Written by By Staff Writer
(CNN) — Around one million years ago, our ancient relatives, Neanderthals, began evolving faster than modern humans and started breeding.
Two new studies suggest that Neanderthals may have been at the centre of a deadly bacterial infection that caused an epidemic of pneumonia.
Both species suffered from a distinct form of pneumococcal infection, suggesting that those living in the same environments were contracting the same bug, researchers from Wake Forest Baptist Medical Center reported in the journal, PLOS Pathogens.
“The question here is: ‘If you put a zombie virus into a pea pod and eat it, what will happen?’ Well, a lot of people actually eat pea pods in Madagascar. This might have been the root of the Ebola crisis,” said study co-author Dr. Emily Ashton, assistant professor of immunology, medicine and pathology at Wake Forest University School of Medicine.
As some diseases can be passed between animals and humans, the researchers hypothesize that hunting for pea pods may have been how the pneumonic plague — a potentially deadly infection from bacteria called pneumococcus — began to spread from humans to chimps and Neanderthals.
Pneumococcus is the single most common cause of pneumonia worldwide, with an estimated 500,000 people dying from the infection each year, according to the World Health Organization.
The disease’s route of transmission is still unclear, and it doesn’t affect all organisms, making it difficult to understand what causative agent may have led to a rapid change in humans’ ability to resist the infection.
“It’s likely that this chimps/Neanderthals pandemic was an extreme strain of pneumococcus, either from dead animals in the chest cavity of people and bats, or from dying baboons or monkeys or small apes,” Ashton said.
Ashton and her team came up with the theory after genetic analysis of 25 male specimens from the Neanderthal population of Argentina revealed it was a strain of pneumococcus associated with a disease in hand-dived macaques (Apalachicola palustris), found in Madagascar, that had led to an epidemic among chimps there, infected the apes and spread to other primate species.
Further research showed that the chimps were already infected with that strain of pneumococcus, indicating that the geographical dispersal of pneumococcus was quite rapid.
With respect to the chimp strain, the team sequenced the genomes of 2,600 genomes of chimps, studying the archaic bacterium and determining that it closely resembled the modern-day bacterium Bacillus anthracis, responsible for spreading pneumococcus around the world.
“What is interesting here is that we are seeing a modern pathogen here that is crossing over to humans. The whole idea of viral mutational leak is, ultimately, about catching a new one,” Ashton said.
Next, the researchers looked at 75 Neanderthal genomes and found this was the same strain as found in “current disease outbreaks.”
“These genomes express a remarkable high diversity of new variants in the pneumococcus,” Ashton said. “It is likely that these genetic variants caused the epidemic.”
While many genes overlap, the team found that many groups of Neanderthals are distinct from other Neanderthals, offering a path toward disease by dabbling in modern human diseases.
Ashton says Neanderthals hunted chimpanzees and macaques, producing a great deal of gut bacteria that would have contaminated both species and could have spread diseases from one species to the other.
The study co-author Dr. Nicholas Eberhardt, a professor of anthropology at the University of Kansas and member of the Open Society Institute, says “it would be exciting to see if modern chimps can share their pneumocporium and if it also affects Neanderthals.”
But human-chimp diseases are among the most formidable of the five types of archaeopteryxian pathogens that affects both humans and apes, Eberhardt said.
“I think it is probably unrealistic to think that humans and chimps can swap bacteria in a similar way as we do with ticks, the remnants of plagues that we share with recent and ancient members of our lineage, and generally, on and on,” he said.
Instead, Eberhardt says, chimps will likely have more disease than we do, and from there the chimps’ bacteria “will move towards Neanderthals.”
“We do know that, in a highly populated and complex biome like in New Guinea, the interactions between humans and other species is what causes the most outbreaks of serious diseases,” he said.