Human language is a key source of communication and information dissemination. However, scientists are still unable to trace the evolution of how our ancestors are able to obtain this distinct trait that other creatures didn’t acquire - until now.
Communication is the Key
The various feats on human evolution had sparked both scientists and researchers alike including some who obstinately admire the theories that Charles Darwin had been popularized.
The human language was thought to have sprouted from a single gene which traversed through time following ancient human populations. But an analysis of this gene, FOXP2, suggest that Homo sapiens’ did not undergo specific changes after all and with that all previous findings simply were inconclusive — much more erroneous rather.
Evolutionists got all excited in 2002 when one team found a genetic mutation called FOXP2 which evoked speaking disruptions in humans. “Research casts doubt on the idea that the FOXP2 gene — linked to language evolution — is special to modern humans,” writes Matthew Warren. This gene was also said to carry two mutations which suggested that language development happened before where Neanderthals had occurred a split into groups.
Evolutionary and population geneticist Elizabeth Atkinson and colleagues decided to revisit the gene’s evolution “to see if FOXP2’s story held up using modern techniques,” she says. The researchers conducted similar statistical analysis on the patterns of genetic variation in FOXP2 as was done in the 2002 study. But this time, they studied more people including those from African descent.
In a selective sweep, one pattern of genetic variants around a gene becomes much more common than other versions of the gene until nearly everyone has the popular version. The result then revealed difference and conflicting information which might disprove the official data concluded from the 2002 study.
When humans migrated out of Africa, certain versions of genes were carried with the migrants and other forms were left behind in Africa. The version of FOXP2 that left with the migrants became more common as the migrant population grew. If FOXP2 were getting swept, it would be the only gene sending out the statistical signal.
The finding doesn’t mean that changes in FOXP2 weren’t important for language evolution, says Kirk Lohmueller, a population geneticist at UCLA. However, assumptions regarding the evolution of species would have to be thought well for a second time.
Selective sweeps were thought to be a major way that natural selection — the process that drives evolution — altered species. But these and other results suggest that selective sweeps were not very common in human evolution.
Many of the traits associated with being human, including speech and language, are controlled by multiple genes, so no one gene may have given a sweep-worthy boost. Or perhaps a speech and language sweep happened, but so long ago that its signal is too weak to pick up now, Lohmueller says.
“The situation’s a lot more complicated than the very clean story that has been making it into textbooks all this time,” says Elizabeth Atkinson.
Even if there was no recent evolution of FOXP2, there is still plenty of concrete evidence that the gene is involved in language, says Simon Fisher, director of the Max Planck Institute for Psycholinguistics in Nijmegen, the Netherlands, and a coauthor of the 2002 study.
Mutations in FOXP2 cause language disorders in humans, and in mice the gene is important for vocalizations and movement—both functions that are crucial to human speech.
Language is complicated, and was never going to be explained by a single mutation in modern humans, Fisher adds. “We need to embrace more-complex accounts that involve changes of multiple genes. In that sense, FOXP2 was only ever going to be one piece of a complex puzzle.”
Brenna Henn, also a population geneticist is now keen to revisit other genes that have been considered important to human evolution, such as Microcephalin, which has been linked to brain development. She worries that an over-reliance on small data sets has skewed our understanding of what makes humans unique.
This gene was first discovered in a family who had language abnormalities and a history of profound speech disorders. Research later touted its importance in human language and evolution after it was further thought to have been involved in language production.
The 2002 study and the scientists behind it were lambasted by critics saying they did shoddy work on the research. A re-analysis had shown that this FOXP2 gene is older than expected. In humans, this mutation is differently seen in primates which exhibited the lack of speech just as with every other animal.
The study reported on Nature, had looked upon genetic variations under these mutations which then revealed a ‘selective sweep’—in which a beneficial mutation quickly becomes common across a population. A swapping of two amino acids in the human version of the gene is of no difference than in other animals’ versions of the gene. FOXP2 is involved in vocal learning in songbirds, and people with mutations in the gene have speech and language problems. Many researchers initially thought that this amino acid swap was what enabled humans to speak.
Despite such questions, the 2002 study has never been repeated. It was based on the genomes of only 20 individuals, including just a handful of people of African ancestry, says Atkinson which mostly came from Europe, Asia and other regions. The re-examined study then found that the signal which thought to have been a selective sweep was probably just a statistical artefact from the various populations being lumped with African descent. With more—and more varied—genomes to study, the team was able to look for a selective sweep in FOXP2, separately, in Africans and non-Africans—but found no evidence in either.
“It’s good that it is now clear there is actually no sweep signal at FOXP2,” says evolutionary geneticist Wolfgang Enard, who was a co-author of the 2002 study.
Two evolutionists look to Bengalese finches (a type of bird species) for clues on how humans learned to speak.
All this makes the domesticated and wild birds a perfect natural experiment to help explore a unique proposal about human evolution: that the building blocks of language are a byproduct of brain alterations that arose when natural selection favored cooperation among early humans. According to this hypothesis, skills such as learning complex calls, combining vocalizations, and simply knowing what each creature wants through communication skills result as a consequence of social traits like kindness.
The idea is rooted in a much older one: that humans tamed themselves. This self-domestication hypothesis, which got its start with Charles Darwin, says that when early humans started to prefer cooperative friends and mates over to aggressive ones which might essentially suggest that they domesticated themselves. Along with tameness came evolutionary changes seen in other domesticated mammals.
There’s still no evidence that FOXP2, often called “the language gene,” gave humans such evolutionary advantage that it quickly adapted through time across the species.
On a view regarding selective sweeps, archaeogeneticist Johannes Krause, who was not involved in the study had said that the gene did not allow humans to settle the world and replace other hominids. Further, some researchers even suggested that FOXP2 was the gene that defines humans which became clear that it did not.