While the ideas in the paper have some merit, I can't resist pointing out one of the flaws in one of the "major discoveries". The discovery that I am talking about is this one -
First, the estimated heritability of autism has been dramatically overstated.In very rough terms, this statement is basically saying that autism is not something that your parent's pass down to you but rather something that is caused by something else. The paper goes into some specific about what this could be, but I am going to focus on this one point for now.
To prove this point, the researchers analyzed some data -
To anticipate the main results of this article, we first demonstrate that autism heritability — defined in the narrow sense as the difference in concordance for autism between monozygotic (MZ) and dizygotic (DZ) twins is not as significant as typically believed.Of course, it always comes back to twins. Most other studies have shown that identical twins are more than twice as likely as fraternal twins to both have a form of autism. But here, the researchers are basically saying that this is not true - that identical twins are not much more likely to both have autism than fraternal twins.
If this result were true, it would signal a a major change in how we think about autism. But, as I was looking through the paper to see what numbers that the authors arrived at, I ran across this statement -
The administrative data we work with do not have a direct measure of zygosity, so we do not know from these data whether twins are MZ or DZ, which is central to the estimation of genetic influence.Wait, what?
One of the major findings of the paper is based on the difference between identical and fraternal twins but the data in the study does not have the ability to tell you which twins are identical and which aren't? So, how can any conclusion be reached about the differences between the two groups when you don't know what the groups are?
A simple and well-established rule that has been shown to give robust zygosity estimates has been developed for this purpose and has been widely used in research on twinning rates and a range of other research questions.So one of the "major discoveries" of the paper - one that disagrees with most other twin studies out there - is not based on actual data but a guess of what the data might look like?
It is a good thing that the proportion of twins that are identical is a constant (oh wait, it isn't) and that factors influencing twin births weren't changing drastically during the study period (oops, they were) and that we know that identical twins aren't more likely than fraternal twins to have autism in the first place (no clue).
There are so many unknowns and possible other factors involved that without this one little, tiny yet fundamental piece of information - whether a set of twins were identical or fraternal - the conclusion based on that data becomes nothing more than a educated guess.
Conclusions should be based on data, not guesses.