and many are unevenly distributed among the races?

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'In Studies of Virtual Twins, Nature Wins Again' | 40 comments (40 topical, 0 hidden) | Trackback

Flawed premise by marvin (2.00 / 0) #1 Fri Sep 05, 2008 at 04:14:37 PM EST

This study merely looked at differences between individuals with different genes who were raised in the same environment. Your question has no final solution that can be provided by that one study.

There is no mention made of any examination of differences between people groups from various geographic regions or cultural backgrounds. You would have to complete further study to determine whether, in fact, Asians have a greater abundance of the intelligence gene, if the Romany have a genetic predisposition towards a transient lifestyle, whether Democrats lack the genes necessary for complete logic, and if Republicans truly do have an evil gene.

I didn't say this study could answer... by chuckles (2.50 / 2) #2 Fri Sep 05, 2008 at 05:26:21 PM EST

... these questions, nor did I say this study (by itself) says anything about race. It does say that intelligence is largely genetic, which is a big break from the tabula rasa view that all the really cool people have.

Sent from my iPhone.

[ Parent ]

Not "largely" by ucblockhead (2.00 / 0) #4 Fri Sep 05, 2008 at 05:51:17 PM EST

You act like 75% == 100%.
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[ Parent ]

How is 75% not 'largely'? by chuckles (2.00 / 0) #7 Fri Sep 05, 2008 at 07:04:10 PM EST

If I thought it was 100%, I would have said "completely". 75% is an overwhelming majority, thus "largely".

Sent from my iPhone.

[ Parent ]

Hardly overwhelming by ucblockhead (4.00 / 1) #8 Fri Sep 05, 2008 at 07:26:08 PM EST

25% means that the same set if genes can result in an IQ that is plus or minus 10-15 points.
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[ Parent ]

Sub-Saharan African average IQ is 70. by chuckles (2.00 / 0) #27 Sat Sep 06, 2008 at 12:28:14 AM EST

White American average IQ is 100. Assuming your argument is correct--that environment explains away 10-15 points--how do you explain the other 15-20 points?

Oh, I know: evil white people invented culturally biased IQ tests in order to make everyone else feel bad. Okay, so how do you explain that East Asians do better than whites with an average IQ of 106? Did evil whites make the IQ tests so they were even more culturally biased in favor of East Asians? Or maybe those IQ tests are simply biased in favor of those with higher general cognition.

Sent from my iPhone.

[ Parent ]

I think Jared Diamond covered this... by atreides (2.00 / 0) #34 Sat Sep 06, 2008 at 05:00:26 PM EST

...when he was talking about New Guinea tribesman who had trouble counting above 10, but could identify 600-800 different types of mushrooms by sight that westerners needed instruments and DNA samples to distinguish and similar cases...

_{He sails from world to world in a flying tomb, serving gods who eat hope.}
[ Parent ]

Wouldn't this suggest... by chuckles (2.00 / 0) #36 Sat Sep 06, 2008 at 05:51:38 PM EST

that New Guinea tribesmen have low general cognition, but excellent visual memory, much like the Australian Aborigines?

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[ Parent ]

: Possible, but I think it means... by atreides (2.00 / 0) #37 Sat Sep 06, 2008 at 07:08:25 PM EST

...what you're testing for and who you're testing as as much a part of IQ tests as anything. Why else do they retool IQ tests every 5 to 10 years? It's because people tend to keep getting smarter in comparison to those tests. Further, eventually the things that are tested for become useless. I've seen grammar school and college entrance exams from the late 1800s/early 1900s. Half the questions tend to be ridiculously easy, half of them are nigh impossible. The impossible ones tend to require apocryphal types of knowledge or specific knowledge in highly specialized subjects that are no longer applicable to modern life.
_{He sails from world to world in a flying tomb, serving gods who eat hope.}
[ Parent ]

Also by ucblockhead (4.00 / 1) #11 Fri Sep 05, 2008 at 07:29:08 PM EST

Note that twin studies can't control for environmental factors that occur before birth. (And it is already well known that maternal drug and/or alcohol use effects IQ.)
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[ Parent ]

Sorry by marvin (2.00 / 0) #17 Fri Sep 05, 2008 at 09:16:23 PM EST

Didn't expect to be taken literally.

In light of your poll question, I only went to the trouble of fabricating a comment just to wrap some text around the term "final solution". Instead, you took me seriously. I must fail at trolling.

I don't actually care much about the topic, as it doesn't really affect my life. Didn't RTFA either, because years of reading /. has taught me that it is rarely necessary.

[ Parent ]

'Instead, you took me seriously. I must fail...' by chuckles (2.00 / 0) #20 Fri Sep 05, 2008 at 10:16:06 PM EST

"... at trolling."

Actually, I believe that means you succeed at trolling.

Sent from my iPhone.

[ Parent ]

Okay by marvin (2.00 / 0) #21 Fri Sep 05, 2008 at 10:26:23 PM EST

Perhaps I fail at finding appropriate levels of subtlety then? The fun ended after I wrote the comment.

[ Parent ]

: If it makes you feel any better . . . by slozo (2.00 / 0) #26 Sat Sep 06, 2008 at 12:10:00 AM EST

. . . I got a good chuckle out of the final solution comment.

It's solid humour, and I find it difficult not to fall into goose step behind it, to try and continue the witty repartee.

[ Parent ]

FYI by ucblockhead (4.00 / 3) #3 Fri Sep 05, 2008 at 05:42:19 PM EST

75% of intelligence due to genetics is completely compatible with the idea that there are no racial differences in intelligence. In other words, all differences in IQ tests by race can be explained by that 25% that is due to nature.
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also by MillMan (2.00 / 0) #6 Fri Sep 05, 2008 at 07:01:43 PM EST

across any two large populations, the difference in average intelligence will still be small. If there were only one gene that determined intelligence, then race might be a good predictor of intelligence, as it is for sickle cell anemia.

When I'm imprisoned as an enemy combatant, will you blog about it?
[ Parent ]

Sure, it's possible. It's just incredibly unlikely by chuckles (2.00 / 0) #12 Fri Sep 05, 2008 at 08:08:42 PM EST

It's quite obvious that different groups of people are physically adapted to their ancestors' homelands through such traits as height, skin pigmentation, muscularity, and body fat (amount & distribution). Isn't it likely that neurological traits have also evolved in distinct ways? Or do you think that genes for neurological traits are evenly distributed among different population groups, despite different selection pressures, as if by some supernatural entity? (Are you a "Creationist"?)

Sent from my iPhone.

[ Parent ]

Incredibly unlikely? by ucblockhead (2.00 / 0) #18 Fri Sep 05, 2008 at 09:34:39 PM EST

That is flat out wrong. It is statistically likely, given the 75% heretability.

It is also pretty unlikely that increased intelligence has a differential advantage between habitats. Are you claiming that it is easier to stay stupid on some continents?
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[ Parent ]

: Incredibly unlikely. by chuckles (2.00 / 0) #25 Sat Sep 06, 2008 at 12:02:11 AM EST

It is also pretty unlikely that increased intelligence has a differential advantage between habitats.

Why do you say that? A powerful brain is expensive to feed. If the environment doesn't reward high g (general cognition), why would such a trait propagate?

Are you claiming that it is easier to stay stupid on some continents?

An environment in which calories are available year-round requires less forethought than an environment in which calories must be stored in preparation for a shortage.

Sent from my iPhone.

[ Parent ]

Two questions come outta this by sasquatchan (4.00 / 2) #5 Fri Sep 05, 2008 at 06:08:14 PM EST

(if we're trolling..) are teh joos a race ? and what about teh gheys ?

teh joos by ucblockhead (4.00 / 1) #10 Fri Sep 05, 2008 at 07:27:50 PM EST

The strongest link between IQ and race ever found is between the ashkenazi jews and high IQ. But even that is only somewhere between 7-12 IQ points, and so is within range of the variation due to non genetic causes.
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[ Parent ]

and are the extra IQ points by sasquatchan (2.00 / 0) #13 Fri Sep 05, 2008 at 08:17:54 PM EST

worth the genetic diseases they are predisposed to ? I forget the list, just that at the first appt with OB (actually the nurse) we had all these questions about if we were european jewish, or russian jewish (or had ancestors that were) .. all to prescreen us for the very sad birth defects they are predisposed to..

[ Parent ]

: It's possible that the genes causing... by chuckles (2.00 / 0) #16 Fri Sep 05, 2008 at 08:37:52 PM EST

the diseases may have benefits that outweigh the disabilities (for the group, obviously not for the afflicted individual), much in the same way that being a carrier for Sickle Cell offers protection against malaria without the drawbacks of having two copies of the gene.
Sent from my iPhone.

[ Parent ]

So the IQ difference is entirely environmental? by chuckles (2.00 / 0) #15 Fri Sep 05, 2008 at 08:26:18 PM EST

There couldn't be selection pressure for genes for IQ or anything like that, right?

I have an idea: maybe the environment influences which genes are successful, and genes influence culture, and the culture becomes part of the environment, resulting in a feedback loop.

Sent from my iPhone.

[ Parent ]

Genes vs. nature by ucblockhead (2.00 / 0) #19 Fri Sep 05, 2008 at 09:36:07 PM EST

You still seem to think that it is either genes or environment. It is not. It is both. Intelligence is only 75% due to genes.

Note that that level of heritability is on par with weight.
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[ Parent ]

Where did I say that? by chuckles (2.00 / 0) #22 Fri Sep 05, 2008 at 10:42:14 PM EST

I never suggested or implied that environment doesn't play a role in intelligence, but I am emphasizing that genes are vastly more influential than environment. According to the article, the ratio is 3:1.

Why do you keep trying to minimize the figure of 75%? You do realize that 0.75 is closer to 1 than it is to 0, right? You do realize that it is closer to 1 by a lot, not by a little, right?

Sent from my iPhone.

[ Parent ]

"Vastly" by ucblockhead (2.00 / 0) #23 Fri Sep 05, 2008 at 11:12:09 PM EST

"Vastly" is your error.

Again, the 25% *easily* explains all observed variation between "races". Given that no one has identified any gene for intelligence that varies by race, the idea that races vary by intelligence is purely unsupported supposition.

You realize that overall IQ scores have risen more than twice the difference between black and white IQ scores in the last hundred years, right? That is, the average early 21st century black man would outscore the average late 19th century white man.

Again, the variation between the "races" is on the order of 6-7 IQ points while a 75% heretability implies a variation of 10-15 IQ points due to "nature".
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[ Parent ]

Your figure of 6-7 IQ points is simply wrong. by chuckles (2.00 / 0) #28 Sat Sep 06, 2008 at 12:43:32 AM EST

Sub-Saharan Africans have an average IQ of 70, while Ashkenazi Jews in the US have an average IQ of 107. That is a 37-point gap between two identifiable population groups.

Sent from my iPhone.

[ Parent ]

Yes by ucblockhead (2.00 / 0) #30 Sat Sep 06, 2008 at 10:47:34 AM EST

And what is the difference in IQ between sub-saharan Africans and African Americans?
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[ Parent ]

African-American average IQ is 85. -nt by chuckles (2.00 / 0) #31 Sat Sep 06, 2008 at 01:24:58 PM EST

Sent from my iPhone.

[ Parent ]

In other words by ucblockhead (2.00 / 0) #32 Sat Sep 06, 2008 at 03:02:50 PM EST

You've just proven that a 15 point IQ gap is due to nature. (Sub saharan Africans vs. African Americans.)
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[ Parent ]

What do you define as 'nature'? by chuckles (2.00 / 0) #33 Sat Sep 06, 2008 at 03:58:05 PM EST

In the nature-versus-nurture debates, 'nature' is usually shorthand for DNA (or some other quality fixed in the subject, regardless of environment), while 'nurture' is shorthand for environment.

I think the 15-point difference between African-Americans and Sub-Saharan Africans is due to (1) environment (industrialized society with better nutrition and education, etc.) and (2) racial admixture with whites.

Why do you think there is a 37-point spread between Sub-Saharan Africans and Ashkenazi Jews in America*? Why is there a 22-point spread between African-Americans and Ashkenazi Jews in America?

*Or, if it makes you more comfortable, pick some other high-IQ group, such as high school students in Hong Kong.

Sent from my iPhone.

[ Parent ]

Why? by ucblockhead (2.00 / 0) #35 Sat Sep 06, 2008 at 05:06:04 PM EST

"Why do you think there is a 37-point spread between Sub-Saharan Africans and Ashkenazi Jews in America?" Environment.
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: Alright. by chuckles (2.00 / 0) #38 Mon Sep 22, 2008 at 03:01:59 AM EST

How do you explain the gap in general cognition between humans and dogs? Is it strictly environmental/cultural, or is there a difference in genetic potential? If genetics plays a role in intelligence differences between species, why can't it play a role in intelligence differences between human populations?
Sent from my iPhone.

[ Parent ]

Don't make me go Diff'rent Strokes on you by georgeha (4.00 / 1) #9 Fri Sep 05, 2008 at 07:26:26 PM EST

: Watchoo talkin' 'bout, Willis ? by sasquatchan (2.00 / 0) #14 Fri Sep 05, 2008 at 08:20:35 PM EST

[ Parent ]

WTF? by ammoniacal (2.00 / 0) #24 Fri Sep 05, 2008 at 11:53:01 PM EST

Children who enter a family through birth: Are they not fucking related?

What special fucking drugs has Dr. Segal been taking?

This coomenat has be n soidnsord by hurricanbe ice malt liqur

Sigh by TheophileEscargot (4.00 / 1) #29 Sat Sep 06, 2008 at 08:37:36 AM EST

The x% genes lead to y% trait things are extremely misleading because of the interaction between genes and environment. Suppose Kid A has genes that make him a slightly faster runner than Kid B. Kid A is identified as an athletic kid, is encouraged to do sports and try out for teams. He does more exercise than Kid B, trains harder than Kid B, and when you time them over the track years later Kid A runs a lot faster. But that's not just because of his genes: it's because of the feedback between genes and environment. Suggested listening material: Understanding Genetics: DNA, Genes, and Their Real-World Applications by David Sadava.

The relationship between IQ scores and intelligence is extremely dubious. It's not even clear that there is a single "g-factor" behind intelligence. There are also enormous cultural aspects to how well someone does on an IQ. How much effort an individual puts into IQ tests, how much experience a person has at sitting down and concentrating on tests, are hugely influenced by culture. Suggested reading material: The Mismeasure of Man by Stephen J. Gould.

Anthropologists no longer even use the term "race". While there are indeed different genetic populations, these rarely map to the culturally-accepted views of the different races. For instance you talk about "sub-Saharan Africans"; but since Africa is the origin of humanity, the genetic diversity of that region is enormous. Suggested listening material: Biological Anthropology: An Evolutionary Perspective by Barbara J. King.
--
Butch and Petey are harsh and unforgiving in their estimation of female beauty.

Gould was a crank by chuckles (2.00 / 0) #39 Mon Sep 22, 2008 at 03:49:32 AM EST

and his book (published in 1981) was largely devoted to debunking Victorian-era phrenologists. It has no relevance in an age of genetic sequencing.

I really like the third bullet point from your link to Barbara J. King:

Did modern Homo sapiens evolve entirely on the African continent, replacing other hominid forms as they fanned out into Asia and Europe? Or did they evolve simultaneously and in the same direction on all three continents?

Why would any intelligent person think this was an either/or issue? The second position, that pre-humans simultaneously and independently evolved into homo sapiens, is easy enough to debunk. An incurious person might conclude that the first position must therefore be true, but a curious person might ask:

Is it possible that homo sapiens arose in Africa, but evolution continued as population groups dispersed throughout the globe? If such evolution occurred, is it likely that new cognitive traits are evenly distributed among groups that have not had contact with each other for tens of thousands of years?

You stated: "Anthropologists no longer even use the term "race"." That is correct, but because using the word "race" is a career-killer. Unlike anthropologists, geneticists are in a better position to talk about race using irrefutable evidence, although for politically-correct reasons they will often substitute terms like "ethnicity", "ethny", "population group", etc.

Oh, and here's a little something that Gould or Lewontin should have read:

An Algorithm to Construct Genetically Similar Subsets of Families with the Use of Self-Reported Ethnicity Information

We present a simple algorithm that uses self-reported ethnicity information, pedigree structure, and affection status to group families into genetically more homogeneous subsets. This algorithm should prove useful to researchers who wish to perform genetic analyses on more-homogeneous subsets when they suspect that ignoring heterogeneity could lead to false-positive results or loss of power. We applied our algorithm to the self-reported ethnicity information of 159 families from the Veterans Affairs Cooperative Study of schizophrenia. We compared these estimates of population membership with those obtained using the program structure in an analysis of 378 microsatellite markers. We found excellent concordance between family classifications determined using self-reported ethnicity information and our algorithm and those determined using genetic marker data and structure; 158 of the 159 families had concordant classifications. In addition, the degree of admixture estimated using our algorithm and self-reported ethnicity information correlated well with that predicted using the genotype information.

The computer-determined ethnicity (based on DNA analysis only) matched self-reported ethnicity in 158 of 159 families. In a few years, the "race is only a social construct" believers are going to have to find a new religion.

Sent from my iPhone.

[ Parent ]

: WTF? by TheophileEscargot (2.00 / 0) #40 Mon Sep 22, 2008 at 01:56:51 PM EST

Stephen Jay Gould was a respected scientist, not a crank. The book may briefly have touched on phrenology, but concentrated on IQ tests and their problems: problems which are still valid today.
The Flynn effect by itself shows the flaws of IQ tests: supposedly an objective test of intelligence, in fact IQ scores change constantly.
That article doesn't say that "The computer-determined ethnicity (based on DNA analysis only) matched self-reported ethnicity in 158 of 159 families". The whole point of that article is that they had to apply an algorithm (loaded with fudge factors) to all kinds of data within the database to get it to match this DNA data.

You stated: "Anthropologists no longer even use the term "race"." That is correct, but because using the word "race" is a career-killer. Unlike anthropologists, geneticists are in a better position to talk about race using irrefutable evidence, although for politically-correct reasons they will often substitute terms like "ethnicity", "ethny", "population group", etc.
So, when the scientific consensus disagrees with your opinion, your opinion must be right and scientists must be "politically correct". Riiiiiight. Stick to clowning, science doesn't suit you.
--
Butch and Petey are harsh and unforgiving in their estimation of female beauty.
[ Parent ]

'In Studies of Virtual Twins, Nature Wins Again' | 40 comments (40 topical, 0 hidden) | Trackback