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sexual selection and natural selection essay
sexual selection and natural selection essay
sexual selection and natural selection essay
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SUMMARY. Studies in the field of ancient DNA began thirty years ago. Key discoveries proved that ancient DNA is an important tool in the search for difficult answers pertaining to our past. Studies on pigmentation genetics showed that adaptation for different UV radiations was the major factor contributing to the formation of the current pigmentation pattern in Europe, but there is evidence which highlights the additional effect of sexual selection. From the various genes described to play a role in the determination of human skin, hair and eye color, HERC2, SLC24A4 and SLC45A2 seem to be most strongly associated with this phenotypic characteristics.
Keywords: ancient DNA, pigmentation genetics, melanin
Introduction
The DNA of archaeological human remains is an important tool in the search for difficult answers on our past: the evolution and the origin of the human species, the origin of our diseases, the genetics and evolution of our phenotypic characteristics. The first results in this field were obtained in 1985 by Pääbo et al from a 2430 years old Egyptian mummy (Kefi, 2011). This study used bacterial cloning to amplify small, old DNA sequences. With the development of improved techniques such as PCR and new generation sequencing technologies, it became possible to isolate and routinely amplify ancient DNA, and to surmount problems related to the alteration of ancient DNA (Rizzi et. al, 2012).
The preservation of ancient DNA depends not only on the age and type of the sample (Grigorenko et. al, 2009), but also on environmental conditions. The alteration of ancient DNA is a consequence of autolysis and microbial degradation, but humidity, high or very variable temperatures and very alkaline or acidic pH also contributes to t...
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...d irides, Pigment Cell Melanoma Research 21: 97-105
Walsh, S., Liu, F., Ballantyne, K.N., Oven, M., Lao, O., Kayser, M. (2011) IrisPlex: a sensitive DNA tool for accurate prediction of blue and brown eye colour in the absence of ancestry infromation, Forensic Science International: Genetics, 5, 170-180
Walsh, S., Liu, F., Wollstein, A., Kovatsi, L., Ralf, A., Kosiniak-Kamysz, A., Branicki, W., Kayser, M. (2013) The HIrisPlex system for simultaneous prediction of hair and eye colour from DNA, Forensic Science International: Genetics, 7, 98-115
Wang, Y., Li, S.M, Huang, J., Chen, S.Y., Liu, Y.P (2014) Mutation of TYR and MITF genes are associated with plumage colour phenotypes in Geese, Asian-Australasian Journal of Animal Science, 27(6), 778-783
Wasmeier, C., Hume, A.N.,Bolasco, G., Seabra, M.C. (2008) Melanosomes at a glance, Journal of cell science, 121, 3995-3999
Paabo’s team discovered an mtDNA sequence from a finger bone they found from around 40,000 years ago, as carbon dating is one of the most commonly used methods of determining a fossil’s age. (Hammer, 70). Also, Neanderthal mtDNA is differs severely from modern human mtDNA. For example, Microcephalin is a gene for brain size during the development of the organism.
When people hear African history their initial thoughts are slavery and segregation, yet there is more to African history than those two events. The reason why many people would only know the American portion of African history is because that is what is predominately taught in most schools. In the movie Hidden Colors 2: The Triumph of Melanin, it goes deeper into the cultural beginning of the African history. As mentioned in the film “90% of African history makes up everything”. Hidden Colors 2 is an exceptional and informative documentary that extends to telling the hidden truths behind the suppression of the black culture.
79%, were heterozygous. We concluded that it is possible to examine small amounts of DNA by
Mitochondrial DNA has a lot of characteristics and features which makes its use very essential in determining the spread of humans throughout the world. Human mitochondrial DNA is solely inherited from mothers. A human’s mitochondrial DNA is the same as his mother’s mitochondrial DNA, which is the same as her mother’s mitochondrial DNA. Researchers can estimate a probability distribution of ancestors’ genes and migration paths through time if they are given a set of mitochondrial gene sequences. It is assumed that all mitochondrial DNA types in the human gene pool can ultimately be traced back to a common matrilineal ancestor that lived approximately 200,000 years ago in Africa.(Oven et al, 386) All human mitochondrial DNA can be traced back to a single mitochondrial DNA known as “mitochondrial Eve”, who lived in Africa a long time ago. Mutations are m...
...G.E., Ioannou P.A., Scheer W.D., Herrera R.J. et al. 1994. Africa origin of human-specific polymorphic Alu insertions. Evolution Vol. 91: pp 12288-12292
This uncovering of Lucy was very fascinating and answered many questions to our human evolution.The search for human ancestry has been ongoing for the past century since the publication of Charles Darwin’s “Origins of the Species”. As more evidence about the ‘branches’ of the evolutionary tree of many distinct animals and species, researchers were able to think of better hypotheses about humans’ ancestors. This scientific hard effort, involving researchers from many variety of fields from Evolutionary Biology to Paleontology. As many pieces of the puzzles were revealed, so grows the great knowledge about the history of life on our planet.
Australopithecus afarensis who existed 3.5 million years ago and a 4.4 million year old skeleton of an Ardipithecus ramidus are the closest science has come to discovering the human lineage. Shattered Ancestry an article written by Katherine Harmon discusses the remains of two hominids found within Ethiopia. These skeletal remains have created a huge controversy within the topic of evolution questioning many assumptions that have been made referencing the human lineage. The skeleton of the Australopithecus afarensis was named Lucy and was discovered in 1974. The evidence of her walking upright on her two feet essentially guaranteed her a spot in the human lineage line. Lucy was a chimplike ape that was said to walk upright making scientists believe the human ancestry was simple. The complete skeleton found in Ethiopia of an Ardipithecus ramidus named Ardi completely changed all assumptions made from scientists about the complexity of the human lineage. These remains have encouraged researches that the human line is not the only lineage to have evolved but the chimpanzee line has undergone drastic changes as well. There are many traits that researchers have always directly linked to the human lineage however since these discoveries occurred researchers are reconsidering. The recent discoveries that have shattered what has always suggested what linked a species to the human lineage have changed the certainty of whether it is possible to confidently identify the human’s last common ancestor. Majority of scientist had forgotten that there would have been many hominid species living together at one time. New theories have been suggested since scientists revealed that the foot of a hominid found called the Burtele site was found ju...
Myers, provider of source material for Edie Heydt's notes from "Human Origins," fall 1997, Alfred. Much of the material in the notes is paraphrased, and the original information sources are unknown.
DNA Timeline: DNA Science from Mendel to Today. (2014). Retrieved May 29, 2014, from http://www.dnai.org/timeline/
Scientists thought that interbreeding would be a logical assumption to the Neanderthal conundrum. Unfortunately, any evidence of DNA from Neanderthals mixed with human DNA is difficult to come by because their fossils are usually tarnished upon finding. That is until Svante Paabo, and his research team from the Max Planck Institute for Evolutionary Anthropology, came across the remains of twenty-four Neanderthals and forty early humans.* All of these fossils were nearly 40,000 years old and were from Germany, Russia, and Croatia. Nine of these fossils (four Neanderthal and five human)
In later years, many European scientists defined race by separating Homo Sapiens into three to six different groups. * Australoid: those from Australia, Melanesian islands * Caucasoid: Europe, North Africa, South west Asia * Mongoloid: East Asia, Siberia, the Americas * Negroid: Central and Southern Africa * Native Americans * Polynesians The scientific justification for these six groups was that members of these groups shared similar physical characteristics and originated in a particular region of the world. During the nineteenth century theories of race were advanced both by the scientific community and in the popular daily and periodical press. One idea that was taken into belief was racial standing based on skull size and features. The human skull was us...
W. Raymond Johnson, The Journal of Egyptian Archaeology, (1996), pp. 65-82, Date viewed 19th may, http://www.jstor.org/stable/pdfplus/3822115.pdf?&acceptTC=true&jpdConfirm=true
No one knew how heredity (passing traits) worked until Gregor Mendel, an Austrian monk, crossbred pea plants in his monastery kitchen garden in 1865. In 1869, gene-hunters found rod-like shape in the nucleus of cells that turned red when dye was added. They named this “Chromosome”, from a Greek word, chroma for color. They also went deeper into the cell and discovered a wispy microscopic thread within the chromosomes, which they named DNA. There were several scientists who did not know about Mendel’s breakthrough at the time, but then in 1900, they rediscovered his experiment and old journal copies.
If they had only recessive genes, there would be no dark eyed, haired or skinned people. This leads to the conclusion that all people have a black ancestor. This is backed up by the well-accepted idea that Africa was the starting place of humanity. As African species travelled north to Europe they made the previous inhabitants extinct.
This meant that over time, humans lost most of their hair on their bodies, leaving their skin exposed. Sweat glands were going to help the body cool down, but they couldn’t protect the skin from harmful UV rays. This is where melanin works its magic, and it’s the reason for the diversity in skin color today. Melanin helps reduce the absorption of wavelengths into the skin (Chaplin, Jablonski, 59).... ...