A collaborative study between The University of Texas at Austin and the University of California, Los Angeles has used advanced statistical techniques to delve into ancient DNA extracted from human skeletal remains.
This research, recently featured in the journal Nature Communications, reveals remarkable insights into how ancient Europeans adapted over a remarkable period of 7,000 years.
Research Methodology
Vagheesh Narasimhan, the lead researcher and an assistant professor in integrative biology and statistics at UT Austin, explains that analyzing ancient DNA allows researchers to effectively track the evolution of historical populations.
The team identified genetic markers that modern genomes might have either obscured or completely lost over time.
The scientists examined over 700 DNA samples gathered from archaeological sites spread across Europe and parts of modern-day Russia, dating from the Neolithic period—around 8,500 years ago—to the late Roman era, approximately 1,300 years ago.
Their analysis uncovered traces of natural selection that pointed to genetic adaptations in response to various environmental challenges.
Such adaptations may be invisible in contemporary European genetic studies, indicating how beneficial traits can diminish or disappear altogether as time progresses.
Adaptive Genetic Changes
Understanding historical events of natural selection through contemporary genetic data can be quite tricky.
Subtle signals that indicate natural selection might fade away over generations, affected by processes like recombination that mix genetic material.
Additionally, random shifts in gene frequencies known as genetic drift, along with population intermixing, can further obscure early adaptive traits.
By focusing on ancient DNA, researchers can take a closer look at the genomes of individuals from more recent pasts, providing them with valuable insights into evolutionary changes that occurred before major genetic alterations took place.
The research team employed a groundbreaking statistical approach specifically designed for analyzing ancient DNA.
This innovative methodology improved their capacity to identify signs of natural selection, outperforming traditional methods.
They organized the DNA samples into four distinct eras: Neolithic, Bronze Age, Iron Age, and Historical.
This categorization allowed them to trace genetic changes related to lifestyle shifts, such as the transition from hunting and gathering to agricultural practices.
Co-first author Devansh Pandey, a graduate student studying cell and molecular biology, emphasized how this new approach enriches our understanding of the timing and mechanics behind the selection of certain traits, especially those that have become less distinguishable in modern genomes.
Key Findings
The study explored the evolutionary shifts connected to the move from hunting and gathering to agriculture, alongside the rise of complex societies.
It uncovered genetic changes associated with increased social interactions among humans and their domesticated animals.
Throughout their investigation, the researchers pinpointed 14 genomic regions that underwent significant selection pressures over the studied periods.
Among these were genes linked to vitamin D production and the ability to digest lactose into adulthood, both exhibiting striking signs of selection, particularly in more recent epochs.
For instance, the capacity to process vitamin D may have benefited early farmers living in regions with limited sunlight, while the ability to digest lactose became advantageous with the rise of dairy farming in Europe.
Narasimhan noted that the ability to digest dairy might have been crucial for survival in times of crop failures and food shortages exacerbated by disease.
Moreover, the research highlighted that genes related to immune responses encountered selective pressures across multiple eras, likely as ancient populations adjusted to new pathogens brought about by agricultural practices and migration.
Interestingly, about half of the adaptive genetic signals recognized were only present in the earliest phases, leading researchers to speculate they might have been lost due to genetic drift or obscured by later population mixing.
This groundbreaking research sheds new light on how ancient European communities navigated environmental challenges over millennia.
It enhances our understanding of why certain traits persisted, vanished, or transformed through time, underscoring the vital role of ancient DNA in reconstructing human history and illustrating how once advantageous traits diminished in significance as early European societies evolved.
Source: ScienceDaily