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Becoming Human

Roselaure Anstral
Roselaure Anstral

1) The document discusses the author's research into human origins and the evolution of modern humans. It seeks to define what makes humans unique and trace the journey from early hominids to Homo sapiens. 2) The author examines how humans diverged from chimpanzees around 4.5 million years ago. There is evidence that early humans and chimpanzees may have interbred as they evolved into separate species. 3) Neanderthals are also discussed as a close human relative. Evidence suggests modern humans interbred with Neanderthals after migrating out of Africa, with gene flow occurring 47,000-65,000 years ago.

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Becoming Human Journey of the origin of Modern Humans Roselaure Anstral May 2, 2014
Roselaure Anstral April 28, 2014 Human Origins Becoming Human Abstract During my 14+ years in school, I have always been drawn to learning how everything began including our origins. I was only aware of two explanations: creation and the big bang. The explanation you choose for your personal self is important because the theory you choose shapes your understanding of what it means to be human and how we came to be what we are today. To answer such questions, I needed a clear definition of what a human is. This definition is not a simple one, and it is one of great controversy, but to be simple- what we consider as human is behaviorally modern humans; factors such as our behaviors plays a big role in our definition in addition to our DNA. The journey or our evolution of becoming a modern human is just as important as the definition. Topics such as reproducing with chimps and Neanderthals are interesting debates that comes up in my research. In the end, I have learned the tools to intellectually communicate with my peers about this controversial and sometime touching subject. My aim was to answer the hard questions and to be able to share what I have learned with those who are open to learning what science really has to say about becoming human. Introduction During my 18 years in school, I have always been drawn to learning how everything began including our origins. I was exposed to many different explanations of what led to me being alive today, at this very moment, writing this very paper. When I was much younger, the dominant explanation in my life was the creation theory- commonly known as the Adam and Eve
Roselaure Anstral April 28, 2014 Human Origins story. Then, while in grade school, I learned of the Big Bang theory but at a very limited and primary level. I basically learned that there was a big explosion that led to stars and then earth then humans and here we are. At that point of my life, I was only aware of two explanations which are the explanations popularly known- creation and the big bang. What is important about the position you choose to follow is that the theory you choose also shapes your understanding of what it means to be human and how we came to be what we are today. During this semester, many questions came up. Questions such as what it means to be human and how did we come to be the way we are today as far as our cognitive abilities, our domination over other species on Earth, and many other factors. There are many articles on the internet that have various speculations but not a clear answer. Recently, I came across a question of whether we (humans) had sex with chimpanzees. This question seemed absurd at the time that I came to know of it, but now I see it as somewhat important because it is about the identity of our species. It is human nature to be curious. People just want to know how it is that we became who we are and this is what I am seeking to answer. Defining what is Human The definition of what it is to be human seems like a simple task at first. However, there are many layers to humanity. To fully define what it is to be Human we must consider the obvious: what can humans do that other animals cannot? For one thing, humans walk in an upright position (Smithsonian, 2014). This is something very unique to our species. The earliest forms of humans climbed trees in addition to walking on the ground (Smithsonian, 2014). Being fully bipedal (walking on two legs) is a fairly new development that took many steps in our evolution from the earliest humanoid to todays humans (Smithsonian, 2014). Being fully
Roselaure Anstral April 28, 2014 Human Origins bipedal occurred approximately 1.9 million years ago (Smithsonian, 2014). The benefit of this is as the environment change, walking on two legs became very helpful for the survival of early humans; the cost however is backaches (Smithsonian, 2014) Due to walking upright, the distribution of all of our weight are just on our two lower limbs instead of on all four. Thus, we are prone to back pain, arthritis, and other skeletal problems (Smithsonian, 2014). Another important factor that allows humans to be human is our brains. Our brains are bigger! It took over 6 million years from the earliest humans for our brains to be the size that they are now (Smithsonian, 2014). This advantage is identified as a key element of our survival and domination on Earth. Modern human brains can store many decades worth of information, collect and process information, deliver an output, solve problems, and create abstract ideas and images, in addition to much more such as the development of language and conceptual learning (Smithsonian, 2014). Conceptual learning is a key factor in our success because we can analyze, predict, and plan. Also the development of language is critical because we can communicate and it allows us to develop collective learning. Collective learning has allowed us to maintain information from centuries ago. Thus, we are able to improve on past information. This is also a key factor in the reason our tools and method of gathering food for example has improved greatly (Smithsonian, 2014). This is also very unique to humans. No other specie on Earth store food or have the sort of advance tools that we have. Chimps, however, do have tools, such as stone anvil and hammer stone; but they do not have collective learning thus they are unable to improve on this simplicity (Smithsonian, 2014).
Roselaure Anstral April 28, 2014 Human Origins These are just a few examples of the characteristics of humans. However, how do we fair in comparison so other species, such as chimpanzees? Chimps look like us and they share some human-like behaviors such as tools (Lemonick et al., 2006). Chimps have complex social hierarchies and they can learn to be communicative and perform complex cognitive task (Lemonick et al., 2006). Also, biologists have reported geographic variations in behavior between different groups for apes that could only come about from the cultural transmission of innovation, similar to humans (University of Zurich, 2011). If we consider these aspects, one cannot help but wonder how we compare genetically. Genetically, we humans DNA sequence is 99 percent identical to that of chimpanzees (Pollard, 2009). 99% is a large amount of genetically being similar to an animal. Mice and rats do not even share such a large genetic similarity (Pollard, 2009). This is an indication that we share a fairly recent common ancestor with the chimpanzees. It also it means that a very small percentage of DNA is responsible for the drastic differences of humans to chimps such as those mentioned before (i.e. agriculture and language) (Lemonick et al., 2006). What about the Neanderthals? They are a form of hominid. Our distant cousins, who share the same genus as us, and yet we have survived and they have not. This makes us the dominate species, however chimpanzees- for example- are not the only species of their genus. Yet we humans are within our genus. One cannot help but wonder why, and how does that play a role in becoming human? Neanderthals- although anatomically similar to modern humans, are not considered human. There is a line crossed in between anatomically modern human versus behaviorally modern humans. Anatomically modern human, are hominids that looked very similar to the way we do now- more so than the chimps and other great apes; whereas,
Roselaure Anstral April 28, 2014 Human Origins behaviorally modern humans is having the cognitive abilities of modern (Pollard, 2009). Our behaviors are what we use as an indication of being human, in addition to our DNA. This leaves a valid question, what about our DNA makes us human. In What Makes Us Different, Lemonick et al. (2006) describes a research study that found that the human version of a gene called FOXP2 plays a huge role in our ability to develop speech and language which evolved within the past 200,000 years after anatomically modern humans first appeared. They compared the protein coded by the human FOXP2 gene with the same protein in various great apes and discovered that the amino-acid sequence that makes up the human variant differs from that of the chimp in two locations which is a very small change that may explain the emergence of all aspects of human speech (Lemonick et al., 2006). As described earlier language is a key factor in the development of behaviorally modern humans (us). They also found that humans with a defective FOXP2 gene have trouble articulating words and understanding grammar- this further supports their findings (Lemonick et al., 2006). Returning to the definition of human, what we consider as human includes our modern behaviors that we all share in addition to our genes; all these factors play a role in defining humanity. However, it is not only the what that is important in explaining humanity, but also the journey or evolution that it took to become human. The Journey: From Chimps to Hominid Mapping our evolution has giving us an understanding of where we have come from and a glimpse as to where we might be going. But here I aim to answer the question in relation to our
Roselaure Anstral April 28, 2014 Human Origins evolution. Two main topics in this discussion are when did we separate from chimpanzees and the Neanderthals? This will consequently give an understanding as to what it is to be a modern human. Revisiting the remarkable similarities of modern humans to chimpanzees and other great apes, it is not only the genetic similarities that are astonishing but also in our behavior (Lemonick et al., 2006). These similarities indicate that we share a common ancestor (Sherwood et al., 2008). However it is the distinct differences both behaviorally and genetically that separates the beast from the man; and these differences are due to evolution (Lemonick, 2006). We humans share a common ancestor with every other species on Earth, more recently with primates- new world monkeys (NWM), old world monkeys (OWM), gorillas, and chimpanzees (Takahata et al., 1997). It is argued that our evolution from this common ancestor and the relationship or interaction between hominids and other primates had an influence on us becoming human (Sherwood et al, 2008). Takahata et al. (1997) discussed the exact separation in the ancestral lineage of primates- this includes humans. They conducted a statistical test which supported their assumption that silent substitutions have accumulated in a clock-like fashion over loci between primate taxa or even among sites within a locus (Takahata et al., 1997). Their results showed that the human ancestral lineage became distinct from the NWM 57.5 million years ago, from the OWM 31 million years ago, from the gorilla 8.0 million years ago, and from the chimpanzee 4.5 million ago (Takahata et al. 1997). Based on their results, the human ancestral lineage separated or branched off more recently from the chimpanzees compared to any other primate. From this study, I gained an understanding as the 99% DNA sequence similarity with chimpanzees and the many shared
Roselaure Anstral April 28, 2014 Human Origins phenotype traits (Sherwood et al, 2008). Another topic that became relevant as I pursued an understanding to the development of humanity is the controversial discussion of whether the chimps and primitive humans interbred. Lemonick et al. (2006) stated a study that compared the DNA from chimpanzees and humans with genetic material from gorillas, orangutans and macaques. What this study found was that the entire human X chromosome diverged from the chimp's X chromosome about 1.2 million years later than the other chromosomes and a plausible explanation is that chimps and humans first split but later interbred from time to time before finally going their separate evolutionary ways (Lemonick et al., 2006). In order for this to be plausible, it would indicate that this first split is not a genetic one but a geographic one. Meaning that our common ancestors went separate ways or directions, but before we became two distinct species (chimps and hominid) we would encounter one another. The offspring of two different species cannot reproduce. In order for reproduction to occur, we would have had to still have been the same species (Cain et al. 1953). Consider horses and donkeys. They are different species yet a male donkey and a female horse can reproduce to create a mule (Davies et al. 1985). However, mules are infertile- they cannot reproduce (Davies et al. 1985). Thus to say that humans and chimps had sex which led to a hybrid and subsequently to modern humans would be incorrect, but rather our common ancestors continued to interbred until there was a definitive or more permanent separations in space and genetically that allowed us to become distinct species. Although we are similar to chimps genetically, we are still very much different. In addition to those mentioned previously, unlike the chimpanzees, there is no other surviving
Roselaure Anstral April 28, 2014 Human Origins species within our genus. We are the only hominids alive. For example, the Neanderthals were of the same genus as us, but they are no longer of existence. Chimpanzees, however, have a living cousin Bonobos- they share the same genus yet are different species (Hare et al, 2007). Their divergence took place about 2 million years ago (Hare et al, 2007). They are socially different from one another. The Bonobos are female dominated, and the Chimpanzees are male dominate (Hare et al, 2007). What is astonishing is how have both species survived, the key is that they live in different, locations and have minimum to no interactions with one another (Hare et al, 2007). Thus this separation allowed their ancestors to evolve separate from each other, forming these two distinct species, which have different social structures. This is a curious development in my research, because it makes me wonder if Chimps and Bonobos continued a frequent interaction after they have already became distinct species, would the chimps kill of the bonobos. (I predict the chimps because they are more aggressive than the bonobos (Hare et al, 2007)). Subsequently, it leaves me wondering about the relationship between the Neanderthals and Homo sapiens. Neanderthals and Homo sapiens Neanderthals are an extinct species of human in the genus differing in DNA by only 0.12% (Meshorer et al, 2014). The first humans with proto-Neanderthal traits are believed to have existed in Europe as early as 600,000350,000 years ago (Bischoff et al. 2003). The Neanderthals weren't nearly as primitive as many assume. Physically, Neanderthal's have a larger cranium than modern humans, indicating that their brain size was larger (Meshorer et al, 2014). They had fire, burial ceremonies, and the basics of what we would call art (Lemonick, 2006). They were advanced--but nothing like what humans have done in the last 10,000 to 15,000 years
Roselaure Anstral April 28, 2014 Human Origins (Meshorer et al, 2014). Genetic evidence suggests that Neanderthals contributed to the DNA of anatomically modern humans, probably through interbreeding between 80,000 and 28,000 years ago with a population of anatomically modern humans (Ricon, 2010). According to Sannkararaman et al. (2012) comparisons of DNA sequences between Neanderthals and present-day humans have shown that Neanderthals share more genetic variants with non-Africans than with Africans. They predicted that this could be due to interbreeding between Neanderthals and modern humans when the two groups met subsequent to the emergence of modern humans outside Africa. They measure the extent of linkage instability in the genomes of present-day Europeans and found that the last gene flow from Neanderthals into Europeans occurred approximately 47,00065,000 years ago. They concluded that this evidence supported the interbreeding hypothesis (Sannkararama et al., 2012). However, similar to the earlier discussion of chimpanzees and hominids, I would agree the same. It would have had to been before a definite separation of the two species, for there to be a continuation in the lineage of the hybrid. But this doesnt account for the fact that Neanderthals no longer exist, whereas chimpanzees and bonobos do. In answering the question of what happened to the Neanderthals, there are three possible explanations. These explanation include violence among the two species (Diamond, 1992); there is also an explanation that states that Neanderthals were a subspecies that bred with modern humans and eventually disappeared due to interbreeding and the dominate species (humans) bred them out (Ricardo, 2000); and the third is environmental factors (Golovanova et al, 2010). All three explanations have one thing in common, nature took its course. The dominant specie
Roselaure Anstral April 28, 2014 Human Origins survived. As mentioned before, what really made us an elite species was the development of our cognitive abilities. Sherwood et al. (2008) examined the evolutionary changes that occurred in the ancestry of Homo sapiens by reconstructing the neural and cognitive traits that would have considered the last common ancestor Neanderthals compared with modern humans. Their results showed that the unique brain growth trajectory of modern humans has made a significant contribution to our species cognitive and linguistic abilities and subsequently our domination as the elite species (Sherwood et al., 2008). Conclusion The question of the mode of the origin of modern humans- Homo sapiens- was what I wanted to answer. Through my own personal journey in finding the facts behind human origins, I have learned who we are as a species. We are a part of nature, we are a species that have dominated our genus cousins and that have evolved the cognitive skills needed to be elite. More importantly we are still evolving. The results of my research support the fact that evolution takes millions of years, thus it is only rational to say that we are still evolving. We have come from the initial separation of chimps and hominids, to that of Neanderthals and Homo sapiens, to now. It was an amazing journey over the course of millions of years, and Homo sapiens came out on top. Going back to the initial first two theories of the development of humanity- was it a divine source of creation that allowed us to dominate in nature or was it simply natural selection and chance. I have concluded that the facts support the latter and this answer alone is what drawn me to this journey in the beginning. There are still more questions that scientist are answering about this journey and so there is still more to learn.
Roselaure Anstral April 28, 2014 Human Origins References Bischoff, James L.; Shamp, Donald D.; Aramburu, Arantza; Arsuaga, Juan Luis; Carbonell, Eudald; Bermudez de Castro, J.M. (2003). "The Sima de los Huesos Hominids Date to Beyond U/Th Equilibrium (>350kyr) and Perhaps to 400500kyr: New Radiometric Dates". Journal of Archaeological Science 30 (3): 27580. doi:10.1006/jasc.2002.0834. Cain, A. J. (1953). Geography, ecology and coexistence in relation to the biological definition of the species. Evolution, 76-83. Callaway, Ewen. (2014). Cross-breeding boosted Homo sapiens' ability to cope with cool climates, but the hybrids may have had trouble breeding. Modern Human Genomes reveal our inner Neanderthal. Nature. http://www.nature.com/news/modern-human- genomes-reveal-our-inner-neanderthal-1.14615- 2014 Davies, C. J., Antczak, D. F., & Allen, W. R. (1985). Reproduction in mules: Embryo transfer using sterile recipients. Equine Veterinary Journal, 17(S3), 63-67. Diamond, Jared M. (1992). The third chimpanzee: the evolution and future of the human animal. New York City: HarperCollins. p. 52. ISBN 0-06-098403-1.OCLC 60088352.) Eran Meshorer, Liran Carmel, et al. (2014)."Reconstructing the DNA Methylation Maps of the Neandertal and the Denisovan". Science.doi:10.1126/science.1250368. Golovanova, Liubov et al. (2010). Significance of Ecological Factors in the Middle to Upper Paleolithic Transition. Current Anthropology 51 (5): 65591.doi:10.1086/656185. JSTOR 656185. Lay summary Science Daily Hare, B., Melis, A. P., Woods, V., Hastings, S., & Wrangham, R. (2007). Tolerance allows bonobos to outperform chimpanzees on a cooperative task.Current Biology, 17(7), 619- 623. Lemonick, Micheal D. et al. (2006). What Makes us Different ? TIME Magazine. http://content.time.com/time/magazine/article/0,9171,1541283,00.html Pollard, K. S. (2009). What makes us human? Scientific American, 300(5), 44-49. Public Library of Science. (2011, November 17). Chimps play like humans: Playful behavior of young chimps develops like that of children. ScienceDaily. Retrieved April 21, 2014 from www.sciencedaily.com/releases/2011/11/111116174735.htm Ricardo Faria, J. (2000). What happened to the Neanderthals?the survival trap.Kyklos, 53(2), 161-172.
Roselaure Anstral April 28, 2014 Human Origins Rincon, Paul (2010-05-06). "Neanderthal genes 'survive in us'". BBC News (BBC). Retrieved 2010-05-07.) Sankararaman S, Patterson N, Li H, P辰辰bo S, Reich D (2012) The Date of Interbreeding between Neandertals and Modern Humans. PLoS Genet 8(10): e1002947. doi:10.1371/journal.pgen.1002947 Sherwood, C. C., Subiaul, F., & Zawidzki, T. W. (2008). A natural history of the human mind: tracing evolutionary changes in brain and cognition. Journal of Anatomy, 212(4), 426- 454. Smithsonian Institute. (2014) What does it mean to be human? National Museum of Natural History. http://humanorigins.si.edu/human-characteristics Takahata, N., & Satta, Y. (1997). Evolution of the primate lineage leading to modern humans: phylogenetic and demographic inferences from DNA sequences. Proceedings of the National Academy of Sciences, 94(9), 4811-4815. University of Zurich. (2011, October 26). Culture in humans and apes has the same evolutionary roots, researchers show. ScienceDaily. Retrieved April 21, 2014 from www.sciencedaily.com/releases/2011/10/111020122313.htm Varki, Ajit.(2013) Dating the Origin of Us. The Scientist Magazine. http://www.the- scientist.com/?articles.view/articleNo/38008/title/Dating-the-Origin-of-Us/

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Becoming Human

  • 1. Becoming Human Journey of the origin of Modern Humans Roselaure Anstral May 2, 2014
  • 2. Roselaure Anstral April 28, 2014 Human Origins Becoming Human Abstract During my 14+ years in school, I have always been drawn to learning how everything began including our origins. I was only aware of two explanations: creation and the big bang. The explanation you choose for your personal self is important because the theory you choose shapes your understanding of what it means to be human and how we came to be what we are today. To answer such questions, I needed a clear definition of what a human is. This definition is not a simple one, and it is one of great controversy, but to be simple- what we consider as human is behaviorally modern humans; factors such as our behaviors plays a big role in our definition in addition to our DNA. The journey or our evolution of becoming a modern human is just as important as the definition. Topics such as reproducing with chimps and Neanderthals are interesting debates that comes up in my research. In the end, I have learned the tools to intellectually communicate with my peers about this controversial and sometime touching subject. My aim was to answer the hard questions and to be able to share what I have learned with those who are open to learning what science really has to say about becoming human. Introduction During my 18 years in school, I have always been drawn to learning how everything began including our origins. I was exposed to many different explanations of what led to me being alive today, at this very moment, writing this very paper. When I was much younger, the dominant explanation in my life was the creation theory- commonly known as the Adam and Eve
  • 3. Roselaure Anstral April 28, 2014 Human Origins story. Then, while in grade school, I learned of the Big Bang theory but at a very limited and primary level. I basically learned that there was a big explosion that led to stars and then earth then humans and here we are. At that point of my life, I was only aware of two explanations which are the explanations popularly known- creation and the big bang. What is important about the position you choose to follow is that the theory you choose also shapes your understanding of what it means to be human and how we came to be what we are today. During this semester, many questions came up. Questions such as what it means to be human and how did we come to be the way we are today as far as our cognitive abilities, our domination over other species on Earth, and many other factors. There are many articles on the internet that have various speculations but not a clear answer. Recently, I came across a question of whether we (humans) had sex with chimpanzees. This question seemed absurd at the time that I came to know of it, but now I see it as somewhat important because it is about the identity of our species. It is human nature to be curious. People just want to know how it is that we became who we are and this is what I am seeking to answer. Defining what is Human The definition of what it is to be human seems like a simple task at first. However, there are many layers to humanity. To fully define what it is to be Human we must consider the obvious: what can humans do that other animals cannot? For one thing, humans walk in an upright position (Smithsonian, 2014). This is something very unique to our species. The earliest forms of humans climbed trees in addition to walking on the ground (Smithsonian, 2014). Being fully bipedal (walking on two legs) is a fairly new development that took many steps in our evolution from the earliest humanoid to todays humans (Smithsonian, 2014). Being fully
  • 4. Roselaure Anstral April 28, 2014 Human Origins bipedal occurred approximately 1.9 million years ago (Smithsonian, 2014). The benefit of this is as the environment change, walking on two legs became very helpful for the survival of early humans; the cost however is backaches (Smithsonian, 2014) Due to walking upright, the distribution of all of our weight are just on our two lower limbs instead of on all four. Thus, we are prone to back pain, arthritis, and other skeletal problems (Smithsonian, 2014). Another important factor that allows humans to be human is our brains. Our brains are bigger! It took over 6 million years from the earliest humans for our brains to be the size that they are now (Smithsonian, 2014). This advantage is identified as a key element of our survival and domination on Earth. Modern human brains can store many decades worth of information, collect and process information, deliver an output, solve problems, and create abstract ideas and images, in addition to much more such as the development of language and conceptual learning (Smithsonian, 2014). Conceptual learning is a key factor in our success because we can analyze, predict, and plan. Also the development of language is critical because we can communicate and it allows us to develop collective learning. Collective learning has allowed us to maintain information from centuries ago. Thus, we are able to improve on past information. This is also a key factor in the reason our tools and method of gathering food for example has improved greatly (Smithsonian, 2014). This is also very unique to humans. No other specie on Earth store food or have the sort of advance tools that we have. Chimps, however, do have tools, such as stone anvil and hammer stone; but they do not have collective learning thus they are unable to improve on this simplicity (Smithsonian, 2014).
  • 5. Roselaure Anstral April 28, 2014 Human Origins These are just a few examples of the characteristics of humans. However, how do we fair in comparison so other species, such as chimpanzees? Chimps look like us and they share some human-like behaviors such as tools (Lemonick et al., 2006). Chimps have complex social hierarchies and they can learn to be communicative and perform complex cognitive task (Lemonick et al., 2006). Also, biologists have reported geographic variations in behavior between different groups for apes that could only come about from the cultural transmission of innovation, similar to humans (University of Zurich, 2011). If we consider these aspects, one cannot help but wonder how we compare genetically. Genetically, we humans DNA sequence is 99 percent identical to that of chimpanzees (Pollard, 2009). 99% is a large amount of genetically being similar to an animal. Mice and rats do not even share such a large genetic similarity (Pollard, 2009). This is an indication that we share a fairly recent common ancestor with the chimpanzees. It also it means that a very small percentage of DNA is responsible for the drastic differences of humans to chimps such as those mentioned before (i.e. agriculture and language) (Lemonick et al., 2006). What about the Neanderthals? They are a form of hominid. Our distant cousins, who share the same genus as us, and yet we have survived and they have not. This makes us the dominate species, however chimpanzees- for example- are not the only species of their genus. Yet we humans are within our genus. One cannot help but wonder why, and how does that play a role in becoming human? Neanderthals- although anatomically similar to modern humans, are not considered human. There is a line crossed in between anatomically modern human versus behaviorally modern humans. Anatomically modern human, are hominids that looked very similar to the way we do now- more so than the chimps and other great apes; whereas,
  • 6. Roselaure Anstral April 28, 2014 Human Origins behaviorally modern humans is having the cognitive abilities of modern (Pollard, 2009). Our behaviors are what we use as an indication of being human, in addition to our DNA. This leaves a valid question, what about our DNA makes us human. In What Makes Us Different, Lemonick et al. (2006) describes a research study that found that the human version of a gene called FOXP2 plays a huge role in our ability to develop speech and language which evolved within the past 200,000 years after anatomically modern humans first appeared. They compared the protein coded by the human FOXP2 gene with the same protein in various great apes and discovered that the amino-acid sequence that makes up the human variant differs from that of the chimp in two locations which is a very small change that may explain the emergence of all aspects of human speech (Lemonick et al., 2006). As described earlier language is a key factor in the development of behaviorally modern humans (us). They also found that humans with a defective FOXP2 gene have trouble articulating words and understanding grammar- this further supports their findings (Lemonick et al., 2006). Returning to the definition of human, what we consider as human includes our modern behaviors that we all share in addition to our genes; all these factors play a role in defining humanity. However, it is not only the what that is important in explaining humanity, but also the journey or evolution that it took to become human. The Journey: From Chimps to Hominid Mapping our evolution has giving us an understanding of where we have come from and a glimpse as to where we might be going. But here I aim to answer the question in relation to our
  • 7. Roselaure Anstral April 28, 2014 Human Origins evolution. Two main topics in this discussion are when did we separate from chimpanzees and the Neanderthals? This will consequently give an understanding as to what it is to be a modern human. Revisiting the remarkable similarities of modern humans to chimpanzees and other great apes, it is not only the genetic similarities that are astonishing but also in our behavior (Lemonick et al., 2006). These similarities indicate that we share a common ancestor (Sherwood et al., 2008). However it is the distinct differences both behaviorally and genetically that separates the beast from the man; and these differences are due to evolution (Lemonick, 2006). We humans share a common ancestor with every other species on Earth, more recently with primates- new world monkeys (NWM), old world monkeys (OWM), gorillas, and chimpanzees (Takahata et al., 1997). It is argued that our evolution from this common ancestor and the relationship or interaction between hominids and other primates had an influence on us becoming human (Sherwood et al, 2008). Takahata et al. (1997) discussed the exact separation in the ancestral lineage of primates- this includes humans. They conducted a statistical test which supported their assumption that silent substitutions have accumulated in a clock-like fashion over loci between primate taxa or even among sites within a locus (Takahata et al., 1997). Their results showed that the human ancestral lineage became distinct from the NWM 57.5 million years ago, from the OWM 31 million years ago, from the gorilla 8.0 million years ago, and from the chimpanzee 4.5 million ago (Takahata et al. 1997). Based on their results, the human ancestral lineage separated or branched off more recently from the chimpanzees compared to any other primate. From this study, I gained an understanding as the 99% DNA sequence similarity with chimpanzees and the many shared
  • 8. Roselaure Anstral April 28, 2014 Human Origins phenotype traits (Sherwood et al, 2008). Another topic that became relevant as I pursued an understanding to the development of humanity is the controversial discussion of whether the chimps and primitive humans interbred. Lemonick et al. (2006) stated a study that compared the DNA from chimpanzees and humans with genetic material from gorillas, orangutans and macaques. What this study found was that the entire human X chromosome diverged from the chimp's X chromosome about 1.2 million years later than the other chromosomes and a plausible explanation is that chimps and humans first split but later interbred from time to time before finally going their separate evolutionary ways (Lemonick et al., 2006). In order for this to be plausible, it would indicate that this first split is not a genetic one but a geographic one. Meaning that our common ancestors went separate ways or directions, but before we became two distinct species (chimps and hominid) we would encounter one another. The offspring of two different species cannot reproduce. In order for reproduction to occur, we would have had to still have been the same species (Cain et al. 1953). Consider horses and donkeys. They are different species yet a male donkey and a female horse can reproduce to create a mule (Davies et al. 1985). However, mules are infertile- they cannot reproduce (Davies et al. 1985). Thus to say that humans and chimps had sex which led to a hybrid and subsequently to modern humans would be incorrect, but rather our common ancestors continued to interbred until there was a definitive or more permanent separations in space and genetically that allowed us to become distinct species. Although we are similar to chimps genetically, we are still very much different. In addition to those mentioned previously, unlike the chimpanzees, there is no other surviving
  • 9. Roselaure Anstral April 28, 2014 Human Origins species within our genus. We are the only hominids alive. For example, the Neanderthals were of the same genus as us, but they are no longer of existence. Chimpanzees, however, have a living cousin Bonobos- they share the same genus yet are different species (Hare et al, 2007). Their divergence took place about 2 million years ago (Hare et al, 2007). They are socially different from one another. The Bonobos are female dominated, and the Chimpanzees are male dominate (Hare et al, 2007). What is astonishing is how have both species survived, the key is that they live in different, locations and have minimum to no interactions with one another (Hare et al, 2007). Thus this separation allowed their ancestors to evolve separate from each other, forming these two distinct species, which have different social structures. This is a curious development in my research, because it makes me wonder if Chimps and Bonobos continued a frequent interaction after they have already became distinct species, would the chimps kill of the bonobos. (I predict the chimps because they are more aggressive than the bonobos (Hare et al, 2007)). Subsequently, it leaves me wondering about the relationship between the Neanderthals and Homo sapiens. Neanderthals and Homo sapiens Neanderthals are an extinct species of human in the genus differing in DNA by only 0.12% (Meshorer et al, 2014). The first humans with proto-Neanderthal traits are believed to have existed in Europe as early as 600,000350,000 years ago (Bischoff et al. 2003). The Neanderthals weren't nearly as primitive as many assume. Physically, Neanderthal's have a larger cranium than modern humans, indicating that their brain size was larger (Meshorer et al, 2014). They had fire, burial ceremonies, and the basics of what we would call art (Lemonick, 2006). They were advanced--but nothing like what humans have done in the last 10,000 to 15,000 years
  • 10. Roselaure Anstral April 28, 2014 Human Origins (Meshorer et al, 2014). Genetic evidence suggests that Neanderthals contributed to the DNA of anatomically modern humans, probably through interbreeding between 80,000 and 28,000 years ago with a population of anatomically modern humans (Ricon, 2010). According to Sannkararaman et al. (2012) comparisons of DNA sequences between Neanderthals and present-day humans have shown that Neanderthals share more genetic variants with non-Africans than with Africans. They predicted that this could be due to interbreeding between Neanderthals and modern humans when the two groups met subsequent to the emergence of modern humans outside Africa. They measure the extent of linkage instability in the genomes of present-day Europeans and found that the last gene flow from Neanderthals into Europeans occurred approximately 47,00065,000 years ago. They concluded that this evidence supported the interbreeding hypothesis (Sannkararama et al., 2012). However, similar to the earlier discussion of chimpanzees and hominids, I would agree the same. It would have had to been before a definite separation of the two species, for there to be a continuation in the lineage of the hybrid. But this doesnt account for the fact that Neanderthals no longer exist, whereas chimpanzees and bonobos do. In answering the question of what happened to the Neanderthals, there are three possible explanations. These explanation include violence among the two species (Diamond, 1992); there is also an explanation that states that Neanderthals were a subspecies that bred with modern humans and eventually disappeared due to interbreeding and the dominate species (humans) bred them out (Ricardo, 2000); and the third is environmental factors (Golovanova et al, 2010). All three explanations have one thing in common, nature took its course. The dominant specie
  • 11. Roselaure Anstral April 28, 2014 Human Origins survived. As mentioned before, what really made us an elite species was the development of our cognitive abilities. Sherwood et al. (2008) examined the evolutionary changes that occurred in the ancestry of Homo sapiens by reconstructing the neural and cognitive traits that would have considered the last common ancestor Neanderthals compared with modern humans. Their results showed that the unique brain growth trajectory of modern humans has made a significant contribution to our species cognitive and linguistic abilities and subsequently our domination as the elite species (Sherwood et al., 2008). Conclusion The question of the mode of the origin of modern humans- Homo sapiens- was what I wanted to answer. Through my own personal journey in finding the facts behind human origins, I have learned who we are as a species. We are a part of nature, we are a species that have dominated our genus cousins and that have evolved the cognitive skills needed to be elite. More importantly we are still evolving. The results of my research support the fact that evolution takes millions of years, thus it is only rational to say that we are still evolving. We have come from the initial separation of chimps and hominids, to that of Neanderthals and Homo sapiens, to now. It was an amazing journey over the course of millions of years, and Homo sapiens came out on top. Going back to the initial first two theories of the development of humanity- was it a divine source of creation that allowed us to dominate in nature or was it simply natural selection and chance. I have concluded that the facts support the latter and this answer alone is what drawn me to this journey in the beginning. There are still more questions that scientist are answering about this journey and so there is still more to learn.
  • 12. Roselaure Anstral April 28, 2014 Human Origins References Bischoff, James L.; Shamp, Donald D.; Aramburu, Arantza; Arsuaga, Juan Luis; Carbonell, Eudald; Bermudez de Castro, J.M. (2003). "The Sima de los Huesos Hominids Date to Beyond U/Th Equilibrium (>350kyr) and Perhaps to 400500kyr: New Radiometric Dates". Journal of Archaeological Science 30 (3): 27580. doi:10.1006/jasc.2002.0834. Cain, A. J. (1953). Geography, ecology and coexistence in relation to the biological definition of the species. Evolution, 76-83. Callaway, Ewen. (2014). Cross-breeding boosted Homo sapiens' ability to cope with cool climates, but the hybrids may have had trouble breeding. Modern Human Genomes reveal our inner Neanderthal. Nature. http://www.nature.com/news/modern-human- genomes-reveal-our-inner-neanderthal-1.14615- 2014 Davies, C. J., Antczak, D. F., & Allen, W. R. (1985). Reproduction in mules: Embryo transfer using sterile recipients. Equine Veterinary Journal, 17(S3), 63-67. Diamond, Jared M. (1992). The third chimpanzee: the evolution and future of the human animal. New York City: HarperCollins. p. 52. ISBN 0-06-098403-1.OCLC 60088352.) Eran Meshorer, Liran Carmel, et al. (2014)."Reconstructing the DNA Methylation Maps of the Neandertal and the Denisovan". Science.doi:10.1126/science.1250368. Golovanova, Liubov et al. (2010). Significance of Ecological Factors in the Middle to Upper Paleolithic Transition. Current Anthropology 51 (5): 65591.doi:10.1086/656185. JSTOR 656185. Lay summary Science Daily Hare, B., Melis, A. P., Woods, V., Hastings, S., & Wrangham, R. (2007). Tolerance allows bonobos to outperform chimpanzees on a cooperative task.Current Biology, 17(7), 619- 623. Lemonick, Micheal D. et al. (2006). What Makes us Different ? TIME Magazine. http://content.time.com/time/magazine/article/0,9171,1541283,00.html Pollard, K. S. (2009). What makes us human? Scientific American, 300(5), 44-49. Public Library of Science. (2011, November 17). Chimps play like humans: Playful behavior of young chimps develops like that of children. ScienceDaily. Retrieved April 21, 2014 from www.sciencedaily.com/releases/2011/11/111116174735.htm Ricardo Faria, J. (2000). What happened to the Neanderthals?the survival trap.Kyklos, 53(2), 161-172.
  • 13. Roselaure Anstral April 28, 2014 Human Origins Rincon, Paul (2010-05-06). "Neanderthal genes 'survive in us'". BBC News (BBC). Retrieved 2010-05-07.) Sankararaman S, Patterson N, Li H, P辰辰bo S, Reich D (2012) The Date of Interbreeding between Neandertals and Modern Humans. PLoS Genet 8(10): e1002947. doi:10.1371/journal.pgen.1002947 Sherwood, C. C., Subiaul, F., & Zawidzki, T. W. (2008). A natural history of the human mind: tracing evolutionary changes in brain and cognition. Journal of Anatomy, 212(4), 426- 454. Smithsonian Institute. (2014) What does it mean to be human? National Museum of Natural History. http://humanorigins.si.edu/human-characteristics Takahata, N., & Satta, Y. (1997). Evolution of the primate lineage leading to modern humans: phylogenetic and demographic inferences from DNA sequences. Proceedings of the National Academy of Sciences, 94(9), 4811-4815. University of Zurich. (2011, October 26). Culture in humans and apes has the same evolutionary roots, researchers show. ScienceDaily. Retrieved April 21, 2014 from www.sciencedaily.com/releases/2011/10/111020122313.htm Varki, Ajit.(2013) Dating the Origin of Us. The Scientist Magazine. http://www.the- scientist.com/?articles.view/articleNo/38008/title/Dating-the-Origin-of-Us/