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Yahoo
28-02-2025
- Science
- Yahoo
Neanderthal 'population bottleneck' around 110,000 years ago may have contributed to their extinction
When you buy through links on our articles, Future and its syndication partners may earn a commission. Neanderthals may have been headed toward their demise much earlier than experts previously thought, new research suggests. In the study, published online Feb. 20 in the journal Nature Communications, researchers discovered that around 110,000 years ago, our closest human relatives experienced a "population bottleneck" that decimated their genetic diversity. A population bottleneck occurs when there is a sudden reduction in genetic variation within a species. Bottlenecks in a species can be brought on by a number of processes, such as climate change, hunting or genocide. The end result of a bottleneck may be a population that is sickly or on the verge of extinction. The scientists identified the bottleneck by analyzing changes in the shape of the Neanderthal inner ear over time. When they analyzed the inner ears of Neanderthal skulls, they discovered that there was an abrupt decline in variation in this bone in skulls dated to the beginning of the Late Pleistocene, signaling a significant change in the Neanderthal skeleton. Typically, comparisons among ancient DNA samples help researchers pinpoint when bottlenecks happened. But in this case, the team used the reduced variation in the Neanderthals' ear bones as a proxy. They focused on the semicircular canals, a set of bony tubes in the inner ear that are fully formed at birth. During life, these canals are filled with fluid, helping to maintain balance and detect head movements, such as shaking or nodding. Because semicircular canals are evolutionarily "neutral" — because their variation does not affect a person's survival — tracking subtle changes in the canals over time can shed light on the size and diversity of a past population. Related: Did we kill the Neanderthals? New research may finally answer an age-old question. Using CT scans, the researchers examined the semicircular canals of 30 Neanderthals from three time periods: 13 from the site of Sima de los Huesos in Spain that were dated to 430,000 years ago, 10 from the site of Krapina in Croatia that were dated to 120,000 years ago, and seven "late" Neanderthals from France, Belgium and Israel that were dated to 64,000 to 40,000 years ago. This analysis revealed that the group of late Neanderthals had significantly lower variation in their inner ear bones than the earlier groups did, which led the researchers to conclude that a genetic bottleneck event occurred more recently than 120,000 years ago. RELATED STORIES —Who was the last Neanderthal? —Neanderthals' blood type may help explain their demise, new study finds —Neanderthals and humans interbred 47,000 years ago for nearly 7,000 years, research suggests "By including fossils from a wide geographical and temporal range, we were able to capture a comprehensive picture of Neanderthal evolution," study co-author Mercedes Conde-Valverde, a biological anthropologist at the University of Alcalá in Spain, said in a statement. The reduction in diversity between early and late Neanderthals "is especially striking and clear, providing strong evidence of a bottleneck event," she said. The findings fit in well with previous discoveries about Neanderthals, such as evidence of population turnover that negatively affected European Neanderthals' numbers. But it is unclear if the same pattern holds for southwestern Asian Neanderthals, like those who lived at Shanidar in Iraqi Kurdistan, the researchers wrote in their study, since their skulls were not available for analysis.
Yahoo
28-02-2025
- Science
- Yahoo
Neanderthal Extinction Linked to Genetic Crisis 100,000 Years Ago
The extinction of the Neanderthals is one of the most intriguing mysteries in paleoanthropology, with researchers speculating everything from shifts in the climate to war with modern humans may have escalated their demise. Many have wondered if our lost human cousins simply didn't have enough variety to cope with these changes. A new study backs up the hypothesis that a dramatic decline in the diversity of their genes prior to their extinction is likely to have played a major role. Carried out by an international team of researchers, the study took a relatively unique approach, using the anatomy of the ear canal and existing Neanderthal genetics to find strong indications of a genetic bottleneck a little over 100,000 years ago. By comparing the shapes of the ear's semicircular canal in fossils from across Europe and western Asia with those in modern-day humans, the researchers could gauge the relative variety of body morphologies among different groups of humans. "The development of the inner ear structures is known to be under very tight genetic control, since they are fully formed at the time of birth," says anthropologist Rolf Quam, from Binghamton University in New York. "This makes variation in the semicircular canals an ideal proxy for studying evolutionary relationships between species in the past since any differences between fossil specimens reflect underlying genetic differences." Crucial to the study was the Croatian fossil site of Krapina (dating back 130,000 years), and several late Neanderthal sites across France, Belgium, and Israel (dating back 41,000-64,000 years). Something apparently happened between those two points to affect genetic variation, shown through ear canal shapes. It points to a big reduction in the number of people in a population prior to a point around 40,000 years ago, when the Neanderthals' time would come to an end. This study doesn't examine any possible reasons for the drop in genetic diversity, but a number of factors have been suggested in the past – ranging from climate change to increased competition. "By including fossils from a wide geographical and temporal range, we were able to capture a comprehensive picture of Neanderthal evolution," says anthropologist Mercedes Conde-Valverde from Alcalá University in Spain. "The reduction in diversity observed between the Krapina sample and classic Neanderthals is especially striking and clear, providing strong evidence of a bottleneck event." However, while the study helps to answer some questions, it also raises some new ones. The fossils in Krapina showed an unexpected level of diversity, similar to that of much older samples going back some 430,000 years. That counters the widely held assumption of a much earlier genetic bottleneck contributing to Neanderthal evolution, making a single reduction in diversity shortly before their extinction more likely. The researchers are keen to apply their ear structure analysis to more samples and sites across the world, which should reveal more about how our distant cousins lived, traveled, and eventually died out. "The present study represents a novel approach to estimating genetic diversity within Neandertal populations," says Quam. The research has been published in Nature Communications. Vesuvius Eruption Turned a Victim's Brain to Glass. Here's How. Norway's Melting Glaciers Are Spilling Out Troves of Lost Artifacts What Is Alexithymia? Your Guide to The Hidden Experience of Millions
