Staff author: Adilia S.

The new research established that nations living far away from Africa have accumulated more harmful gene mutations than the ones in the historical centre of human civilization.

The Swiss scientists give us reasonable arguments stating that a big number of gene mutations were acquired during human resettlement from the African continent. The study insists these 50-thousand years old changes still influence our gene pool today because once they have emerged it’s highly improbable that they disappear within a limited gene pool.

The harmful mutations accumulated because people travelled from Africa in small tribes, which caused mutations to persist rather than perish. The study was conducted by Swiss Institute of Bioinformatics (SIB).

Harmful Mutations of Genes

It is believed that a modern man appeared in Africa about 150,000 years ago. After living there for 100 thousand years, some of them abandoned their habitat, spreading first to the Asian continent. Moving further East, certain groups crossed the Bering Strait and colonized America.

Laurent Excoffier and his associates worked out theoretical patterns of their research based on the idea that people travelled in small groups. Thus being separated from their main population and ancestors, they would have to gradually acquire some adverse mutations, due to limited gene pool and children born to close relatives.

The amount of the mutations, researchers thought, would depend on the distance from Africa: The further away, the more mutations they expected to find. In simple words, a Mexican would bear a greater number of gene mutations than an African man.

To check their ideas the researchers took advantage of the modern NGS method (next-generation sequencing), which allowed to decipher genetic codes of a person’s genome.

Scientists have studied the genetic data of people from 4 demos outside of Africa (see the image):

• Siberia (Russia)
• Mexico
• Cambodia
• Pakistan

The African nations, where genomes were studied:

• Algeria
• Namibia
• Congo

The researchers modeled the spatial resettlement of gene changes. Their initial ideas were confirmed: The number of harmful gene mutations grew with the distance from Southern Africa, Science Daily reports.

Harmful mutations have accumulated in tribes during human resettlement from Africa. Image by Swiss Institute of Bioinformatics. (Click to enlarge)

The major cause for the greater number of such mutations is that survival of the fittest is not effective in small groups as it is in larger ones. In addition, natural selection processes had less time to work in such groups that emerged during the resettlement. Small traveling tribes cultivated harmful mutations, in a way. African genomes had the least amount of harmful mutations.

The scientists assert that small mutations of genes developed in a way as if they were treated neutral during the resettlement, which potentially occurred over 1000 generations.

It stands to mention that the resettlement took place about 50,000 years ago yet it still has an influence on the current genetic diversity because the mutations are passed on from generation to generation. The research was made possible due to the latest advancements in the ability to analyse vast amounts of data.

* NGS method enables to decipher the human genome (determine the precise order of nucleotides within a DNA molecule). This is the newest method for studying human diversity of genes. Not so long ago it was used during in vitro fertilization (IVF), as it can detect chromosomal abnormalities in embryos, and select the most viable.

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