Paleogenetics

Paleogenetics is the study of the past through the examination of preserved genetic material from the remains of ancient organisms. Emile Zuckerkandl and Linus Pauling introduced the term in 1963, long before the sequencing of DNA, in reference to the possible reconstruction of the corresponding polypeptide sequences of past organisms. The first sequence of ancient DNA, isolated from a museum specimen of the extinct quagga, was published in 1984 by a team led by Allan Wilson.

Paleogeneticists do not recreate actual organisms, but piece together ancient DNA sequences using various analytical methods. Fossils are "the only direct witnesses of extinct species and of evolutionary events" and finding DNA within those fossils exposes tremendously more information about these species, potentially their entire physiology and anatomy.

The oldest DNA yet sequenced dates to around two million years ago and was extracted from sediments in northern Greenland.

Applications

Evolution

Similar DNA sequences and their encoded proteins are found in different species. This similarity is directly linked to the sequence of the DNA (the genetic material of the organism). Due to the improbability of this being random chance, and its consistency too long to be attributed to convergence by natural selection, these similarities are best explained by common ancestry. This allows DNA sequences to be compared between species. Comparing an ancient genetic sequence to later or modern ones can be used to determine ancestral relations, while comparing two modern genetic sequences can determine, within error, the time since their last common ancestor.

Ancient DNA research allows scientists to uncover how past organisms lived, including insights into their health, genetics, and interactions with their environment. A method used is called metagenomics which studies all the DNA in an environmental sample to identify different organisms

Human evolution

Genetic data can provide a new understanding for the evolution of human genes and how diseases are transmitted. Ancient archaeological human remains have been a way to see how human structure has changed over time.

Using the thigh bone of a Neanderthal female, 63% of the Neanderthal genome, allowing comparison of billions of bases to the modern human genome. It showed that Homo neanderthalensis were the closest living relative of Homo sapiens, until the former lineage died out 30,000 years ago. The Neanderthal genome was shown to be within the range of variation of those of anatomically modern humans, although at the far periphery of that range of variation. Neanderthals and modern humans share more DNA with each other than either does with chimpanzees. It was also found that Neanderthals were less genetically diverse than modern humans, which indicates that Homo neanderthalensis grew from a group composed of relatively few individuals. DNA sequences suggest that Homo sapiens first appeared between about 130,000 and 250,000 years ago in Africa.

Paleogenetics opens up many new possibilities for the study of hominid evolution and dispersion. By analyzing the genomes of hominid remains, researchers can trace their lineage and estimate common ancestry. The Denisova hominid, a species of hominid found in Siberia from which DNA was able to be extracted, may show signs of having genes that are not found in any Neanderthal nor Homo sapiens genome, possibly representing a new lineage or species of hominid.

Evolution of culture

Looking at DNA can give insight into lifestyles of people of the past. Paleogenic research has linked genetic changes to cultural and behavioral development in early human life.Neandertal DNA shows that they lived in small temporary communities. DNA analysis can also show dietary restrictions and mutations, such as the fact that Homo neanderthalensis was lactose-intolerant.

Archaeology

Recovery and reconstruction of ancient DNA

Many advances have been made to studying archeological remains, such as the recovery of ancient DNA.

The areas prone for researchers to collect DNA include bone and teeth.

Ötzi

thumb|The reconstructed mummified remains of Ötzi the Iceman. His preserved DNA brought more understanding to ancient human genetics.

Ötzi died around 3,300 B.C., and his remains were discovered frozen in the Eastern Alps, near the Austria- Italy border in 1991 by a couple of hikers. His genetic material was analyzed in the 2010s. His DNA brought insight into prehistoric life, or more precisely, into the Copper Age of Europe. According to his DNA, Ötzi had brown eyes and a tan complexion. Further study found that he was lactose intolerant, it was assumed by scientists that this allele was rare to see in the Copper Ages, it was originally thought this allele gained popularity in the Middle Ages.

Challenges

Ancient remains usually contain only a small fraction of the original DNA of an organism, often fragmented into very short sequences. These short fragments can make genome assembly and accurate sequence alignment difficult, especially in species with no close modern relatives. This is due to the degradation of DNA in dead tissue by biotic and abiotic decay. DNA preservation depends on a number of environmental characteristics, including temperature, humidity, oxygen and sunlight. Remains from regions with high heat and humidity typically contain less intact DNA than those from permafrost or caves, where remains may persist in cold, low oxygen conditions for several hundred thousand years. In addition, DNA degrades much more quickly following excavation of materials, and freshly excavated bone has a much higher chance of containing viable genetic material. Distinguishing between evolutionary variation from chemical errors requires advanced computational programs for these processes to be repeated. Scientists use the models and repeated experiments to set apart the differences. They can use their genetic finding along with archeological evidence to better understand a civilization.