ANTH 1020-014 Human Origins
Instructor: Potter, Terri
Student: Nicholson, Erick
April 10th 2015
Assignment: Research Paper, Discuss the two theories of Modern Human Origins (Regional Continuity and Replacement). Describe each theory. Critically evaluate the merits of the two models; presenting fossil and genetic evidence that supports either one. Discuss which model you think is the most correct and why.
Regional Continuity theory, also called multiregional evolution, was put forth by Milford Wolpoff of the University of Michigan and by Alan Thorn of the Australian National University. It argues that our early hominid ancestors migrated out of Africa 1.8 million years ago and spread out around the world thus the evolution of modern humans took place in different parts of the world simultaneously. This theory places great emphasis on the notion of steady evolutionary alterations. Evolution of this kind is kept at a regular rate due to an amalgamation of cultural progress and ‘gene flow’ thus keeping all the different parts of the globe evolving at the same pace. Alan Thorn suggested that gene flow can be likened to that of individuals swimming in a pool – “although they maintain their individuality, they are often influenced by the spreading ripples made by the activity of other people in the water”. This, they suggest, is the “equivalent of genes flowing between populations” (Wolpoff, M and Thorne, A)(Edwards, S Anthro Journal)
To help support this theory Dennis O’Neil claim that there has been a continuity of some anatomical traits from archaic humans to modern humans in Europe and Asia. The Asian and European physical characteristics have antiquity in these regions going back over 100,000 years. They point to the fact that many Europeans have relatively heavy brow ridges and a high angle of their noses reminiscent of Neanderthals. Similarly, it is claimed that some Chinese facial characteristics can be seen in an Asian archaic human fossil from Jinniushan dating to 200,000 years ago. Like Homo erectus, East Asians today commonly have shovel-shaped incisors while Africans and Europeans rarely do. This supports the contention of direct genetic links between Asian Homo erectus and modern Asians. (O’Neil, D) When it comes to looking at genetics for an answer to the question, is this right. Genetics dose show a more common ancestor 200,000 years ago but it also shows that there was interbreeding with the species that all ready existed in an area and with the homo aspens coming out of Africa.
Replacement theory, also called the “Out of Africa Model”, emphasizes that modern humans first evolved in Africa and only later dispersed to other parts of the world, where they replaced the hominids that all ready lived there (Jurmain, R, Kilgore, L and Trevathan, W 285). In the last few years this theory has been split into two Versions, the first one emphasizes complete replacement, and like it sounds they think that about 200,000 years ago, what we consider modern humans arose in Africa and completely replaced the populations of Europe and Asia, with no inter breeding of any kind (Stringer and Andrews 1988). The second theory is called partial replacement, as it sounds, it’s a partial replacement of the local population. We have a replacement population coming out of Africa but instead of just replacing the current population it is interbreeding with the existing people and evolving to what we think of as modern humans.
When we look at fossil records to prove these theories, one study I found was by biologist Andrea Manica of the University of Cambridge in the U.K., where her team compared 4666 male skulls from 105 worldwide populations. They conclude that the diversity of cranial shape within a population falls off the farther it is from Africa, Similar results came from a second study of 1579 female skulls. The researchers could find no evidence for multiple centers of diversity outside Africa, as might be predicted by the multiregional model. They concluded that their results strongly support the Out of Africa model (Balter, M). Another thing to look at in the fossil record is age, so far, the earliest finds of modern Homo sapiens skeletons come from Africa. They date to nearly 200,000 years ago on that continent. They appear in Southwest Asia around 100,000 years ago and elsewhere in the Old World by 60,000-40,000 years ago. Unless modern human remains dating to 200,000 years ago or earlier are found in Europe or East Asia, it would seem that the replacement model better explains the fossil data for those regions (O’Neil, D).
When we look at the genetic side of things, we can look at mitochondria DNA (mtDNA) and that will show what some people call a mitochondrial Eve, who lived 200,000 years ago and that can be traced back to Africa, (Can, R Stonking, M and Wilson, A) and the indigenous African population have far greater genetic diversity than do other populations from else where in the world. (Jurmain, R Kilgore, L and Trevathan 286)(Can, R Stonking, M and Wilson, A) We might also consider the genetic variation between populations groups, or the lack there of. The high degree of similarity between human populations stands in strong contrast to the condition seen in our closest living relatives, the chimpanzees. In fact, there is significantly more genetic variation between two individual chimpanzees drawn from the same population than there is between two humans drawn randomly from a single population. Furthermore, genetic variation between populations of chimpanzees is enormously greater than differences between European, Asian and African human populations. The low amount of genetic variation in modern human populations suggests that our origins may reflect a relatively small founding population for Homo sapiens (Johanson, D).
What I think? I’m not convinced that ether model is wholly correct by themselves, they both have difficulty accounting for all of the fossil and genetic data, I think that a blending of them, (all be it a little heavy on the replacement side) is what makes the most sense with the evidence that is set forth in all that I have read. We have the mtDNA that dose set a genetic mother and a most likely location for her, but at the same time the whole genome shows that there was interbreeding going on, sense we still show signs of Neanderthal DNA in the population. This says that they where not just replaced out right by the migrating population coming out of Africa at the time, but rather they where slowly absorbed into the larger African Homo sapiens population. This would make sense when you think, there were so few Neanderthals compared to Homo sapiens, that with each successive generation, the children of Homo sapiens and Neanderthals looked more like Homo sapiens and less like Neanderthals. In the end, all that was left of Neanderthals were those few genes that were passed along in many people's DNA (Newitz, A). Through that absorbing of other DNA and the principles of evolution we can see how regional continuity would have taken the large chunk of African Homo sapiens and allowed such a large and varied out come of phenotypes that we currently have, while at the same time keeping our genome so close that its easier to find more differences in two chimpanzee’s than two humans.
Instructor: Potter, Terri
Student: Nicholson, Erick
April 10th 2015
Assignment: Research Paper, Discuss the two theories of Modern Human Origins (Regional Continuity and Replacement). Describe each theory. Critically evaluate the merits of the two models; presenting fossil and genetic evidence that supports either one. Discuss which model you think is the most correct and why.
Regional Continuity theory, also called multiregional evolution, was put forth by Milford Wolpoff of the University of Michigan and by Alan Thorn of the Australian National University. It argues that our early hominid ancestors migrated out of Africa 1.8 million years ago and spread out around the world thus the evolution of modern humans took place in different parts of the world simultaneously. This theory places great emphasis on the notion of steady evolutionary alterations. Evolution of this kind is kept at a regular rate due to an amalgamation of cultural progress and ‘gene flow’ thus keeping all the different parts of the globe evolving at the same pace. Alan Thorn suggested that gene flow can be likened to that of individuals swimming in a pool – “although they maintain their individuality, they are often influenced by the spreading ripples made by the activity of other people in the water”. This, they suggest, is the “equivalent of genes flowing between populations” (Wolpoff, M and Thorne, A)(Edwards, S Anthro Journal)
To help support this theory Dennis O’Neil claim that there has been a continuity of some anatomical traits from archaic humans to modern humans in Europe and Asia. The Asian and European physical characteristics have antiquity in these regions going back over 100,000 years. They point to the fact that many Europeans have relatively heavy brow ridges and a high angle of their noses reminiscent of Neanderthals. Similarly, it is claimed that some Chinese facial characteristics can be seen in an Asian archaic human fossil from Jinniushan dating to 200,000 years ago. Like Homo erectus, East Asians today commonly have shovel-shaped incisors while Africans and Europeans rarely do. This supports the contention of direct genetic links between Asian Homo erectus and modern Asians. (O’Neil, D) When it comes to looking at genetics for an answer to the question, is this right. Genetics dose show a more common ancestor 200,000 years ago but it also shows that there was interbreeding with the species that all ready existed in an area and with the homo aspens coming out of Africa.
Replacement theory, also called the “Out of Africa Model”, emphasizes that modern humans first evolved in Africa and only later dispersed to other parts of the world, where they replaced the hominids that all ready lived there (Jurmain, R, Kilgore, L and Trevathan, W 285). In the last few years this theory has been split into two Versions, the first one emphasizes complete replacement, and like it sounds they think that about 200,000 years ago, what we consider modern humans arose in Africa and completely replaced the populations of Europe and Asia, with no inter breeding of any kind (Stringer and Andrews 1988). The second theory is called partial replacement, as it sounds, it’s a partial replacement of the local population. We have a replacement population coming out of Africa but instead of just replacing the current population it is interbreeding with the existing people and evolving to what we think of as modern humans.
When we look at fossil records to prove these theories, one study I found was by biologist Andrea Manica of the University of Cambridge in the U.K., where her team compared 4666 male skulls from 105 worldwide populations. They conclude that the diversity of cranial shape within a population falls off the farther it is from Africa, Similar results came from a second study of 1579 female skulls. The researchers could find no evidence for multiple centers of diversity outside Africa, as might be predicted by the multiregional model. They concluded that their results strongly support the Out of Africa model (Balter, M). Another thing to look at in the fossil record is age, so far, the earliest finds of modern Homo sapiens skeletons come from Africa. They date to nearly 200,000 years ago on that continent. They appear in Southwest Asia around 100,000 years ago and elsewhere in the Old World by 60,000-40,000 years ago. Unless modern human remains dating to 200,000 years ago or earlier are found in Europe or East Asia, it would seem that the replacement model better explains the fossil data for those regions (O’Neil, D).
When we look at the genetic side of things, we can look at mitochondria DNA (mtDNA) and that will show what some people call a mitochondrial Eve, who lived 200,000 years ago and that can be traced back to Africa, (Can, R Stonking, M and Wilson, A) and the indigenous African population have far greater genetic diversity than do other populations from else where in the world. (Jurmain, R Kilgore, L and Trevathan 286)(Can, R Stonking, M and Wilson, A) We might also consider the genetic variation between populations groups, or the lack there of. The high degree of similarity between human populations stands in strong contrast to the condition seen in our closest living relatives, the chimpanzees. In fact, there is significantly more genetic variation between two individual chimpanzees drawn from the same population than there is between two humans drawn randomly from a single population. Furthermore, genetic variation between populations of chimpanzees is enormously greater than differences between European, Asian and African human populations. The low amount of genetic variation in modern human populations suggests that our origins may reflect a relatively small founding population for Homo sapiens (Johanson, D).
What I think? I’m not convinced that ether model is wholly correct by themselves, they both have difficulty accounting for all of the fossil and genetic data, I think that a blending of them, (all be it a little heavy on the replacement side) is what makes the most sense with the evidence that is set forth in all that I have read. We have the mtDNA that dose set a genetic mother and a most likely location for her, but at the same time the whole genome shows that there was interbreeding going on, sense we still show signs of Neanderthal DNA in the population. This says that they where not just replaced out right by the migrating population coming out of Africa at the time, but rather they where slowly absorbed into the larger African Homo sapiens population. This would make sense when you think, there were so few Neanderthals compared to Homo sapiens, that with each successive generation, the children of Homo sapiens and Neanderthals looked more like Homo sapiens and less like Neanderthals. In the end, all that was left of Neanderthals were those few genes that were passed along in many people's DNA (Newitz, A). Through that absorbing of other DNA and the principles of evolution we can see how regional continuity would have taken the large chunk of African Homo sapiens and allowed such a large and varied out come of phenotypes that we currently have, while at the same time keeping our genome so close that its easier to find more differences in two chimpanzee’s than two humans.
ANTH 1020-014 Human Origins
Instrutor: Potter, Terri
Student: Nicholson, Erick
Reference Page
ePortfolio: www.nicholsonerick.weebly.com
Text Book Human Origins 2013 p284 - 287
By Robert Jurmain, Lynn Kilgore and Wenda Trevathan
Strange and Andrews 1988 Sciences vol 241 p 773 - 774
Science magazine July 2007 - Out of Africa, The sequel by Michael Balter
Nature magazine January 1987 by Rebecca Can, Mark Stonking and Allen C Wilson
Collegiate Journal of Anthropology (anthrojournal) Analysis of two competing theories on the origin of homo sapiens, by Sophie Edwards July 07, 2012
actionbiosciences.org/evolution/johanson.html
Origins of modern Humans : Multiregional or Out of Africa? by Donald Johanson May 2001
www.anthro.palomar.edu/homo2/mod_homo_4.htm by Dennis O’Neil
www.i09.com/a-long-anthropological-debate-may-be-on-the-cusp-of-res-512864731
A long anthropological debate may be on the cusp of resolution
filed to Human evolution June 2013 by Annalee Newitz
Instrutor: Potter, Terri
Student: Nicholson, Erick
Reference Page
ePortfolio: www.nicholsonerick.weebly.com
Text Book Human Origins 2013 p284 - 287
By Robert Jurmain, Lynn Kilgore and Wenda Trevathan
Strange and Andrews 1988 Sciences vol 241 p 773 - 774
Science magazine July 2007 - Out of Africa, The sequel by Michael Balter
Nature magazine January 1987 by Rebecca Can, Mark Stonking and Allen C Wilson
Collegiate Journal of Anthropology (anthrojournal) Analysis of two competing theories on the origin of homo sapiens, by Sophie Edwards July 07, 2012
actionbiosciences.org/evolution/johanson.html
Origins of modern Humans : Multiregional or Out of Africa? by Donald Johanson May 2001
www.anthro.palomar.edu/homo2/mod_homo_4.htm by Dennis O’Neil
www.i09.com/a-long-anthropological-debate-may-be-on-the-cusp-of-res-512864731
A long anthropological debate may be on the cusp of resolution
filed to Human evolution June 2013 by Annalee Newitz