Hominid Skull Analysis

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This year, inspired by previous conversations in this group about using hominid skulls in the classroom, my colleagues and I worked to develop a lab analyzing variation in hominid skulls.  The original scaffolding for the lab came from an internet find created by ENSI (my typical process usually involves taking ideas from what others have done and mushing it all together until it resembles some sort of coherent learning experience.  Sometimes it works).

The basic idea was that students would look at a variety of hominid and primate skulls, take measurements of some key adaptive features, and attempt to interpret the evolutionary significance of said adaptations/changes. The original lab seems to be directed towards students with a more complete background in anatomy.  Since we were working with freshman biology students (and our goal was not to teach expertise in anatomy) we refocused on a few key features and walked the students through each of those measurements in the lab.  Our main focus(hope), after the measurements were complete, was to have the students really think about why each of the species had the characteristics that they did and how we got to where we are today.

I began with a discussion on what a hominid was and a short discussion on human evolution.  I then showed them “Dawn of Humanity” which is an amazing NOVA special on the discovery of Homo naledi.  It’s 2 hours long so I only showed the second half that focuses on the discovery of this new species.  It is really an amazing video that shows what all goes into the discovery of a hominid.

Next, I introduced the lab and discussed the expectahominid3tions and demonstrated a few key measurements and how to use the calipers.  Then I set them free.  I had one hominid(or primate) on each lab station and had each group take all the measurements on their specimen (about 15 minutes for the first one) and then rotate to a new lab bench and start over with the new specimen.  They get quicker each time (about 8-10 minutes on average per specimen) 7 specimen in total.  You could either hominid2print out the instructions for measurements (in color would be best), or I just had them as a pdf and had the students access them with ipads.

After measurements are complete there is a 1 paragraph description of the specimen (provided by “Skulls Unlimited”) that does a nice job describing the organism.  This information, paired with the measurements are what the students use to answer the analysis questions.  I also have the students choose 1-3 key measurements that they feel early illustrate transitional adaptations to graph. (shown above)

I was a little hesitant to dig into this (get it?) at first because I am certainly no expert on hominid skull anatomy (hopefully we didn’t make any big errors in our set up but feel free to let us know if we did). However, once we got started and I saw the results I was very pleased.  As long as the students took the time to read the species descriptions and took careful measurements, they did a good job and demonstrated a good understanding of the material.  So, here you go.  From our classrooms to yours.

I hope I attached the documents correctly…

_Homonid cranium measurements STUDENT

_Hominid Bone Clone Descriptions

 

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2 thoughts on “Hominid Skull Analysis

  1. I did some work with this back when I was in the classroom. I don’t see how to attach my file, so will just paste it into this post. Anyone wanting the original file can email me and I will send it to them. As you can see from my post, my objective was slightly different from Chris’. I used miniature skulls from Carolina since they were cheaper than full size replicas. I also came across this site, http://morphosource.org/index.php. I haven’t investigated thoroughly, but the initial post I saw indicated that the site had 3D images to manipulate and a downloadable program for 3D printers for the images. Chris’ work looks great. Hope this adds an idea or two for some of you. Much of the formatting was lost when I copied and pasted, but you can get the general idea. As I said, feel free to email me if you want the digital file. BTW, I also used this with freshmen and I really enjoyed the requirement for them to actually generate ratios from their measurements. Just liked whenever I could require the use of math skills in my classroom helping build the idea that math and science aren’t separate disciplines.

    Primate Skulls Comparison
    By: Harry McDonald
    816-863-7580 – cell
    913-897-9630 – Home
    biologycctrack@hotmail.com

    This activity is designed to help students understand that, in fact, anthropologists can “know what they are talking about” when they find a fossil skeleton, or part of a fossil skeleton, and they identify the species of the organism. More specific knowledge about fossil analysis is possible, but the preceding is the main motivation of the author. As you use this activity, any comments on problems or inaccuracies will be welcomed by the author, who can be reached by any of the means above.

    You will need a set (or two) of primate skulls. I recommend the miniature primate series marketed by Carolina Biological. I have used these for several years with great success.

    The activities for this lab are based on information and activities found in the Stones and Bones curriculum originally developed and marketed by the Los Angeles Public Schools. I don’t believe the curriculum is still marketed. In any case, I have considerably simplified the descriptions of the activities and the questions are essentially my own.

    I have the students complete the two data tables and answer all the accompanying questions. Directions for each type of reading are on the second and third pages of the handout. When students are finished, considerable small group and class discussion can be centered around the data.

    Name __________________________________ Hour ______

    For each skull, determine the following and record in the table.

    Sagittal crest: present or absent
    Supra-orbital ridge: present or absent
    Prognathism: present or absent
    Brain case: large, medium or small relative to the overall skull
    Dental arch: parabolic or parallel
    Condylar index: record
    Ratio of upper facial height to cranial length: record

    Skull Sagittal Supra- Prognathism Brain Dental Condylar facial/
    crest orbital case arch index cranial
    ridge ratio

    Gorilla

    Chimpanzee

    Australopithecus
    afarensis

    Australopithecus
    boisei

    Homo erectus

    Homo sapiens
    neanderthalensis

    Homo sapiens

    Conclusion:

    What trends do you see that would help you identify a skull as belonging to one or the other of these species? Justify your answer by citing the data you feel identifies the trend.

    Based on this data, do you feel that it is reasonable for anthropologists to identify the species of a primate fossil when all they find is a skull? Explain

    Sagittal crest: This is a bony ridge along the midline of the top of the cranium that provides attachment for jaw muscles.

    Question: What would you infer from the presence or absence of a sagittal crest?

    Supra-orbital ridge: This is a bony ridge across the upper portion of the eye sockets.

    Question: What might be inferred by the presence or absence of this feature?

    Prognathism: This refers to the protrusion of the lower parts of the face below the eyes. This would be called a muzzle. A lack of this feature would produce a face that basically forms a vertical plane and would be described as flat.

    Question: For what type of features might a protruding face be adaptive? Briefly explain yourself.

    Brain case: Size of the brain case should be related to the overall skull size. A small brain case compared to a large skull may be larger than a large brain case compared to a small skull.

    Question: What would this feature indicate about a hominid?

    Dental arch: Determine whether the sides of the jaw are parallel to each other or do they form an arch or parabola.

    Question: What might we infer about a primate based on this feature?

    Condylar Index: This index measures how far forward or backward on the skull it connects or balances on the backbone. Bipedal organisms would have this balance point located more forward than would quadrupedal animals. Obviously this index is a major indicator of whether an animal walked upright.

    Procedure: 1) Find the plane that goes from the bottom of the eye socket through the top of the ear opening. This is called the Frankfurt Plane. 2) On this plane, measure from the most posterior point of the skull to the point immediately above the hole where the spinal cord enters the skull. This will be measurement A. You will notice two bony “bumps” that surround this opening. These are called the occipital condyles and are the actual point of attachment of the skull to the spine. 3) On this plane, measure, from this same point above the occipital condyles, forward to a point immediately above the most anterior point of the skull. (This is usually a point in space immediately above the tip of the jaw.) This will be measurement B. 4) The index is computed by the following equation: Condylar Index = A/B X 100

    Ratio of upper facial height to cranial length:

    Upper facial height: This is the distance from the top of the nasal bone to the central point on the upper jaw. This will be measurement C.

    Cranial length: This is the distance from the most forward point of the brow to the most posterior point on the skull. This will be measurement D.

    Calculate the ratio using the following formula: Ratio of upper facial height to cranial length = C/D X 100

    Skull A B C D A/B X100 C/D X 100
    Gorilla
    Chimpanzee
    A. afarensis
    A. boisei
    H. erectus
    H. neanderthalensis
    H. sapiens

    Question: Based on the Condylar indexes you have calculated, which organisms would you say most likely are bipedal?

    Question: What pattern do you see when comparing face size to cranial size?

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