Neoteny Led To Big Human Brain

I mentioned, in an earlier post, that Philipp Khaitovich, of the Max Planck Institute for Evolutionary Anthropology, had followed up the idea that neoteny - the retention of juvenile traits - might be mirrored in the pattern of gene expression in the brain - i.e. certain genes might have their activity delayed ct. chimps. For those of you interested in this idea (I deal with it in the domestication chapter in NOT A chimp) this is a very accessible Scientific American piece.

Language Is The Key To Theory Of Mind

In Chapter 10 of NOT A CHIMP I present a short account of the work of Rebecca Saxe on theory of mind - social intelligence. Saxe has shown on several occasions that the representation of higher order ToM - things like beliefs and desires - can only be facilitated by language. This would mean that it was always beyond chimps and any other animal species. This NS article recounts her recent work presenting congenitally blind adults - they have been blind all their lives - with audible questions to test whether they could understand the concept of a false belief in the head of another. The same "social brain" regions lit up as those in sighted people on equivalent tests. This suggests that we don't depend on interpreting facial expressions or gestures to judge the mental states of others. Saxe's observations are backed up by further work on profoundly deaf Nicaraguan people by Jennie Pyers who not only showed that adolescent deaf signers, with a more complicated signing grammar than first generation signers, were more advanced on tests of theory of mind, but that the older generation caught up on theory of mind the better their signing became with practice.

How We Understand Others' Emotions

This paper, in PNAS, links with the previous post. How can we accurately guage another person's emotions? According to this group of Columbia University neuro-scientists we use a combination of parts of the human mirror neuron system and regions involved in theory of mind - mental state attribution - notably the superior temporal sulcus and medial prefrontal cortex. See my chapter 10 - Inside The Brain - for related detail.

I Smell Your Fear!

Is it true that we can literally smell someone's fear - and act accordingly, with an empathetic response? What is the neural basis for this? This team of German scientists have supplied the answer. Using an olfactometer they supplied the smell of sweat produced by heavy exercise and that produced by anxiety to volunteers. When they smelled fear fMRI results indicated that areas of the brain associated with social intelligence - part of the "social brain" - the insula, precuneus and cingulate cortex - together with parts of the brain that process higher order attentional stimuli - the thalamus and dorsomedial prefrontal cortex - were very active. Here is clear evidence for how raw and basic sensory material can be processed in the brain to produce complex social behaviour.

Competition Led To Big Human Brain

David Geary, and colleagues, from the University of Missouri have tested 3 theories that have tried to account for the dramatic expansion of the human brain: climate change, ecological demands and social competition, by collecting data from over 100 hominid skulls. They find the greatest support comes for social competition as the prime mover because population density had the greatest effect on skull size. Powerful support for Robin Dunbar's "Social Brain" theory for scaling in brain size throughout the primates and up to Man.