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FOXP2 and Language Evolution

Updated on May 16, 2012
Structure of the FOXP2 protein.
Structure of the FOXP2 protein. | Source
Rendering of DNA
Rendering of DNA | Source

In the early 1990s, a team of doctors from the Child Health Institute in London were finding themselves baffled by a group of patients with a severe language and speech disorder. The mysterious disorder affected about half of the members of a three-generation span of a single London family who would later be identified in the medical literature as the KE Family.

KE family members who had the disorder had both physical and cognitive impairments that affected their ability to communicate. This included difficulty performing fine motor movements of the face and mouth necessary for speech, inability to answer simple word problems, difficulty understanding complex sentence structure, and reduced IQ scores on both verbal and non-verbal tests.

In 1996, the physicians brought the case to the Wellcome Trust Centre for Human Genetics in Oxford, where a team led by geneticist Dr. Simon Fisher. Given the generational nature of the disorder, Fisher's team suspected that the cause was a single-gene mutation somewhere on chromosome 7, but narrowing down exactly which gene was responsible was a difficult problem.

The solution came as a stroke of luck - an entirely unrelated patient nicknamed CS was presented to the team displaying similar language and cognitive difficulties. In this patient, a portion of chromosome 7 had been broken off and spliced onto a different chromosome. The break occurred in the middle of a gene known as FOXP2. Sequencing of this gene in the KE family found a point mutation - a DNA copying error substituting one nucleotide for another - in affected members of the family. A single guanine (G) had been replaced with adenine (A) in a critical part of the gene, causing the gene to code for one wrong amino acid in the protein produced.

This single mutation created both physical and mental impairments to language ability in the KE family, and a break in this gene had caused similar impairments in the patient CS. The conclusion was that the FOXP2 gene was extremely important to language development.

The FOXP2 protein of the Zebra Finch is 98% identical to ours, separated by just eight amino acids.
The FOXP2 protein of the Zebra Finch is 98% identical to ours, separated by just eight amino acids. | Source

The Molecular Evolution of FOXP2

FOXP2 is named for the Forkhead Box Protein P2 for which it codes. This highly complex protein, which gets its name from its forked appearance, is a type of protein known as a transcription factor. Transcription factors act as facilitators, enabling the DNA of other genes to make RNA, and thus make other proteins to perform functions for the organism. In other words, forkhead proteins are regulators that turn genes on or off, a process known as gene expression.

Though FOXP2 was widely described in the popular press as a "language gene" and in some cases presented as "uniquely human," it is in fact a very old gene. Very similar versions of FOXP2 are found not only in other mammals such as chimpanzees, mice, and bats, but it is also found in birds, fruit flies, and even single-celled organisms such as yeast. During embryonic development in humans and other mammals, FOXP2 regulates formation of the brain, esophagus, lungs, heart, and several other internal organs.

Later in life, the gene continues to enable development of language and communication pathways. This has been demonstrated by experiments using zebra finches - a type of songbird that learns new songs every year and modifies their songs during the mating season. When the birds were injected with RNA that inhibited the function of FOXP2, they had difficulty learning and remembering new songs, and their songs came out garbled and off-key.

Comparisons of the gene sequence in different modern organisms demonstrates that it has undergone very little change throughout its evolutionary history. In genetics, this is referred to as being highly conserved. In the 75 million years since the mammal lines that became mice and humans diverged, the gene sequence has changed by only three amino acids. Two of these happened very recently - just in the five million years since the human and chimpanzee lines diverged.

Interestingly, one of the amino acid changes that occurred after the human-chimpanzee split also happened in echolocating bats, suggesting that human language and bat echolocation are controlled by similar gene regulation pathways. An even more interesting finding is that the Neanderthal genome contains a version of FOXP2 identical to that found in modern humans, suggesting that Neanderthals may have been capable of complex language.

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    • mwilliams66 profile image

      mwilliams66 5 years ago from Left Coast, USA

      A fascinating read. Very articulate writing.

    • somethgblue profile image

      somethgblue 5 years ago from Shelbyville, Tennessee

      Let me say that was an excellent Hub Article, think if they would have injected the birds (subject) with enhanced RNA the possibilities are endless.

      Do they have any idea why the gene mutated in the KE family, natural, environment . . . ?

    • scottcgruber profile image
      Author

      scottcgruber 5 years ago from USA

      mwilliams66: thank you very much for reading!

      Somethgblue: glad you enjoyed it! I didn't see anything about what caused the KE Family's mutation, but it could simply have been a copying error in production of a sperm or egg cell three generations back. Point mutations are pretty common - in a genome of 3.2 billion base pairs, mistakes are bound to happen now and then. It's just rare when they happen in such a critical gene.

    • somethgblue profile image

      somethgblue 5 years ago from Shelbyville, Tennessee

      I'm wondering if it is something that may form naturally as a precursor to another form of communication. I suspect that our evolution is built around how we perceive our world and communicate with those on it.

      I suspect that my own limited knowledge of perception is keeping me from truly understanding a great deal of what I consider mysterious concepts, ideas and natural phenomenon.

      Mwilliams66 and I share one thing for sure and that is the unquenchable thirst for knowledge which if balanced with an open mind can be something special.

    • Joyus Crynoid profile image

      Joyus Crynoid 5 years ago from Eden

      Great article. One minor point: the name "forkhead" derives from the name of a mutation in fruit flies ("fork head"), which was eventually traced to the gene that was found to encode a transcription factor. In fact many developmental regulatory genes were first discovered by geneticists working with fruit flies (Drosophila melanogaster), and named to describe the defects that develop when the gene is mutated or absent. So fork head mutants have develop a defective 'forked' head.

    • nifwlseirff profile image

      Kymberly Fergusson 5 years ago from Villingen Schwenningen, Germany

      I wonder if it's also responsible for mimicry? The Australian lyrebird adds new songs to his repertoire, but only copying other sounds he hears. Great article!

    • Kate Mc Bride profile image

      Kate McBride 4 years ago from Donegal Ireland

      This is the first time I have read anything about genetics and I really liked this hub. Voted it up and interesting. Thanks for sharing it.

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