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Anth 125 Introduction to Biological Anthropology
Dr. Darlene Applegate
Spring 2008
GROUP LAB PROJECT 3:
FOSSIL HOMINID IDENTIFICATION

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INTRODUCTION

All extinct and extant humans are classified within the family hominidae or hominid. For our purposes, all bipedal apes are considered human; realize, however, that some researchers consider only extant Homo sapiens as "human" and refer to extinct bipeds as "pre-humans." Two subfamilies of hominids are recognized by most scientists; australopithecines are a diverse and now extinct subfamily and hominins include contemporary humans as well as other species of the genus Homo.

Though consensus is lacking, most paleoanthropologists, or those anthropologists who specialize in the study of human origins and evolution, recognize at least six genera of humans and over 20 species of humans. Instead of learning each of these species, in this introductory course we will group species into only four categories for comparative purposes. Based on skull morphology, we will compare and contrast gracile australopithecines, robust australopithecines, temporally early (about 2.4 to 0.5 mya) hominins, and temporally late (about 0.5 mya to 30 kya) hominins.


OBJECTIVES

• to review important features of human skeletal biology, especially features of the skull
  

• to review the physical characteristics of fossil hominid species
  

• to distinguish among different types of fossil hominids
  

KEY TERMS

• extinct
• extant
• hominidae / hominid
• bipedal
• human
• australopithecine subfamily
• hominin subfamily
• paleoanthropologist
• gracile
• robust
  
• mya (million years ago)
• kya (thousand years ago)
• morphology

• skull
• cranium
• mandible
• hyoid
• cranial vault / brain case
• incisor
• canine
• premolar
• molar
• sagittal crest
• post-orbital constriction
• brow ridge
• facial profile
• prognathic
• orthognathic
  
• cheek bone
• mandible
• chin
  

• ancestral trait / primitive trait
  
• derived trait

HUMAN SKULL MORPHOLOGY

The human skull is a collection of almost 30 bones that form a protective covering around the brain and provide a platform for the face and sensory organs. The three main parts of the skull are the cranium (the bones surrounding the brain and the bones comprising the face), the mandible (lower jaw bone), and hyoid (a small, horseshoe shaped bone under the mandible). The portion of the cranium surrounding the brain is the cranial vault or brain case. The four types of teeth in the human skull are the incisors (front four teeth in both the upper and lower jaws), canines (slightly pointed tooth behind the incisors in each quadrant of the mouth), premolars (two broad, two-cusped teeth behind the canines in each quadrant of the mouth), and molars (two-three, five-cusped teeth behind the premolars in each quadrant of the mouth).

All human species had the same skull bones and features, but the relative shapes and sizes of the skull bones and features vary and, therefore, can be used to distinguish among different types of fossil hominids. Of the many possible traits used to identify fossil hominid skulls, we will focus on the following eleven traits.

• cranial vault: the portion of the cranium surrounding the brain, which in early humans is small and elongated but becomes larger and more round in later humans

• sagittal crest: a bony ridge that runs from behind the eyes toward the back of the skull along the midline of the skull, which is present primarily among the robust australopithecine species

• post-orbital constriction: the degree to which the cranial vault is pinched or constricted behind the eye orbits, which is most prominent among robust australopithecines

• brow ridges: the bony ridge above both of the eye orbits, which become smaller over time but not significantly so until Homo sapiens
  

• facial profile: from the side view, the lower face and mouth area will project outward (prognathic) in early humans or will be fairly flat (orthognathic) as in later humans, especially Homo sapiens
  

• cheek bones: from the front, note the size and projection of the cheek bones

• nose: the nasal bones are flat in early humans but projecting in later humans
  

• mandible: the size of the lower jaw decreases over time

• canine teeth: the size and projection of the canine teeth decreases over time

• molar teeth: the size of the molar teeth decreases over time

• chin: the chin is absent or receding in nearly all humans except some late hominins, in which the chin is present or projecting
  

   
FOSSIL HOMINID IDENTIFICATION

Taken as a group, the aforementioned eleven skull traits may be used to distinguish among groups of fossil hominids. Some fossil hominids exhibited ancestral or primitive forms of skull features. For example, robust australopithecines retained a sagittal crest, which is observed in other fossil ape forms such as Miocene apes. Other fossil hominids exhibited derived forms of skull features and therefore more closely resemble contemporary humans. For instance,

The following table provides an efficient means of identifying fossil hominids. Keep in mind, however, that while an individual fossil will have a majority of traits that characterize a particular group, it may not exhibit all expected traits. The images are provided below for comparative purposes.

TRAIT	GRACILE AUSTRALOPITHS	ROBUST AUSTRALOPITHS	EARLY HOMININS	LATE HOMININS
cranial vault	small, elongated	small, elongated	medium sized, slightly elongated to sub-rounded	medium to large sized, sub-rounded to rounded
sagittal crest	usually absent, but may be present in males	present	absent	absent
post-orbital constriction	moderate	significant	slight	slight
brow ridges	large	large	moderate to large	small to large
facial profile	very prognathic	very prognathic, concave or "dished in"	less prognathic, may be concave	less prognathic to orthognathic
cheek bones	moderate	large and broad	moderate	small to moderate
nose	non-projecting or flat	non-projecting or flat	slightly projecting	projecting
mandible	large	very large	moderate	small to moderate
canine teeth	large. slightly projecting	large, non-projecting	small, non-projecting	small, non-projecting
molar teeth	large, broad	very large and broad	moderate size	moderate to small size
projecting chin	absent	absent	absent	may be present

Figure 1. Front and side views of two gracile australopithecines.
Image from http://fossils.valdosta.edu/fossil_pages/fossils_ter/p22.html



Figure 2. Front and side views of three robust australopithecines.
Images from http://www.hofesh.org.il/articles/science/branches.html
http://peinandoelmono.tripod.com/galeria_a.htm



Figure 3. Front and side views of two early hominins.
Images from http://www.msu.edu/~heslipst/contents/ANP440/rudolfensis.htm
http://www.boneroom.com/casts/images_hominid/



Figure 4. Front and side views of three late hominins.
Images from http://posters.sonik.us/details/this-neandertal-skull-from-wadi-amud-is-about-60000-years-old-1008584.html
http://www.kalyx.com/store/images/SD_0269.jpg
http://www.paleodirect.com/bh004.htm


ASSIGNMENT

The fossil hominid identification assignment will be completed in class by students working in groups. Each student in the group will complete his/her own answer sheet in pencil.

Examine each of the eight skull specimens. Using the information provided in this lab overview as well as in class lecture and the textbook, identify the type of hominid and record the answer clearly on the answer sheet. Do not provide more information than what is requested.

Each group will have about five minutes to work with each specimen.

The group project will be completed within the allotted class time.

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Last updated on April 3, 2008
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