

Meta-analysis of heritability of human traits based on 50 years of twin studies [pdf] - gwern
http://www.gwern.net/docs/2015-polderman.pdf

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harperlee
I have to say, while it is a bit offtopic, that this is a beautiful paper
(from the purely aesthetical / visual information display perspective).

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e_modad
Isn't it? Kudos to the authors for a super clear paper. The graphs make
everything crystal clear. Succinct and clear graphs are oddly satisfying for
me.

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kbenson
I'll gladly look at anything submitted by gwern, or hosted at his site, but
can someone help out with a summary and some interpretations? I'm both not
familiar enough with the field to be confident I am taking away the right
conclusions form what is said, and without enough time to give to this topic
to rectify that.

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e_modad
Sure. So here are a few of the highlights of the paper:

\- They looked at nearly every single twin study over the last 50 years

\- The combined population of the all the studies is 14 million twin pairs

\- The results strongly suggest that every human trait is heritable as they
didn't find one trait that had 0% heritability.

\- The most surprising result for me is that across all the traits they
compiled, the heritability is 49%. Which is much much lower than I would have
expected.

There's a few more interesting points about monozygotic vs dizygotic, but I'll
spare you the technicalities since it has a narrower scope of interest.

As always, thanks Gwern for the informative post.

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gwern
> \- The most surprising result for me is that across all the traits they
> compiled, the heritability is 49%. Which is much much lower than I would
> have expected.

But much much higher than almost all people would believe.

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bumbledraven
> > The most surprising result for me is that across all the traits they
> compiled, the heritability is 49%. Which is much much lower than I would
> have expected. > But much much higher than almost all people would believe.

People's casual usage of the term heritability doesn't match the way it's used
in scientific contexts. For instance, people wouldn't normally say that the
trait of "being a slave" is explained by genetics, but the heritability (in
the technical sense) of being a slave in the mid 1800's USA was rather high.

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gwern
> but the heritability (in the technical sense) of being a slave in the mid
> 1800's USA was rather high.

No, it wouldn't be. Monozygotic black twins would have the exact same chance
as dizygotic black twins of being slaves, and slavery would cluster in
families, with whole families tending to be free or slave, leading to very
high shared/nonshared environment estimates.

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togedoge
I had to read some of secondary sources to understand the implications of this
paper.

Ultimately, studies show that on average human traits are typically due 1/2 to
genetics and 1/2 to environment. However, some traits are more skewed one way
or the other. For example, bipolar disorder among twins was about 70% due to
genetics and 30% due to environmental factors. All traits researched were
somehow impacted by genetics.

Also for about a third of traits, the nature part wasn't dependent on a
specific gene, so gene isolation to help predict traits is not always
possible.

What other major takeaways from this study do you find interesting?

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Houshalter
Here is one guys opinion: [http://infoproc.blogspot.com/2015/05/fifty-years-
of-twin-stu...](http://infoproc.blogspot.com/2015/05/fifty-years-of-twin-
studies.html)

>The most interesting aspect of these results is that for many traits there is
no detectable non-additivity. That is, gene-gene interactions seem to be
insignificant, and a simple linear genetic architecture is consistent with the
results.

We already knew this sort of from animal studies and evolutionary theory. But
it's interesting to see it confirmed in humans.

The implications of this, is that it will be very easy to predict phenotypes
from genetics. We don't need to model complicated interactions between genes
like many people thought, and can simply take the genes that correlate the
most with a desired trait.

This means you could do a large enough study and find every gene that
correlates with intelligence, and create the optimal combination. Creating
humans orders of magnitudes more intelligent than any human who has ever
lived.

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togedoge
Thanks! That is interesting. I would love to see that happen -- even if there
are ethical issues to consider. Maybe we can start by making the most
genetically intelligent rabbits or something.

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hyperpallium
mobile warning: 10MB

