Earth’S Occupants Have Clearly
Earth’s occupants have clearly been around for an extensive amount of time, given the fact that the Earth itself is over 4.6 billion years. Finding out how old our home planet is, through the use of lead dating, was difficult enough for Clair Cameron Patterson and George Tilton. Narrowing down the origin of our species requires rigorous effort and constant theory challenging. Throughout recent history, the two leading arguments, Multiregional and Out of Africa, present valid theories that counter each other. However, more recent evidence has been presented to further confirm one of the two hypotheses.
The Multiregional Evolution of Humans by Alan G. Thorne and Milford H. Wolpoff presents the argument that the rise of Homo sapiens was not confined to any one territory. Rather, this “rise” was a marvel that happened all through the whole geographic range where people once lived. Therefore theorizing that Homo Erectus left Africa, scattered into different parts of the Old World and gradually became present day people, or modern day humans, through evolution.
The Out of Africa theory hypothesizes that H. Sapiens relocated out of Africa and replaced all other populations without the use of interbreeding. This argument theorizes that H. Sapiens, or modern humans, emerged in a single region, presumably Africa which includes the Middle East. The “Eve” argument is presented as the first record of Mitochondrial DNA which is traced back to Africa, about 200,000 years.
Mitochondrial DNA plays a huge role in the argument for and against each of the two hypotheses. Mitochondria is only acquired from one’s mother and serves as a marker for maternal heredities. Whereas the Y chromosome is passed from father to son. The mtDNA contains 37 genes, which are all fundamental for normal human function. The favorable position on mitochondria is that it clones itself as opposed to recombining.
As we discussed in lecture on Nov. 7, there are 4 kinds of skeletally and genetically distinct hominins: Neandertals, which were predominantly located in Western Europe, Denisovans, located in Eastern Eurasia, Hobbits from Flores Island, and H. Sapiens located in Africa. Denisovans are cousins of Neadertals but there are no actual fossils, but a small piece of a pinky bone, found. Interestingly enough, the small piece of pinky bone brought in a high quality genome. These hominids and their locations add more evidence to prove that the Multiregional hypothesis is more accurate than Out of Africa. Later in lecture on the 21st of November, we discussed that Neandertals lived when modern humans lived, therefore Neanderthals do not come before humans.
In the article, The Multiregional Evolution of Humans, the “Noah’s Ark” model is introduced. The theory is also known as the “Garden of Eden”, where the biblical reference to “Eve” comes from, according to Chris Stringer in Genetics and Genealogy: Article 20. According to ScienceDaily, the investigation on Eve depended on a correlation of 10 human hereditary models to decide when she lived utilizing an alternate arrangement of suppositions about the way people moved and migrated over Earth’s land.
Christ Stringer was a young graduate student when he took to Europe and theorized that “Neandertals in Europe were not ancestors of modern humans there…but a separate species that had been completely replaced by modern humans” (p. 363 Revolution Human Evolution). When the news of mtEve was released, many believed she was the only woman living at the time of her existence. This assumption is easily shut down due to the reminder of the existence of Java man and Lucy, who both beat Eve in age.
The behavior between modern and premodern humans is divided by a fine line. During our class lectures we discussed how they might have interacted with one another and how they began to modernize through their tool making and whatever social skills they had developed. One topic we discussed was Shanidar 1. Accoring to the Smithsonian, National Museum of Natural History, suffered a blow to the head, damaging the part of the brain that controls the right side of his body. Nevertheless, he could not fend for himself. Scientist estimated that he lived for another 30 years which seems impossible without the help of another in his group. By this time, these Neandertals showed dependency on each other which is something modern humans show. The tool making evolution is the most intriguing because the different types of stone tools they made and for which purpose they were used for. The tool making process when from stones to hafting, which is the process of affixing small stone bifaces and flakes in wood to make spears and knives, a process we went over in lecture on Nov. 08.
One big argument against the Multiregional model is the lack of “huge levels of gene flow in early continents” (p. 59, African Genesis of Humans). The two authors discuss the anatomical characteristics were not inherited but were a result of the evolution they went through when settling and colonizing the island of New Guinea. The argument of the characteristics are referring to the theory that similarities in geographic race do not always mean they are closely related in mtDNA. Later the article goes on to acknowledge that the idea of one human species overcoming and replacing another one seems unlikely. However they give logical, possible contributions to this possible outcome. Some speculate that some sort of disease whipped out one group of humans. Cavalli Sforza, a geneticist and professor at Stanford University, speculates that “ancestors of modern humans may have developed some modern trait, such as advanced language skills, that effectively cut them off from breeding with other hominids.” (p. 61) The article also states that fossil finds in caves at Qafezeh suggest modern humans and Neandertals lived in close quarters but there was little to no evidence that they interbred.
The article “The Neandertal in the family” closely examines the polymerase chain reaction, or PCR. This is the act of extracting DNA from ancient tissue and comparing it to living populations. The sensitivity of the method made it subject to contamination which later made the use of other methods and procedures very likely. Svante Pääbo, a Swedish biologist who specializes in evolutionary genetics. One of the originators of paleogenetics, he has worked widely on the Neadnertal genome. In recent years, as palaeogenomics grows in specialist laboratories. Now, the new techniques enable scientists to extract DNA from even the most dissipated fossils to extract the parts of a genome they are more invested in. While Pääbo set off to answer the question on whether or not Stringer’s theory was correct, he came upon fossils that had been contaminated by Stringer’s DNA, only making his voyage for the answers more difficult. During this trip, Pääbo found that Neandertals did have a genome distinguishable from ours.
Throughout the readings we have been assigned, the one that grabbed my attention while discussing the topic of these two hypotheses was “Tangled Roots: Mingling among Stone Age peoples muddies humans’ evolutionary story” By Bruce Bower. Bower mentions both Christ Stringer and Milford Wolpoff, two anthropologists I previously mentioned. Bower reminds the audience that Stringer is a “key architect of the formerly dominant Out of Africa model” but is later “caught off guard by reports of interbreeding” which the model strongly opposes the possibility of. Up until this news, the Out of Africa model was the dominant and presiding hypothesis among the two.
The emergence of modern humans with modern anatomy and behavior came about between 300 cya and 40 kya. Anatomically modern humans, or AMH, are those that are skeletally identical to humans living today. One example of an AMH, according to Science Magazine is the worlds oldest H. sapien fossil found in Jebel Rhoud which is an archeological site located in Morocco. (Gibbons, 2017)
In the article, a map is shown with the paths of H. erectus, H. heidelbergensis, and H. sapiens. H. erectus, evolved 2 million years ago, travels from Africa, through Asia, and down to Indonesia where they evolved into Hobbits. H. heidelbergensis, a H. erectus descendant, originated in an unknown location and later spread to Africa and parts of Southern Europe and Asia where they later evolved into Neandertals. In Africa about 130,000 years ago, a line of H. heidelbergensis becomes H. sapien and they migrate from Africa about 60,000 years ago. Later, H. sapiens move to parts of Europe and then to Indonesia and onto Australia 10,000 years later. They make the cross into North and South America about 14,000 years ago. This visual map that shows the journey of our ancestors begins to prove that the Multiregional model is more accurate than the Out of Africa model. When this model was released, the theory of anthropologist Fred Smith and anthropologist Erik Trinkaus, began to seem more accurate with the model. Although H. sapiens did originate from Africa, the proof of interbreeding between H. sapiens and Neadertals and Deisovans arose.
Throughout our class lectures, the reading assignments, the two articles given for the take home essay and my own research, I believe the Multiregional Model proves to be the most accurate given the information given to us both old and new. Interbreeding and evolution are two of the main components of my point of view in this conclusion. Interbreeding has been proven in almost all the points made and many of the articles I read, where the Out of Africa model leaves it out. The idea of one human population whipping out another with little to no evidence of it seems highly unlikely, even with the given possibilities of how it happened.
The Multiregional hypothesis theory is overall best supported by the evidence given. After going through the older articles and funded the updated versions of the theories presented, the Out of Africa model seemed to be dominant all the way through until about the last 10 years when more evidence against the theory arose.