sorry, folks. there’s going to be another blogging lull around here for the next couple of weeks. for the same crazy, out-of-my-control reasons that i mentioned a couple of weeks ago.

i am around! just busy (d*ng it!).

in the meantime, here’s robert plomin on behavioral genetics. courtesy of DKshad0w! (^_^)


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scott has a post up — Five Case Studies On Politicization — in which he mentions the last post i wrote on rotherham, etc. — stop creating a climate of fear! i tried a couple of times to leave a comment there, but i keep getting an error message (“Not Acceptable!”), so since i’m absolutely lacking in patience, i’m just leaving my response here rather than to try and try again over there.

you might want to read scott’s whole post first. or at least section iii in which the gang-rape business is brought up. here’s my response:

@scott – “I have no doubt that her outrage is genuine. But I do have to wonder why she is outraged about this and not all of the other outrageous things in the world. And I do have to wonder whether the perfect fit between her own problems – trying to blog about race and genetics but getting flak from politically correct people – and the problems that made Rotherham so disastrous – which include police getting flak from politically correct people – are part of her sudden conversion to political activism.”

well, first of all, this wasn’t “sudden.” i’ve been writing about rotherham and the larger scandal of which it is a part since 2012. you’ve just missed it:

diversity über alles

secondly, why am i so particularly outraged about the pakistani gang-rape thing going on in britain (and very likely some other european countries — belgium for one)? i’m not sure — i’ve asked myself the same question. i think the reason is that it brings together multiple elements, each of which angers me on its own, but when added together absolutely enrages me. (i admit it — i become quite irrational when i think about rotherham, etc.) those elements are: the abuse of young children, ill-considered immigration policies, class “war” (or whatever you want to call it), and the seemingly willful ignorance of politically correct people. oh, and the lies told by the media, too, although that is sort-of a subset of political correctness really.

you might ask — in fact, you do — why don’t i get upset about other atrocities in the world. like, for example, FGM in sudan or egypt. well, while i do think that FGM is a terrible practice and people should stop it, i’m all for letting peoples decide how they want to conduct their affairs in their own countries. it’s no business of mine if in afghanistan or yanomamo society they marry girls off at age 12. it *is* my business when girls in the west are tortured — tortured — and pimped out by gangs of whomever. (you should know that i also lived not too far from rotherham for a handful of years, so i identify with the place and the people, as they say.)

however, and i think you may have missed this, the main target of my anger in that post was not the gang rapists or immigrants but the politically correct crowd, *specifically* the ones who scream RACIST!! at the drop of a hat. the social workers and police officers in rotherham were *very* clear on the fact that they held their tongues and did nothing out of fear of being labelled racists and, therefore, of losing their jobs. this is not a joke anymore. this is not a stupid argument on twitter or facebook where feathers might get ruffled, but everyone goes home pretty much unscathed. in this case, people got hurt. children got hurt. directly because of the climate of fear that politically correct idiots have created.

they need to know that they have blood on their hands this time. they need to start thinking about *exactly* what they’re achieving.

see also: sex and “the other”

(note: comments do not require an email.)

The Earliest Group Of Modern Humans To Branch Off Survived Until Just 2,300 Years Ago – h/t mr. robert ford!

Archaeologists unearth remains of oldest Norman ever found which ‘fills gap in our knowledge of pre-Neanderthal evolution’“On a bend of the river Seine near Rouen in Normandy, archaeologists have found the remains of the oldest Norman ever discovered. The three bones from the left arm of a pre-Neanderthal should shed fresh light on a little-known period. In particular, they could help scientists to understand the evolution of the squat, muscular hunters who died out 30,000 to 40,000 years ago, just after the first humans arrived in what is now Europe. The discovery of the bones at Tourville-la-Rivière, 14km south of Rouen, is exceptional because ‘this is a period with very few fossils’, according to Bruno Maureille, a palaeontologist at the National Centre for Scientific Research. He said the arm bones, dating from 200,000 years ago, in the Middle Pleistocene era, were ‘the only known example from northern Europe’.”

The first South Americans: Extreme living“After humans arrived in South America, they quickly spread into some of its most remote corners.”

How ancient DNA is rewriting human history“‘Human history is not one of stasis….’ The genetic record shows that for the past tens of thousands of years, mixed human ancestry is the rule and not the exception.” h/t hbd bibliography!

Treasure trove of ancient genomes helps recalibrate the human evolutionary clock

EmTech: Illumina Says 228,000 Human Genomes Will Be Sequenced This Year

Europe the birthplace of art? Cave art shows Indonesia has a claim“Using this method, the researchers determined that one of the hand stencils they sampled was made at least 39,900 years ago and that a painting of an animal known as a pig deer was at least 35,400 years old. In Europe, the oldest known cave painting was of a red disk found in a cave in El Castillo, Spain, that has a minimum age of 40,800 years. The earliest figurative painting, of a rhinoceros, was found in the Chauvet Cave in France; it goes back 38,827 years.”

Ancient Plague’s DNA Revived From A 1,500-Year-Old Tooth – justinian plague. – h/t debbie kennett!

New Genetic ‘Operating System’ Facilitated Evolution of ‘Bilateral’ Animals

Draft of paper about Amish“[T]he difference in mean AQ ['amishness'] between young Amish men and their non-Amish neighbors is about 2.8 standard deviations. In the IQ world this would correspond to a group different of 42 points. In the stature world this would correspond to a height difference of about 8 inches.” – from henry harpending. see also Amish v. English from steve sailer.

Does evolutionary theory need a rethink? – no. – see also Evolution Ever Evolves from razib.

Widespread signals of convergent adaptation to high altitude in Asia and America

Evolutionary behavioral genetics“We describe the scientific enterprise at the intersection of evolutionary psychology and behavioral genetics — a field that could be termed Evolutionary Behavioral Genetics — and how modern genetic data is revolutionizing our ability to test questions in this field.”

coolest story! a MUST READ!: Finding Clues in Genes of ‘Exceptional Responders’“One study at Memorial Sloan-Kettering Cancer Center tested a drug called everolimus that is approved for kidney and breast cancer. Researchers asked if it could treat bladder cancer. Forty-five patients received the drug. Two responded. ‘The verdict was, “O.K., I guess everolimus does not work in bladder cancer,” ‘ said Dr. David Solit, the principal investigator. But then there were those two patients — one, in particular. Her cancer had spread to her abdomen. She was expected to live less than a year, and there was no treatment for her. But with everolimus, her tumors disappeared. ‘I was at a clinical meeting, and everyone was saying this drug did not work,’ Dr. Solit said. ‘I said, “It worked for her.” ‘ The investigators found out why. Her cancer had a mutation in a gene that made it dependent on a protein, mTOR, for growth. Everolimus squelches the activity of mTOR. The woman is still taking everolimus, and her cancer has not recurred.”

Are adoption gains on the g factor? A meta-analysis“g loadings and adoption gains yield a correlation of −1.” – from te nijenhuis, jongeneel-grimen, and armstrong. – h/t erwin schmidt!

The high heritability of educational achievement reflects many genetically influenced traits, not just intelligence“Genetic research has shown that intelligence makes a major contribution to the heritability of educational achievement. However, we show that other broad domains of behavior such as personality and psychopathology also account for genetic influence on GCSE scores beyond that predicted by intelligence. Together with intelligence, these domains account for 75% of the heritability of GCSE scores. These results underline the importance of genetics in educational achievement and its correlates.” – (because there’s more to hbd than just iq!)

Psychology in the 21st Century“Highly recommended: slides from a recent talk ['The Genetic Architectures of Psychological Traits'] by James Lee.”

Replicability and Robustness of Genome-Wide-Association Studies for Behavioral Traits“Our results show that large and therefore well-powered genome-wide-association studies can identify replicable genetic associations with behavioral traits.”

Intelligence Is Critical to the Future of Humankind“A conversation with Douglas Detterman, editor of the journal Intelligence” – h/t holtz!

Crime, income, educational attainment and employment among immigrant groups in Norway and Finland – new paper from emil kirkegaard.

Is there no population genetic ‘support’ for a racial hereditarian hypothesis? – h/t jayman! who tweeted: “Racial admixture studies across the Americas all find relationship between ancestry & educational attain. as expected.”

Heavier babies do better in school“A study of children in Florida found that those who were heavier at birth scored higher on math and reading tests in the third to eighth grades.”

Practice Does Not Make Perfect“We are not all created equal where our genes and abilities are concerned.”

another MUST READ, this one from steve sailer: The Bell Curve 20 years later: A New Caste Society. – see also: ‘The Bell Curve’ Turns 20 from robert verbruggen.

Race, Income, and Test Scores – also from robert verbruggen.

The role of lactase persistence in precolonial development“It is shown through a number of specifications that country-level variation in the frequency of lactase persistence is positively and significantly related to population density in 1,500 CE; specifically, a one standard deviation increase in the frequency of lactase persistent individuals (roughly 24 percentage points) is associated with roughly a 40 % increase in precolonial population density.”

Common variants and the biological and genomic architecture of human height“The latest from the GIANT collaboration. They are also estimating ~ 10k causal variants in total, with 697 now identified at genome-wide significance…. With ~1k variants to work with, we can expect progress on the question of whether the ~1 SD group difference in height between north and south europeans is due to selection. Uniformly higher SNP frequencies in the north for variants that slightly increase height would be strong evidence of selection.” – original research paper: Defining the role of common variation in the genomic and biological architecture of adult human height

Big Chickens“More evidence that common genetic variants can produce many standard deviations of change in average phenotype.”

The Giant Mutations in the Human Genome“It turns out that there is a class of giant DNA mutations that share features of developmental disorders: They are surprisingly common, frustratingly diverse, and hard to categorize. Researchers are now discovering that these mutations play a big role in developmental delay disorders. The baffling symptoms are a consequence of the underlying genetic turmoil…. These large mutations are called ‘copy number variants’ or CNVs, and they add or subtract copies of genes.”

Genetic and nonshared environmental factors predict handgun ownership in early adulthood“Analyses revealed a stronger concordance for gun ownership among identical twins as compared to fraternal twins and univariate ACE model results indicated genetic (57%) and nonshared environmental (43%) factors explained the variance in handgun ownership.” – h/t amir sarislan!

Different tastes for different individuals – h/t jayman! who tweeted: “Genetic evidence of recent evolutionary differentiation in taste response across the world.”

From Kale To Pale Ale, A Love Of Bitter May Be In Your Genes

Here’s why you’re bouncing off the walls: the genetics of coffee consumption“Coffee consumption has now been linked to eight genetic variants.”

Do Political Attitudes and Religiosity Share a Genetic Path? – h/t avi tuschman!

Unpacking “evil”: Claiming the core of the Dark Triad

The slow and fast life histories of early birds and night owls: Their future- or present-orientation accounts for their sexually monogamous or promiscuous tendencies – uh oh. i’m a night owl!

Later school start time ‘may boost GCSE results’“Thousands of teenagers are to get an extra hour in bed in a trial to see whether later school start times can boost GCSE results. University of Oxford researchers say teenagers start functioning properly two hours later than older adults…. Prof Russell Foster, director of sleep and circadian neuroscience at Oxford University, said that getting a teenager to start their day at 07:00 is like an adult starting theirs at 05:00.”

How Iceland’s Genealogy Obsession Leads to Scientific Breakthroughs

Infidelity and kin selection: Does cheating seem as bad when it’s “all in the family”?“[C]ontrary to predictions generated by kin selection theory, participants tended to report that they would feel worse if their partners had sex with their relatives. We propose several explanations for the current findings and discuss their implications for kin selection theory.” – h/t neuroskeptic!

Anthropologists find that even among egalitarian forager-farmers, social status can impact health and happiness

Africa is on time“Using survey data on African income distributions and national accounts GDP, we estimate income distributions, poverty rates, and inequality indices for African countries for the period 1990–2011. We show that: (1) African poverty is falling rapidly…. All classes of countries, including those with disadvantageous geography and history, experience reductions in poverty. In particular, poverty fell for both landlocked as well as coastal countries; for mineral-rich as well as mineral-poor countries; for countries with favorable or with unfavorable agriculture; for countries regardless of colonial origin; and for countries with below- or above-median slave exports per capita during the African slave trade.” – h/t mugwump!

Ethnic Divisions and Production in Firms“A body of literature suggests that ethnic heterogeneity limits economic growth. This paper provides microeconometric evidence on the direct effect of ethnic divisions on productivity. In team production at a plant in Kenya, an upstream worker supplies and distributes flowers to two downstream workers who assemble them into bunches. The plant uses an essentially random rotation process to assign workers to positions, leading to three types of teams: (a) ethnically homogeneous teams, and teams in which (b) one or (c) both downstream workers belong to a tribe in rivalry with the upstream worker’s tribe. I find strong evidence that upstream workers undersupply non-coethnic downstream workers (vertical discrimination) and shift flowers from non-coethnic to coethnic downstream workers (horizontal discrimination), at the cost of lower own pay and total output.” – spite! it’s so funny. – h/t ben southwood!

Statistics in educational research – on statistical significance and p-values from andrew sabisky.

Social Network Analysis Shows Direct Evidence for Social Transmission of Tool Use in Wild Chimpanzees – h/t razib!

Reparations for Slavery? – from those who can see.

Researchers Have Identified The Origin Of The HIV/AIDS Pandemic

The Human Genome Is In Stalemate in the War Against Itself

Winter is coming: do you really need a flu jab? – from tom chivers who tweeted: “On the flu jab, and the evidence, and lack of evidence, thereof.”

(Re)Becoming Human“As the sun set over Lake Eyasi in Tanzania, nearly thirty minutes had passed since I had inserted a turkey baster into my bum and injected the feces of a Hadza man – a member of one of the last remaining hunter-gatherers tribes in the world – into the nether regions of my distal colon. I struggled to keep my legs in the air with my toes pointing towards what I thought was the faint outline of the Southern Cross rising in the evening sky. With my hands under my hips – and butt perched against a large rock for support – I peddled an imaginary upside down bicycle in the air to pass the time as I struggled to make sure my new gut ecosystem stayed put inside me. With my butt cheeks flexed and my, you know what puckered, I wondered if I had just made a terrible mistake….”

Strange Seeds on Distant Shores – a look at albion’s seed and american nations, etc., etc. – h/t jayman!

Remains of Alexander the Great’s Father Confirmed Found

Diversity: A Nature & Scientific American special issue – *facepalm*

Philosophy is a Bunch of Empty Ideas: Interview with Peter Unger – (^_^)

bonus: New particle is both matter and antimatter – phreaky physics!

bonus bonus: Physicist turns smartphones into pocket cosmic ray detectors – really cool physics!

bonus bonus bonus: A Kindle loaded with e-books is heavier than an empty one – so there!

bonus bonus bonus bonus: The Questioning of John Rykener, A Male Cross-Dressing Prostitute, 1395 (in london) – shocking!

bonus bonus bonus bonus bonus: Around the world in 400,000 years: Journey of the red fox“[T]his new research shows that the red foxes of North America and Eurasia have been almost entirely reproductively isolated from one another for roughly 400,000 years. During this time, the North American red fox evolved into a new species distinct from its Old World ancestors…. The new genetic research further suggests that the first red foxes originated in the Middle East before beginning their journey of colonization across Eurasia to Siberia, across the Bering Strait and into North America, where they eventually founded the North American population.”

bonus bonus bonus bonus bonus bonus: Cosmic Karma: Mosquitoes Have Flying, Blood-Sucking Parasite of Their Own

bonus bonus bonus bonus bonus bonus bonus: Kangaroos have three vaginas!

(note: comments do not require an email. and just to make your head asplode…. (^_^) )

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columbus landing on hispanola

spock star wars mashup

there were a handful of science news stories out this past week about how a couple of researchers reportedly discovered a case of “group selection” in certain spiders (Anelosimus studiosus or tangle web spiders): for example, see Proving ‘group selection': Spider colonies need the correct mix of personalities to survive and Elusive Form of Evolution Seen in Spiders. a bunch of people on twitter got all excited about this finding, because they wonder if (some of them i think hope that) group selection might also apply to groups of humans. i agree: that would be very interesting to know one way or the other. so i went and read the original paper — Site-specific group selection drives locally adapted group compositions — to see what these guys had found.

before i offer up my admittedly layman’s thoughts on this paper, let me first say what a really neat piece of research this was! if there existed a nobel prize for geeky dedication and sheer nerdiness, these guys would’ve won it! — and i mean that as a compliment! the researchers, pruitt and goodnight, studied groups of tangle web spiders in the wild, captured some and brought them back to their lab, conducted personality tests on the spiders (yes! there are apparently personality tests for spiders!), painstakingly painted those little dots on the backs of individuals to keep track of them (you know, like how they sometimes do with bees), bred the spiders, released new groups of them back into the wild, and checked up on them one and two generations later to see how they fared. this is some really cool research! nerds ftw! (^_^)

but did they find evidence for group selection?

weeeellll, no, i don’t think so.

to begin with, right at the start of the paper pruitt and goodnight (p&g) define group selection as “selection caused by the differential extinction or proliferation of groups.” eeeehhhh, as far as i understand it, that’s not really the definition of group selection, and even the authors admit that their definition is a “broad” one.

group selection is more accurately defined as when “natural selection [operates] between groups of organisms, rather than between individuals.” in contrast, p&g’s broad definition could theoretically include cases in which natural selection worked between individuals (individual selection) which also just incidentally happened to result in the proliferation of the group to which the lucky selected individuals belonged. an example of this is the selection for lactase persistence in some humans in which those individuals who could drink milk as adults were able to leave behind more descendants than those individuals who could not. while lactase persistence might indeed have benefitted groups of milk-drinking individuals, natural selection did not act on the group, but rather on the individuals in that group. (pretty sure i stole this example from @supermisdreavus, but i can’t find where he said that right now.)

in other words, you always need to work out what the target of selection is: the group or the individuals that make up the group. (really it’s ultimately the genes, but — oh, nevermind.) remember that “‘a fleet herd of deer’ is really just a herd of fleet deer.”

so, really, the discussion could end right here, because i don’t think the authors are talking about group selection proper. but, since i’ve read the whole paper, i’ll carry on. (yes, i’m one of those people who’s never learned to quit while they’re ahead!)

a. studiosus spiders live either as solitary individuals or in groups where they cooperate on tasks like hunting and the raising of young. the individuals that live together in groups are, on average, more closely related to one another than those that live alone [pdf] — they’re generally as related to one another as though they were half-siblings. one reason why they’re probably not more related to one another in these groups — like to the degree that ants or bees in colonies often are — is that the males move between groups. remember that.

the personality types of the individual spiders in a. studiosus groups come in two sorts: docile and aggressive. the docile spiders are typically pretty laid back and aren’t much bothered by the presence of other spiders (even spiders from other species), whereas the aggressive individuals like their space — they’ll chase off other individuals. individuals of both types are found in groups of a. studiosus, but the frequencies vary. from the paper:

“At…high-resource sites, small colonies were dominated by docile females and the frequency of aggressive individuals increased with colony size. By contrast, at low-resources sites, small colonies were dominated by the aggressive phenotype and the frequency of the docile phenotype increased with colony size.”

well, that doesn’t sound too surprising at all. in locales where there is plenty of resources, there are more laid back individuals in the colonies, prolly ’cause being laid back works just fine. in areas where resources are lacking, more aggressive individuals do better. btw, they found that the heritability of these personality types in the spiders is 0.66.

groups that have more docile individuals (i.e. the ones in high-resource areas) are at a greater risk of invasion by other types of spiders which, over the long-term, tends to be a really bad thing for an a. studiosus colony (i.e. it’s usually destroyed). groups that have more aggressive individuals (i.e. the ones in low-resource areas) tend in bad times to experience too much “egg case cannibalism.” needless to say, that’s not a good thing over the long-term either.

what p&g did in their study was to introduce into the wild — into differing environments — groups having varying frequencies of these personality types [source]:

“He [pruitt] took spiders from warrior-heavy colonies and used them to assemble new groups that were heavy on the nannies. He also used spiders from mostly docile colonies to create warrior-laden groups. In addition, he assembled control groups that matched the composition of their original groups.”

what they found was that after three generations:

“60 percent of the colonies were extinct. Control groups that returned to their ancestral homes tended to do well, and those that were transplanted into a new environment generally died. Neither of these outcomes was much of a surprise.

The most interesting results came from colonies made up of spiders that had been forced into a composition different from the one they grew up in — warrior-majority colonies containing spiders from mostly docile groups, for example. The colonies whose composition fit the new environment tended to survive. But over time, surviving colonies reverted to their members’ original group composition. The warrior-majority colonies went back to having more nannies, for example. On the face of it, this is bizarre behavior; if the colonies are well-suited to their environment, why not maintain that ratio? It seems that some innate sense, perhaps encoded in the spiders’ genes, pulled the colony back to its original configuration, even though this change meant the colony would perish.”

well, i dunno. is that really “bizarre behavior?” i mean, if the personality types of a. studiosus are really highly heritable (0.66), is it strange that a population having come from a bunch of docile individuals should regress toward a docile mean? and vice versa? don’t forget, too, that the individuals in these groups are all related to one another as though they were half-siblings, so presumably individuals of either personality type might carry a great many genes of the other type in their genomes. (don’t know about that — i’m just guessing here, tbh.)

what really made me question whether or not this is “bizarre behavior” is the way in which the researchers bred the spiders when they had them in captivity [from the methods section at the end of the paper]:

“Females were mated randomly to a male of like behaviour type from their same source population, but which was collected from a source colony >5m distance.”

hmmmm. i dunno about that. they mated all the females with males of the same personality types, docile or aggressive? i’m guessing that they did this in order to reduce the number of possible confounding factors in the study, but i’m afraid they might’ve added something to the mix here that wouldn’t be found in nature, i.e. a 100% assortative mating rate (for personality type). mightn’t this almost guarantee that individual spider lineages would regress to their original personality-type means? docile females always mated with docile males and aggressive females always mated with aggressive males? that seems unlikely to happen in nature, especially given the fact that the males normally leave their colonies and move to others. (btw, male a. studiosus spiders prefer moving into colonies over mating with lone females. typical males, favoring harems! (~_^) )

p&g offer a number of explanations for how the frequencies of personalities in the groups might change over time:

“How native spiders are actually able to adjust their composition is unknown, but plausible regulatory mechanisms include developmental plasticity in the docile:aggressive phenotypes, policing of group membership, phenotype-biased dispersal, and/or selective cessation of reproduction.”

they reject the first explanation (the plasticity one) on the basis (in part) of the rather high heritability of spider personality types which they found. i’m inclined to agree with them on that.

out of their other reasons, policing of group membership and selective cessation of reproduction are behaviors that can be easily explained by natural selection between individuals, especially in populations that have rather highly related individuals so that levels of altruism are pretty high. the selective cessation of reproduction occurs, for instance, in some ant colonies since, due to the really high degrees of relatedness between individuals, the inclusive fitness payoffs are really large (eg. if you share three-quarters of your dna with your sister’s offspring, there’ll be a greater genetic payoff in helping her to reproduce rather than reproducing yourself, since you’d only share half of your genome with your offspring). that’s individual selection, not group selection. h*ck! both behaviors also occur in meerkat groups, although they, of course, show much less specialization of individuals than ants or bees. the policing of group membership can also be plausibly explained by natural selection between individuals — for example, aggressive individuals keep at bay all sorts individuals because that’s good for aggressive individuals (who are typically found in sparse environments).

so, i’m not at all convinced that pruitt and goodnight have found an example of group selection. i think they’ve found that genetics (as indicated by the heritability of the spiders’ personality traits) and natural selection certainly shape the average characteristics of groups, but it looks to me as though the seemingly “bizarre behaviors” that they found can easily be explained by individual selection. in fact, i’m more than a little concerned that due to the way they bred the spiders, p&g may have affected the outcomes of the reintroduced groups.

see also: The False Allure of Group Selection from steven pinker.

(note: comments do not require an email. a. studiosus group web!)

so this paper was making the rounds on twitter earlier in the week…

Demonstrating the Validity of Twin Research in Criminology [pdf]

…and everyone was like, “you have GOT to read this!” so i did. and, yeah, it’s really good! i highly recommend having a read of it.

the paper was written as a response to another paper entitled Pulling back the curtain on heritability studies: Biosocial criminology in the postgenomic era.

postgenomic? wt…? what planet do those guys live on?

anyway…Demonstrating the Validity makes many very right and very interesting points including the following:

1) a common assumption in behavioral genetics analyses is that human matings are random (they’re not — there’s a whole lot of assortative mating when humans go forth and multiply) and that assumption can lead to an underestimate of heritability estimates.

2) another assumption — the equal environments assumption (i.e. that both identical and fraternal twins share equal environments as kids) — leads to an overestimate of heritability estimates.

the authors of the paper show, however, that since these two assumptions are often found together in twin studies, that the over- and underestimates wind up more or less balancing each other out (see below — and see the paper!).

(i, of course, couldn’t help thinking that if assortative mating leads to underestimates of heritability, what would lots of inbreeding in a population do? so far, all twins studies have come from w.e.i.r.d. populations, though — afaik — so the inbreeding issue prolly doesn’t matter. but, if you should ever see some heritability estimates coming out of saudi arabia or sicily, heads up!)

other important points from the paper [my emphases in bold]:

When multiple divergent methods converge to illustrate a consistent finding, it is logically reasonable and empirically sound to accept as valid the results of the divergent methods. The primary reason for such a conclusion is the nonoverlapping assumptions underlying the various methods. This dynamic is illustrated in the convergence in findings between classical twin design studies and various molecular genetics methodologies. GCTA and CSG studies are examples of methodologies that are not subject to the same assumptions as classical twin designs and yet provide convergence in terms of the differential influence of genetic and environmental factors on a variety of behavioral phenotypes, including antisocial behavior. In direct contrast to the appraisal provided by Burt and Simons, the most cutting-edge research emanating from molecular genetics relies heavily on the findings of classical twin design studies and is continually providing empirical support for the validity of such studies.”

oh yeah!

also:

“We have shown empirically that violations of the assumptions of behavioral genetics studies do not invalidate heritability estimates. This is not a matter of opinion but a matter of mathematical evidence. Under certain conditions, our calculations and simulations revealed that heritability estimates will be slightly upwardly biased (probably no more than 5–10 percentage points). Under other conditions, heritability estimates will be downwardly biased (probably no more than 5–10 percentage points). Under the most likely condition, where multiple violations occur simultaneously, the biasing influences of assumption violations wash out, with upwardly biasing factors canceling downwardly biasing factors. Moreover, the overall pattern of findings flowing from the 61 studies examining the EEA revealed the same conclusions offered by our calculations and simulation data. Needless to say, no ‘fatal flaw’ in behavioral genetic methodologies or assumptions has been discovered and the conclusion that ‘all of these models are biased toward inflating heritability and underestimating shared environmental influences’ (Burt and Simons, 2014: 226, emphasis in original) is unequivocally incorrect.”

good stuff! read the whole thing here! and don’t miss all the supplementary materials here!

(note: comments do not require an email. identical. almost.)

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