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Chapter II. Evolution of the Human Mind >> Arrival of modern humans

Arrival of modern humans

DNA analysis indicates that all modern humans descend from a single tribe that lived in Africa about 50,000 years ago. Human DNA has about six billion base pairs. DNA accumulates mutations over time at a relatively predictable rate. These mutations, that may be neither beneficial nor harmful, allow scientists to use DNA as a molecular clock. By counting the differences in the number of mutations between any two lineages, we can track back to a common ancestor.

DNA samples have been collected from thousands of people around the world and DNA analysis was performed separately on mitochondrial DNA, on the Y-chromosome, and on the complete human genome. All mitochondria are passed from mother to offspring. Mutations accumulated in the mitochondrial DNA can be used to trace back to the most recent maternal common ancestor for all currently living humans. Mitochondrial Eve is traced to about 140,000 years ago. Mitochondrial Eve was not the only woman at the time, however all people are descendents of that woman.

Similarly, Y-chromosomal Adam, the most recent paternal common ancestor, from whom all Y-chromosomes in living men are descended, is traced to about 60,000 years ago.

The most reliable data are obtained from analysis of a complete human genome. This analysis indicates that all modern humans are descenders of a single tribe that left Africa about 50,000 years ago. That tribe grew in size until it split and a subgroup of settlers moved further. This process repeated itself until the entire world was colonized. The DNA analysis indicates that archaic Homo sapiens arrived in Europe as early as 35,000 years ago. The skeletal remains and artifacts left by archaic Homo sapiens support the conclusions of the DNA analysis.

The archaic Homo sapiens who left Africa about 50,000 years ago were, in nearly every respect, similar to modern humans. They are often referred to as Cro-Magnon, after the cave of Crô-Magnon in southwest France, where the first specimen was found, or simply as early modern humans. The mental abilities of the early modern humans are best understood when artifacts left by Neanderthals are compared to those left by early modern humans.

Comparison of early modern humans to Neanderthals

Because Neanderthals left an excellent record of artifacts and were abruptly replaced by modern humans who did the same, the Neanderthals present us with a particularly instructive measure by which to judge the uniqueness of the human mind. Recall that Neanderthals spread throughout Europe between 500,000 and 200,000 years ago. Neanderthals disappeared from the planet about 30,000 years ago. For comparison, early modern humans spread throughout the world between 50,000 and 30,000 years ago. The earliest Homo sapiens sites in Europe date back to 35,000 years ago, and just 5,000 years later the formerly ubiquitous Neanderthals were gone. There is a dramatic difference between the artifacts left by Neanderthals and those left by early modern humans. Artifacts left by Neanderthals include Mousterian stone tools and wooden spears. Strikingly, Neanderthals left no symbolic objects, certainly not before contact had been made with early modern humans. The Neanderthal practice of burying the dead may have simply been a way of discouraging hyena intrusion into their caves. In any case, Neanderthal burials completely lack the “grave goods” that would indicate the belief in an afterlife.

Early modern humans, on the other hand, left plenty of symbolic objects, including elaborate burials, objects of art, bone needles (bone needles with an eye are known from 26,000 years ago) [7] , kiln-baked ceramics, etc. Grave goods, such as decorative symbolic artifacts, were included in the burials along with the corpse. Also included were objects from daily life that could be desirable for the deceased in the afterlife, suggesting the existence of religious believes. For example, an elaborate early human burial dated to about 30,000 years ago in Sungir (near Vladimir, Russia), included an adult male and two juveniles carefully interred with an astonishing variety of decorative and useful objects. The adult male was wearing a tunic on to which thousands of drilled and polished mammoth–tusk beads had been sewn.

An elaborate burial of a 60-year-old found in Sungir, near Vladimir, in Russia. The man is wearing bracelets, necklaces, pendants, and a tunic onto which hundreds of mammoth-ivory beads are sewn. Two juvenile burials were found at the same site. Dating: 28,000-year-old skeleton. Photograph Source: Novosti Photo Researchers, Inc., Illustration: © Libor Balák.

Early modern humans left exquisite sculptures that demonstrate both the powers of natural observation and arbitrary stylization. They painted spectacular multicolor animal images on the walls of caves. They made music using sophisticated wind instruments. They engraved notations on bone plaques that clearly involved some form of recordkeeping. They ornamented their bodies with bracelets, necklaces, pendants, and decorated everyday objects such as scraper handles.

The striking difference between the symbolic art left by early modern humans and artifacts left by Neanderthals suggests a lack of mental synthesis in Neanderthals and a presence of mental synthesis in early modern humans. The constant refinement of technology by modern humans contrasts markedly with a pattern of slow technological innovation that we observed in the evolution of Homo, where each improvement took nearly a million years. Again, this supports the presence of mental synthesis in early modern humans and a lack of it in all Homo species before Homo sapiens. In fact, in 30,000 years that passed since modern humans spread around the planet, we created civilizations, produced artwork, and built cities. This was a remarkably short period of time. The likely reason is that modern humans are capable of synthesizing new objects in their mind in the process of mental synthesis.

Early modern humans' art. Early modern humans painted spectacular multicolor animal images on the walls of caves and created exquisite sculptures that demonstrate both the powers of natural observation and arbitrary stylization:.

From left to right: Venus of Willendorf, Oolitic limestone (24,000 BC) Naturhistorisches Museum, Vienna, Austria, Venus of Dolní Vestonice, ceramic (26,000 BC), Venus of Lespugue, tusk ivory (25,000 BC) Musée de L'Homme, France.

Image of a horse from the Lascaux caves (16,000 BC).

Cave painting in Lascaux, France (16,000 BC).

The fate of the Neanderthals

Neanderthals did not have the capacity for mental synthesis and did not have a synthesizing language. Therefore they were very limited in their ability to protect themselves against a group of well-coordinated modern humans who were able to better organize themselves using mental planning and a synthesizing language. To realize the importance of a synthesizing language, imagine yourself limited to a non-synthesizing language. That is, you are only allowed to use words that describe your feelings and elements of nature. Using only those words, try to command a brigade of soldiers to advance on an enemy’s fort. The best you will be able to do is to make your soldiers follow you as one group, thrusting themselves onto the enemy in an attempt to stab them with spears. A synthesizing language would have allowed modern humans to command an organized attack: to encircle the hideout and to attack from all sides simultaneously.

What happened to the Neanderthals? They could have died on their own or interbred with modern humans. It is unlikely, though, that Neanderthals died on their own; they lived in Europe for over 200,000 years and died within several thousand years after the arrival of modern humans. Comparison of modern human DNA to Neanderthal DNA from a 40,000-year-old bone found in Croatia, as well as to Neanderthal DNA from Spain, indicates no genetic evidence of interbreeding between early modern humans and Neanderthals.

It is possible that interbreeding of early modern human males with Neanderthal females produced infertile offsprings (just as the offspring of a male donkey and a female horse - mules - are infertile). This could explain the absence of Neanderthal genes in the modern human genome.

It is also possible that early modern humans killed Neanderthals for food. Most scientists agree that modern humans played some role in the extinction of large mammals. Before modern humans arrived, North America was home to giant wooly mammoths for nearly 4.8 million years, ground sloth (a mammal that was the size of a modern elephant) for about 9 million years, bear-size beavers, camels, and other large mammals. The archeological evidence indicates that these animals and 70 other species disappeared around 11,000 years ago: that is nearly as soon as modern humans arrived in the New World.

There is strong scientific evidence that cannibalism was practiced among many of our ancestors. Thousands of human bones were uncovered intermixed with animal bones in settlements ranging from small villages to large towns. Human and animal bones were processed in a similar fashion. The skulls and bones were broken with stone tools for access to nutrient-rich brains and bone marrow. Dr. Tim White analyzed over 2,106 pieces of bone from at least 29 Native American men from an Anasazi site in the Mancos Canyon of southwestern Colorado. The bones invariably indicated that “people extracted the brain and cracked the limb bones for marrow after removing the muscle tissue.” These findings provide convincing evidence of prehistoric cannibalism.

In fact, early modern humans must have been great at hunting. Mental synthesis provided an excellent planning tool to prepare an attack and a synthesizing language could guide a hunting gang in the execution of a very effective attack.