Thursday, January 22, 2015

Fat Tails, The Precautionary Principle, and GMOs

I recently just wrote a blog post over at my applied econometrics blog (Econometric Sense) about fat tails and risk modeling. At the end of the post I mentioned Nassim Taleb's paper regarding the precautionary principle and GMOs (Jayson Lusk has a nice discussion of this on his blog as well and Nassim was a guest with Russ Roberts recently on EconTalk) as an example of one related application. If we boil down the concept of fat tails, we are basically talking about the probability or frequency of some extreme event being higher than what we would expect under 'normal' circumstances. Here is a nice anectdote from the models and agents blog:

"It’s 10am, your rottweiler has just chewed your Italian leather boots, your wife has burnt your pancakes and your mistress is on the phone proclaiming that “it’s over because, really, you’re pretty lousy in bed.” Oh yeah, and while you’re at it, your broker is leaving you a message that the stock market is crashing and you’ve lost a third of your savings. A bad hair day? No, my friend. You’re likely living in a fat tail!..."

So in his paper, Nassim and his coauthors work through some pretty complicated mathematics and based on definitions related to things like fat tails, fragility, ruin, harm, uncertainty etc. (in the appendix) conclude that what they refer to as a non-naive version of the precautionary principle should be applied to GMOs.

I probably need to read the paper again and spend more time in the appendix and maybe it will all sink in, its technical. In the EconTalk podcast one interesting way Nassim presents GMOs is through a Hayekian lense:

"Hayek effectively looked at nature as a format by which things--he sort of like thought of nature directly and indirectly and thought of the organic directly or indirectly as operating according to his principle of distributed knowledge. And technologies. And tinkering--away from that central planning mode....But let's say now, a Soviet planner, one that comes to nature. Aha--GMOs."

Reading between the lines, I think he wants to think (which I concur) of nature as a spontaneous order of checks and balances and that recombinant DNA techniques are like a top down planning approach that ignores or bypasses this process. But...biotechnology actually represents a small incremental genomic disruption in a system compared to a wholesale genomic disruption like conventional breeding or mutagenesis (used in organic methods as well). If a Hayekian model applies, I would think you could make the same argument against other methods of crop improvement as well.

Again, I think Nassim's idea is that the spontaneous order of nature provides checks and optimizes the 'use of knowledge' within the natural system, but GMOs circumvent this in a way similar to planning in an economic system does (which leads to negative outcomes). This seems to also come out in his paper: 

"Unlike GMOs, in nature there is no immediate replication of mutated organisms to become a large fraction of the organisms of a species. Indeed, any one genetic variation is unlikely to become part of the long term genetic pool of the population. Instead, just like any other genetic variation or mutation, transgenic transfers are subject to competition and selection over many generations before becoming a significant part of the population. A new genetic transfer engineered today is not the same as one that has survived this process of selection."

"The limited existing knowledge generally does not include long term testing of the exposure of people to the added chemical, even in isolation. The evaluation is independent of the ways the protein affects the biochemistry of the plant, including interactions among the various metabolic pathways and regulatory systems—and the impact of the resulting changes in biochemistry on health of consumers."

I must give Nassim credit, in the podcast he makes it a point that verbalizing these notions of risk and ruin is much less precise than doing it mathematically. But, if we know nothing about the math, if we assume it is completely correct, I would think that if his mathematical reasoning would argue for the precautionary principle in the case of GMOs (because of genetic disruptions circumventing the protections we get from nature's spontaneous order) then it would apply in the same way to more drastic genomic changes associated with mutagenesis or crossing with wild relatives. What would we have left to eat? 

The literature certainly indicates that GMOs may be the less benign approach to crop improvement, and to appeal to Hayek in another way, our knowledge of the specifics of genetic disruptions from biotechnology is much more precise and less assuming than conventional approaches.

Research on Genomic Disruptions

Batista R and others (2008). Microarray analyses reveal that plant mutagenesis may induce more transcriptomic changes than transgene insertion. Proceedings of the National Academy of Sciences of the United States of America 105(9): 3640–3645

Baudo MM, Lyons R, Powers S, Pastori GM, Edwards KJ, Holdsworth MJ, Shewry PR. (2006). Transgenesis has less impact on the transcriptome of wheat grain than conventional breeding. Plant Biotechnol J. 2006 Jul;4(4):369-80

See also: Biotechnology and Genetic Disruptions

1 comment:

Levi Russell said...

I'm trying really hard not to just dismiss all this as the equivalent of anti-vaxxer nonsense. Taleb can draw up page after page of complex mathematics and not get close to the actual issue. The idea that biologists can't evaluate risks is absurd. The biologists are the ones who understand the causality. Statisticians can never claim that their models can capture real-world causality (n.b. this is coming from an applied economist).

Humans have been modifying plant and animal genes for thousands of years. The fact that the modern variant looks scary to Taleb doesn't make it dangerous.