Do our modern skulls house stone-age minds?
Lead: Lauren Maurice

3/31/2015

Summary by Seth Goodnight

Do our modern skulls house stone-age minds?

The discussion opened with a description of two major schools of thought about the source of knowledge in humans; empiricism and nativism. The Empiricist school of thought holds that all human knowledge comes from experience, though there are innate capacities and capabilities. Those capacities allow us to form knowledge. Nativists (or rationalists) believed that we have a large amount of innate knowledge that is independent of experience.

There was some discussion as to the nature of what would be innate or learned, primarily focused on fears (spiders specifically). Are those fears learned through experience (either direct or indirect), or are they innate?

The presentation went on to describe the tenets of evolutionary psychology. These are that 1) the human brain is a product of natural selection, 2) the human brain adapted to solve particular problems faced by our hominid ancestors, 3) the cognitive capabilities that our ancestors developed to solve problems were heritable, transmitted from parent to offspring, and 4) the brains we have now are very similar to those of our ancestors thousands of years ago. This is further modified by the modularity theory which states that the human brain is analogous to a series of miniature computers, each one adapted to solve a specific set of problems.

This theory was explained (to some extent) by the presence of a region in the brain that was adapted to facial recognition. However, this region is also active with other visual recognition tasks, which calls into question the specificity of that particular “mini-computer”. The question was also raised about how that region functions in people who are blind. While no one knew the facial recognition, there have been experiments which found that people who have lost their sight were using their visual cortexes to process braille.

The next topic that came up was plasticity in human brains, and how we can recover from brain injuries. Young children can lose an entire hemisphere and still function almost normally. As people age that plasticity is lost. This is also evidenced in the ability to learn languages. Children under the age of 12 can learn a language natively much more easily than people over that age. This also shows up in children who haven’t learned any language (either as a result of neglect or living as feral children). After a certain age they are simply not able to develop a functional language. Noam Chomsky’s universal grammar theory also came up. This theory states that there are certain innate parameters to any language that are set in the brain (what he called the language organ) at a very young age. One of the most remarkable aspects of language learning is the rate at which it occurs. Children learn up to 50 new words per day, and intuitively know the grammatical structure of a language (something that can take years for adults to master). Another aspect of our reduced language learning capacity that was discussed was the ability to learn specific phonetic sounds of a language. Not only does one lose the ability to make sounds that are not part of their language, but they also lose the ability to hear them (at least for some sounds).

We moved on from language to talk about culture and social learning. Some animals (humans included) build on the work and learning of previous generations. We talked about how orphaned animals have to be raised in a way that they will learn the skills they need to survive (hunting, feeding, etc.), otherwise they can’t function in the wild. On the other hand, we discussed how a lot of animals have very complex innate behaviors, such as spider webs and homing behaviors. We discussed the degree of parental care and how many of these animals have little or no interaction with their parents, and thus no chance to learn from them. When it came to the topic of social learning, we talked about what kinds of organisms are able to learn from each other. We had several examples of birds and mammals that exhibit social learning, but no examples from other vertebrates or invertebrates.

The discussion then moved to human evolution, and how culture and society have or have not affected it. One example of how culture can influence human evolution is lactase persistence. Most mammals lose the ability to produce lactase after they are weaned. In cultures that keep animals for dairy products, there is a lower percentage of lactose intolerance. This is used as a counter argument to the claim from evolutionary psychology that humans haven’t had enough time to evolve away from a hunter-gatherer society. This claim was also questioned on the basis that modern humans would not be able to survive alone in the forest; we simply wouldn’t have the knowledge to do so. One possible response was that we still have the same mental framework that enabled our immediate ancestors to be successful hunter-gatherers, but we are never put into a situation where we need to learn those skills. It was also pointed out that modern society was built by human minds, and thus would be constructed to fit how our minds are structured. Finally, the example of lactase persistence was called into question because it is a very simple trait based on one gene, and thus would be able to change very rapidly in a short time-frame. Mental characteristics are the product of many genes and external factors, so they would take much longer to be influenced by natural selection. A change in the expression of a single gene would most likely result in a severe disability.

We talked about the evolution of language, and the two different but non-conflicting schools of thought about how it evolved. One theory is that language evolved from a set of structural devices and rules as a way to strengthen social groups, foster cooperation, and build trust. The other theory is that it evolved through cumulative culture, is socially learned, and is built upon by successive generations. We discussed the different forms of communication seen in animals (mainly dolphins and monkeys), and how they relate to specific pieces of important information such as food or predators. Dolphins have shown the ability to learn new sounds to describe objects, and can even teach those to other individuals. Monkeys can alter the intent of their communication to trick others into dropping food trying to hide from a nonexistent predator. Both examples indicate that language may have evolved from simple communication systems, but can be adapted to fit new purposes.

The presentation ended with the question “Has human evolution sped up to match the new problems faced in modern times?” Individual answers to this question tended to change based on the working definition of evolution. Some felt that evolution was indeed speeding up because we are able to deal with so many different problems. Others thought that this isn’t truly evolutionary adaptation, rather it is a result of learning and cumulative knowledge. While genetic evolution may not have sped up, our ability to handle difficulties has thanks to our collective knowledge. The discussion then moved to the effect of medicine on human evolution. Modern medicine has allowed people to survive and reproduce despite debilitating genetic conditions. This has altered the human gene pool, and it is evolution (though not by natural selection). The widespread use of soap, disinfectants, antibiotics, and immunizations has altered how human immune systems develop. Allergies may have developed as a result of cleanliness; as people are not exposed to potential allergens on a regular basis, they can develop an allergy to them. There was also the question of whether or not people are being vaccinated against too many diseases, and if that could potentially be harmful.