Heritability of life span is about 50% when heritability is redefined

Related: https://news.ycombinator.com/item?id=46845650

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Pertinent quote from this article:

Everyone seems to be interpreting this paper as follows:

    Aha! We thought the heritability of lifespan was 23-35%. But it turns out that it’s around 50%. Now we know!

I understand this. Clearly, when the editors at Science chose the title for this paper, their goal was to lead you to that conclusion. But this is not what the paper says. What it says is this:

    We built a mathematical model of alternate universe in which nobody died from accidents, murder, drug overdoses, or infectious disease. In that model, heritability was about 50%.