There's no such thing as a "gene for language". A Tweetorial to help explain why. In one branch of human genetics we search for correlations between particular gene variants that people carry and variations in an observed trait (normal variability and/or pathology)...1/9
"A gene for X" has become convenient shorthand to talk about associations between variation at these distant levels (genes & traits). This fuels a popular misconception of genes as abstract entities that can directly specify traits, including key aspects of human behaviour...2/9
What do genes really do? Many carry info for building proteins - strings of amino acids that fold into specific 3D structures with distinct jobs. Your genome has >20,000 such genes, encoding the molecular machinery of a cell (enzymes, signals/receptors, transporters, etc)...3/9
A brain is built via diverse cellular mechanisms. Precursors of neurons divide & proliferate, move to their final locations, become specialized, with outgrowths (dendrites/axons) that connect to other neurons. All these processes rely on networks of proteins working together..4/9
Learning = strengthening/weakening of connections in relevant brain circuits. Genes & proteins play crucial roles in those processes too. BUT there's no 1-to-1 mapping between a single gene & any specific neural circuit. Mappings from circuits to behaviour are also complex...5/9
An example. We found that people with rare mutations of the FOXP2 gene have speech & language deficits, while general cognition is less affected. It's frustrating how often FOXP2 is dubbed the "gene for language", despite us emphasizing how misleading this framing can be...6/9
FOXP2 encodes a protein that switches on/off many other genes, not just in brain, also some non-neural tissues (e.g. lung, gut, heart). It's not exclusive to humans, but has an evolutionary history spanning hundreds of millions of years. We see it in rodents, birds, fish etc..7/9
A few subtle, potentially interesting, changes to FOXP2 sequence arose on our lineage. But contributions of this gene to human traits are built on functions that are evolutionarily ancient. Experimental data suggest complex effects on neural connectivity & plasticity...8/9
FOXP2 is not here specially to bestow you with the gift of the gab. It has multiple roles in diverse tissues, across many species. Mutations have disproportionate effects on speech & language; asking how/why gives useful insights. Nuance is crucial, no language genes required.9/9
