Why do lemons taste sour? The puzzle of innate qualia.

A really nice recent paper reported the identification of a family of proteins that seem to act as sour taste receptors. They are expressed in our taste buds and allow us to detect the positively charged hydrogen ions produced by acidic substances. This is important because it lets us identify foods that are unripe or spoiled by bacterial growth, like sour milk. The discovery of these sour receptors is a big step forward – it adds to our understanding of how different kinds of chemicals are detected in the sensory neurons of the tongue and processed in the brain. But it leaves one really big question unanswered – why do sour things taste like that?
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Why does eating a lemon produce that specific reaction – the scrunched up face, puckered lips, eyes squinting, head drawn back, eyebrows raised in surprise? This is an incredibly universal and apparently innate reaction – you can see it in unsuspecting babie…

Lessons for human genetics from genetic screens in model organisms

Why did the axon cross the midline? That seems like a simple enough biological problem to solve. In the developing nervous system, especially in the anatomically simple spinal cord, some nerve cells send a slender nerve fibre (called an axon) across the midline of the nervous system to connect to cells on the other side. The projections of other neurons are restricted to the same side as their own cell bodies. The connections between the two sides are crucial in coordinating movement of the two sides of the body. But, more importantly for this discussion, this system is simple enough to be genetically tractable – at least it seems so.
When I arrived as a graduate student in the lab of Corey Goodman at the University of California at Berkeley, his group had just carried out a genetic screen in fruit flies to try and understand how this developmental decision was controlled. Flies have an equivalent of a spinal cord, called the ventral nerve cord, and Corey and his colleagues had spent m…

Panpsychism – not even wrong. Or is it?


“Like father, like son”: Testing folk beliefs about heredity in the arena of assisted reproduction.

“The apple doesn’t fall far from the tree”. “Chip off the old block”. “Cut from the same cloth”. “Black cat, black kitten”. “Chickens don’t make ducks”. “He didn’t lick it off the stones”. “It’s not from the wind she got it”. “She comes by it honestly”.
Every culture seems to have its own phrases describing the power of heredity – not just for physical traits, but also for behavioural ones. (Those last three are peculiar to Ireland, I think). This folk wisdom, accumulated from centuries of observation of human behaviour, seems to reflect a widespread belief that genetic effects on behaviour and personality are strong, indeed dominant over effects of upbringing.
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Of course, folk wisdom can be wrong. And old folk sayings may not reflect current thinking – perhaps people’s opinions on the subject have changed. Indeed, if you were to take academic discourse on the subject as a barometer of views of the general public, y…