sciencetech-blog

comments

Many of us were taught that Native American populations were almost wiped out by diseases such as tuberculosis, brought to the New World by European explorers.

But a new theory suggests the arrival of seals and sea lions could in fact be to blame.

Scientists believe the marine animals brought the disease to South America where it spread - long before Christopher Columbus arrived in 1492.

Scientists believe that seals  and sea lions brought tuberculosis to South America where it spread to people long before Christopher Columbus arrived in 1492

While estimates vary, it is thought that 95 per cent of the 20 million people living in the Americas before the Europeans arrived were killed by 'new' diseases carried by explorers.

Anthropological geneticists Anne Stone of Arizona State University and Johannes Krause of the University of Tubingen in Germany have studied pre-Columbian Mycobacterial tuberculosis genomes.

The team examined TB DNA from 1,000-year-old skeletons found in Peru as well as other samples and compared them to a dataset of modern genomes.

They found a clear relationship to TB lineages in animals - especially seals and sea lions. 

Their study, published in the journal Nature, describes 'unequivocal evidence' that TB spread to American Indian populations before any explorers arrived.

'Skeletal evidence of tuberculosis is present in the archaeological records in both the Old World and New World,' said Elizabeth Tran, of the National Science Foundation's Division of Behavioural and Cognitive Sciences.

'The source of tuberculosis in the New World long has been a question for researchers.

'This paper provides strong evidence that marine mammals may have been the likely culprits, bringing tuberculosis to South America long before Europeans arrived there.'

Scientists think that once European tuberculosis strains arrived in the Americas, they completely replaced the strains brought over by seafaring animals.

This confused diagnosis of the impacts on Indian populations as researchers struggled to identify which tuberculosis strain was involved in American Indian deaths.

'We are not sure what the timeframe was for the replacement of American strains by European strains after contact,' said Dr Stone.

'It is likely that the new European strain, which is more virulent, was a culprit - particularly since tuberculosis is really good at spreading during times of social crowding and distress.'

Scientists think that once European tuberculosis strains arrived in the Americas - carried by explorers such as Christopher Columbus (illustrated), they completely replaced the strains brought over by seafaring animals

Africa has the largest variety of TB strains, suggesting the pathogen likely originated there and spread.

This study supports the theory that humans gave the disease to animals and within the last 2,500 years, marine animals carried the disease from Africa to South America where they gave it back to humans.

Dr Krause said: 'The connection to seals and sea lions is important to explain how a mammalian-adapted pathogen that evolved in Africa around 6,000 years ago could have reached Peru 5,000 years later.'

It is hoped that the study could help to understand the recent emergence of the disease.