The following are selected abstracts or excerpts from, or minimally, titles of research papers, and links to PDF files you may download.
Patterns of hominid evolution
Roots and Branches
Since the discovery of Australopithecus nearly 80 years ago (Dart 1925), there have been many additions to, and occasional removals from, the hominid fossil record. Correspondingly, the apparent pattern of hominid evolution, as well as explanations for that pattern, also changed (Foley 2002). The prevailing historical descriptions of human evolution are closely linked to the nature of the fossil record as it is perceived at any one moment in time. For example, Darwin, (1874) in the virtual absence of any relevant fossil record, conceptualized human evolution as co-evolving changes in stature, locomotion, form and utility of the hands, use of technology, and enlargement of the brain. Today we know that upright posture and bipedalism evolved far earlier than the use of stone tools or a large brain, decoupling these quintessential human traits …
From the late 1970s through the early 1990s, numerous hominid fossil finds, the identification of several distinct species, and the more accurate dating of fossil deposits resulted in a rich record of hominid evolution for the period of about 3.2 to 1.5 million years ago. A suite of traits associated with several different hominid species became apparent, including a form of bipedalism different from modern humans, megadonty and thick enamel associated with large chewing muscles, and the use of lithic technology by 2.6 mya (Semaw 2000). However, almost every researcher working in African palaeontology has recognized that the description of the pattern of early hominid evolution was in part shaped by vagaries of the fossil record, owing to biases in where research was carried out, what was preserved, and possibly also the order in which fossils were found.
Gaps and other biases in the fossil record have and always will obscure the exact temporal pattern of early hominid evolution, but in recent decades the fossil record has matured significantly. It may now be possible to newly characterize the hominid fossil record – to revise our description of the pattern of hominid evolution – in a way that would suggest a revision in how we understand the process of that evolution. …
These observations may allow the pattern of hominid evolutoin prior to about 1.5 mya to be described as having two phases:
Phase I: The initial separation of a population of early hominids from a chimpanzee-like last common ancestor (LCA) somewhere around 6 or 7 million years ago followed by about 3 to 4 million years of low species diversity and primarily phyletic evolution. This initial rise of hominids involved novel dietary and locomotory or positional adaptations, but these changes were relatively small in magnitude. It may be possible to consider these earliest hominids to have been one of a variety of chimpanzee-like forms, with a somewhat different (perhaps moderately specialized) diet and different but overlapping habitat preference, and otherwise not extraordinary.
Phase II: Between roughly 3.2 and 2 – 1.5 million years ago, hominids underwent a species radiation involving a diversification of dietary and habitat preferences, varying degrees of encephalization, varying degrees of increase in molar size, and changes in technology, distributed unevenly among the genera Australopithecus, Paranthropus, and Homo.
Ethnoarchaeology and interpreting the paleolithic record
Environmental determinants of site formation: a comparison of ethnoarchaeological work in the Kalahari Desert and Ituri Forest with implications for the “emergence” of human culture
Alison S. BROOKS (George Washington University) and Greg LADEN (University of
Ethnoarchaeological work in two regions of Africa suggests that hunter-gatherer archaeological sites are most likely to form when landscape points are used repeatedly, even if only very briefly, over a long period. Long-term repeated use of a landscape point is most likely for campsites in the Ituri, since forest clearing for new campsites is difficult. In the Kalahari, on the other hand, long-term landscape use is most intense at water-points used for ambush hunting during seasonally restricted periods. Since the location of forest clearings is likely to change over a period of centuries, while the location of water points is likely to remain constant, archaeological sites accumulate in the Kalahari and the Ituri at different rates. This ethnoarchaeological prediction is confirmed by archaeological survey in the two regions. In addition, computer simulation comparing forested environments with more open and semiarid ones suggests that climatic change alone could account for the “emergence” of archaeological sites representing a population of early hominids that already used tools but did not concentrate their behaviors spatially over long time periods.
Distribution and redistribution of game by foragers: How, why, and can we see it in the
Greg Laden and Martha Tappen
Department of Anthropology
University of Minnesota
Minneapolis, Minnesota. USA
Most tropical and temperate foragers traditionally engage in distribution and redistribution of hunted game. Corresponding to this is primary butchery (for initial distribution) and secondary butchery (after redistribution, for cooking). The anatomical pattern of primary butchery is determined partly by anatomical constraints, but also (perhaps mainly) by the cultural practice of distribution and redistribution, and is nearly identical across a wide range of foragers. This butchery pattern is potentially observable in the archaeological record. Cultural practices governing or facilitating distribution and redistribution vary dramatically from place to place and probably over time, although the reasons for having a distribution and redistribution practice for game are predicted to be similar for all foragers. We describe the distribution-redistribution system (in particular, for the Efe Pygmies of Zaire) and its archaeological correlates, and offer possible explanations for this system based on socio-ecological theory, ethnographic observation, and literature search.
Bones and Bushes: Soil Carbon Isotopes And Animal Bone Distributions
Paper presented at the 1994 meetings of the American Anthropological Association, Atlanta
Martha J. Tappen and Greg Laden
Department of Anthropology
11 Divinity Avenue
Cambridge MA 02138
Ancient landscapes are only rarely preserved in the geological record. The contemporaniety of features on such landscapes is difficult to establish. The interaction between plants and animals, and among animals, should follow general ecological principles, but are represented as a tangled, time averaged, and generally mucked-up record. However, there do exist laterally extensive paleosols, which by their very nature are in place and not redeposited, and so can be assumed to contain spatially meaningful traces (bones and stone artifacts, etc.) of the kinds of events that we are interested in…
Major transitions in human evolution (mainly having to do with food and sex)
The Raw and the Stolen: Cooking and the Ecology of Human Origins
Richard Wrangham, James Holland Jones, Greg Laden, David Pilbeam, and NancyLou Conklin-Brittain
Cooking is a human universal that must have had widespread effects on the nutrition, ecology, and social relationships of the species that invented it. The location and timing of its origins are unknown, but it should have left strong signals in the fossil record. We suggest that such signals are detectable at ca. 1.9 million years ago in the reduced digestive effort (e.g., smaller teeth) and increased supply of food energy (e.g., larger female body mass) of early Homo erectus. The adoption of cooking required delay of the consumption of food while it was accumulated and/or brought to a processing area, and accumulations of food were valuable and stealable. Dominant (e.g., larger) individuals (typically male) were therefore able to scrounge from subordinate (e.g., smaller) individuals (typically female) instead of relying on their own foraging efforts. Because female ?tness is limited by access to resources (particularly energetic resources), this dy namic would have favored females able to minimize losses to theft. To do so, we suggest, females formed protective relationships with male co-defenders. Males would have varied in their ability or willingness to engage effectively in this relationship, so females would have competed for the best food guards, partly by extending their period of sexual attractiveness. This would have increased the numbers of matings per pregnancy, reducing the intensity of male intrasexual competition. Consequently, there was reduced selection for males to be relatively large. This scenario is supported by the fossil record, which indicates that the relative body size of males fell only once in hominid evolution, around the time when H. erectus evolved. Therefore we suggest that cooking was responsible for the evolution of the unusual human social system in which pair bonds are embedded within multifemale, multimale communities and supported by strong mutual and frequently con?icting sexual interest.
The rise of the hominids as an adaptive shift in fallback foods: Plant underground storage organs (USOs) and australopith origins
Greg Laden and Richard Wrangham
We propose that a key change in the evolution of hominids from the last common ancestor shared with chimpanzees was the substitution of plant underground storage organs (USOs) for herbaceous vegetation as fallback foods. Four kinds of evidence support this hypothesis: (1) dental and masticatory adaptations of hominids in comparison with the African apes; (2) changes in australopith dentition in the fossil record; (3) paleoecological evidence for the expansion of USO-rich habitats in the late Miocene; and (4) the co-occurrence of hominid fossils with root-eating rodents. We suggest that some of the patterning in the early hominid fossil record, such as the existence of gracile and robust australopiths, may be understood in reference to this adaptive shift in the use of fallback foods. Our hypothesis implicates fallback foods as a critical limiting factor with far-reaching evolutionary e?ects. This complements the more common focus on adaptations to preferred foods, such as fruit and meat, in hominid evolution.
Dynamic Atomism, Fitness Dependent Systems, and The Evolution of Selected Information (Memes) in Humans and Related Species
Greg Laden and Ora Elquist
The present work is a combination of three initially separate efforts:
1) Development of a general theory of fitness and replication that does not hinge specifically on either genetic systems or “co-evolution” (which in turn may privilege genetic systems by isolating them as a special milieu for evolutionary process).
2) Development of a model for the evolution of certain unique human traits, especially specialization and division of labor (by sex, age, etc.) and increasing dependence on and use of technology for ecological exploitation.
3)Investigation of the use of “meme theory” or similar concepts for understanding the relationship between humans and other species (mainly domestic animals).
The Naked Truth: The fallacy of genetic Adam and Eve
National Center for Science Education Reports.
Morphological variation in maize phytoliths
This is a study to independently (somewhat) test the idea that morphological characteristics of maize phytoliths vary in relation to genetic heritage to a sufficient degree to use these characteristics to classify phytolith populations into likely existing or ancient archaeological genetic populations. The study looks at sources of variation and concludes that genetic variation is a likely cause of a lot of it. This paper is published in HISTORIES OF MAIZE IN MESOAMERICA: MULTIDISCIPLINARY APPROACHES
Manganese dioxide staining as a taphonomic tool in interpreting hominid evolution
Our objective in this paper was to get a handle on the amount of time over which, say, a hominid skull would have to lay around unburied but in the shade (i.e., in the bushes or in a rock crevasse) in order to accumulate a descent amount of lichen which would, in turn, mark the bones sufficiently to leave a fossil imprint.