Pääbo is considered to be the founder of paleogenetics. This field of science studies the past through examination of preserved genetic material found in remains of ancient organisms. It was his development of pioneering technologies that allowed for the genomic sequencing of Neanderthal DNA.
“The thing that’s amazing to me is that you now have some ability to go back in time and actually follow genetic history and genetic changes over time,” Svante Pääbo, PhD (above), director of the Max Planck Institute for Evolutionary Anthropology, stated in a news conference, Reuters reported. “It’s a possibility to begin to actually look on evolution in real time, if you like.” Development of modern clinical laboratory techniques for identifying and tracking disease outbreaks have already evolved due to these findings. (Photo copyright: Max Planck Institute for Evolutionary Anthropology.)
Comparing Neanderthal DNA to That of Modern Humans
Back in the mid-1990s, Pääbo and a team of researchers decoded relatively short fragments of mitochondrial DNA of a Neanderthal male. They discovered through their analysis that the DNA from the Neanderthal varied considerably from the genome of contemporary humans. This validated the belief that modern humans are not direct descendants of the Neanderthals.
Pääbo’s research team found nearly all (99.9%) of the Neanderthal DNA they studied to be heavily colonized by bacteria and fungi. That required them to create solutions for assembling the short components of mitochondrial DNA like a huge puzzle.
To accomplish this, the team had to:
Work under clean room conditions to prevent the accidental introduction of their own DNA into their experiments.
Establish more efficient extraction methods to enhance the output of Neanderthal DNA.
Generate complex computer programs that could compare the ancient DNA fragments with reference genomes of both humans and chimpanzees.
“Neanderthals are the closest relatives of humans today” said Pääbo in the press release. “Comparisons of their genomes with those of modern humans and with those of apes enable us to determine when genetic changes occurred in our ancestors. In the future, it could also be clarified why modern humans eventually developed a complex culture and technology that enabled them to colonize almost the entire world.”
Pääbo’s team succeeded in reconstructing their first version of the Neanderthal genome in 2010. Their comparisons between the genomes of Neanderthal and modern humans proved that the two groups had produced common offspring about 50,000 years ago and that this genetic contribution did influence human evolution.
The genome of modern non-African people still contains about 2% Neanderthal DNA.
“We have found around 30,000 positions in which the genomes of almost all modern humans differ from those of Neanderthals and great apes,” Pääbo added. “They answer what makes anatomically modern humans ‘modern’ in the genetic sense as well. Some of these genetic changes may be the key to understanding what distinguishes the cognitive abilities of today’s humans from those of now extinct hominids.”
Those with Neanderthal DNA More Susceptible to Severe COVID-19 Infection
Pääbo’s research also found that Neanderthal DNA may have affected the immune systems of modern people. During the COVID-19 pandemic, his work verified that individuals who carry a gene variant inherited from Neanderthals are more prone to severe forms of the illness than those who do not have that gene variant.
“We can make an average gauge of the number of the extra deaths we have had in the pandemic due to the contribution from the Neanderthals,” Pääbo said in a 2022 lecture, Reuters reported. “It is quite substantial, it’s more than one million extra individuals who have died due to this Neanderthal variant that they carry.”
Pääbo’s research team continues to develop new methods for reconstructing DNA fragments that are even more biodegraded, and which present in smaller amounts. Their ultimate goal is to investigate even older DNA and genetic material that is scarce due to climate conditions.
The DNA technologies pioneered by Pääbo to sequence Neanderthal DNA are being used widely in many clinical laboratory and research settings today. They include forensic science and the ability to collect DNA from human remains hundreds of years old to identify infectious disease outbreaks and study how today’s human genome has adopted new mutations.
Advancements in genetic sequencing continue to enable microbiologists and genetic scientists to explore the origins and mutations of deadly diseases
Microbiologists and researchers can now study the gene sequence of 5,000-year-old bubonic plague bacteria. The scientific team that achieved this feat of gene sequencing believes this is the oldest case of the ancient strain of the plague found to date.
For microbiologists, this demonstrates how advances in gene sequencing technologies are allowing scientists to go further back in time to look at how the genomes of bacteria and viruses have evolved and mutated. This helps science understand the process of genetic mutation, as well as learning which mutations survived because they could more easily infect humans.
Missing Gene has ‘Dramatic Influence on Virulence’ of Plague
To conduct their study, the researchers sequenced the genomes of samples from the teeth and bones of four hunter-gatherers and tested the remains for bacterial and viral pathogens. They found evidence of Yersinia pestis (Y. pestis) in the dental remains of a 20- to 30-year-old male dubbed RV 2039.
The jaw bones used for the research were discovered in the late 1800s in the Rinnukalns, a stone age settlement unearthed in present-day Republic of Latvia in the late 19th century.
Missing Genetic Element in Ancient Bacterium
The scientists were surprised to find evidence of Y. pestis in the remains and noted that the analysis of the microbe lacked a crucial genetic element observed in later strains of the bacteria. Missing was the gene that allows biting fleas to act as vectors to spread the plague to humans.
“But even a small shift in genetic settings can have a dramatic influence on virulence,” he added.
This absent gene also is responsible for creating the pus-filled buboes associated with the Black Death (bubonic plague) that occurred in the 1300s. The Black Death killed 75 million to 200 million people worldwide, mostly in Eurasia and North Africa. It is to date the most fatal pandemic recorded in human history.
A Less Lethal Bubonic Plague?
Although RV 2039 most likely perished from the bubonic plague, the researchers believe his strain of the infection was more mild, less contagious, and not as lethal as the later genetic mutations of the bacteria that caused the Black Death pandemic. The researchers concluded that the man most likely contracted the disease through a bite from an infected rodent or other animal, the press release notes.
“Isolated cases of transmission from animals to people could explain the different social environments where these ancient diseased humans are discovered,” Krause-Kyora said in the press release. “We see it in societies that are herders in the steppe, hunter-gatherers who are fishing, and in farmer communities—totally different social settings but always spontaneous occurrence of Y. pestis cases.”
From Animal Bite to Flea Infection in 7,000 Years’ Worth of Mutations
The Y. pestis bacteria that infected RV 2039, the researchers surmised, most likely split from its predecessor, Yersinia pseudotuberculosis, which first appeared on Earth about 7,000 years ago. It most likely took Y. pestis over a thousand years to acquire all the mutations necessary for flea-based transmission of the bacteria to humans, the researchers noted.
“What’s most astonishing is that we can push back the appearance of Y. pestis 2,000 years farther than previously published studies suggested,” Krause-Kyora said. “It seems that we are really close to the origin of the bacteria.”
It is unknown how many cases still occur worldwide due to unreliable diagnoses and poor reporting in developing countries. However, data from the World Health Organization (WHO) states that there were 3,248 cases of plague reported worldwide between 2010 and 2015, including 584 deaths. Currently, the three most endemic countries for plague are the Democratic Republic of the Congo, Madagascar, and Peru.
The researchers’ findings illustrate how advances in gene sequencing technologies are helping microbiologists, virologists, and genetic scientists understand the affect mutations have on diseases that have plagued humans since the beginning of humanity itself.
Will this lead to new genomic diagnostics? Perhaps. The research is worth watching.