For our Zoom meeting on May 5, Dr. Michelle (Mica) Glantz, Chair of the Department of Anthropology and Geography at CSU, summarized recent research on Neandertal DNA and the resulting revelations about their relationship to modern humans. She started by saying that over the past 10 years there has been an avalanche of new data from fossil remains. To view the full program, CLICK HERE.Although not currently related to Neandertals, she pointed out that with the recent dramatic warming of the Arctic, a number of well-preserved mammal fossils (including a couple cave bears and a puppy, all with hair, flesh, and even stomach contents) have been exposed by melting permafrost in the Siberian Arctic, allowing unprecedented analysis of DNA thousands of years old. She is eagerly anticipating the discovery of a frozen Neandertal (or one of the other human relatives) with an attendant deluge of detailed DNA analysis of those near Homo sapiens relatives. Outside of the DNA contributions, she was also excited by the detailed information that these fossils provide with respect to date of death and temporal range of the species.
Before delving into the Neandertals, per se, she summarized the relationships of the various hominin (members of the genus Homo) groups and current knowledge about their paths of migration. The first hominin (ape-like individuals walking on two feet) arose in Africa some seven million years ago and apparently stayed in Africa for some five million years. Starting some two million years ago, Homo erectus started moving into Eurasia, heading first to the East to present-day Georgia, China, and Indonesia. Only later did some of the migratory pathways get into present-day Europe. The Neandertals (whom she also refers to as European archaics) are first documented in Europe around 400 kya (thousand years ago) based on stratigraphic dating of stone tools (or around 185 kya based on actual Neandertal fossils). It currently appears that there were on the order of four different hominin populations (including modern-looking humans) interbreeding across Eurasia. The result is that modern humans typically have 1% to 4% Neandertal genes.
Although fossil Neandertals were first discovered in the Neander Valley of Germany several years before publication of “Origin of Species” (and were interpreted to be from an archaic race of humans, leading to accentuating the differences from modern humans and producing the interpretation of Neandertals as being ape-like and of low intelligence), Dr. Glantz focused on the trove of Neandertal fossils and associated artifacts that were found in 1899 in a cave at Krapina in Croatia. This trove (including material from 80 dentally distinct individuals), along with less abundant discoveries from other areas, gives a good feeling for the physical diversity of the Neandertal population and, with painting on cave walls, fine stone tools, articles for personal adornment (including symbols that presumably were to convey information), small flutes, assortments of bones of large and small animals, numerous healed injuries (including one healed hand amputation) indicative of hunting of large animals, and formal burials is central to the modern interpretation of Neandertals as highly intelligent with well-developed social systems and capable of all of the behaviors of which we are capable. There is even some indication that they developed primitive writing.
In 2010, DNA was surprisingly extracted from three 35 kya (thousand years ago) bones from three separate Neandertal females, allowing the creation of a composite genome. Comparison of this genome with five individuals from around the world shows that Eurasian people have around 1% to 4% Neandertal genes, rising locally to around 6% (e.g, in Taiwan). Neandertal genes are very rare in Africa.
What does this genetic information tell us? In a general sense, it indicates that the Neandertals were widely dispersed across Eurasia and interbred with some frequency with modern human ancestors. It is thus unlikely that modern humans killed off the Neandertals. At the more detailed level, since genes tend to persist if they are useful, the presence of Neandertal genes in the modern human genome indicates that they are useful. In particular, Neandertal genes seem to contribute to immune function (surprisingly, one gene seems to decrease the risk of contracting Covid-19, whereas another seems to increase the risk of contracting Covid-19), skin color, hair color, some aspects of metabolism, and tolerance for cold weather. One Neandertal gene is identical to the one in modern humans that allows the making of sounds for symbolic communication. Another causes sperm cells to be slow compared with sperm from modern humans, suggesting that one contribution to the demise of the Neandertals may have been that modern humans simply outbred them.
In response to a question, Dr. Glantz indicated that the reliability of interpretations from commercial DNA tests is dependent on the size of the sample against which the individual sample can be compared. As a result, the interpretation may change with time as the size of the sample population is increased.