Karen L. Baab, Ph.D.

Assistant Professor

Midwestern University
Arizona College of Osteopathic Medicine
Department of Anatomy         

Agave 201E
19555 N. 59th Avenue
Glendale, AZ 85308

Office: (623) 572-3737

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Ph.D. Anthropology The Graduate Center (City University of New York) 2007
MA Anthropology    Hunter College (City University of New York) 2003
BA       Anthropology & History  Muhlenberg College 2000


Homo erectus is an extinct species closely related to living humans with an extensive paleontological record spanning more than one million years from sites in East and South Africa, Eurasia and East and Southeast Asia. Despite this wealth of fossils, there are many unanswered questions concerning the systematics of this group of fossils. My research is focused on clarifying issues surrounding alpha taxonomy and evolutionary history of Homo erectus and other closely related hominin species, including the so-called "Hobbits" of Flores, Indonesia (Homo floresiensis). This work takes advantage of advances in three-dimensional (3D) imaging, including computed tomography (CT) scanning and laser surface scanning, as well as shape analysis via 3D geometric morphometrics. My lab also investigates the pattern and process of morphological and taxonomic diversification in Malagasy lemurs, and whether these processes are related to shifts in ecology.

Research projects:

Defining Homo erectus:

This project assesses whether the cranial shape of Homo erectus is distinct in comparison to other closely related Homo taxa using 3D geometric morphometrics. Data were collected from a large sample of putative Homo erectus fossils, including recent additions to the hypodigm. This project will elucidate the nature of cranial shape variation in fossil Homo and how this variation is related to differences in size. It will also clarify how various fossils or fossil samples relate to the "core" Homo erectus sample from Java. This work builds on my previous research documenting the degree of shape variation in this sample, as well as shape differences within this group.

The Enigmatic Hominins from Flores:

An intense debate has ensued since the 2004 announcement of hominin remains on the island of Flores, Indonesia. While the majority of workers have embraced these remains as representatives of a late-surviving but morphologically primitive species of hominins, Homo floresiensis, a vocal minority suggest that these are actually modern humans suffering from a pathological condition. My collaborators and I are evaluating the most recent diagnosis for the Flores hominins, that of Down Syndrome (or trisomy 21). Our analysis addresses issues related to the brain, skull, and postcranial skeleton. Preliminary results were presented at the 2015 American Association of Physical Anthropology meetings.

The Systemic Robusticity Hypothesis:

Cranial robusticity has played a key role in defining and diagnosing Homo erectus, but the underlying etiology of cranial robusticity is poorly understood. Increased physical activity is one factor that influences limb bone thickness. According to the systemic robusticity hypothesis (SRH), it may also produce thicker cranial bones via a systemic endocrine response. One prediction of the SRH is that limb bone and cranial bone thickness should be correlated across individuals and possibly populations. This project tests this prediction using CT scans of associated crania and limb bones from single individuals across numerous populations. Funded by the Leakey Foundation.

Morphological and Ecological Diversification in Lemurs:

The lemurs of Madagascar are taxonomically, ecologically and morphologically variable, but the extent to which diversification along these three axes is linked is unknown. A previous analysis found only weak support for a relationship between cranial shape and ecology, but this is a complex question that demands multiple approaches. We are currently evaluating differences in mandibular shape against predictions from biomechanical theory in closely related pairs of species that differ in their diets. Preliminary results will be presented at the 2015 Society of Vertebrate Paleontology meetings.

Selected Publications

Full List on ResearchGate

Baab, K.L. Defining Homo erectus. (2015) Henke, W. and Tattersall, I. (Eds.). Handbook of Paleoanthropology. New York: Springer, pp. 2189-2219. *Invited* LINK

Baab, K.L. Phylogenetic, ecological, and allometric correlates of cranial shape in Malagasy lemuriforms. (2014) Evolution. 68: 1450-1468. LINK

Baab, K.L., McNulty, K.P., and Harvati, K. (2013) Homo floresiensis contextualized: A geometric morphometric comparative analysis of fossil and pathological human samples. PLoS ONE 8(7): e69119.  LINK

Baab, K.L., McNulty, K.P. and Rohlf, F.J. (2012) The shape of human evolution: a geometric morphometrics perspective. 21: 151-165. *Invited* LINK

Baab, K.L., Freidline, S.E., Wang, S.L, Hanson, T. (2010) Relationship of cranial robusticity to cranial form, geography and climate in Homo sapiens. American Journal of Physical Anthropology. 141: 97-115.  LINK

Baab, K.L., McNulty, K.P. (2009) Size, shape and asymmetry in fossil hominins: the status of the LB1 cranium based on 3D morphometric analyses. Journal of Human Evolution. 57: 608-622. LINK

Baab, K.L. (2008) The taxonomic implications of cranial shape variation in Homo erectus. Journal of Human Evolution. 54: 827-847. LINK