Researchers identified the spectacular genetic diversity of Mexican populations.

The study looked out almost one million genetic variants among over 1,000 individuals, a University of California, San Francisco news release reported.

"Over thousands of years, there's been a tremendous language and cultural diversity across Mexico, with large empires like the Aztec and Maya, as well as small, isolated populations," Christopher Gignoux, PhD, who was first author on the study, said in the news release. "Not only were we able to measure this diversity across the country, but we identified tremendous genetic diversity, with real disease implications based on where, precisely, your ancestors are from in Mexico."

Medical diagnoses are often based on a patient's stated heritage; being defined as Latino or African-American, which often include diverse combinations of ancestry, can lead to dangerous misdiagnoses and incorrect treatments.

"In lung disease such as asthma or emphysema, we know that it matters what ancestry you have at specific locations on your genes," Esteban González Burchard, MD, MPH, professor of Bioengineering and Therapeutic Sciences, and of Medicine, in the UCSF schools of Pharmacy and Medicine, said in the news release. "In this study, we realized that for disease classification it also matters what type of Native American ancestry you have. In terms of genetics, it's the difference between a neighborhood and a precise street address."

The study included "511 people from 20 indigenous and 11 mestizo (ethnically mixed) populations," the news release reported. They compared their findings with two previous studies that looked at Mexican-American children.

The team found three "distinct gender clusters" in different regions of Mexico. The Seri people that live along the mainland coast of the Gulf of California and the Mayan people called Lacandon that live near the Guatemalan border are as genetically different as the Europeans and Chinese.  

There was also a significant difference in lung capacity between mestizo individuals and those of Mexican ancestry. The team found genetic origins were directly related to lung function.

"This can shape public health and public policy," Burchard said. "If you're testing a group of kids who are at risk for asthma or other health conditions, you want to do it in an area where the frequency of the disease gene is highest. We now have a map of Mexico that will help researchers make those clinical and public health decisions."