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, 23 April 2009

Chromosome breakpoints contribute to genetic variation.

In chapters 6 and 7 of NOT A CHIMP I explain how large structural upheavals in the genome, involving segmental duplication of large sections of DNA, inversions, and deletions, can lead to novel sources of genetic variation because they can either produce a new family of genes, or dupes, upon which natural selection can differentially act, or because they disrupt genes or families of genes when chromosomal breakpoints occur within genes or close by. Now a team led by Harris Lewin, of the University of Illinois, has shown that such chromosome breaks do not occur randomly, invariably occur in gene-rich parts of chromosomes, as opposed to genetic deserts, and in areas abounding in copy number variants of genes, insertions and deletions. Furthermore, different classes of genes are associated with breakage-susceptible to breakage-resistant parts of chromosomes, the former over-represented with genes for immune system and muscle contraction, for instance. Yet more evidence that structural tectonics in the genome are, if anything, more important than prosaic point mutations in the genetic code in providing raw material for natural selection to operate on.

Ape behaviour reveals secrets of human evolution

Nice article from Dan Jones, mainly about how Robin Dunbar and various colleagues are investigating the affects on primate group size of climate and thus food availability, to get an ecological handle on human evolution. Raises interesting questions: as you move from chimps to Australopithecenes, brain/cranium size increases, suggesting larger social groups. But how did Australopiths eke out a sufficient existence to support larger groups and bigger brains? Did they roam more, temporarily fission into small groups, or (very unlikely) eat meat?

The article also goes on to look at how sexual dimorphism reduces from chimps to Homo erectus and man, suggesting a trajectory toward monogamy. How was female behaviour changing, and what had that to do with food availability? Jones also reports on work by Karen Isler and Carel van Schaik who plotted brain size against fecundity for over 1200 animal species. Normally, when brain size increases fecundity goes down, because of the inordinate investment in grey matter, but humans have the biggest brains of all animals and much higher fecundity than the great apes and earlier hominins. The answer? Allometernal care - helpers at the nest. It works for big-brained birds too. For primates, including us, they calculated the magic number for brain size at which reproductive effort will be compromised if step-mothers don't kick in - one litre!

Tuesday, 21 April 2009

How our brains process admiration and compassion

When we feel admiration for the Mother Theresas of this world, or compassion for someone in great emotional or physical pain, we draw quite literally on gut feelings. As this paper by Hannah and Antonio Damasio, and others, shows, these sort of social stimuli are registered in the anterior insula, anterior cingulate cortex, and precuneus - all parts of the brain dubbed "the social brain". The insula, in particular, is the place where gut feelings of pain, disgust etc. are translated into much higher-order social intelligence because nerve impulses from our viscera - visceral sensations - excited by external stimuli (called interoception), pass to the insula and cingulate and then on to prefrontal cortex where they are translated into appropriate emotional responses. See chapter 10 of NOT A CHIMP for more detail. Many of these areas have evolved uniquely in size or internal structure in humans.

Monday, 20 April 2009

What makes us human?

Here's a nice round up of some of the major breakthroughs over the past few years in the hunt to "find the genes that make us human" from Katie Pollard of UC Santa Cruz. Few surprises but a good precis of her own efforts to find HARs - highly accelerated regions of DNA that have lain conserved in mammalian genomes for millennia and then sprung to evolutionary life uniquely in humans. FOXP2, ASPM and AMY1 - all dealt with extensively in NOT A CHIMP - also get a look in.

Dogs out-smart chimps in Harvard exams

Here's a new addition to the "dogs are the new chimps" line I flagged in the side-bar. It specifically relates to the ability of dogs to accept a variety of cues from a human as to the location of food. A task chimps fail miserably. The key point here is that, despite being further away from us genetically, dogs have evolved a superior form of social intelligence to chimpanzees in certain areas. Picking up clues from humans being one of them. See chapter 8 in NOT A CHIMP for more details.

Could early humans climb trees?

The term "hominin" came into fashion a number of years ago to denote the "bipedal apes" - meaning extant humans and all human ancestors since the split from the common ancestor 6 million years ago - as opposed to any of the other great apes. When did our ancestors become truly bipedal, and did it mean that they had to sacrifice agility in tree-climbing in order to do so? Until recently, however, there were, apparently, no good biomechanical studies of chimpanzee limbs versus hominin limbs that could settle the matter. Now, Jeremy DeSilva has compared the detailed anatomy of talus (a bone in the lower ankle) and tibia (shinbone) between a number of chimpanzees and fossil early humans dating back to 4.12 million years ago. He finds that "chimpanzees engage in an extraordinary range of foot dorsiflexion and inversion during vertical climbing bouts" - far in advance of that which the early human ankle was capable. He concludes that, if early hominins could climb trees at all, they were doing it "in a manner decidedly unlike modern chimpanzees."

Neoteny in gene expression in human brain

In chapter 11 of my book I describe the process by which I believe humans domesticated themselves, compared to chimpanzees. The principle idea evokes a process called neoteny, first described by Ashley Montagu and Steven J Gould, which involves so-called heterochronic shifts in the timing of development from foetus to adult - a staggering or delaying of the developmental clock such that important stages in development get prolonged and delayed. For e.g. childhood and adolescence. Corresponding changes in body, skull and jaw morphology are noticed as a result of neoteny, which might explain Homo sapiens' more gracile morphology. Although neoteny has been reported in the pattern of switching on of flows of adeno-corticoseroid stress hormones and some brain neurotransmitters, this concept has not been applied to gene expression - the timing of active protein production in genes. Now a research group including Philipp Khaitovich and Svante Paabo has reported just such a study, documenting a startling number of genes exhibiting delays in their protein-producing activity unique to humans. These genes are all active in the pre-frontal cortex, evolutionarily the most recent, and advanced, part of the human brain and seem mainly concerned with growth and development of grey matter. "There is a human specific neotenic shift in gene expression during postnatal maturation of the human prefrontal cortex, causing adult humans to resemble juvenile chimpanzees in their expression profiles." Importantly, they point out, the period when this delayed gene expression finally kicks in corresponds to the period of dramatic re-sculpting of synapse connections in the brain which we associate with late adolescence and early adult maturity - when the pefrontal cortex is finally taking on its adult organization. "Delayed grey-matter maturation in the human prefrontal cortex may extend the period of neuronal plasticity associated with active larning, thus providing humans with additional time to acquire knowledge and skills". As the father of a late-teen son, I sincerely hope they are right!!