Sarah Knapton, Telegraph (London), August 20, 2014
Disease-riddled Europeans, carrying tuberculosis across the Atlantic, have long been blamed for wiping out huge populations of Native Americans.
But new research has found that the deadly bugs which killed millions were probably spread by seals and sea lions, long before Christopher Columbus first arrived in the New World in 1492.
A study which looked at tuberculosis strains in bones discovered in Peru found they were closely linked to those found in sea mammals.
The research shows that tuberculosis is likely to have spread from humans in Africa to seals and sea lions, who then carried the disease to South America and transmitted it to Native populations long before Europeans landed on the continent.
“What we found was really surprising. The ancient strains are distinct from any known human-adapted tuberculosis strain,” said Anne Stone, Professor in Human Evolution at Arizona State University.
“We found that the tuberculosis strains were most closely related to strains in seals and sea lions.
“Our results show unequivocal evidence of human infection caused by sea lions and seals in pre-Columbian South America.
“Within the past 2,500 years, the marine animals likely contracted the disease from an African host species and carried it across the ocean to coastal people in South America.”
The researchers believe that once tuberculosis was established in South America, it moved north and infected people in North America before European settlers arrived with new strains.
It was previously thought that roughly 95 percent Native Americans were killed by European diseases, accounting for around 19 million people. Although the team said strains from Europe were ‘a culprit’, they believe that TB was already well established.
In the study, researchers collected genetic samples of tuberculosis DNA from across the world. Africa has the most diversity among tuberculosis strains, implying that the pathogen probably originated from the continent and spread.
The team also studied the genomes from skeletons in Peru dating from around 750 to 1350 AD and found tuberculosis was already present.
“It was a surprise for all of us to find that tuberculosis, formerly believed to have spread around the world with ancient human migration events, is in fact a relatively young disease,” said study author Dr Kelly Harkins of Arizona State University.
Tuberculosis is one of the most persistent and deadliest infectious diseases in the world, killing one to two million people each year.
The team hope the findings will help understand the speed and process of adaptation of diseases cross species.
“Tuberculosis is a disease that is on the rise again worldwide. This study and further research will help us understand how the disease is transmitted and how the disease may evolve,” said Jane Buikstra, a collaborator on the study who identified tuberculosis in most of the cases utilized in the research.
The study was published in the journal Nature.