I very much like Nina Jablonski and have been following her anthropological work for years. I have had the pleasure of talking with her several times. My most memorable encounter with her was walking across the Cal Berkeley campus discussing my theory of human evolution, Selection – Natural, Sexual, Artificial and Eveish. This is my exploration of the idea that, Human evolution was controlled by emergent human women. Which was driven by Intelligent Design — of humans by humans and for humans. The theory is that in the beginning it was women communicating to other women their appreciation of some guy which guided human evolution. It was the verbal aspect of this sexual selection procedure, that these women were sharing, which had a bit of heritability. That tiny bit of heritability recycled upon itself many times over slowly improving until it created the full-blown language which all humans now receive as part of their genetic heritage. Here is link to a comic use of that idea with a woman communicating the mmmm feeling of appreciation to us. Although in this case it is responses to appreciation of food not men but it might as well be about men because it is exactly the same type of communication. That of auditory acceptance of some perception of a good thing is what got humanity started on its verbal development. At the first usage of this mmmm these people were still living in a purely sexual selection type of evolutionary development environment but with this single act they were now transformed into an evolutionary cycle of what is now termed artificial selection. That term had until now been limited to the last few hundred years of farm animal and crop selection by farmers but it is the same type of actions being modulated by human verbal communication. We are not rating other animals in this artificial selection process, we are rating other people for mate selection and friend selection. I am just applying that concept to the evolution of humans and their language ability.
The moment of the first mmmm was the most important moment in all human history because it made us verbal human beings and from that all the rest of the qualities which make us so successful a species sprang into being. Standing upright is important for creating our physical appearance so we could throw stones to keep predators away. It was critical to our ability to walk upright among the big carnivores. That ancient act is visible in fossils in the formation of the human heel. It permitted our ancestors to use their hands for carrying stones and throwing them. But, it wasn’t our big brains which helped us outsmart the carnivorous it was the heel which permitted us to carry a supply of rocks and throw them at carnivorous which kept them back at first. After many years of the experience of being annoyed with thrown stones when they came even close to these upright apes the predators developed genetic responses to avoid us. But, these were not humans as we know them because they could not speak and create culture the way we modern people can and do. Nowadays all of these dangerous animals avoid us to the degree that even children can walk safely in the woods and only packs of animals will willingly approach even a single human being. A single wild carnivore attacking a human here in the US is so rare that it will get national news coverage. Predators natural fear of us is a pre-human heritage which our ancestors gave us and it is important but it didn’t make us human — speech made us human.
Jablonski proposes in the Scientific American Feb, 2010 p. 43-49 article The Naked Truth: Why Humans Have No Fur that humans lost their ancestral hominid hair so they could walk better in the hot treeless African savannas. She admits that it is a strange adaptation since all other above ground animals on that savanna have fur/hair and all primates other than ourselves have hair. Unfortunately, after a basically excellent background article about skin she doesn’t develop good reasons for our hairlessness which shows acutely in the concluding paragraph which should be summarizing the now obvious arguments proving the case. Instead the conclusion is a weak statement:
We also employ body postures and gestures to broadcast our emotional states and intentions. And we use language to speak our mind in detail. Viewed this way, naked skin did not just cool us down—it made us human.
What is that? Is it a new idea that we are hairless in order to provide better social communication because the hairiness somehow prevents body postures and gestures to broadcast our emotional states and intentions. Is this such a powerful evolutionary force that we suddenly evolved from homo ergasters into homo sapiens. I think not and there is a far simpler way to explain our hairlessness.
There were big problems facing Lucy and her kind other than the African weather variations. After all if the weather and climate was so bad they couldn’t survive they wouldn’t have been there but would have died out earlier. The big problem was big cats. Lucy’s partial solution to the hungry cat problem was to sleep in trees at night hanging onto branches with her prehensile feet. In the day when on the ground traveling or searching for food she would carry and throw stones at carnivores. As she spent more time on the ground she evolved into the Turkana Boy body type, who was fully terrestrial and would have had trouble sleeping in trees without constructing a dwelling there. Instead, he built camp fires and kept a good collection of throwing stones and other weapons to fend off predators and may have built simple huts which kept him out of sight of predators. The predators soon learned that they should avoid campfires because whenever they came near them they got hit with flying stones.
There is a down side to having camp fires if you are covered with an abundance of fur/hair and that is that sometimes it catches fire. That has to be unpleasant and disabling even if it doesn’t kill you. Those people who had the least fur/hair would be quickly selected for with a strong selection pressure and by the time of the Turkana boy Homo ergaster with his modern body plan, except for the head, he would have been hairlessness. Soon after there were campfires there would be descendents who were hairless. When they became hairless they would have probably started developing some form of clothing such as an old animal hide draped over themselves. That would protect them from the direct sun on hot days and from the chill of the side away from the fire.
All of these developments came before human speech developed and so these would be pre-human developments. Thus from the beginning all humans were relatively hairless because hairlessness predates humanity.