A skeleton excavated from a grave in Croatia has reignited the intense debate raging over whether the explorer Christopher Columbus and his crew introduced syphilis to Europe in the 15th century.

A new study claims to have disproved the theory, instead suggesting the sexually transmitted disease, which can result in death, was present in Europe before the explorers returned from the Americas.

The disease, which is caused by the bacteria, treponema pallidum, causes symptoms ranging from a sore throat and rash to problems with the heart, blood vessels and brain which can trigger stroke, heart disease, dementia, paralysis and even death.

Ever since the first case was recorded in Europe in 1495 - three years after Columbus's first voyage to the New World - experts have argued over its origins.

Three core theories exist attempting to explain where it first emerged, and its rapid spread through Europe at the end of the 15th century.

Experts have long debated the origin of syphilis. A popular theory is that the disease originated in the New World, the Americas, and was transported to Europe by the explorer Christopher Columbus and his crew

The sexually transmitted disease causes symptoms ranging from a sore throat and rash to problems with the brain, heart and blood vessels that can trigger stroke, heart disease, paralysis and even death

Scientists at the University of Split in Croatia claim to have unearthed a skeleton of a man showing signs of syphilis dating from a Roman grave. They claim the bent thigh bone, pictured, is proof of the disease

The first, the Columbian theory, assumes syphilis was introduced to Europe in 1493 by a ship arriving from the Carribean islands.

The second suggests the disease was first present in Africa, and was brought to Europe by slaves arriving in Spain and Portugal.

And, the third theory assumes syphilis was present in both the old and new worlds, and that four different syndromes developed.

Despite this abundance of theories, the definitive origin of the disease remains an enigma.

A team of scientists from the University of Split in Croatia set out to test the three theories, examining the remains of people unearthed from the Dalmatian area of Croatia, ranging from different historical periods.

They conclude 'the Columbian theory of syphilis origin is not sustainable', citing evidence of syphilis on the bones of a man, aged 20 to 29, who was excavated from a grave dating from the Roman era.

But experts remain sceptical.

Dr Rob Knell, a reader in evolutionary ecology at Queen Mary's University in London, said one skeleton 'showing apparent syphilitic changes does not constitute much in the way of a weight of evidence' to disprove the Columbian theory.

He told MailOnline: 'Firstly, it is only a single skeleton - this means that it is very hard to draw much in the way of conclusions from it, because apparent syphilitic changes in a single skeleton could be the consequence of chance deformities that were not a consequence of the disease.

'With only a single skeleton it is very hard to conclude much about the potential causes of the changes observed.

'Secondly, we know that there were other treponenmal diseases in Europe or Africa before Columbus, such as Yaws, and these can cause skeletal changes as well.

The disease can cause major changes to bones

'Without a decent sized sample, my understanding is that it is hard to distinguish syphilitic changes in bones from changes caused by other treponema diseases.'

He said this discovery is the latest in a series of pre-Columbian skeletons with 'apparent syphilitic changes', with a similar study emerging 'every few years'.

'These are always isolated skeletons with questionable pathology,' he told MailOnline. 'And they always seem to get forgotten about pretty quickly.'

Dr Bruce Rothschild, a professor of medicine at the University of Kansas and expert in the origins of diseases like syphilis, echoed Dr Knell's doubts.

Professor Rothschild told MailOnline while the subject is 'important and pertinent today, the article is not valid'.

He said the bone abnormalities appear to be the result of abnormal growth rather than syphilis.

He said the thinning of the cortex of the femur, seen on the X-ray, is 'the opposite of what one sees in syphillis', rather suggesting the man suffered fibrous dysplasia.

He told MailOnline: 'Syphilis is clearly a New World 'product'.

'Despite many efforts to suggest otherwise, there is no Old World evidence of syphilis prior to 1492.

'The disease derives from Yaws in North America between 2000 and 1800 years ago, on the Colorado Plateau above the Mogollon Ridge.

'The suggestions of pre-Columbian syphilis in Europe are based on inadequate understanding of terminology.'

The new study was published in the Journal of Sexual Medicine and involved Croatian scientists analysing a random sample of 403 skeletons, from a collection of 3,000.

Of those, 135 came from five excavation sites archeologically dated to the Iron Age, the prehistory era.

An antique sample of 134 skeletons were taken from more than 1,000 graves excavated from Solin-Smiljanovac or Salona, a Roman colony.

The remaining 134 samples dated from the medieval and new age eras, and were taken from two excavation sites dating from 14th to 19th centuries.

The oldest skeletons, from the prehistory and antique eras, were used as a control group.

The scientists claim their finding disproves the theory that Columbus transported the disease to Europe aboard the Santa Maria and other ships

SYPHILIS: A FATAL SEXUALLY TRANSMITTED DISEASE The disease is a bacterial infection, often caught by having sex with an infected person. The bacteria that cause syphilis are called treponema pallidum. They can enter the body through close contact with an infected sore, normally during vaginal, anal or oral sex. The disease can also be caught by sharing sex toys with someone who is infected. Pregnant women can pass the disease to their unborn child, which can cause stillbirth or death shortly after labour. Spyhilis is caused by bacteria called treponema pallidum, which can enter the body through close contact with an infected sore, normally during vaginal, anal and oral sex In some cases the disease is passed through injecting drugs with infected needles. Symptoms of syphilis develop in three stages. It begins with a painless but highly infectious sore on the genitals, or around the mouth. If another person comes into contact with the sore, which lasts from two to six weeks, they can become infected. Secondary symptoms of the disease include a skin rash and sore throat, which typically last for a few weeks. Once they disappear a sufferer will experience a phase with no symptoms, which can last for years. The next stage, the most dangerous, follows. The symptoms of the final stage vary depending on which part of the body the infection spreads to. It can affect the brain, nerves, eyes, heart, bones, skin or blood vessels, causing a range of illnesses including stroke, dementia, paralysis, blindess, deafness, heart disease and death. Source: NHS Choices Advertisement

Given the most accepted theory, the Columbian theory, supports the fact syphilitic changes will only be found on skeletons dating from the 15th century or later, this group were studied to assess if any signs of spyhilis could be found prior to Columbus' return to Europe.

Prior to this study, only one case of venereal syphilis was found on a female skeleton from the 15th to 17th century.

The team's findings revealed just one skeleton had anomalies that suggested infection with syphilis.

It dated from the antique excavation site in Solin-Smiljanovac, and the scientists concluded it belonged to a man aged between 20 and 29 years old.

Changes to the femur, or thigh bone, found suggest the man had fallen victim to the disease.

The authors conclude: 'Because of everything stated, we believe that the Columbian theroy of syphilis origin is not sustainable.

'Syphilis was most likely to present in the old world, but not to the extent that is was in post-Columbian time.

Dr Rob Knell, from Queen Mary's University in London said one skeleton is not enough to disprove the Columbian theory

'It is interesting and indicative that no evidence of syphilis was found in graveyards from post-Columbian time in this research, and in the territory of present-day Croatia, only few cases of probable syphilis were published.

'All evidence supports the theory that syphilis is not a new illness, but its manifestations were randomly recorded or misclassified.'

They said they believe 'more excavations with more skeletons examined will support the syphilis prior to 1492'.

Dr Knell challenged those scientists who back the theory that syphilis pre-dates Columbus' return to Europe to produce a molecular family tree for the bacteria, which is better than those currently used to show syphilis is more closely related to Old World treponema, than New World.

'Or they should find a skeletal assemblage with a decent sample size of apparently syphilitic changes that would allow a better assessment of whether the changes observed were really caused by syphilis.

'Or they should sequence DNA from pre-Columbian bacteria and use the sequence to show that the bacteria in question were the causative agents of syphilis, and not a related treponema.

'They also need to come up with an explanation of why the disease changed in virulence and went from being unknown in 1490 to a dreadful and widely recognised scourge a few years later.'

He told MailOnline: 'There is considerable evidence that venereal syphilis evolved in the New World and was then transported to Europe shortly after Columbus' discoveries in 1492.

'This evidence includes DNA sequencing studies that show that the bacterium which causes syphilis is most closely related to other, similar diseases in the New World, skeletal evidence showing syphilitic changes in large numbers of pre-Columbian skeletons in places like the Dominican Republic, and also the rather more circumstantial evidence regarding the changes in virulence caused by syphilis after it first appeared in Europe.

'For the moment the only good explanation for this change in virulence is that the disease was freshly introduced from a different population where it had been evolving to deal with defences possessed by the host population, which the European population did not have, allowing the disease to largely avoid any immune response for the European hosts and cause very severe disease.'