Click on the cover to link to OUP's e-catalogue then turn to the biology section.

Interview Podcast with George Miller

Interview Podcast with George Miller
Click on the pic to link to the NOT A CHIMP podcast on Blackwell's Website

Preface to "Not A Chimp: The Hunt For The Genes That Make Us Human"

In many ways, this book is born out of frustration for a professional career in popular science television where ideas about comparative primate cognition, and the similarities and differences between us and our primate relatives, have continually circled me but constantly evaded my grasp in terms of the opportunity to transform them into science documentary. On the plus side, keeping a watching brief for over a quarter of a century on subjects like comparative animal cognition and evolution allows you to watch a great deal of water flow under the bridge. Fashions come and fashions go - specifically, perspectives on the similarity - or otherwise - of human and ape minds.

I remember the first Horizon science documentary about the chimpanzee Washoe, the great ape communicator, using American Sign Language to bridge the species barrier. And, later, Kanzi the bonobo jabbing his lexicon. These were the apes, as Sue Savage-Rumbaugh has put it, that were "on the brink of the human mind".

I remember when the pre-print of Machiavellian Intelligence, by Andrew Whiten and Dick Byrne, plopped onto the doormat of the BBC Antenna science series office in 1988. Suddenly primatology had become a great deal more exciting. Could primates, and especially higher primates like chimpanzees, really be as full of guile, as dastardly, as cunning, and as manipulative as the eponymous Florentine politician? Could they really reach deep into the minds of other individuals to see what they believed and what they wanted, and turn that information into deception?

I remember discussing primate cognition with a young Danny Povinelli, as we sat finger-feeding ourselves shrimp gumbo and new potatoes out of plastic Tupperware containers in a Lafayette restaurant surrounded by an alligator-infested moat, before returning to his kingdom - the New Iberia Research Centre - where the University of Louisiana had lured him back to his native deep South by turning a chimpanzee breeding centre for medical laboratory fodder into a primate cognition laboratory with one of the largest groups of captive chimpanzees in the country. He looked like a kid who had just been thrown the keys to the tuck shop.

In those days Povinelli shared the zeitgeist - spread by Whiten's and Byrne's work, and started by Nick Humphrey and Alison Jolly before them - that, since the most exacting and potentially treacherous environment faced by chimpanzees and other primates was not physical, but the social environment of their peers, they had evolved a form of social cognition very much like our own, in order to deal with it. This was further elaborated into a full-blown "social brain" hypothesis by Robin Dunbar, who related brain neocortex size to social group size throughout the primates and up to man. Povinelli's early work reflects this optimism for the mental life of apes, but both ape-language and ape-cognition research was subjected to a cold douche of searching criticism during the 1990s, and misgivings set in regarding the effectiveness of the experiments that had been constructed to guage ape cognition. Now the worm has turned again, with a number of research groups emerging with bolder and bolder claims for the Machiavellian machinations of primate minds, only to be powerfully countered by the curmudgeonly skepticism, chiefly by Povinelli, that these researchers are merely projecting their mental life onto that of their subjects; that, rather in the frustrating manner of Zeno's arrow that could never quite reach its target because it continually halved its distance to it, no experiment constructed thus far can actually get inside the mind of a chimp and show us exactly what it does and doesn't know, or how much, about the minds of others or the way the physical world works. One influential part of the world of comparative animal cognition talks of a continuum between ape and human minds and shrinks the cognitive distance between us and chimps to almost negligible proportions, while another returns us to the unfashionable idea that human cognition is unique, among the primates, after all.

When I began writing this book the working title was "The 1.6% that makes us human". My aim had always been to scrutinize the impression put about in the popular science media that humans and chimps differ by a mere 1.6% in our genetic code - or even less - and that it therefore makes complete sense that this minuscule genetic difference translates into equally small differences in cognition and behaviour between apes and man. However, contemporary genome science and technology, over the last few years, have dramatically advanced the power and resolution with which scientists can investigate genomes, eclipsing the earlier days of genomic investigation that gave rise to the "1.6% mantra".

As with comparative cognitive studies, conclusions on chimp-human similarity and difference in genome research depend crucially on perspective. To look at the complete set of human chromosomes, side by side with chimpanzee chromosomes, at the level of resolution of a powerful light microscope, for instance, is to be overwhelmed by the similarity between them. Overwhelmed with a sense of how close our kinship is with the other great apes. True, our chromosome 2 is a combination of two chimp chromosomes - giving humans a complement of 23 chromosome pairs to 24 in chimps, gorillas and orang-utans - but even here you can see exactly where the two chimp chromosomes have fused to produce one. The banding patterns you visualize by staining the chromosomes match up with astonishing similarity - and that banding similarity extends to many of the other chromosomes in the two genomes. However, look at a recent map of the chromosomes of chimps and humans, aligned side by side, produced by researchers who have mapped all inversions - end-on-end flips of large chunks of DNA - and the chromosomes are all but blotted out by a blizzard of red lines denoting inverted sequence. Now you become overwhelmed by how much structural change has occurred between the two genomes in just 6 million years. True, not all inversions result in changes in the working of genes - but many do - and inversions might even have been responsible for the initial divergence of chimp ancestor from human ancestor.

The extent to which you estimate the difference between chimp and human genomes depends entirely on where you look and how deeply. Modern genomics technology has led us deep into the mine that is the genome and has uncovered an extraordinary range of genetic mechanisms, many of which have one thing in common. They operate to promote variability - they amplify differences between individuals in one species. We now know, for instance, that each human is less genetically identical to anyone else than we thought only three years ago. When we compare human genomes to chimpanzee genomes these mechanisms magnify genetic distance still further. I have tried, in this book, to follow in the footsteps of these genome scientists as they dig deeper and deeper into the "Aladdin's Cave" of the genome. At times the going gets difficult. Scientists, like any explorers, are prone to taking wrong turnings, getting trapped in thickets, and covering hard ground, before breaking through into new insights. I hope that those of you who recoil from genetics with all the visceral horror with which many regard the sport of pot-holing will steel yourselves and follow me as far as I have dared to go into Aladdin's Cave. For only then will you see the riches within and begin to appreciate, as I have, just how limited popular accounts of human-chimpanzee genetic difference really are. Let me try and persuade you that this is a journey, if a little arduous at times, that is well worth taking.

There are a number of scientists around the world who have the breadth and the vision to have begun the task of rolling genetics, comparative animal cognition, and neuroscience into a comprehensive new approach to the study of human nature and this is part, at least, of their story. They strive to describe the nature of humans in terms of the extent to which we are genuinely different to chimpanzees and the other great apes. Somehow, over 6 million years, we humans evolved from something that probably resembled a chimpanzee (though we cannot yet be entirely sure) and the answer to our evolution has to lie in a growing number of structural changes in our genome, versus that of the chimpanzee, that have led to the evolution of a large number of genes that have, effectively, re-designed our brains and led to our advanced and peculiar human cognition.

If you don't believe me, hand this book to your nearest friendly chimpanzee and see what he makes of it!

Thursday, 28 January 2010

Premotor Cortex Responsible For Perception And Production Of Prosody

Prosody, as the authors point out, is the melody and intonation of speech and involves the rhythm, rate, pitch and voice quality to relay both linguistic and emotional information. It has long been known, they say, that the production of prosody is an area where the premotor cortex is specialized, and it was thought that the perception of prosody took place mainly in the right temporal lobe. They set out to test whether or not the premotor cortex was also involved. They discovered shared networks for production and perception of emotional prosody in motor-related regions of the left inferior frontal gyrus and another region in the dorsal premotor cortex. They discovered shared netqworks for perception and production of linguistic prosody in the left inferior frontal gyrus too, together with the anterior cingulate cortex and insula (two prominent parts of the "social brain".) Here is the start of their conclusions:

"We found areas in the premotor cortex, including the left inferior frontal gyrus and the left dorsal premotor cortex were active for both the perception and production of prosody. This was true for both emotional prosody and linguistic prosody. These results are consistent with previous findings of activity in premotor regions during prosody perception. The current result indicates a link between perception and production, where brain areas that are commonly thought to be involved with motor planning are also active for perception. While there have been numerous previous reports of perceptual processing in motor areas for action observation, for the sounds of actions, and even for speech, to our knowledge this is the first report of “mirror” processing for prosody. It may indicate that some components of prosodic perception involve mapping the heard speech to areas that are important for producing that same speech. Such mapping of acoustic signals to articulatory signals is reminiscent of the motor theory of speech perception."

So, we are back in disputed "mirror neuron" territory again - and especially the possible role of mirror neurons in the perception and production of speech - hence the reference to a motor theory of speech acquisition. They go on:

Interestingly, our data indicate that common motor areas for production and perception of prosody were found in only the left hemisphere (left IFG and premotor cortices). This was true for both linguistic and emotional prosody. Thus, while emotional prosody perception and also prosody production are known to activate the right hemisphere, “mirror” regions for prosody seem to be stronger in the left hemisphere. This is consistent with all previous reports of an auditory mirror system as being lateralized to the left hemisphere, and may indicate a special role in the left premotor cortex for more multimodal processing (motor, visual, and auditory), while the right equivalent areas instead may be stronger in motor and visual properties rather than auditory properties."

This is consistent with a multi-modal role for the anterior language centre of the brain - Broca's area. Now we get to the "social brain" bit:

"Prosodic ability is known to correlate with deficits associated with affective components of empathic processing. This is best observed in individuals with psychopathy. These individuals, who often score low on emotional aspects of empathy, also tend to score poorly on the ability to perceive prosody. Our behavioral results further support a positive correlation between ability to perceive prosody and ability to feel emotional aspects of empathy. We found that individuals who scored higher on measures of empathy showed more activity during emotional prosody perception in anatomically the same premotor areas that we previously found to be active for the perception and production of prosody, including the bilateral inferior frontal gyrus and premotor cortex. They also were found to show less activity in this region during neutral prosodic intonation, indicating that more empathic individuals utilize premotor regions for emotional prosodic perception, but less for non-emotional stimuli. This data support the notion that components of empathy to emotional stimuli may rely on simulation processes carried out, in part, by motor-related areas. Thus, in order to understand someone else's prosodic intonation, we may simulate how we would produce the given intonation ourselves, which in turn may be a component of the process involved in creating empathic feeling for that individual. These data indicate that individuals who score higher on scales of affective empathy also show more activity in motor-related areas during prosody perception. Our findings extend previous correlations between the mirror neuron system and individual differences in empathy to include, for the first time, an emotional auditory stimulus: happy or sad prosodic intonation."

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