Scientists claim to have recovered the oldest DNA known Homo sapiens from human remains found in Europe, and the information is helping to reveal our shared history with Neanderthals .
Ancient genomes sequenced from 13 bone fragments discovered in a cave beneath a medieval castle in Ranis, Germany, belonged to six individuals, including a mother, daughter and distant cousins who lived in the region about 45,000 years ago, according to the study published Thursday. Monday (12) at Nature magazine. The genetic codes carried evidence of Neanderthal ancestry.
The researchers determined that the first humans who lived in Ranis and the surrounding area likely encountered and had children with Neanderthals about 80 generations ago, or 1,500 years ago, although this interaction did not necessarily happen in the same location.
Scientists have known since the first Neanderthal genome was sequenced in 2010 that the first humans interbred with Neanderthals, a bombshell revelation that bequeathed a genetic heritage still traceable today. However, exactly when, how often, and where this critical and mysterious junction in man’s history occurred has been difficult to determine.
A broader study on Neanderthal ancestry, published this Thursday (12) in Science magazinewhich analyzed information from the genomes of 59 ancient humans and 275 living humans, corroborated the more precise timeline, finding that the majority of Neanderthal ancestry in modern humans can be attributed to a “single shared, prolonged period of gene flow.”
“We were much more similar than we were different,” said Priya Moorjani, senior author of the Science study and assistant professor in the department of molecular and cellular biology at the University of California, Berkeley, at a press conference. “The differences that we imagined between these groups to be very large were in fact very small, genetically speaking. They appear to have intermingled for a long time and lived side by side for a long time.”
The research identified a pivotal period that began about 50,500 years ago and ended about 43,500 years ago — not long before the now-extinct Neanderthals began to disappear from the archaeological record.
During this 7,000-year period, early humans encountered Neanderthals, had sex, and gave birth to children quite regularly. The peak of activity was 47,000 years ago, the study suggests.
The investigation also showed how certain genetic variants inherited from our Neanderthal ancestors, which make up between 1% and 3% of our genomes today, varied over time. Some, such as those related to the immune system, were beneficial to humans during the last ice age, when temperatures were much colder, and continue to confer benefits today.
The two studies give “substantial confidence” that humans and Neanderthals exchanged genes, something geneticists describe as introgression, said evolutionary geneticist Tony Capra, professor of epidemiology and biostatistics at the University of California’s Bakar Institute for Computational Health Sciences. , San Francisco.
“Genetic data from this crucial period in our evolution is very rare,” Capra, who was not involved in the research, said in an email. “These studies emphasize how having even a few ancient genomes provides a powerful perspective that has allowed the authors to refine our understanding of human migration and Neanderthal introgression.”
Scientists working on the two research projects decided to publish their work at the same time when they realized that they had separately reached a similar conclusion.
Research in Science found that genetic variants inherited from our Neanderthal ancestors are unevenly distributed across the human genome. Some regions, which scientists call “archaic deserts,” are devoid of these genes.
These deserts probably developed quickly after the two groups interbred, within 100 generations, perhaps because they resulted in birth defects or diseases that would have affected the offspring’s chances of survival.
“This suggests that hybrid individuals who had Neanderthal DNA in these regions were substantially less fit, likely due to severe disease, lethality or infertility,” Capra said in an email. In particular, the X chromosome was a wasteland.
Capra said the effects of disease-causing Neanderthal variants could be greatest on the X chromosome, perhaps because it is present in two copies in females but only one copy in males.
“The X chromosome also has many genes that are linked to male fertility when modified, so it has been proposed that part of this effect could have come from introgression leading to hybrid male sterility,” he said.
The Neanderthal genetic variants most frequently detected in ancient and modern Homo sapiens genomes are related to traits and functions that included immune function, skin pigmentation, and metabolism, with some increasing in frequency over time.
“Neanderthals lived outside Africa in harsh ice age climates and were adapted to the climate and pathogens of these environments. When modern humans left Africa and interbred with their ancestors, some individuals inherited Neanderthal genes that presumably allowed them to adapt and thrive better in the environment,” said Leonardo Iasi, co-lead author of the Science paper and a doctoral candidate at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.
Individuals living on Ranis had 2.9% Neanderthal ancestry, not unlike most people today, the Nature study found. The new timeline allows scientists to better understand when humans left Africa and migrated around the world.
This suggested that the main wave of migration out of Africa was essentially completed 43,500 years ago, because most humans outside of Africa today have Neanderthal ancestry originating from this period, the Science study suggested.
However, there is still a lot that scientists don’t know. It’s not clear why people in East Asia today have more Neanderthal ancestry than Europeans, or why genomes from this period show little evidence of Homo sapiens DNA.
While the sequenced genetic codes of Ranis individuals are the oldest in Homo sapiens, scientists have previously recovered and analyzed DNA from Neanderthal remains dating back 400,000 years.
The individuals who inhabited the cave were among the first Homo sapiens to live in Europe. These first Europeans numbered a few hundred and included a woman who lived 230 kilometers away in Zlatý kůň in the Czech Republic.
DNA from her skull was sequenced in a previous study, and researchers involved in the Nature study were able to connect her to individuals from Ranis.
These individuals had dark skin, dark hair and brown eyes, the study found, perhaps reflecting their relatively recent arrival from Africa. Scientists continue to study remains from the site to reconstruct their diet and how they lived. The family group was part of a pioneer population that eventually became extinct, leaving no trace of ancestry in people alive today.
Other lineages of ancient humans also became extinct around 40,000 years ago and disappeared just as Neanderthals eventually did, said Johannes Krause, director of the archaeogenetics department at the Max Planck Institute for Evolutionary Anthropology. These extinctions may suggest that Homo sapiens did not play a role in the disappearance of Homo neanderthalensis.
“It’s interesting to see that human history is not always a success story,” said Krause, one of the senior authors of the Nature study.
This content was originally published in Oldest human DNA reveals the lost branch of the human family tree on the CNN Brasil website.
Source: CNN Brasil
Charles Grill is a tech-savvy writer with over 3 years of experience in the field. He writes on a variety of technology-related topics and has a strong focus on the latest advancements in the industry. He is connected with several online news websites and is currently contributing to a technology-focused platform.
