Category: Science

Brian Palmer has a very weak article in Slate trying to make the case that “Twin studies are pretty much useless.” The article is supposed to be about the problem of twin studies as a method but it begins by raising the specter of eugenics. As if that were not enough guilt by association, Palmer then argues that twin studies threaten democracy or at least they would if they were true. (The argument is unclear but seems to rest on the false assumption that if genetics matters then nothing else does. Need I quote the tiresome point that poor eyesight has high heritability but that doesn’t make eyeglasses useless etc.)

After having muddied the waters, the author’s primary argument is this:

Twin studies rest on two fundamental assumptions: 1) Monozygotic twins are genetically identical, and 2) the world treats monozygotic and dizygotic twins equivalently (the so-called “equal environments assumption”). The first is demonstrably and absolutely untrue, while the second has never been proven.

On the first point, the fundamental assumption is not that MZ twins are identical but that they are more identical than fraternal twins. The math is a bit easier if you assume that MZ twins share all of their genes and fraternal twins share 50% on average but this is not necessary. In fact, if you take into account that MZ twins differ genetically this raises the variation that you should ascribe to genetics. If twin one smokes and twin two does not and you assume that they share 100% of their genes then you must conclude that smoking does not vary with genes. If the twins share only 99.99% of their genes then smoking may vary with genes.

On the second point (the equal-environments assumption), Palmer writes as if comparing MZ and DZ twins was the only source of heritability estimates. In fact, heritability estimates are found by looking at twins raised together and twins raised apart, siblings and siblings raised apart, parents and child correlations and so forth and the results from these studies are broadly similar.

Even more important, for an article that goes on about “modern genetics” the author seems completely unaware that it is now possible to do a whole-genome analysis. That is, instead of assuming that siblings share 50% of their genes on average it is possible to estimate, sibling-pair by sibling-pair, how many genes siblings share and then correlate that with various characteristics. Obviously, it takes a lot more data to do a study like this but it has been done. Visscher et al., for example, use data from 3,375 sibling pairs to estimate the heritability of height. Interestingly, they find a heritability of 0.8, very close to that found in traditional studies.

Using whole-genome methods it is not necessary to assume equal environments for MZ and DZ twins. In fact, using these methods you can do genetic studies across unrelated individuals. For example, in Genome-wide association studies establish that human intelligence is highly heritable and polygenic, the authors note:

Data from twin and family studies are consistent with a high heritability of intelligence, but this inference has been controversial. We conducted a genome-wide analysis of 3511 unrelated adults with data on 549 692 single nucleotide polymorphisms (SNPs) and detailed phenotypes on cognitive traits. We estimate that 40% of the variation in crystallized-type intelligence and 51% of the variation in fluid-type intelligence between individuals is accounted for by linkage disequilibrium between genotyped common SNP markers and unknown causal variants. These estimates provide lower bounds for the narrow-sense heritability of the traits.

Twin studies have their problems, just like any method. The thrust of recent advances–advances which have been made to analyze and surmount the kinds of objections that Palmer raises–however, is that the results from twin studies are robust.

Ok, here is a final and telling point.  Palmer argues that “Mutations and environmental factors cause measurable changes to the genome as life progresses.” Now that is true but you can judge how eager Palmer is to discredit twin studies regardless of the science by how he quickly concludes from this something which is truly laughable:

By the time a pair of twins reaches middle age, it’s very difficult to make any assumptions whatsoever about the similarity of their genes.

When we take a position that isn’t willing to embrace evolution, when we take a position that basically runs counter to what 98 of 100 climate scientists have said, what the National Academy of Science – Sciences has said about what is causing climate change and man’s contribution to it, I think we find ourselves on the wrong side of science, and, therefore, in a losing position….I can’t remember a time in our history where we actually were willing to shun science and become a – a party that – that was antithetical to science. I’m not sure that’s good for our future and it’s not a winning formula.

Here is more.  The recent evidence, by the way, is making matters look worse, not better.

From Anil Gupta, bad news:

To be sure, China’s R&D expenditure increased to 1.5% of GDP in 2010 from 1.1% in 2002, and should reach 2.5% by 2020. Its share of the world’s total R&D expenditure, 12.3% in 2010, was second only to the U.S., whose share remained steady at 34%-35%. According to the World Intellectual Property Organization, Chinese inventors filed 203,481 patent applications in 2008. That would make China the third most innovative country after Japan (502,054 filings) and the U.S. (400,769).

But more than 95% of the Chinese applications were filed domestically with the State Intellectual Property Office—and the vast majority cover “innovations” that make only tiny changes on existing designs. A better measure is to look at innovations that are recognized outside China—at patent filings or grants to China-origin inventions by the world’s leading patent offices, the U.S., the EU and Japan. On this score, China is way behind.

The most compelling evidence is the count of “triadic” patent filings or grants, where an application is filed with or patent granted by all three offices for the same innovation. According to the Organization for Economic Cooperation and Development, in 2008, the most recent year for which data are available, there were only 473 triadic patent filings from China versus 14,399 from the U.S., 14,525 from Europe, and 13,446 from Japan.

Starkly put, in 2010 China accounted for 20% of the world’s population, 9% of the world’s GDP, 12% of the world’s R&D expenditure, but only 1% of the patent filings with or patents granted by any of the leading patent offices outside China. Further, half of the China-origin patents were granted to subsidiaries of foreign multinationals.

That’s the worst news you are likely to read today.  By the way: “…the allocation of government funds for R&D projects is highly politicized.”

The glasses can send me this information thanks to a built-in camera linked to software that analyses Picard’s facial expressions. They’re just one example of a number of “social X-ray specs” that are set to transform how we interact with each other. By sensing emotions that we would otherwise miss, these technologies can thwart disastrous social gaffes and help us understand each other better. Some companies are already wiring up their employees with the technology, to help them improve how they communicate with customers. Our emotional intelligence is about to be boosted, but are we ready to broadcast feelings we might rather keep private?

For one thing, it could be used to improve the efficiency of sales calls, albeit at a cost to privacy.  The full article is here and Robin Hanson thinks we might ban such devices.

Terrafugia, Inc., the Woburn, Mass., company developing a flying car or “roadable aircraft” called the Transition, says it received special exemptions from the National Highway Traffic Safety Administration.

The exemptions, which are particular to vehicles that fly and drive on roads, will allow the company to begin delivering the Transition when it is ready late next year. They allow the Transition to use plastic windows instead of standard automotive safety glass, and tires that aren’t normally allowed on multi-purpose vehicles.

The company says laminated safety glass used on cars for decades would add too much weight and could fracture in a way that would obscure the pilot’s view through the windshield. Lightweight polycarbonate windshields used in aircraft are designed in part to withstand impacts with birds, which are generally more of a hazard to pilots than drivers.

The article is here and for the pointer I thank Alex.

It is an interesting question, incidentally, why pain has to be so damned painful. Why not equip the brain with the equivalent of a little red flag, painlessly raised to warn, “Don’t do that again”? In The Greatest Show on Earth , I suggested that the brain might be torn between conflicting urges and tempted to ‘rebel’, perhaps hedonistically, against pursuing the best interests of the individual’s genetic fitness, in which case it might need to be whipped agonizingly into line. I’ll let that pass and return to my primary question for today: would you expect a positive or a negative correlation between mental ability and ability to feel pain? Most people unthinkingly assume a positive correlation, but why?

Isn’t it plausible that a clever species such as our own might need less pain, precisely because we are capable of intelligently working out what is good for us, and what damaging events we should avoid? Isn’t it plausible that an unintelligent species might need a massive wallop of pain, to drive home a lesson that we can learn with less powerful inducement?

That is from Richard Dawkins, via The Browser, still the best site on the internet.