True Left

The Fatty Acid Desaturase (FADS1) gene is associated with the synthesis of FADS1 protein, an enzyme secreted in the liver and shown to be associated with the conversion of shorter chain fatty acids to longer length active forms. The FADS1 protein is found to be associated with the conversion of omega 3 and omega 6 from plant based fats to functional and longer forms like EPA, DHA and arachidonic acid (AA). Animal meat, fish and eggs are already rich in EPA, DHA and arachidonic acid, which reduces the need for the FADS1 protein. People with the C variant of the gene are found to be associated with reduced activity of the protein.

Individuals who do not produce sufficient amount of fatty acids need to consume more animal foods to meet requirements, while individuals who can convert plant-based oils to EPA, DHA and arachidonic acid would benefit from consuming a diet that is rich in vegetable oils and lower in omega-6-rich animal meats.
...
Ancestry:

The FADS1 single nucleotide polymorphism that we include is found to have a significant association with the fatty acid composition in our blood. The ancestral allele C (rs174547) was predominant among the hunter gatherers and, with the start of farming, the allele T became the predominant allele.

Cornell researchers describe a genetic variation that has evolved in populations that have historically favored vegetarian diets, such as in India, Africa and parts of East Asia.
...
The vegetarian allele evolved in populations that have eaten a plant-based diet over hundreds of generations. The adaptation allows these people to efficiently process omega-3 and omega-6 fatty acids and convert them into compounds essential for early brain development and controlling inflammation. In populations that live on plant-based diets, this genetic variation provided an advantage and was positively selected in those groups.
...
Analysis using data from the 1,000 Genomes Project similarly found the vegetarian allele in 70 percent of South Asians, 53 percent of Africans, 29 percent of East Asians and 17 percent of Europeans.

“Northern Europeans have a long history of drinking milk and they absorbed enough end products from milk for long-chain fatty acid metabolism so they don’t have to increase capacity to synthesize those fatty acids from precursors,” said Ye.