Even experts are ignorant What crayfish can teach us about the limits of human knowledge

Every summer, bookshops lay out stacks of blockbusters designed to be devoured in an afternoon and forgotten in a week. But at UnHerd we prefer books that leave a lasting impression. In this series of Summer Reads, our contributors recommend overlooked books that will engage and enrich you, not just distract you.

At the absolute heart of our current political and cultural turmoil is the issue of authority. Epistemic authority, if you want to be fancy about it: the difficulty of knowing what’s true, and who we can trust to tell us the truth. This ties together the widespread mistrust of “elites” and the “mainstream media”, the fear about the way in which data can be used to manipulate us, the notorious rejection of “experts” and the universal scourge of “fake news”.

So if you were looking for a book that touches on this issue, but does so in an original enough way to mark it out from its hordes of competitors – and an enjoyable enough way to be read on a sun-lounger – you could do a lot worse than Michael Blastland’s thought-provoking The Hidden Half: How The World Conceals Its Secrets.

There are scores of books – from Daniel Kahneman’s Thinking Fast and Slow to Hans Rosling’s Factfulness – that investigate the cognitive biases and blind spots in the human brain, which form the basis for behavioural economics and the dark psychological arts of political campaigning. We’ve all now read a lot about the recency effect, availability biases, confirmation bias, anchoring and all the rest of it; we’re quite happy to trust the idea that our own minds are untrustworthy.

Blastland’s approach differs a little bit. Instead of concentrating on how our brains lead us astray, he looks instead at how much more mysterious and unknowable the outside world actually is – even were we able to look at it straight.

And, most winningly of all, he does so with special reference to a species of parthenogenetic crayfish.

Here’s a thing. In 1995 in an aquarium in Germany, this crayfish called the marmokrebs appeared out of nowhere. It hadn’t teleported in: it had come into being through (we assume) a random mutation. And the first thing scientists noticed about this new species was that there weren’t any males. Every marmokrebs was genetically identical: a clone of a single ancestor, the marmokrebs Eve.

This offered scientists a fantastic opportunity to disentangle nature and nurture. If members of the species are all genetically identical, any differences must – as anybody would happily concede – down to environmental influences, right? So experiments were made in which marmokrebs were raised in utterly identical controlled environments – same water pH, same food, same light, same temperature, the whole works.

And here’s the marmalade-dropper: these genetically identical, identically raised crayfish were wildly, wildly different from each other. They varied in size by as much as twenty times; they had different numbers of mouthparts and wholly different markings; they reproduced at different times; they exhibited entirely individual behaviours and preferences; they showed preferences for different foods.

In practically every respect, they were as different as could be.

So what caused these differences if not genetics or environment? Answer: we don’t know. And most laypeople – myself included, before I’d read Blastland’s book – didn’t even know we didn’t know. You, like me, probably thought that the argument in science was between genes and environment; not between genes and environment and… this other thing. Yet this other thing – this hidden half, called “enigmatic variation” – doesn’t just apply to crayfish. As much as half of human variation can’t be accounted for, writes Blastland, by either genetic or environmental factors.

The story is a caution against the idea that such knowledge as we have is a stable or reliable thing. And from there, Blastland roams across vast areas of inquiry, showing us how little we actually know.

You all know by now, for instance, that economic forecasting isn’t hugely reliable; perhaps it seems obvious that that’s in the nature of the thing. Animal spirits, irrational exuberance and all that, right?

But economic reporting, it turns out, is just as dodgy. Not only do we not know what’s going to happen, we don’t know what did happen. ONS figures for the economy two or three years ago continue to be revised in light of what has followed – and are often subject to confidence margins that can make the difference between a boom and a recession (Blastland cites one where a fall in unemployment of 3,000 was sombrely reported with a confidence margin of +/-77,000 – i.e. the figure could be a rise of 74,000 rather than a fall of 3,000).

And then there’s the “replication crisis” in the social sciences, where results on which whole subsequent fields of research have been built turn out to be, literally, junk science. Again, as many as half of the accepted results in the whole of social science or medicine are feared to be unreliable or plain wrong. The experiments simply don’t replicate. Even medicines that we know work may only work for a tiny percentage of patients – and we can’t predict which ones and we don’t know why.

Blastland’s book is invigorating, though, because it’s not making the case for disregarding all our knowledge about the world, rejecting any sort of expertise or academic data and going with our tribal instincts. Rather, he argues that we need to be humbler in our approach to what we do and don’t know and the methods we use to arrive at our conclusions.

Politicians, scientists and reporters should put aside the blustering pretence of absolute confidence and – by sharing their doubt and caution – become more trustworthy. The first step to understanding the world better is acknowledging the limits of our current understanding. To be able to say: it’s more complicated than it looks. The wise man, as it’s sometimes said, knows how little he knows.

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Sam Leith is literary editor of The Spectator. His latest book is The Haunted Wood: A History of Childhood Reading.

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