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David P. Tracer

Prone to Crawl: Pre-bipedal Perambulation, Parenting and Parasites in Papua New Guinea

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Will Baby Crawl? Maybe yes, maybe no, says anthropologist David Tracer, whose study of children in Papua New Guinea supports the view that milestones of child development vary with culture.

The Au people of the Anguganak village live deep in the remote lowland rainforests of Papua New Guinea. David Tracer, a biological anthropologist specializing in maternal-child health, is the only researcher to have worked among the Au for the past 23 years. "They're people that I have really come to value both as research subjects and as friends," he says. His recent work among Au infants from birth to age 30 months challenges assumptions about what constitutes "normality" in early growth and development.

"Although we know a lot about patterns of growth in weight and stature in different populations, we know almost nothing about neuromuscular and motor skill development outside of the western industrial context," Dr. Tracer notes. Yet despite this lack of comparative data, standards of motor skill attainment based on the sequence and timing seen in the United States and Europe are widely regarded to be universal. "Part of the motivation for this project was simply that in over two decades of working among the Au, I had never seen an infant crawl" he says. "They also seemed to universally go through a 'scoot' phase, shuffling along in an upright position on their bottoms prior to walking. I became interested in why their pattern of early locomotor development was so different from our own."

He performed quantitative analyses of locomotor development on over 100 children. Some of the tests are administered to children while they are in an upright posture (e.g., sitting) while others are administered while they are in a horizontal posture (e.g., prone or supine). The pattern of test results that he noted was surprising...

Dr. Tracer will discuss his findings indicating that parenting behaviors and the risk of contracting parasites play a key role in channeling Au children's early locomotor development. He will also discuss his idea that crawling is a relatively recent novelty in the scheme of human evolutionary history.


Dr Tracer David P. Tracer, PhD, is Professor of Anthropology and Health & Behavioral Sciences at the University of Colorado Denver College of Liberal Arts and Sciences and Professor of Public Health at the University of Colorado Anschutz Medical Campus. He received his BA in Anthropology from Brandeis, and MA and PhD in biological anthropology from the University of Michigan.

He writes: My main area of expertise is human ecology; that is, the reciprocal relationship between organisms, in this case, humans, and their environments understood within an evolutionary framework. For the human organism, the "environment" includes the diverse physical, behavioral, and wider sociocultural milieus within which they are found and to which they must successfully adapt. To date my research has examined aspects of both human biology and behavior within such a framework. In the biological arena, my research has focused on various aspects of maternal and child health including nutrition, growth and development, and determinants of fertility. Within the area of behavioral ecology, I have been interested in testing predictions derived from life history theory and parental investment theory as well as an examination of social norms such as reciprocity, altruism, bargaining, and punishment. All of these areas are represented in my two-decade long and currently still ongoing field-based research project among the Au lowland forager-horticulturalists of Papua New Guinea.

© 2004 Colorado Café Scientifique