The September issue of Cognition, a psychology journal, includes an article (abstract) by Simon Fisher in Oxford that reviews the current understanding of the FOXP2 gene, sometimes called (in a gross mischaracterization) “the language gene.” Fisher was a member of the team that originally reported the gene in a letter published in Nature (available here).
News of a gene linked to language caused an immediate sensation and has inspired extensive research and even more speculation. If you believe that speech evolved from sign language, there is peer-reviewed, published material saying FOXP2 supports your case (e.g., here). If you believe the critical step in language was the rise of a recursive syntax, again there is FOXP2 material for you to cite (see here). Schizophrenia is your field? Check out FOXP2 (e.g., here).
There has, of course, also been much experimental and clinical work exploring this important discovery. (For an example of recent clinical work confirming FOXP2’s impact, see here).
Fisher’s article, subtitled “Tracing the connections between genes and cognition” finds that the work has inspired numerous erroneous conclusions that are almost inevitable when genes are considered abstractly rather than biologically. He says:
Genes do not specify behaviours or cognitive processes; they make regulatory factors, signalling molecules, receptors, enzymes, and so on, that interact in highly complex networks, modulated by environmental influences, in order to build and maintain the brain.
Even with that caveat, however, it is clear that certain mutations in the human FOXP2 lead to serious speech problems.
The human FOXP2 gene is member of the “forkhead gene” family, one of the must fundamental and conservative genes in the genome. (A “conservative” gene is one that changes very little between species, suggesting that there are strong selective pressures to keep it as it is.) It is a “transcriptional regulator,” meaning that it regulates the first biochemical step in the expression of a gene. It switches genes on and off during the creation of a body’s tissue. Basically, it says to a gene, “Get to work,” and then some time later, “Stop. That’s enough of your growing for now.”
The amazing thing about the FOXP2 gene is how little it has changed over time, and how much it has changed recently in the human line. The original report on FOXP2 said:
The evolutionary lineages leading to humans and mice diverged about 70 million years (Myr) ago. Thus, during the roughly 130 Myr of evolution that separate the common ancestor of humans and chimpanzees from the mouse, a single amino-acid change occurred in the FOXP2 protein. By contrast, since the human and chimpanzee lineages diverged about 4.6—6.2 Myr ago, two fixed amino-acid changes occurred on the human lineage whereas none occurred on the chimpanzee and the other primate lineages, except for one change on the orang-utan lineage.
In other words between about 70 million years ago and about 5.5 million years ago, the FOXP2 gene on the primate line experienced one mutation, a rate of 1 change in 64.5 million years. Now that’s a conservative gene!
The effect of the recent human mutations is only expressed if both parents carry them. In this regard, FOXP2 changes are like blue eyes. Both parents must contribute the blue-eyed gene if the baby is to have blue eyes. But blue eyes are relatively rare compared to the more dominant dark eyes, while the FOXP2 gene has become essentially universal in the human genome. Some kind of very strong selection has been underway to chase out all hint of the pre-human version of FOXP2.
The gene was discovered through the investigation of a family (called the KE family) that for at least three generations had a severe speech disorder affecting about half of the children (just the ratio you would expect in a case where a single, dominant gene led to the disorder). They have trouble controlling the fine movements of the lower half of their face, that is the tongue and jaw. They also have some other linguistic and syntactical impairments whose relation to the problems of articulation are not obvious.
Somehow the human FOXP2 gene alters tissue growth (presumably) in the brain giving people the ability to shape very precisely the sounds they make with their mouth.
Efforts to date the mutation put it within the past 200,000 years, making it co-incident with the appearance of Homo sapiens. While that is a very provocative finding, inspiring anybody with half an imagination to rev their engines, it is usually a good idea to treat genetic findings conservatively. We still have no idea of what areas in the brain are switched on and off by the human FOXP2 gene, so speculations about its place in the human story soon run ahead of the data.
On the other hand, it is a real piece of information, something to fit into the bigger picture.
- Neanderthals: the FOXP2 mutation appears to have occurred hundreds of thousands of years after our line and Neanderthal’s went their separate ways. It suggests that Neanderthal could not control their jaws and tongue to the extent we can, which is also in keeping with fossil evidence about Neanderthal speech organs. (See this blog’s post.) That is not the same as saying the Neanderthal had no speech, but it does make a strong case for the claim that Neanderthals could not articulate as sharply as their H. sapiens neighbors.
- Culture’s “Big Bang”: if you take the cultural Big Bang literally (Discussed in this post), the FOXP2 change suggests a neat cause and effect. We got the ability to distinguish phonetically between mine and thine and we were quickly on our way to seizing the world. On the other hand, if you are a Big Bang skeptic, this mutation suggests a late-blooming piece in the puzzle. We had been developing tone of voice, listening, semantics, maybe even syntax for a very long time and now we were able to put it all together into a steady stream. Look out, you Neanderthals; here we come!
One final question concerns the selection pressures to drive the dominant older form of FOXP2 out of the H. sapiens genome. What were they? What is the benefit of having everybody be a talker? We all know that, to sound a little like Mel Brooks, it’s good to be a talker, but just how does that translate into the complete replacement of a dominant gene with a recessive one?