Today’s New Reason To Believe

Posted by Fazale ‘Fuz’ Rana, Ph.D.

Neanderthal Speech Gene May be Due to Contamination

Nobody really likes a potty mouth, including anthropologists. But it looks like these scientists will have to put up with “contaminated” language from Neanderthals, at least if the results of new work are valid. It appears as if the recovery of the so-called language gene from the remains of Neanderthals is not authentic, but instead may be due to contamination from human DNA.

The question of whether or not Neanderthals possessed language capacity has precipitated much controversy. Anatomical studies are ambiguous towards this end. (See Who Was Adam? for a detailed discussion.) To help resolve this issue a team from the Max Planck Institute turned to ancient DNA analysis to probe for the language gene in the Neanderthal genome.

In 2001, a research team from the United Kingdom reported that mutations in the FOXP2 gene cause severe language disorders. Presumably the FOXP2 protein plays a key role in controlling the development of brain and facial structures that support aspects of human language capacity.

An initial evolutionary analysis of the FOXP2 gene, conducted in 2002, indicated that the human variant arose about 200,000 years ago. Subsequent work, published later that year, placed the origin of the human FOXP2 gene at about 100,000 years ago. From an evolutionary standpoint, this 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.

However, to everyone’s surprise, the team from the Max Planck Institute did isolate the human variant of the FOXP2 gene from a recently recovered Neanderthal specimen. This result was interpreted by some as evidence that Neanderthals had language. If so, it creates problems for the RTB human origins model, which predicts that Neanderthals and other hominids should behave in nonhuman ways, and, therefore, should not have the capacity for language.

Did Neanderthals possess language ability? At the time that the recovery of the Neanderthal language gene was announced I wrote:

The very real possibility exists that this result stems from contamination by human DNA. Clearly, the research team went to painstaking efforts to avoid contamination. Anthropologists suited up in clean room gowns and face masks to excavate the Neanderthal remains using sterilized tools. They designed the extraction protocol to avoid isolating any human DNA and ran the appropriate controls to ensure the Neanderthal DNA samples had no human contamination. In spite of these heroic efforts, the possibility of contamination cannot be ruled out. The team from the Max Planck Institute introduced contamination into the Neanderthal genome sample they were previously working with and wrongly interpreted this as evidence for human-Neanderthal interbreeding.

It looks like my initial assessment was right. A research team for the University of Chicago re-assessed the likelihood that Neanderthals possessed the human variant of FOXP2 by looking at the genetic variation associated with this gene among modern human populations. They concluded that the scenario proposed by the Max Planck workers—namely the human variant arose prior to the time that Neanderthal and human lineages diverged from a common ancestor—is inconsistent with the genetic patterns observed among modern humans. They also estimated that the human variant of FOXP2 arose about 42,000 years ago. This result falls in line with earlier estimates, which places the origin of the human variant between 100,000 and 200,000 years ago.

The Chicago scientists suggest two possible scenarios to explain the recovery of the human variant of the FOXP2 gene from Neanderthal remains. First, humans introduced the language gene into the Neanderthal gene pool through interbreeding. They assert that if low levels of interbreeding took place between humans and Neanderthals, this could account for the appearance of the human language gene in the Neanderthal genome. This conclusion is not well supported by other studies, which have failed to find any direct evidence for interbreeding.

The other possibility is that the DNA extracted from Neanderthals was contaminated with modern human DNA. Even though the Max Planck Institute scientists took every precaution to avoid contamination and even ran controls to ensure that their samples were free from contaminants, human DNA, which is ubiquitous, could have easily made its way into the sample. The team from the University of Chicago raises questions about the effectiveness of the control samples. They assert that the controls selected by the Max Planck team do not necessarily ensure contaminant-free Neanderthal DNA samples.

It is really beginning to look like Neanderthals didn’t have language capacity after all—just contaminated language. Now I’d like to know who’s going to volunteer to wash their mouths out with soap.

Posted by Fazale ‘Fuz’ Rana, Ph.D.

Dental Anatomy Gives Important Clues on Hominid Growth and Development

For a little kid, losing teeth is a rite of passage. Each tooth that falls out (or gets unceremoniously yanked loose) serves as a sign that the child is growing up, as, one by one, baby teeth make way for permanent teeth.

The same is true for hominids, which are often interpreted as transitional intermediates between an ape-like creature and modern humans. Hominid tooth eruption, deposition of microanatomical structures, and tooth wear occurred at characteristic times during their growth and development and throughout adulthood. Because of the relationship between dental anatomy and life history, paleoanthroplogists study these features to gain important clues about the behavior and lifestyle of these now-extinct creatures.

Two recent research projects examined dental features of Paranthropus robustus and Neanderthals. Both studies indicate that these two hominids developed and behaved in decidedly nonhuman ways, extending the separation between the hominids and modern humans in accord with RTB’s human origins model.

RTB Human Origins Model and the Hominids

Instead of viewing these creatures as evolutionary intermediates, RTB’s biblical creation model regards the hominids found in the fossil record as animals created by God’s direct intervention. These primates existed for a time and then went extinct. RTB’s model considers the hominids to be remarkable creatures that walked erect, and possessed some level of limited intelligence and emotional capacity. This allowed these animals to employ crude tools and even adopt a type 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. The model reserves this status exclusively for modern humans.

The RTB’s conceptual scheme treats the hominids as analogous to, but distinct from the great apes. Because of this, 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.

One study examined facial features and tooth wear for 19 specimens assigned to Paranthropus robustus. This hominid lived between about 2 and 1.2 million years ago in South Africa. (Evolutionary biologists don’t think that this hominid is part of the lineage that led to modern humans. Instead they place P. robustus, along with its two sister species, P. boisei and P. aethiopicus, as an evolutionary side branch and dead end.)

The research team noted that for male specimens the most extensive dental wear correlated with fully developed adult features. Those males with underdeveloped adult characteristics showed little dental wear. This pattern was not noted for females in the sample. These observations indicate that males took a longer period of time to develop than females and imply that P. robustus displayed sexual dimorphism, with males possessing a significantly larger body size than females.

Sexual dimorphism impacts mating strategy. Primates like gorillas that display sexual dimorphism based on body size have a social organization centered on a large dominant male who mates with a harem of females. This means that Paranthropus, and by extension the other Australopithecines, employed a mating strategy similar to gorillas.

In contrast, modern humans display relatively limited sexual dimorphism. As a consequence, males and females form mating pairs.

This work indicates that the Australopithecines were biologically and behaviorally distinct from modern humans, in accord with predictions made by the RTB model. The study also widens the gap between the Australopithecines and hominids that belonged to the Homo genus. According to paleoanthropologist J. Michael Plavan:

The finding challenges a theory that early hominids had a relatively low level of sexual dimorphism, inherited from a common ancestor shared with chimpanzees…Instead, the primitive condition may have been more gorillalike, and our female ancestors may not have closed the gap until recently, perhaps in Homo erectus in the past 2 million years.

The implication: the transition in mating behavior (and the accompanying growth and development process) must have happened rapidly.

Another study examined microanatomical features of Neanderthal teeth as a way to assess the rate of growth and development for these hominids. Biological rhythms produce incremental features in the enamel and dentine throughout childhood that can be used as a record for the individual’s life history.

Earlier studies using these markers have been inconclusive about the growth and development of Neanderthals. Some studies indicate that these hominids grew into adulthood at a pace similar to that of modern humans. Other work suggests that the rate of growth and development was accelerated when compared to human beings.

The most recent study took the most-detailed and comprehensive look at the microanatomical characteristics of Neanderthal teeth. Based on this work, the researchers concluded that Neanderthals grew at a much more rapid rate than modern humans. To say it another way, a prolonged childhood and relatively slow life history appears to be unique to modern humans. And these differences in the length and pace of childhood have important consequences for social organization.

Based on this work, it appears as if Neanderthals are both biologically and behaviorally distinct from modern humans. Once again this finding comports with RTB’s human origins model. Scientific advance makes it increasingly possible to make a scientific case that human beings are distinct from the hominids in a way that harmonizes with the notion that humans are uniquely made in God’s image.

While it is commonplace for human children to put their baby teeth under a pillow in the hope that the tooth fairy will exchange it for “gold,” it’s unlikely that Neanderthal children ever went through such a ritual. They grew up too fast.

Posted by Fazale ‘Fuz’ Rana, Ph.D.

Does the Presence of a “Speech” Gene Mean Neanderthals Had Language? An article recently published in Current Biology has generated a lot of excitement about the possibility of Neanderthal language capacity. Scientists from the Max Planck 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. What does this mean for RTB’s biblically based human origins model?

Last week I provided some background information needed to understand the work of the Max Planck scientists. This week I will detail their findings and discuss the implications of their research for the RTB human origins model.

Controversy surrounds the question of whether or not Neanderthals possessed language capacity. Anatomical studies remain ambiguous. (See Who Was Adam? for a detailed discussion.) To help resolve this debate the team from the Max Planck Institute turned to ancient DNA analysis to probe for the language gene in the Neanderthal genome.

In 2001, a research team from the United Kingdom reported that mutations in the FOXP2 gene cause severe language disorders. Presumably the FOXP2 protein plays a key role in controlling the development of brain and facial structures that support aspects of human language capacity.

An initial evolutionary analysis of the FOXP2 gene, conducted in 2002, indicated that the human variant arose about 200,000 years ago. Subsequent work published later that year placed the origin of the human FOXP2 gene at about 100,000 years ago. From an evolutionary standpoint, this 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.

To everyone’s surprise, the team from the Max Plank Institute isolated the human variant of the FOXP2 gene from a recently recovered Neanderthal specimen. Some have interpreted this result as evidence that Neanderthals had language. If so, what does this mean for the RTB human origins model which predicts that Neanderthals and other hominids should behave in non-human ways?

Did Neanderthals possess language ability? This conclusion is premature for a number of reasons.

First, the very real possibility exists that this result stems from contamination by human DNA. Clearly, the research team went to painstaking efforts to avoid contamination. Anthropologists suited up in clean room gowns and face masks and used sterilized tools to excavate the Neanderthal remains. They designed the extraction protocol to avoid isolating any human DNA and ran the appropriate controls to ensure the Neanderthal DNA samples had no human contamination. In spite of these heroic efforts, the possibility of contamination cannot be ruled out. The Max Planck researchers previously introduced contamination into a Neanderthal genome sample they were working with and wrongly interpreted this as evidence for human-Neanderthal interbreeding.

Even if these results are taken at face value, it still doesn’t mean that Neanderthals possessed language. As discussed last week, the presence of the FOXP2 gene is necessary for language in humans, but not sufficient. Myriad other genes must be present and properly expressed to give humans the ability to speak. To date, these other genes have not been identified in humans, let alone Neanderthals.

It is also conceivable that the Neanderthal FOXP2 gene is distinct from the human variant. The researchers did not isolate the entire FOXP2 gene. Instead they isolated the portion of the gene where the distinguishing features of the human variant reside. It could well be that when the entire gene is sequenced other regions it will display unique Neanderthal signatures.

Another troubling aspect of this study is that its results run contrary to other studies. For example, if Neanderthals had the human version of the FOXP2 gene, then from an evolutionary perspective the origin of the gene must have taken place prior to the time that Neanderthals and humans shared a common ancestor, which would be at least 500,000 to 750,000 years ago. Yet, as mentioned last week, evolutionary analyses place the origin of the human variant between 100,000 and 200,000 years ago. Additionally, the archeological evidence and brain-structure studies don’t support the existence of Neanderthal language. (See Who Was Adam? for details. Also, see a past TNRTB entry about Neanderthal division of labor.)

Did Neanderthals have language ability? In spite of the discovery of the so-called language gene in Neanderthals, the question still remains unresolved.

Still, the work by the scientists from the Max Planck Institute demonstrates the power and potential of ancient DNA studies to help us move toward resolving important scientific controversies.