Although the human genome has basically the same genes from one person to the next, there is a huge amount of variation in the sequence of genes; some variations are small while others are very large, some of them have huge biological consequences while others are more subtle. Genetic studies rely on databases that carry sequence information for the genome. At one time, there weren't many human genomes that had been completely sequenced and could be used as a reference. The ones that had were mostly of European ancestry. About 16 percent of the world's population is of European descent but these individuals represent about 80 percent of genetic data. But researchers know that lack of diversity is a problem, and some are trying to change that. Studying the variations in the genome in different groups will tell us more about many things including human evolution, migration, or how biology and disease are connected to the genome.
The human genome contains about three billion bases, the vast majority of which don't sit in protein-coding genes. There is a huge amount of variation in the genome; this study alone has identified 4.8 million new variants that are found in Middle Eastern populations, which may provide new insight into disease or open up fresh research questions.
Many groups of people have historically been underrepresented in genetic studies. That's left gaps in our understanding of history, which can't be filled by other fields like archaeology. Now reporting in Cell, scientists have generated 137 genome sequences from eight populations from the Arabian Peninsula, the Levant (which includes Syria, Jordan and Lebanon), and Iraq. The work was done with linked-read sequencing, and will fill some of the knowledge gaps.
"The Middle East is an important region to understand human history, migrations, and evolution: it is where modern humans first expanded out of Africa, where hunter-gatherers first settled and transitioned into farmers, where the first writing systems developed, and where the first major known civilizations emerged," noted Mohamed Almarri of the Wellcome Sanger Institute. "However, despite this importance, the region has been historically understudied in genomic studies."
This research suggested that there was a huge decrease in Arabian populations about 6,000 years ago, a time which coincides with a change in the climate of Arabia from green spaces to desert. The researchers also found genetic changes that spread quickly in the population, suggesting that the environments and lifestyles were shifting quickly. Agriculture is thought to have been developed in the Levant, and there was a huge growth in population there.
The study also found that Middle Easterners are descendants of the same population that migrated out of Africa about 55,000 years ago. There is also significantly less Neanderthal ancestry in Arabian poeple compared to other Eurasian people.
"We found 4.8 million variants that were not previously discovered in other populations," Haber said. "Hundreds of thousands of these are common in the region, and any of them could hold medical relevance."
The researchers found that in some populations, there was an increase in genetic variants that are linked to type 2 diabetes in the past 2,000 years. Some of these variants may have once been beneficial, but are now disease-linked.
The investigators are planning to follow up on some of these findings to learn more about their biological relevance.