Does the Presence of “Speech” Gene Mean Neanderthals Had Language?
An article recently published in Current Biology has everyone talking about whether or not Neanderthals talked.
Scientists from the Max Plank Institute at Leipzig, Germany, announced the isolation of the so-called language gene from a Neanderthal specimen recently recovered in Spain. Some anthropologists interpret this discovery as evidence that Neanderthals had language. If so, what does this mean for RTB’s biblically based human origins model?
Before tackling this question, I will spend this week providing background information needed to appreciate the work of the scientists from the Max Plank Institute. Next week I will discuss implications of their research for the RTB human origins model.
These hominids appear in the fossil record between 250,000 and 150,000 years ago and go extinct about 30,000 years ago. Neanderthals were confined to western Asia, Europe, and the Middle East. Popular views about human origins position Neanderthals as immediate predecessors to modern humans. Other, more sophisticated treatments of human evolution, like multiregionalism, argue that these hominids gave rise only to European people groups.
Most paleoanthropologists now maintain that Neanderthals represent an evolutionary side branch and dead end. This position derives support from anatomical and developmental studies that indicate that Neanderthals are not only a distinct species from modern humans, but also could not have evolved to produce the first human beings.
This recognition gains powerful confirmation from ancient DNA studies. To date, paleoanthropologists have isolated mitochondrial DNA from fifteen Neanderthal specimens (for the latest results see a recent Nature article), have sequenced this DNA, and have compared it to human DNA. In all cases, the Neanderthal DNA varies to such an extent that it forces anthropologists to conclude that these hominids could not have given rise to modern humans. (For a detailed discussion of this work see Who Was Adam?)
Anthropologists have even recovered nuclear DNA from Neanderthal remains and again conclude no direct evolutionary connection between these two species. Additionally, no compelling evidence for interbreeding between humans and Neanderthals exists, despite highly publicized claims to the contrary. These results all bode well for the RTB human origins model.
The RTB View of Hominids
RTB’s biblical creation model views the hominids found in the fossil record as animals created by God’s direct intervention. These creatures existed for a time and then went extinct. RTB’s model considers the hominids to be remarkable creatures that walked erect, possessed some level of limited intelligence, and emotional capacity. These features allowed them to employ crude tools and even adopt some level of “culture” much like baboons, gorillas, and chimpanzees. While the RTB model posits that the hominids were created by God’s divine fiat, they were not spiritual beings made in His image. RTB reserves this status exclusively for modern humans.
RTB’s creation model treats the hominids as analogous to, but distinct from, the great apes. Therefore, the model predicts that anatomical, physiological, biochemical, and genetic similarities will exist among the hominids and modern humans to varying degrees. But since the hominids were not made in God’s image, they are expected to be clearly distinct from modern humans, particularly in their cognitive capacity, behavior, “technology” and “culture.”
In summary, the RTB model predicts that the hominids, including Neanderthals, should be biologically and behaviorally distinguishable from modern humans. Clearly, this is the case from a biological standpoint. Did Neanderthals behave in fundamentally different ways than modern humans? Did these creatures behave in a manner that reflects the absence of God’s image? Archeological evidence provides the means to assess these questions.
The vast proportion of the archeological record associated with Neanderthals indicates that these creatures behaved in relatively unsophisticated ways compared to modern humans. (See further discussion in Who Was Adam? and in other short RTB articles.)
Neanderthals made comparatively simpler tools with relatively unsophisticated manufacturing practices compared to modern humans. Neanderthals left behind no real evidence for symbolic thought and advanced cognitive capacity. They did not produce art or music. They showed no evidence for religious expression. These creatures did bury their dead, but the burials were clearly non-ritualistic in nature.
But did Neanderthals possess language? The anatomical evidence is ambiguous on this count. In an attempt to make progress, the research team from the Max Plank Institute decided to take a different approach. They turned to ancient DNA analysis and looked for the language gene in the Neanderthal genome.
The Language Gene
The FOXP2 gene has been recently dubbed the “language gene.” This gene codes for a DNA-binding protein. These types of proteins regulate gene expression when they interact with DNA, turning genes on and off. The FOXP2 protein plays a key role in the development process in mammals for a number of organ systems and exists at high levels in fetal brain tissue. In the fall of 2001, a research team from the United Kingdom reported that mutations in the FOXP2 gene cause severe language disorders. People who suffer from this genetic defect can’t properly control their lips and tongues, which affects their ability to talk. They also can’t use and understand grammar nor can they understand many speech sounds. Presumably the FOXP2 protein plays a key role in controlling the development of brain and facial structures that support aspects of human language capacity.
This gene cannot be the only one responsible for human language. Likely, language derives from the activity of a complex network of gene interactions that dynamically vary through the course of development. The FOXP2 gene represents only one of these genes. If this gene, or any gene that plays a role in human language ability, becomes defective then a breakdown in the ability to communicate verbally occurs. The FOXP2 gene can be likened to a part of an automobile engine. If that part’s defective (like a bad sparkplug), the engine will not run properly, or at all. Still, the operation of that particular part doesn’t explain how the whole engine works. An engine consists of numerous components, each of which plays a critical role in its operation by interacting with other components in a carefully orchestrated fashion.
If an auto mechanic is trying to figure out how a new car engine works, he can learn a lot if one of its parts breaks. When an engine part stops working, the “symptoms” displayed by the engine provide valuable understanding, not only as to what that component does, but also how the engine in its entirety operates. When it comes to human language abilities, researchers have yet to catalog all the genes involved, let alone how the genes interact to generate language capacity. Still, the FOXP2 gene gives researchers important insight into human language development and abilities, even if this understanding is limited. Such knowledge will increase as researchers uncover new genetic defects that affect language ability.
The Language Gene and Evolution
The Max Plank Institute researchers studied the FOXP2 gene from an evolutionary perspective, since this gene appears to control key aspects of brain development essential for human language capacity. These researchers discovered that of the 715 amino acids that comprise the FOXP2 protein, only three differences exist between the human and mouse protein, and only two amino acids differ between the human protein and that of the great apes. Based on an evolutionary perspective, the team concluded that because of the key role that the FOXP2 gene plays in development, it has been highly resistant to mutational change. Presumably, any mutation that alters its structure, and hence function, would be so disruptive to the development process that death would result. In other words, natural selection prevented mutations from occurring in the FOXP2 gene.
Based on protein-structure prediction methods, the Max Plank team determined that the human FOXP2 protein adopts a different shape than the mouse or great ape proteins. Also, they noted that this shape change creates a phosphorylation site on the protein. These sites serve as locations for the cell’s machinery to attach phosphate groups to proteins. As a result of phosphorylation, the protein’s shape—and function—becomes altered, sometimes dramatically. By attaching and removing phosphate groups, the cell’s machinery can cause a protein to switch back and forth between two functional states, like an on/off button.
The hypothesized altered shape of the human FOXP2 protein and the presence of a phosphorylation site led the Max Plank scientists to conclude that the FOXP2 gene influences gene expression and, hence, development in dramatically different ways in humans compared to the great apes and other mammals. This difference accounts for the aspects of brain structure that allows humans to uniquely possess language capacity.
The researchers explained the structural and functional differences between human and the great ape versions of the FOXP2 protein as a consequence of mutations to the FOXP2 gene-molecular changes that led to the evolution of human language. Employing molecular clock analysis, they concluded that these mutations occurred less than 200,000 years ago, roughly at the time modern humans first appeared. Another more recent study places the time of the mutations at about 100,000 years ago.
From an evolutionary perspective, this date is well after the time that humans and Neanderthals allegedly split from a common ancestor. Accordingly, Neanderthals should not possess a human-like FOXP2 gene and, therefore, language ability.
But this is not what the Max Plank scientists found when they directly probed Neanderthal remains for the FOXP2 gene. More to talk about next week.
|Part 1 | Part 2|