This week’s Odds & Ends focus on our collective past … which I hope offers some respite from this last week’s bleak preview of our collective future. - jp
TITLE: The last days of the Neanderthals
https://www.nationalgeographic.com/history/article/neanderthals-extinction-homo-sapiens
EXCERPTS: Today it is believed that Neanderthals and H. sapiens, our species, began to emerge about 400,000 years ago, the former in Europe and the latter in Africa. But for about 200,000 years the skeletal differences between the two were very specific, and they are only discernible to experts. From 200,000 years ago, and especially from 120,000 years ago, the anatomical characteristics of Neanderthals—those that can be seen in the bones—started to become much more evident. However, it is still not really known what their external appearance was like. It would have varied according to the geographic zone or the specific population. We know that H. sapiens were probably dark-skinned, but they would not have looked the same in tropical locations as they did in North Africa. By the same reasoning, Siberian Neanderthals would probably have looked very different from Mediterranean Neanderthals.
Although archaeologists do not see too many differences between Neanderthals and H. sapiens in terms of technology, diet, or how they occupied the territory, the first migrant H. sapiens who arrived in Europe brought Upper Paleolithic cultures with them. These included aspects that may have been of great importance in adapting to a world in crisis: needles for sewing elaborate clothing, harpoons for fishing and hunting aquatic animals, spear-throwers for long-distance hunting, and, above all, an impressive panoply of ornaments that indicate the existence of complex networks for long-distance exchange between groups.
Coexistence has been documented through hybrid fossils. These include Oase 1 from the Pestera cu Oase (Romania), a jaw with a mixture of traits from H. sapiens and Neanderthals; and fossils from Bacho Kiro Cave (Bulgaria), which had one grandparent from each species just six to 10 generations before their birth. It has also been proposed that the transitional cultures between the Middle and Upper Paleolithic, such as the Châtelperronian, may have been the product of an exchange of ideas between the two human groups, which coexisted for at least three millennia in most of Europe.
Perhaps the reproductive strategy was enough for modern humans to ecologically displace Neanderthals. Neanderthals may have devoted much effort to raising few children, an ecological strategy that favors specialized predators that live in balance with the environment. By contrast, newly arrived H. sapiens would have had more opportunistic ecological strategies, in which little effort was invested in the raising of large numbers of offspring, even if they had a relatively low probability of surviving into adulthood. Since small differences in the mortality rates of competing populations led to the extinction of the less competitive one, H. sapiens could have displaced other hominins in their global expansion.
What seems to be ruled out is aggressive confrontation: There is not a shred of evidence that H. sapiens deliberately “exterminated” Neanderthals. This is not a dichotomy between two homogeneous and differentiated human species. Both groups were diverse culturally and (most likely) phenotypically (that is, in their external appearance.)
In some places and in some populations, they must not have differed too much. Nevertheless, contact between the two populations in Europe was likely sporadic. The extinction process of the European Neanderthals happened over an extended period of more than 5,000 years. The structure of Neanderthal populations (small, highly inbred groups), their reproductive strategies, their place in ecosystems, climate chaos, and the reduction in their main prey all created a discouraging panorama. Even large volcanic eruptions and meteorite impacts have been proposed as events that complicated matters for them.
Perhaps if H. sapiens had not been expanding out of Africa, Neanderthal populations would have recolonized all of Eurasia in the following interglacial period for the umpteenth time from their refuges in southern Europe. Maybe they would have lasted many millennia longer. We will never know.
Our species expanded around the globe at a speed never seen before and to areas that had never been visited by other hominins. In addition to the Neanderthals, H. sapiens met other humans of different species along the way: Denisovans in Central Asia, Homo luzonensis in the Pacific, Homo floresiensis in Southeast Asia, and surely others yet to be discovered.
If, after 160 years of studying Neanderthals, we still do not have a definitive answer about their extinction, the path to understanding the disappearance of other human species appears equally long, and no less fascinating.
TITLE: Neanderthal 'population bottleneck' around 110,000 years ago may have contributed to their extinction
https://www.livescience.com/archaeology/neanderthal-population-bottleneck-around-110-000-years-ago-may-have-contributed-to-their-extinction
EXCERPTS: 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.
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.
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.
TITLE: Single Amino Acid Mutation May Have Helped Shape Human Language Ability
https://scienceblog.com/single-amino-acid-mutation-may-have-helped-shape-human-language-ability/
EXCERPTS: A tiny genetic change that emerged in early humans may have played a role in our unique vocal communication abilities, according to a new study published in Nature Communications.
Researchers at The Rockefeller University have identified a single amino acid substitution in a protein called NOVA1 that’s unique to modern humans and appears to influence vocalization patterns in mice engineered to carry this human-specific genetic variant.
The study provides insight into how small genetic changes accumulated during human evolution might have contributed to our distinctive capacity for spoken language.
“NOVA1 is a neuronal RNA-binding protein expressed in the central nervous system and is essential for survival in mice and normal development in humans,” explained the research team, led by Yoko Tajima, César D. M. Vargas, and Robert B. Darnell.
NOVA1 is highly conserved across mammals, meaning it’s remained virtually unchanged through millions of years of evolution. But somewhere in our lineage after the split from our common ancestors with Neanderthals and Denisovans, a single letter in our genetic code changed, resulting in the substitution of an isoleucine with a valine at position 197 of the NOVA1 protein.
This I197V variant is now nearly universal in modern humans. When the researchers analyzed genomic data from over 650,000 people, they found that only six individuals carried the ancestral version of this gene – five of whom were of Asian descent.
To understand what functional effects this tiny genetic change might have, the team used CRISPR gene editing to create “humanized” mice carrying the modern human version of NOVA1 rather than the ancestral version present in most mammals.
Remarkably, these mice developed normally, but when researchers analyzed their brains, they found subtle differences in how NOVA1 affected the processing of RNA – the intermediate molecule between DNA and protein – in genes related to brain function.
The most intriguing finding came when they recorded vocalizations from these mice. Both pups separated from their mothers and male adults during courtship exhibited altered ultrasonic vocalization patterns compared to normal mice.
The study builds on previous research into genes potentially involved in human language evolution. FOXP2, sometimes called “the language gene,” has been studied extensively since its discovery in a family with severe speech and language problems. Interestingly, the researchers note that the vocalization changes in their humanized NOVA1 mice share similarities with those previously observed in mice carrying human versions of FOXP2.
However, unlike FOXP2 variants which are also present in Neanderthals, the NOVA1 I197V change appears unique to modern humans, suggesting it arose more recently in our evolutionary history.
TITLE: West Africa’s rainforests were an important center for early modern human evolution, study finds
https://www.jpost.com/archaeology/archaeology-around-the-world/article-843969
EXCERPTS: The study argues that human evolution occurred in several regions and habitats, reflecting a complex history of population subdivision, confirming the predictions of the pan-African model of human evolution. "This work reflects a complex history of population subdivision, in which different populations lived in different regions and habitat types," said Professor Eleanor Scerri, head of the Human Paleosystems research group at the Max Planck Institute of Geoanthropology, according to Scientias.
These findings challenge previous assumptions that rainforests were unimportant habitats for early humans.
AND via GIZMODO:
“Convergent evidence shows beyond doubt that ecological diversity sits at the heart of our species,” said Eleanor Scerri, an archaeologist at the Max Planck Institute of Geoanthropology and study senior author. “This reflects a complex history of [Homo sapiens] population subdivision, in which different populations lived in different regions and habitat types,” she added. “We now need to ask how these early human niche expansions impacted the plants and animals that shared the same niche-space with humans. In other words, how far back does human alteration of pristine natural habitats go?”
According to savanna hypothesis of human evolution, our ancient human ancestors’s transition from forested habitats to open landscapes millions of years ago favored the development of crucial features and behaviors such bipedalism, the use of tools, and hunting strategies. The study ultimately challenges the tendency to overlook the role of rainforests in the consequent development of modern humans, and questions what, if any, further evolution occurred as a result of some members of our species choosing to live among trees again. And to Scerri’s point, this raises important questions about the potential ways in which our species altered these rainforests upon their return.
Ultimately, the study rewrites the history of prehistoric human habitats, and paves the way for studying the long-overlooked role of rainforests in the development of modern humans.
SEE ALSO:
Ancient DNA Reveals the Surprising Origins of Attila’s Huns. Genetics Point to an Ancient Mongolian Empire
https://www.zmescience.com/science/news-science/ancient-dna-origins-huns/
Did Iron Age 'begin' in India? Tamil Nadu dig sparks debate
https://www.bbc.com/news/articles/c62e36jm4jro
In Iron Age Britain, Descent Was Matrilineal
https://www.sapiens.org/archaeology/iron-age-britain-adna-descent-matrilineal/