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How Climate Change Warming Wiped Out the Neanderthal Fertility!



The extinction of Neanderthals was a complex process influenced by various factors, with climatic changes playing a significant role. During the last ice age, the Earth experienced fluctuating temperatures that directly affected the availability of crucial animal and plant food sources for Neanderthals. This environmental pressure forced Neanderthals to continually adapt in order to survive in a changing landscape. As Neanderthals struggled to cope with the challenges posed by the shifting climate, early humans emerged as formidable competitors. Unlike Neanderthals, early humans possessed more versatile survival strategies, allowing them to thrive in diverse environments and effectively exploit available resources.


This adaptability likely enabled early humans to encroach upon Neanderthal territory and compete for essential resources such as food, water, and shelter. While it is tempting to envision a scenario of direct conflict between Neanderthals and early humans leading to the former's extinction, the reality may have been more nuanced. Rather than engaging in deliberate eradication efforts, early humans may have unintentionally outcompeted Neanderthals for resources, gradually diminishing their population over time. In essence, the extinction of Neanderthals was a culmination of environmental pressures, competition for resources, and the differential adaptive capabilities of early humans and Neanderthals. By examining these complex interactions, we gain a deeper understanding of the intricate dynamics that shaped the fate of our ancient relatives, the Neanderthals.


Climate change may have played a more important role in the extinction of Neanderthals than previously believed, according to a new study published in the journal, Proceedings of the Natural Academy of Sciences. The Neanderthals were the human species closest to ours and lived in Eurasia for some 350,000 years. However, around 40,000 years ago -- during the last Ice Age and shortly after the arrival of phenotypically African anatomically modern humans in Europe -- they became extinct.


For years, the cause of their extinction has been a subject of curiosity. Was it the advent of modern humans that led to their downfall, or were there other contributing factors? Our research indicates that climate change could have played a significant role in the Neanderthals' extinction. It is believed by many scholars that modern humans with darker skin were better adapted to survive the warmer periods due to their suitability for warmer climates, compared to Neanderthals. Additionally, melanin may have played a crucial role in safeguarding DNA and their reproductive capabilities. Current science proves Neanderthal genes reduced human fertility in a climate changed environment.


Genomic studies have shown that Neanderthals interbred with modern humans, and that non-Africans today are the products of this mixture. The antiquity of Neanderthal gene flow into modern humans means that genomic regions that derive from Neanderthals in any one human today are usually less than a hundred kilobases in size. However, Neanderthal haplotypes are also distinctive enough that several studies have been able to detect Neanderthal ancestry at specific loci. We systematically infer Neanderthal haplotypes in the genomes of 1,004 present-day humans. Regions that harbor a high frequency of Neanderthal alleles are enriched for genes affecting keratin filaments (straight hair growth), suggesting that Neanderthal alleles may have helped modern humans to adapt to non-African colder environments.


When we identify multiple Neanderthal-derived alleles that confer risk for disease, suggesting that Neanderthal alleles continue to shape human biology. An unexpected finding is that regions with reduced Neanderthal ancestry are enriched in genes, implying selection to remove genetic material derived from Neanderthals. Genes that are more highly expressed in testes than in any other tissue are especially reduced in Neanderthal ancestry, and there is an approximately fivefold reduction of Neanderthal ancestry on the X chromosome, which is known from studies of diverse species to be especially dense in male hybrid sterility genes. These results suggest that a big part of the explanation for genomic regions of reduced Neanderthal ancestry is Neanderthal alleles that caused decreased fertility in males when moved to a modern human genetic background.





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