Population genetics is concerned with the genetic basis of evolution. The objects of study in population genetics are typically the frequencies and fitnesses of genotypes in a population. In the population genetics sense, evolution is the change of genotype frequencies over time, which may or may not be due to natural selection. The time scale of evolution is an exceedingly long one, so it is difficult to follow much genetic change in populations. Rather, population genetics is driven by constructing mathematical models of evolution and then checking if their predictions are met by natural populations.

In a 1991 commentary in the journal Genetics, Richard Lewinton wrote:

"When I entered Theodosius Dobzhansky's laboratory as a graduate student in 1951, the problematic of population genetics was the description and explanation of genetic variation within and between populations. That remains the problematic 40 years later in 1991."
It is no less central to the field in 2001.

Genetic variation is of central importance because evolution can only happen when there is variation to act on in a population. This understanding has helped to make population genetics the basis of modern evolutionary theory.

Population Movement Traced through a Maternal Line


This is an extract from my degree thesis, kind of the remotly interesting bit (if you're in to this kind of thing). I might post some links to a more simple look which spells out what it all means if people want)

Human migratory patterns can be determined by various means, irrespective of the technique used all have one thing in common, the information is derived. This means that we can only get glimpses in to the past by examining artefacts or remnants of that time and trying to work out what that artefact can tell us.

Archaeologists often ascertain who might have lived in a certain area by the finding of a distinctive household item that has survived in to the present, such as a specially crafted hairpin. Firstly the archaeologist would look for distinguishing marks to tell what particular tribe might have owned such at item, then carbon dating it to ascertain how long ago this might have been. Evolutionary geneticists use very different tools but essentially a similar approach. Firstly a particular stretch of DNA once found, would be examined for distinguishing features i.e. mutations that might identify its haplogroup.
Secondly it could be compared to a known sample and by the use of a molecular clock, a time of divergence could be ascertained. This is useful for dating particular settlements, if for instance a group left the mainland to live on an isolated island their DNA would diverge / become distinctively different.

The genetic differences could be compared, to then give a rough idea of when they separated i.e. when the island was settled. These techniques of looking at modern DNA and ascertaining its history have lead to information about global population movements. This has been possible since the original movement leading to new settlements was a very slow process due to the many problems encountered by early man allowing genetic mutation to keep up.

The problems primarily faced by evolutionary biologists, is to figure out what an ancestral DNA sequence might have looked like. A stretch of DNA is needed which most accurately represents the generations before to allow it to be grouped with others from the same ancestor. Also the mutations present should give direct information on it’s past and not be influenced by environmental factors. A solution was the use of mitochondrial DNA (mtDNA).
MtDNA is particularly useful, its genome is known and it contains areas within its genome, which are highly prone to mutation. This mutation rate is necessary as it can resolve differences in populations to a higher degree. Mitochondrial DNA is inherited solely from the mother so a more accurate picture of the previous generation is given without the interference of recombination as happens in nuclear DNA. There are also multiple copies of mtDNA in a cell so there will be more copies of a particular locus within a mitochondrion than there would be from nuclear DNA.

In summary, mtDNA analysis allows a 'peek' in to a persons maternal lineage. This allows more accurate information to be compiled as recombination is not an important factor. Using these techniques families can be traced, race determined and early population movements can be assertained. If you trace it back far enough, you can find Mitochondrial Eve.

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