It is estimated that there are up to 8,000 distinct languages spoken around the world today.  At birth, the human mind is capable of learning and understanding any of these languages; an impressive feat given how uniquely complex they are.  The fact that humans are able to understand and communicate with one another in such a way that even our closest primate relatives cannot has long been supposed to be the result of some sort of genetic distinction separating us from the rest of the animal kingdom. 

In 2002, scientists believed they had found this genetic distinction in the form of a gene called FOXP2.  Their early studies suggested that FOXP2 was linked to the development of language in humans, and in humans’ ability to manipulate the brain, lungs, and vocal chords to make the complicated suite of sounds and movements resulting in speech.

However, the expression of FOXP2 in humans – and its presence in other species – is anything but simple.  Research has revealed that FOXP2 isn’t expressed just in the brain, but in a host of other tissues and organs throughout the body.  Moreover, FOXP2 isn’t unique to humans, but is found in many species, from chimpanzees to field mice.  It’s the version of FOXP2 we humans carry that is distinct from those of other species.  So it is the differences in FOXP2 across species that has been at the heart of scientific research into the origins of complex language.

A few years after the FOXP2 gene’s possible role in promoting complex language skills was announced in 2002, scientists analyzing ancient DNA extracted from Neanderthals, our closest fossil ancestors, found that they had the same version of FOXP2 as humans.  This discovery was revolutionary, as it meant that humans may not have been the first species capable of complex speech and language. It also pushed back the appearance of this version of FOXP2 to at least 350,000 years ago.

Recently, the focus of genetic research into FOXP2 has focused on the specific role FOXP2 plays in our language ability.  Was it involved in enhancing our cognitive abilities?  Our motor skills? Our breathing patterns?  The results of scientists’ most recent effort to uncover the answers to these questions are in the May 29th issue of Cell, in a paper published by researchers from the Max-Planck Institute of Evolutionary Anthropology.

In order to advance our understanding of FOXP2, the scientists chose to examine its expression in mice, a surprisingly strong model for many human biological systems.  The chief difference in FOXP2 between humans and many other species such as mice boils down to two changes in the gene.  At some point in human prehistory, these changes arose and quickly became universal in the FOXP2 of humans.

To see what effect those changes might have had, the Max Planck scientists altered the copies of FOXP2 in mice to be identical to the copies of FOXP2 in humans.  They then examined any changes that took place surrounding the cognition and vocal skills of the genetically altered mice, to see how they might be affected by the supposedly advanced copy of FOXP2.  And, while the linguistic skills of the mice failed to rival our own, the scientists did see some surprising changes.  First, they found that the altered mice showed changes in their brain circuitry that bore some similarity to that of humans.  And perhaps most intriguing, the altered mice had distinct ultrasonic vocalizations that differed from their unmodified brethren.  Ultrasonic vocalizations, sometimes referred to as chirps or squeaks, are used by mice to communicate to each other, such as to warn of a predator.  When the young altered mice were separated from their mothers, something that usually elicits many such squeaks, they emitted ultrasonic vocalizations that were distinctly different in intensity and frequency than their counterparts.  The authors argue that the altered FOXP2 in the mice was influencing the type of squeaks that they were making when separated from their mothers.  And the scientists therefore believe there is some kind of connection to language development.

But what does all this mean to humans?  The past several years of research into FOXP2 has revealed that human patients who carry at least one non-functional version of the gene (i.e., the version of the gene found in species other than humans) have problems producing the facial movements necessary to form words.  It had been thought that part of the function of FOXP2 in humans was to develop motor control needed to articulate our mouths, vocal chords, and esophagus to produce complex language.  Many experts have also proposed that FOXP2 in humans plays a role in the development of both the lungs and the esophagus – both of which are vital to speech.  This most recent study shows that by simply tweaking FOXP2 in mice, we see a noticeable change in how they communicate.

Clearly, there is much more work to be done and many more questions to be answered.  In the future, these researchers envision going even further to understand exactly how FOXP2 influences our ability to communicate with each other.  Their next goal?  To understand the exact mechanics behind the version of FOXP2 found in humans, so that they can finally piece together its importance in giving us the power of speech.

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When scientific research is published, the authors often confess that they wish they’d collected more data. Critical reviews of research studies often say the same thing. Indeed, if there’s anything scientists love, it’s more data.

Which is why the members of an international team of genetic anthropologists led by Sarah Tishkoff of the University of Pennsylvania are probably quite pleased with themselves. In a new study published this week in Science, the team took the concept of “more is more” to heart by collecting and analyzing the DNA of thousands of people, mostly from Africa, so that they might uncover more clues to not only the genetic make-up of modern Africans, but also the genetic history of Africans and non-Africans alike.

The scientists’ first step was to collect DNA from a diverse set of Africans. Africa is the most culturally and linguistically diverse place on Earth, so it was important to take a wide sample of individuals from all corners of the continent. In total, they collected 2,432 DNA samples from 113 diverse and distinct groups of people from across the African continent as well as 60 non-African groups. They sampled everyone from the Mozabite Berbers of Morocco to the hunter-gatherer San of the Kalahari Desert, and many in between.

But the hard work didn’t stop there. The scientists then examined 1,327 genetic markers across the human genome for each individual studied. While many studies focus on a particular part of the genome such the mitochondrial DNA or the Y chromosome, this study took a comprehensive approach. Finally, the researchers used sophisticated statistical techniques, piecing together how these populations from Africa and around the world were the same, and how they were different.

The results confirmed that Africa has the highest genetic diversity of any continent, as many scientists have proposed. In fact, the authors found genetic diversity to decrease the further one traveled away from Africa. Genetic diversity is often used as a measure of how long ago humans inhabited a region — conventional wisdom places the earliest humans in East Africa, which had exceptionally high genetic diversity according to this study, though an analysis by the researchers put the origin of the human expansion farther south near the border of Namibia and Angola.

The study also shed light on the incredible genetic diversity among African populations, said Roy King, a professor of psychiatry and anthropological geneticist from Stanford University:

Not only did farming and pastoral communities differ from hunter-gatherers, but within the broad range of agricultural populations of West and West-Central Africa — from which many African Americans derive their ancestry — the authors also found some genetic diversity. For example, the Dogon of Mali, although geographically near the Mandinka of Senegal, cluster with North African Berber populations. Thus, this study supports the notion that not only is Africa varied in culture — art, music, religion and language — but also harbors a rich genetic diversity across its multitude of ethnic groups.

The authors also found a loose connection between the genetics of a population and its language. However, there were a few exceptions, most often the result of a population adopting a new language within the last few thousand years.

The sheer size and diversity of the DNA samples collected allowed the researchers to construct a human family tree based on their analyses. Not unexpectedly, the tree they constructed fits well with current theories on the genetic relationship between Africans and non-Africans; namely that all non-Africans are descended from a particular group or groups of people who were the first humans to migrate out of Africa tens of thousands of years ago.

This study is important for a multitude of reasons. It has been able to confirm theories from the archaeological, cultural, and linguistic records on the origins and movements of Africans and non-Africans.

“It fits nicely with earlier genetic studies, while subverting the early 20th century colonialist idea of sub-Saharan Africa as constituting a homogeneous genetic an cultural unit,” King said.

It also creates a new resource that historians, linguists, archaeologists and scientists from a range of other disciplines can use in their own work. If we are lucky, this study will bring forth a flurry of activity surrounding the origins and history of the African continent, and the people who live there.

Credit: istockphoto/Erie

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