Showing posts from 2018

Genetics, IQ, and ‘race’ – are genetic differences in intelligence between populations likely?

Last week (May 2nd 2018) the Guardian published a piece by me headlined “Why genetic IQ differences between ‘races’ are unlikely”. In it, I argued that the genetic architecture and evolutionary history of intelligence make it different from other traits and inherently unlikely to vary systematically for genetic reasons between large population groups.
Image credit: I was rather quickly (and, in some cases, rather aggressively) taken to task by a number of population geneticists on Twitter for being vague, overly general and hand-wavy, and for ignoring or not citing relevant papers in population genetics. Or indeed, for being flat out wrong. (See also a critique here). Some of those criticisms may well be valid, but some reflect the limitations of writing a short piece for the general public, so I wanted to go into more detail here on my reasoning.
The other criticism was that I seemed to be making statements as if they were str…

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?
 Image credit:
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…