Out of Africa: The Origin of Our Species (Part 10)

Language and Speech

Note: I started reading Africa: A Biography of the Continent by John Reader. The following posts will basically summarize what I find interesting in the book as I’m reading it. None of the ideas or thoughts are of my own. 

It comes without saying that language and speech were only possible with the development of the brain. Together, they pushed the evolution of homo sapiens to what it is today. Large segments of the neocortex, the most recently evolved portion of the cerebral cortex, is wired with neural circuits that transmit the capacity to comprehend language and develop speech. These are one of the most distinguished specializations within our species.

The process appears to have started around 1.5 million years ago with Homo Erectus (see Part 5), whose fossils show that the voice box was already present and whose brain size was significantly large, making it very capable to develop some kind of linguistic communication. Some language experts have pointed out that the most ancient surviving languages came from Africa. However, this theory is widely debated since no tangible proof can be produced about the root origin of language.

Richard Wrangham, a professor of biological anthropology at Harvard University and a co-director of the Kibale Chimpanzee Project, found that within groups of the Gombe chimpanzees social groupings and individual behavior were highly dependent on the availability of food. When all members of the group are well fed and satisfied they tend to have playful interactions and overall peaceful existence. However, when food is scarce, the behavior of the individual becomes to maximize selfish satisfaction, which makes the chimpanzees behave in a less altruistic manner.

Wrangham also studied the ecology and behavior of the Mbuti people of the Ituri rainforest in the Democratic Republic of Congo. He found that language gives the advantage of keeping a level of understanding instead of resorting to physical conflict; when otherwise in a case of chimpanzees violence would’ve inevitably erupted, people extend the line of verbal communication. This observation came about when a group of hunters of the Mbuti pygmies had killed an elephant (a rare event in the community) and brought the caracas to the village. Soon others from nearby communities joined, excitement erupted, and the atmosphere got tense. While the hunters worked on cutting up the parts of the animal, tight groups of people were pushing, shoving, and shouting about who gets what. Eventually the hunters were told by the people of the village to honor the obligations of kinship and give meat to their relatives. Old debts and favors were exchanged for meat, and new deals were made. Talking reduced the fighting. 

Language was only made possible after the evolutionary stages that hominids went through in the African savannas. Teeth and jaws evolved such that the species would be able to eat a varied diet of vegetable and animal foods (see Part 4), the naked skin and upright stance allowed the species to roam around during the hottest hour of the day (see Part 7), and the whole body system allowed for the development of a large cognitive brain (see Part 8) in which reason was put before immediate instinct. These adaptations were all beneficial in their own right, each evolving as a consequence of the environment and whatever the pre-existing circumstance was at the time; none was "designed" to facilitate future evolutionary development. Together they created the circumstance from which speech and language evolved. 

Thanking a group of Ewe kids for letting me have my picture taken with them (Togo, 2013).

Robin Dunbar, a professor of Evolutionary Psychology at the University of Oxford, concluded that language is a response to social imperatives primarily, and related to hunting and gathering only secondarily. He also noted that there is a strong correlation between the size of the neocortex among primates and the size and social complexity of the group in which they lived: the larger the neocortex the larger the social group. Lemurs for example, with a small neocortex in proportion to the rest of their brain, live in groups of less than five. Chimpanzees, with four times the ratio of the neocortex to the rest of the brain, live in groups of fifty five. So in evolutionary terms, the correlation between larger neocortex and group size suggests that the benefit of living in larger groups had been the selective advantage which favored the evolution of the primate’s brain. What size of a group does this trend predict for the ratio of human neocortex to brain? 148 individuals in a group (see Dunbar’s Number).

Individuals are not consciously aware of this number, so what does hold them together in groups of just the right number?

Among primates in general, and apes in particular, individuals live in a web of interactive relationships that are formed and enforced by the act of grooming. The practical purpose is to remove insects and debris from the pelt, but grooming also provides the means to express pleasure and reconciliation between members of the group. Wrangham predicts that was the elephant incident to occur with a group of chimpanzees like it did with the Mbuti people, the chimpanzees would’ve spent hours grooming each other after the event in an attempt to mend the harm done. 

The problem with grooming as a process of communication and bonding within a social group is time consuming. And the amount of time devoted to grooming is proportional to the number of individuals in the group. If a group of chimpanzees consists of about 55 chimps, and they spend 20% of their time grooming, social primates in human-size groups of 150 would have to devote 35% to 45% of their time to grooming. This would take a significant amount of time from any group of species. It would’ve been impossible for human ancestors to keep up with roaming the planes of Africa in search of food resources, in high heat conditions, with that much attention given to grooming. Dunbar suggests that language took human evolution through the grooming constraint on group size, and the size of the neocortex was large enough to handle this change. 

As a result, people talk, and unlike with grooming, they have the ability to do so while engaging in other activities, and they can address several individuals at the same time. Dunbar also points out that since talking replaced grooming for the sake of making communication more efficient, and as grooming can only happen 1:1, the talker should be able to communicate at a ratio higher than that, i.e. to be able to communicate at the same time to more than one person. This ratio is calculated (148 ÷ 55), the ratio of human group of 148 to a chimpanzee group of 55 gives 1:2.7 (one speaker and 2.7 listeners, making a group of 3.7 individuals). He found that the conversation groups he monitored indeed consisted of 3.4 individuals on average. A group larger then four members had the tendency to fragment into two or more smaller conversation groups. As for the topic of conversation, Dunbar observed that social relationships and personal experiences accounted for about 70% for conversation time, half of which was about people not present. As it turns out, it is pretty important to exchange information about people who are not present because it allows humans to coordinate social relationships effectively among dispersed groups.

One more picture from Togo!