Why My Early Modern Human Ancestors Smell Like Teen Spirit
Last month I used this column to look at my Neanderthal ancestors. Since I have a little less than 2% Neanderthal DNA, that also means that 98+% of my DNA is traceable to the early “modern humans” who displaced the Neanderthals. So this month, in the interest of fairness, I want to look closely at the differences between my modern human ancestors and their cousins, my Neanderthal ancestors. This is deep genealogy, part two.
I study genealogy to hold a mirror up to myself. Who were these people? What were their lives like? What do their successful adaptations tell me about how present day humans like me operate in the world? What can I learn about myself?
The Genetic Clock
The human genome is amazing. Not only does it contain all of the genes that get turned on and off to make us into humans and not mice or worms, but it also can function as a sort of clock. Most of our DNA does not code for genes. There are vast sequences of base pairs that get passed on from one generation to the next simply because they are on the chromosomes along with the functional genes — they go along for the ride.
Because mutations happen at a predictable rate, scientists can look at these “junk” sequences in present-day humans and compare them to the same section of DNA found in fossil remains. Based on the number of differences between the samples, and using the estimate that a new generation happens about every 25 years, scientists can date fossil remains. They can also extrapolate to determine how long ago the owners of two fossil samples share a common ancestor.
According to radiocarbon and this DNA “genetic clock” evidence, anatomically modern humans, Homo sapiens, evolved about 300,000 to 200,000 years ago in Africa from Homo erectus. These same types of evidence show that about 45,000 years ago, as groups of these modern humans left Africa, they encountered Neanderthal humans (who had diverged from Homo erectus about 500,000 to 600,000 years ago) in the part of the Middle East known as the Levant. This was a key moment because as these two species of early humans encountered each other, the physically weaker modern humans began to displace the physically stronger Neanderthals, even as there was some interbreeding. This process took about 5000 years until the last enclaves of distinct Neanderthals disappeared.
Why did Anatomically Modern Humans displace Neanderthals?
There are several theories that I discussed last month in my essay on Neanderthals.
The old idea was that modern humans were just superior to Neanderthals and they out-competed them or killed them off. Recent studies have revealed that it was more complicated than that.
To me, the most intriguing theory centers on the importance of adolescence and elderhood to early modern human communities.
Much of the speculation about the advantages held by modern humans focuses on differences in social grouping size between the two species. Research shows that Neanderthals stayed in small direct-kin groups of 20 to 40 people, while modern humans lived and moved in larger groups, likely 100 to 150 people (as proposed by evolutionary anthropologist Robin Dunbar). In an encounter between Neanderthals and modern humans, the larger groups might have had an advantage, possibly because these modern humans had a secret weapon: adolescents.
The Evolution of Adolescence: Why Social Group Size Was Such a Big Deal
Something kept Neanderthal groups small. It is possible that evolutionary adaptations to hunting might have limited Neanderthal group size. Neanderthals had evolved to be specialized hunters of big animals, and one idea is that because their diet depended on hunting, it may have meant that larger groups were harder to sustain when prey was periodically scarce.
By contrast, the modern humans who evolved in Africa had a more varied diet, which probably included significant calories from plant sources. They did not need the extreme strength and endurance that the Neanderthals evolved to chase down and tackle large prey animals, and therefore their smaller (though taller) bodies used fewer calories per day. Their decreased caloric needs and greater reliance on plants may have permitted a greater population density of modern humans in a similar amount of space, allowing them to form larger groups. Larger groups had advantages, but the larger group size meant that modern humans had to cooperate beyond immediate kin groups, and thus there were likely strong selection pressures for social skill development.
Fossil evidence from Neanderthal skeletons suggests that Neanderthals became anatomically adult by 12 years old. This is a short adolescence compared to modern humans, who become anatomically adult by 16 to 18 years old. Extended adolescence for modern humans was a costly adaptation; it delayed by several years the entry of young people into adulthood. An adaptation this costly must have had distinct advantages. Evolution gave modern humans a special period that Neanderthals didn’t get.
Adolescence is a time of intense creativity, risk-taking, and extreme sensitivity to social information. Those are prime traits needed to develop social skills and to adapt to new situations. These social skills may have allowed modern humans to form larger societies that were more successful in coordinated hunting, gathering, and warfare.
The Ins and Outs of Social Group Complexity
If what makes us uniquely Homo sapiens is our ability to form social groups beyond kin groups, then that characteristic might also be trouble for us. Every adaptation comes with potential risks and rewards.
When you remember your early teen years, you probably remember it as one of the most intense periods of your life. Everything about social life is magnified in early adolescence, especially noticing who is in the “in-group” and who is in the “out-group.” This is a key step to developing social intelligence.
Early modern humans evolved to work in synchrony with others for common goals. Participating in common goals meant inclusion and survival. Early humans needed to distinguish between who was in and who was out. Paying attention to social information was life or death for early modern humans. A person can feel a sense of positive integration into the “in-group,” developed through shared struggle and challenge.
There is a flip side. For every in-group, there is an out-group. The sensitivity and focus needed to form functional social groups means that we are also primed to exclude people who do not belong. This is why cliques rule in Junior High.
Early humans would have lived in an environment rich with social information and feedback from the community. Through experience in extended adolescence, they would have developed social intelligence and ideally outgrown the clique-y behavior of early adolescence.
The larger group size would have allowed young people to use their creative time to specialize, resulting in cultural innovation and adaptation. There could be artists and tool makers and musicians and shamans. In the smaller Neanderthal groups, there might not have been enough resource to support specialists, since everyone was needed to pursue basic needs. Brain science has shown that adolescence is a “use it or lose it” time when neural connections are either being strengthened through the myelination process or pruned because of disuse. The flowering of creativity comes from real work in the community.
Mentalizing: The Key Skill Needed to Navigate Extended Adolescence
I work with teens as a Montessori adolescent guide. I can see the great lengths young adults go to in order to be included. This is a sensitive period for all of the ills that come when people do not feel included: loneliness, depression, addiction, eating disorders, and self-harm, to name a few.
Inclusion is key to gaining a sense that one has something to contribute to the community and that the community recognizes this contribution. Once a person’s feeling of inclusion is tied to feeling connected to the “in-group,” then that person is set up to make a lifetime of positive contributions to all of the future communities they are connected to. Inclusion allows young people to confidently become their quirky, creative selves.
Modern human brains, while smaller than Neanderthal brains, are arranged differently. In our brains, we have a more prominent prefrontal cortex. This is the part of the brain that finishes development during later adolescence, and it is associated with abstract thought. Scientists talk about this type of thought as “mentalizing,” and they postulate that mentalizing is key to the ability of modern humans to develop complex social networks.
Mentalizing allows the thinker to imagine reality as perceived by another person. Modern humans routinely are able to not only imagine what another person might be thinking about us, but we can also imagine what another person might be thinking about a third person. It can go on, where well-developed modern humans can construct and easily imagine social complexity of up to five different players. We learn mentalizing by doing it.
The Essential Role of Community in Adolescent Development
This is the journey of adolescence. We develop our social intelligence through interaction with a responsive community. We find place and purpose in the world by becoming a contributing community member. We have sensitivity, risk-taking, creativity, and increasing powers of mentalizing to help us along on this journey. It is a process of repeated recognized contributions to community.
The community we live in is key to our development as adolescents. If we have a community that encourages us to use our mentalizing powers to imagine the realities of others, we develop more empathy and social awareness. If instead, our community focuses on simple in-group versus out-group awareness, then we miss the benefits of this sensitive period and we can get stuck, never outgrowing exclusion and negativity towards out-group people. It is as if we don’t make it out of early adolescence.
The Role of Elders
In addition to an extended adolescence, modern humans lived 20–30 years longer than Neanderthals, with a new class of elders providing wisdom and knowledge for community survival. Both the adolescents with their risk-taking, and the elders with their wisdom and experience, made modern humans better able to solve community-wide issues.
The Mirror of Deep Genealogy
By recognizing that many of the traits that make me human evolved in the context of interactive groups of about 150 individuals, I can see where present-day society might be failing me. I might be unnecessarily triggered by social media. I might be susceptible to charismatic leaders who tell me that I am in the “in-group.” I might spend too much time trying to figure out where I fit in the social hierarchy.
But I also know that I am primed to coordinate with other people. I am ready to read social cues and respond with empathy. I am able to think about people thinking about people thinking about people, and I can use that complex thinking to become more aware of the impacts of my actions. I can rise above in-group versus out-group thinking, and I can create conditions for the teens I work with to rise above that type of thinking.
Something happened 200,000 years ago that made us into modern humans. 200,000 years ago is not that long ago. It is only about 8000 generations, a blink of an evolutionary eye. Extended adolescence is the most recent addition to human development, and adolescence still feels like a primal, untamed period of life. This knowledge helps me have patience with the young adults I work with. The fact that many people are functionally stuck in early adolescence also helps me make sense of current events. The past illuminates the present.
My sources for this essay include the many excellent articles about early modern humans and Neanderthals available online in Psychology Today. Robin Dunbar’s work is also widely available on the internet, including YouTube. The emphasis on the paramount importance of adolescence is my own and based on 20-plus years working with adolescents as a Montessori teacher and researching about that age. There are countless books printed on the subject of adolescence, one that I recommend is The Primal Teen, by Barbara Strauch.
