Relationship between Neanderthals and Homo sapiens - Literature review Example

Name: Lecturer: Course: Date: Relationship between Neanderthals and Homo sapiens Neanderthals and modern humans co-existed together for long periods of time until the later became extinct approximately 28,000 years ago. The first Neanderthal species were discovered in 1989. However, that finding was not enough to sufficiently link the Neanderthal as a possible human ancestor (King, et al., 18). This was not until the second half of the 19th century when more fossils were discovered. More fossils that represent the remains of Neanderthals have been discovered ever since. These thousands of fossils include those of babies, children and adults. This paper will look at changes in thinking about Neanderthals from a Kuhnian point of view and different kinds of evidence that caused the paradigmatic shift in scientific theories about the relationship between Neanderthals and Homo sapiens. From these archeological findings, much more is now known about the place of the Neanderthal in the human ancestry. Thomas Kuhn is credited for having introduced the idea of “paradigms” to philosophy of science. Every paradigm is anchored on a process of “normal science”. However, paradigms can shift through a scientific revolution which is the last stage of scientific disciplines also known as “normal science”. (Khun, 16). The revolutionary stage is where one paradigm transitions to another paradigm. Science, according to Kuhn, is built upon by leaps and bounds, and progression that are dictated by a number of elements that are within a paradigm. The wheels of normal science began to turn when the first near complete skeleton of a Neanderthal was discovered in 1908 in France. It was the fossil of “The Old Man of La Chapelle” found inside a small cave that was near La Chapelle-aux Saints.” The skeleton comprised of the jaw, skull, much of its vertebrae, and small limbs. Additionally, it had most of his long hand and leg bones, as well as some smaller bones of the hands and feet (Templeton, 1508). The skull that is now well preserved shows a forehead that is noticeably receding and low, a protruding mid-face. The other feature was a heavy brow ridges that signified that of the Homo neanderthalensis. It is estimated that “The Old Man of Chapelle” was quite old when he died, since it was discovered that his bone had re grown on his gums and he had several teeth missing, which could have happened decades before he died (Relenthford, 559). The fact that he lacked so many teeth could mean that his food would have to be ground for him for him to be able to eat of it. The skeleton of the “Old Man of la Chapelle” was reconstructed by scientist Pierre Marcellin Boule. Te reconstruction was significant because it bolstered popular culture’s perception that Neanderthals were just some dim-witted brutes. That reconstruction of this skeleton which took place in 1911 indicated that Neanderthals had severely curved spines similar to that seen in large apes like gorillas (Mackleprang, and Rubin, 224). This pointed to a lack of intelligent and an early man who was generally primitive. However, this was shattered by more reexamination of the skeleton of the Old Man in the 1950s indicated that actually many features that had long been believed to be unique to Neanderthals indeed fell within the range of variations of the modern human being (Kring, et al., 27). It was discovered that the findings from the earlier reconstruction of the Old Man was affected by a “gross deforming osteoarthritis” that the Old Man suffered. These new findings attracted great interest which led to a more thorough evaluation on the skeleton by scientist Erik Trinkaus who after reexamining the entire skeleton concluded that the Old Man suffered from a degenerate joint disease. It was also concluded that the deformity caused by this was not the reason that affected the first reconstruction undertaken by Boule on the Old Man’s posture (Relenthford, 560). Boule’s reconstruction of the Old Man was informed by the fact that he was particularly disinclined to embrace the hypothesis that held that Neanderthals were ancestors of the modern man. This can be attributed to his skewed reconstruction of a brutish, stooped creature. Boule’s prejudice negated scientific objectivity, a misconception that got universally accepted by many paleoanthropologists for several decades later. This reconstruction by and large placed man on the side branch that stemmed from the human evolution tree. That later reconstruction affected scientific thinking about human evolution because it became certain that Neanderthals are the closest extinct relatives of modern humans. The reconstruction of the Old Man (which was the most significant, yet most controversial Neanderthal discovery) showed that the individual’s skull had a large middle part on the face, and that his cheek bones were angled, had a huge nose that conveniently served to humidify and warm cold and dry weather for them (Green, et al., 425). Further, their bones were stockier and shorter than ours, which must have been another special adaptation for living in the cold environments of their days. However, the size of their brains were just like ours, though theirs were often a just bit larger. There have been various misconceptions on the evolution tree that has predictably generated many debates on the key taxa involved in the science of human evolution. Scientists now hold true that in a phylogeny, details regarding relatedness is manifested by the pattern of branching, as opposed to the order of taxa as it appears at the tips of the tree. Further, those organisms that share a branching point that is more recent (i.e. those that have a more recent common ancestor) are more correlated or closely related than those organisms that are connected by branding points which are more ancient (i.e. branching points that is closer to the root of the tree) (Templeton, 1515). Taxa that appear at or near the top-right side of the phylogeny has been portrayed as being more advanced in many ways than other organisms on the tree. However, this has been corrected by scientists who have collectively originated the view that in evolution, the use of the words “advanced” and “primitive” is wrong and that they do not apply. The paradigm shift has been informed by the understanding that these value judgments have no place in the realm of science. However, there are no qualms that one form of trait could be ancestral to another form of trait that is more derived, but it would be wrong to say that one form is therefore more primitive and the other more advanced (Mackleprang, and Rubin, 230). This would be trying to imply that evolution is progressive – which is not the case. The other point to note is that where an organism is placed on the phylogeny does not indicate how specialized or adaptive or extreme its traits are, but rather it indicates its relationship with other organisms. The branching patterns contain information in a phylogeny, but that information is not contained in the order of the taxa as they appear at the tips of the tree. Exploring ancient DNA is quite challenging in terms of finding credible and sufficient material that can be relied on after the fossils have undergone decomposition. It is also challenging in trying to eliminate modern human contamination. Organisms decompose after they die, in addition, it is a known fact that water, air and microbes break down DNA. In a span of 100,000 years, an organism’s DNA is usually destroyed in its totality. DNA from ancient fossil is usually found in small quantities, and that which is found is usually damaged and fragmented. Contamination of the DNA is the other factor that has always been difficult to solve. This is clouded by the fact that it is substantially difficult to detect contamination. This is because humans and Neanderthals share a large part of their genetic material. This in effect makes it difficult to distinguish some DNA sequence. It is for this reason that researchers developed new ways of analyzing results generated from ancient DNA sequence which seeks to find out whether contamination has occurred, and in what quantities (Kring, et al., 26). This has led to a number of successful sequencing of ancient DNA which devised ways of dealing with potential contamination. The first of those efforts was led by Swedish geneticist Svante Pääbo who was leading a team from Max Planck Institute to make the first breakthrough of sequencing on a Neanderthal (Green el al. 2008). Pääbo’s lab produced evidence contained in a draft sequence of the genome of the Neanderthal that suggested inbreeding between the modern Homo sapiens and Neanderthals. This DNA evidence points to a fact that the modern Homo sapiens and the Neanderthals coexisted; the evidence also points to a change in some aspects of the human genome, which occurred after the split between the Neanderthals and human. Studies of Neanderthal fossils DNA which began in the 1980s and culminated in a number of Neanderthal genome later offered unique window of understanding the lives and traits of our hominin relatives. Further, the evidence served as a key to unlock the long held mystery of whether Neanderthals coexisted with Homo sapiens. A landmark finding to that extent was originated Pääbo, as stated, who after drawing on genetic and fossil clues was able to explore what we now know about the ancestry of modern humans. His finding explored the relationship between humans and Neanderthals and details on the nature of the interactions that existed between the two species (Green, 416). While finding the lost genome, Pääbo discovered that the modern human is indeed all part Neanderthal, with an exception of those whose heritage is entirely African. Physical anthropologist and archeologists have for long debated the evolutionary relationship between modern humans and Neanderthals. This debate has revolved around the similarities and differences the structure and shapes of their bones, and the design of the artifacts. However, there was no significant understanding of how these differences might have arisen. The lengthy academic arguments have been annulled by a revolution brought about by evidence on studies on ancient DNA which was started by Pääbo and recounted with sheer brilliance in his his book Neanderthal Man: In Search of the Lost Genomes. The success of Pääbo and his team extraction DNA from the ancient fossils found that the lineages of modern humans and Neanderthals had split approximately 270,000 and 440,000 years ago (Paabo, 103). This was a finding that bolstered rather than negated existing views. Additionally, and more surprisingly is that their finding concluded that people whose heritage is not African (i.e. Europeans, Asians) have approximately 5 percent of their DNA coming from Neanderthals. Their agreement paint a scenario where it is likely that a section of modern humans migrated from Africa approximately 50,000 years ago, settled in the Middle East where they coexisted (lived together) and even interbred with Neanderthals (Paabo, 56). It would be expected that over time that DNA would be diluted with the progressive human generation succession, however the DNA has been persistent to this day. This would be suggestive of an indication that some variations of the Neanderthal genes have given modern humans in Asia and Europe adaptive capabilities that are more enhanced over their African Homo sapiens ancestors. This DNA evidence on the inbreeding changes the way we have always believe about the expansion of modern human from Africa. Further, it negates the strictest scenario that has suggested that modern humans anatomically replaced ancient or archaic hominines in totality without the likelihood of inbreeding. Nevertheless, even with the inbreeding between modern humans and Neanderthals, much of our genomes are traced back to Africa (Paabo, 27). The data also paints a clearer picture of when that inbreeding might have occurred. Neanderthal DNA and that of modern Homo sapiens are equally related as was seen in samples from China, Papua New Guinea and France. In that regard, data showed that admixture between Neanderthals and moderns must have taken place before the time that Eurasian population split. Remains of both Neanderthals and modern human which date back approximately 100,000 years ago have been discovered in the Middle East 9Green, et al, . It is believed that there were not many inbreeding activities during that period in time, which explains the kind of result that this study generated. Research by Kring et al. (23) indicates that Neanderthal mtDNA sequence is significantly different from that of modern human’s mtDNA. A conclusive comparison between Neanderthals and moderns and chimpanzees sequence produced interesting results. The finding indicated that most sequence among human differ from each other by substitutions of 8.0 on average, further, chimps and human sequence differ from each other by an average of 55.0 substitution. Additionally, modern human and Neanderthal sequences differ by substitutions of 27.0 on average. In that regard, is mtDNA information indicate that the last common ancestor of modern humans and Neanderthals dates back between about 55,000 to 690,000 years (Relethford and Rubin, 563). This means that it is four times older than the mtDNA pool of modern human bolstering the notion that Neanderthals did not substantially contribute to the genome of the modern human. A second mtDNA sequence derived from a Neanderthal whose age was estimated to be 29,000 was discovered in Mezmaiskaya Cave in Russia. The two Neanderthal sequences were consistent with the fact that Neanderthal mtDNA sequence was substantially different from that of modern humans. These two mtMDA findings served as a confirmation that it was highly unlikely that Neanderthals contributed to the genome of modern humans (Green, et al, 2008). Neanderthals are therefore the end of line of modern evolution following Homo erectus and not direct ancestors of the modern humans because Neanderthals were an evolutionary dead end. Works Cited Green, R. E., Malaspinas, A.-S. Krause, J., Briggs, A., Johnson, P., Uhler, C., Meyer, M., Good, J., Maricic, T., Stenzel, U. A complete Neandertal mitochondrial genome sequence determined by high-throughput sequencing. Cell 134: 416-426, 2008. Print Khun, Thomas S. The structure of scientific revolutions. (50th edn) Chicago, IL: The University of Chicago, 2012. Print Krings, M., Stone, A., Schmitz, R.W., Krainitzki, H., Stoneking, M., Pääbo, S. Neandertal DNA Sequences and the origin of modern humans. Cell 90: 19-30, 1997. Print Mackelprang, R., Rubin, E.M.. New tricks with old bones. Science 321: 221-212, 2008. Paabo, Svante. Neanderthal man: In search of the lost genomes. New York, NY: Basic Books, 2014. Print Relethford, J. H. Genetic evidence and the modern human origins debate. Heredity 100: 555-563, 2008. Print Templeton, A. Genetics and recent human evolution. Evolution 61(7): 1507-1519, 2007. Print Read More