How Climate Change Caused the Neanderthals Extinction!

The extinction of Neanderthals and the reduction of their direct genetic descendants are multifaceted events shaped by numerous factors. Among these, one of the primary causes was climate change.

Neandertal DNA is associated with a disorder in which the blood clots too much due to increased activity of a gene called SELP. It may have been helpful to inherit the Neandertal gene in the Stone Age when closing a wound quickly was a major concern, how this gene is affected by diseases such as Sars and covid variants is being explored now!

Homo heidelbergensis, found in Europe and Africa, is the progenitor of several future human species, including Homo sapiens, Neanderthals, Denisovans, and others. Geneticists assert that Homo sapiens and Neanderthals shared a common ancestor until approximately 588,000 years ago, after which they became isolated and evolved independently.

Homo sapiens continued their evolution in Africa. Anthropologists describe Homo sapiens skeletons as gracile, meaning they were tall, slender, and adapted for heat dissipation and running. In contrast, Neanderthal skeletons are characterized as robust—short, sturdy, and designed for conserving heat. Neanderthals evolved and predominantly lived in isolation in Western Europe and Asia until their extinction around 30,000 years ago, with theories regarding their disappearance ranging from mere chance to significant climate changes.

Neanderthals (archaic humans) inhabited Europe and parts of Asia for several hundred thousand years. Approximately 40,000 years ago, the remnants of their once extensive population coexisted with anatomically modern humans from Africa (Homo sapiens).

Several factors likely contributed to their extinction first being Climate Change! During the last Ice Age, the climate fluctuated significantly. Neanderthals were adapted to cold environments, but rapid changes might have affected their ability to find food and survive. As Homo sapiens migrated into Neanderthal territories, competition for resources intensified. Homo sapiens had more sophisticated tools, better social structures, and most likely superior cognitive abilities.

Interbreeding and Hybridization: Genetic research indicates that there was interbreeding between Neanderthals and Homo sapiens, potentially contributing to the ancestry of modern Europeans. Nonetheless, the hybrid descendants encountered difficulties due to genetic mismatches. A collaborative team of researchers from various institutions, including Cornell University, has introduced a novel set of computational genetic tools to investigate the genetic consequences of interbreeding between modern humans and Neanderthals around 50,000 years ago. This study specifically focuses on individuals who are descendants of those who left Africa before the extinction of Neanderthals, particularly those of European descent.

The study indicates that certain Neanderthal genes contribute to traits in modern humans, particularly those affecting the immune system. However, it also reveals that, over generations, the genes of modern humans are predominating. "We discovered that a number of genes identified as part of the modern human immune, metabolic, and developmental systems may have played a role in human evolution following our ancestors' exodus from Africa," stated April (Xinzhu) Wei, co-lead author of the study and assistant professor of computational biology in the College of Arts and Sciences.

Although the study utilized a dataset predominantly comprising white individuals from the United Kingdom, the novel methods devised by the researchers pave the way for extracting evolutionary insights from additional extensive databases to further explore the genetic impact of archaic humans on contemporary humans. These findings could also furnish evolutionary biologists with fresh perspectives on how the remnants of such events can have both advantageous and adverse effects.

Today, Europeans and Asians carry, on average, between 1.5 percent and 4 percent Neandertal DNA. A flurry of new studies suggests that the genetic hand-me-downs may once have helped modern human newcomers to the cold steppes of Asia and mountainous regions of Europe adjust to their new homes. But these genetic bits and pieces may no longer be helpful, and may even raise the risk of depression, heart disease, skin conditions, genetic diseases, Down's syndrome allergies and other maladies. Present-day people participating in the 1000 Genomes project inherited one of three versions, or haplotypes, of immunity genes. Neandertals passed haplotype III to all non-Africans, and some Asians also inherited Neandertal haplotype IV. Those versions of the immunity genes may have helped human ancestors fend off new pathogens, but now contribute to allergies.

The Neandertal variants most strongly associated with depression were located near circadian clock genes, which synchronize the body’s rhythms with the sun, the researchers found. The pineal gland is a photo-neuro-endocrine organ situated inside the brain, that secretes serotonin, melatonin and N, N-dymethyltriptamine. Neanderthal heritage may be the reason many Europeans and Asians have dysfunctional or non-functioning pineal glands. Present both in diurnal and nocturnal vertebrates, the pineal gland is responsible for the secretion and release of melatonin, a hormone regulated by the circadian rhythm and suppressed by light stimuli.

Ancient African civilizations, including Kemet, referred to the gland as the master gland or the third eye. With the advent of technology and microscopy, the pineal gland has also been dubbed "The Third Eye" by modern scientists, largely due to its histological resemblance to the lateral eyes of vertebrates. The discoveries derived from the research of melatonin has acknowledged that although humans are not considered photo-periodic beings, this hormone highlights seasonal traits that may lead to seasonal affective disorders, and in the short term, to depression or “jet-lag” disturbances from abrupt changes in time zones.

The pineal gland is currently recognized as a photo-neuro-endocrine transducer that constitutes an essential component of the brain. It provides insights into the circadian rhythm, thereby linking the external environment to the internal biochemical and physiological requirements and functions of the human body. Researchers suggest that a non-functioning pineal gland may predispose individuals to mental illness.

Neanderthals had a different culture, technology, and lifestyle. Most likely more aggression Their inability to adapt to new cultural practices might have contributed to their decline. A new model suggests the practice of cannibalism may have contributed to the Neandertals' extinction. Although individuals can benefit from cannibalism, especially in resource-poor areas, the species as a whole may not. Neandertals may have practiced cannibalism even when other resources were plentiful, though the reason why is not fully understood.

Disease and Epidemics: Exposure to novel pathogens could have weakened the Neanderthals' populations, contributing to their eventual extinction.

While Neanderthals have disappeared as a distinct species, their genetic footprint remains in some modern humans. The decline in Neanderthal genetic influence can be attributed to:

Dilution Over Generations: As Homo sapiens populations expanded and intermingled, the proportion of Neanderthal DNA that was not beneficial for survival diminished in the gene pool.

Natural Selection: Genetic variants are subject to natural selection. Some Neanderthal genes that were once advantageous may have become obsolete as environments evolved, such as the current man-induced global warming. Random shifts in allele frequencies might also cause the disappearance of certain Neanderthal variants and physical traits like freckles, red hair, green or blue eyes, and pheomelanin dominance.

Purifying selection and natural attrition may have resulted in the elimination of harmful Neanderthal variants from the gene pool. Moreover, ongoing gene flow between populations could have diminished the Neanderthal genetic influence. The relatively smaller Neanderthal populations, in comparison to Homo sapiens, would have faced greater difficulty in preserving their genetic traits. Neanderthals encountered a myriad of environmental, cultural, and genetic obstacles, which collectively contributed to their demise. Nonetheless, their genetic imprint persists in our DNA, offering a window into our ancestral past.