ISS 220
Evolution of behavior Primate models Ethnographic analogy
Homology- trait shared by two or more species through inheritance from a common ancestor Analogy- trait shared by two or more species that are functionally similar, but unrelated in evolutionary terms Biological studies can utilize both homologies and analogies
http://www.fs.fed.us/r8/el_yunque/wildlife-facts/2007/wildlifefacts_images_2007/2-brazilian_free-tailed_bat.jpg http://johnbokma.com/mexit/2006/12/31/butterflyresting.jpg
http://www.seawayort.com/images/ XrayHand.jpg http://www.ucmp.berkeley.edu/vertebrates/flight/batwing.gif
Both behavioral AND physical traits can be inherited Behavioral similarities between closely related species (i.e. humans and chimps) are more likely to be homologies than are behaviors between distantly related species (i.e. birds and humans) Behavioral studies of homologies and analogies are useful in different ways
Ethology- the study of the behavior of organisms under natural conditions
Examples: Baboons and Chimps
Why baboons? Baboons exhibit complex social behaviors Baboons live in South and East African savannah environments, just like our early hominid ancestors http://farm4.static.flickr.com/3544/3543065479_1fdeefde58.jpg
Baboons live in large social groups Social structure is not rigid- more of a network of social alliances Males protect their troop from predators and other troops, but they do not have a formal dominance hierarchy Females choose their mates and form important alliances with one another
Perhaps the social lives of our extinct hominid ancestors were similar to that of modern baboons An analogy for early hominid behavior? At the very least, these types of studies inform us about the range of possible primate adaptive behaviors
Baboon and human lineages have been on separate evolutionary trajectories for about 25 million years. We can cautiously look to their behaviors for clues about our past.
JANE GOODALL! You should know who she is. Humans and chimps share obvious physical resemblances, but many aspects of their social interactions are also similar to humans Particularly long/strong mother-infant bond Social hierarchies maintained in complex/ multifaceted ways (violence, gesturing/ vocalizing, physical contact) Cooperation (i.e. protection, food sharing) Fluidity in group membership http://images2.fanpop.com/image/ photos/13100000/chimpanzeeanimals-13168110-250-372.jpg
Much of the information on chimps is also applicable to bonobos, but Bonobos walk upright more often Bonobos are more peaceful and share more food Bonobos use sex as a way to strengthen group bonds and ease social tensions http://elementy.ru/images/news/ bonobo_walking_300.jpg
Similarities between human behavior and that of our closest living ancestor may be homologous, in part due to similar behavioral regimes inherited from a common ancestor 5-6 million years ago. However, keep in mind that we (and they) have been evolving separately and uniquely since we diverged
Ethnography- The study and systematic recording of human culture Ethnographic analogy- An analytical technique in which descriptions of modern or historically known human groups are used as a model for interpreting the archaeological record
Some researchers use observations of modern hunter-gatherer societies to infer behavior among our ancient ancestors Ju/ houansi are Kalahari hunter-gatherers who are sometimes looked at as a good model for our earliest ancestors because they live in similar environments.
Foraging peoples generally live in small groups of related families Foraging groups are generally egalitarian And (of course) people in foraging groups navigate a very complex network of social relationships Maybe some of this was also true for our early ancestors
Modern H/G groups are MODERN!!! H/G groups have very complicated and interesting cultures They are not unevolved. Their cultures have evolved over large periods of time, just as ours have. They can never be a perfect analogy for interpreting early hominid behavior.
Behavioral studies involving non-human primates and modern hunter-gather societies shed light on a subset of the range of possible biosocial behaviors among our early ancestors. BUT- Neither non-human primates nor modern hunter gatherer people are living fossils - They are evolved (and evolving) and specialized for their temporal and environmental situations