Exploring human demography is a tricky business, yet it is also vitally important if we want to know about our past. This is of particular interest for the population of Finland who are genetically very different from other European populations.
New research has sought to trace the curious history of the Finns. Xiaoming Liu, assistant professor in the Department of Epidemiology, Human Genetics and Environmental Sciences at UTHealth School of Public Health, has developed a new population genetics model which could explain why the genetic composition of Finnish people is so different from that of other European peoples.
What Liu found was that a previously unknown population bottleneck had occurred amongst the Finnish population at some point between 10,000 and 20,000 years ago.
A bottleneck is a period of time when population size decreases drastically, before recovering. Often, bottlenecks happen as a result of migration, environmental changes, disease, or war. Interestingly, the bottleneck which hit the Finns did not affect other European populations.
As there are fewer people left after a fall in population, subsequent generations have fewer genetic differences, leading to a distinct genetic group. This, Liu argues, was the case in Finland.
“Inferring human demographic history using genetic information can shed light on important prehistoric evolutionary events such as population bottleneck, expansion, migration and admixture, among others,” Liu wrote in his study, published in the most recent edition of Nature Genetics. “It is also the foundation of many population genetics analyses, as demographic history is one of the most important forces shaping the polymorphic pattern of the human genome.”
Liu and his colleagues at UTHealth developed a new method for analysing prehistoric populations. Previously, researchers could either predefine a demographic model, or try to be model-flexible when they studied the genetics of a population. Clearly, the second model-flexible method is better suited for more exploratory analyses.
Liu’s new method is a form of model-flexible analysis, called the Stairway Plot. The Stairway Plot models the frequency of singly nucleotide polymorphisms (SNPs) in whole genome sequences of hundreds of individuals. Liu and his team applied this model to a sample of thousands of genomes, collected as part of the 1000 Genome Project, an international research initiative to catalogue human genetic variation.
Genomes from nine different populations from European, African and Asian ancestries were examined by Liu and his colleagues.
On top of the Finnish bottleneck, the team also confirmed a previously found bottleneck amongst the African population between 100,000 and 200,000 years ago. According to Liu, this African bottleneck could well be associated with the origin of the modern human.
The precise cause of the Finnish bottleneck remains a mystery; Liu notes that any suggestion of a possible cause would be mere conjecture.
Liu’s research reveals why and when the genetic divergence amongst the Finnish population occurred: a population bottleneck between 10,000 and 20,000 years ago. Exactly what caused this bottleneck, however, is unknown.
For more information: www.nature.com
Image courtesy of Wikimedia Commons user: Ikiwaner