Saturday, October 6th, 2007
For the full day schedule, download the Conference Poster
Open symposium with public lectures - RSVP required
NYU, 19 West 4th (corner of West 4th St & Mercer St)
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Seeing the forest through the seeds: mechanisms of primate behavioral diversity from individuals to populations and beyond
Understanding the evolution of primate behavioral diversity requires multi-level approaches that encompass individuals, populations, and the effects of individuals and populations on each other. At one level are analyses of individual behavior patterns under different ecological and demographic conditions. At another level are the effects of individual behavior on the demography and genetics of local populations, which in turn shape the behavior and biology of their individual members. Multi-level studies across populations and over time provide insights into the range of behavioral variation that particular species can express, and are necessary for distinguishing the species-specific behavior patterns upon which evolutionary comparisons are based. Cliff Jolly’s long-term field studies of baboons provide a model of multi-level approaches in primatology.
The power and the glory: the strength of great apes and the speed of humans
In The Seed Eaters that he published in 1970, Cliff Jolly developed a causal model of human origins. He was one of the first to attempt this and the paper has since become a classic. I have not such grand goals, but rather seek to understand a major difference between the living great apes and humans. Maynard Smith and Savage showed over 50 years ago that the musculo-skeletal systems of mammals can be adapted for power at one extreme, and speed at the other, but not both. Great apes are adapted for power – chimpanzees have been shown to be about 4 times as strong as young, fit humans when normalized for body size. The corresponding speed that human limb systems gain at the expense of power is critical for effective human activities such as running, throwing, and tool making. The fossil record can shed light on when the change from power to speed occurred.
Having a Jolly good time--together!, or, evolution by cooperative interaction
Darwin gave us a few simple principles by which to understand the process of evolution, or what happens across the generations of individuals. He stressed competition as its basis. Recently, we've learned to see much of biology as not about evolution, but, broadly speaking, about development -what happens within the generation of individuals, but across the generations of their cells. Again, a few simple principles apply, and they show that much of life is about cooperation. Understanding how cooperation evolves at all levels of life is a major challenge. Since this will require a zone of hybridization of many traditional areas of biology, we can anticipate that a Jolly time will be had by all.
Elucidating population histories using genomic sequences
In 1993 Cliff Jolly astutely suggested that rather than quibbling over species definitions and classifications, energy would be better spent investigating multidimensional patterns of variation and gene flow among populations. Until now however, genetic studies of wild primate populations have been limited to very small proportions of the genome. Access to the complete genome sequences of humans, chimpanzees and other primates makes it possible to design studies surveying substantial amounts of sequence variation at multiple genetic loci in representatives of closely related, but distinct, wild primate populations. Such data can be analyzed with new approaches that not only estimate when populations diverged, but also the relative amounts and directions of subsequent gene flow. Such analyses are likely to re-emphasize the difficulty of achieving consistent species and subspecies definitions by revealing the extent of variation in the amount and duration of gene flow accompanying population divergences.
Viewing human evolution: backwards, forwards, and sideways
There are at least three chronological perspectives from which to interpret the fossil and other evidence for human evolution. The least defensible starts from the physical and behavioral peculiarities of our species, and looks backwards in time, looking for indications of each distinctive human trait in the fossil record. This approach encourages teleological thinking, tends to shoe-horn evolutionary change into a unilinear “progression” of “grades”, and distorts the functional interpretation of early ancestral forms. A forward-looking, clade-based perspective, by contrast, views human evolution not as a ladder, but as series of points of decision and division. At each one, human ancestors adopt new lifeways, giving up some existing strategies, and often forgoing alternative adaptive pathways. In reconstructing their natural history, derived and ancestral traits are equally significant. Those traits that foreshadow the human condition merit no special consideration if fossil forms are evaluated not as imperfect “precursors” or unimportant “cousins”, but primarily as living entities in their contemporary context. This perspective, however, immediately begs questions of cause and process. Necessarily, these do focus on evolutionary novelties: why did lineage X speciate; what shifts in function and natural history can account for the new character-states of its more derived descendants? The history of each lineage, is of course unique, and it is all too easy to construct explanatory narratives that are plausible but untestable, because unrelated to more general patterns or laws in evolutionary biology. This is where the third, comparative, perspective can help – looking “sideways” to identify analogous trends, and informative contrasts, in other evolving lineages, often far removed phylogenetically from the hominins. This means showing parallels in particular features against a background of difference. Comparison does not imply demonstrating overall resemblance, much less finding perfect living avatars for extinct forms. In this essay, phenomena from the evolution of papionin monkeys are used (again) to suggest interpretations of several crucial phases in human evolution: the origins of the hominin lineage itself; the novelties of Homo erectus; the population structure of Neandertals and their contemporaries; the origins of “culture-as-we-know-it” in Homo sapiens, sensu stricto, and, finally, the relationship between genes, demographic history, and cultural diversity within Homo sapiens. In line with the liminal theme of the meeting, one of these suggestions is an ancient relic, another is more recently published, and the other three are speculative and untested.