Saturday, January 28, 2017

The limits of biological designs

Allometry, biological constants, and theoretical limits to human IQ augmentation. .

Karlin tweeted - Are there any good articles making the case that IQ augmentation thru GWAS/CRISPR will be *harder* than Hsu/@razibkhan/@charlesmurray think?

That discussion thread mentions Kevin Mitchell's piece on mutation load (genetic load) as decreasing human intelligence from some ideal (Platonic form?) That is the first idea that came to my mind and it almost certainly plays some large role. But I'd like to suggest another way of looking at limits to IQ augmentation.

Allometry scaling is a way of getting at biological features that are constant across species by adjusting (typically) for body size. (Allometry seems to have some of the appeal in biology that physical constants do in physics.)

For flavor.
Sizing Up Allometric Scaling Theory (2008)
Wikipedia for general background,

Wikipedia mentions (quoting here)
West, Brown, and Enquist in 1997 derived a hydrodynamic theory to explain the universal fact that metabolic rate scales as the ¾ power with body weight. They also showed why lifespan scales as the +¼ power and heart rate as the -¼ power. Blood flow (+¾) and resistance (-¾) scale in the same way, leading to blood pressure being constant across species.[31]

The limit on total lifespan (i.e. maximum lifespan) of species being scaled to body weight suggests a limit across species on the evolutionary design of heart muscle (or cardiovascular systems.)
(Which by the way is why I find hummingbirds interesting, for if any species has broken the design barrier on hearts it is most likely them.)

It doesn't seem implausible to me that in the evolutionary design process of human brains those that are functioning at around 160 are already at or near the limit of maximum biological design, in the same way as heart muscle tissue -- Though with the difference being that humans are the solitary species that have reached such a hypothetical limit first. (I tend toward skepticism about the ability of current IQ test designs to meaningfully discriminate between IQ's in the highest ranges.)


  1. .. And tying it closer to the cardio-vascular limitations, recent article saying cerebral blood flow increased 600 percent in human lineage. ..

  2. CRISPR IQ's

    "Natural selection uses up genetic variation" is an old debate, with recent evidence accumulating in favor of more soft sweeps than hard sweeps. Changes in existing gene allele frequencies, versus new alleles through mutations.)
    (The famous Hawks et al paper from years ago on IQ evolution was largely framed around hard sweeps, if I recall correctly. )

    Selection strikes back softly, by Razib Khan (Feb. 2017) .. @gnxp_posts

    It seems to me this might be an additional argument toward the idea that already existing available genetic resources have been optimized for maximum intelligence around IQ's of 160.

    In general, I think crispr IQ's will almost certainly be 'a thing' to some degree, but I suspect pushing IQ's much above 160 in less than 20 years is 'only' around 20 percent, if that.

    But there is another important additional point that needs making here. People vastly underestimate the difference between IQ's of 160 and IQ's of 140, let alone 100. There are many reasons for this and a good deal of writing could be spent on this topic. It's informational filter bubbles all the way up. People self-assort in many ways into social groups where the individual members tend to have similar IQ's. This is especially true in Junior High School through graduate school when social attitudes and interaction styles are being calibrated. Then there are also the issues of group IQ (See Timothy Bates's recent paper on this), national IQ's, and 'smart fractions' of national IQ's. One of the under-sufficiently-addressed issues in recent globalization I think is the increased mobility and honest-signaling of talent resulting in concentrations in the most successful super-giant tech corporations. It is talked and written about in a vague way, but I want more numbers.

    Even if crispr IQ's tops out at around 160, and only 1 percent of the population of some country (even a small country) uses the technology, I think the effects will be history-altering.