A Comparison of Hominins Using 3D Printed Fossil Jaws

Author	Grade Level	Time Frame	Featured Picture
Molly Selba | PhD Student Anthropology Michael Ziegler | M.S. Student Geology Claudia Grant | PhD Student Educational Technology University of Florida	Adaptable to different Middle School levels	One 50-minute class period

DRIVING QUESTION

How did different hominins adapt to a variety of environments?

LEARNING GOALS

• Collecting data in order to compare and contrast tooth size and learn about tooth morphology.
• Relating shape and size of teeth with available diet.

COLLABORATIONS

Students work in groups of two or three observing, measuring teeth and collecting data.

STEM INTEGRATION

Science: The role of a paleontologist is to reconstruct the lives of various extinct species through the analysis of the bones that they left behind. Specifically, by measuring the teeth of extinct species, paleoanthropologists can reconstruct their diet. This method is used on fossils of all different kinds and is even used to learn more about our closest human relatives.

Technology: Students can plot STL files to the printer, if they are printing or they can view 3D models online.

Mathematics: Students will be measuring and conducting basic mathematical operations in order to find answers.

ASSESSMENT

• Students filled out a lab worksheet to organize data
• Students printed out their given .STL file
• Students recorded data from their 3d printed fossil

ANCHORING EVENT & PROCEDURE

1. Using the 3D printed models, find information you think will help you identify similarities and differences between the two hominin mandibles and how they might relate to the tree on this website: http://humanorigins.si.edu/evidence/human-family-tree
2. Watch this YouTube video and start thinking about the different tooth types and discuss their function:

In this lab exercise, you will play the part of the paleoanthropologist and have to determine the diet of two species of hominins. The term ‘hominin’ refers to humans and all of their direct ancestors. One of the mandibles provided for you is from Homo heidelbergensis, a hominin that lived approximately 700 thousand years ago in Africa. H. heidelbergensis was a species very similar to modern humans in terms of body proportions, dental adaptations, and cognitive ability (Rightmire, 2009). The other mandible provided for you is Paranthropus boisei, a species that lived in Africa around 2 million years ago. Their brains were roughly the size of modern chimps and gorillas despite having a fairly small body size (approximately 65 lbs. adult females and 85 lbs. for adult males) (McHenry, 1992). Both of these species had drastically different diets, which are reflected by the shape and size of their teeth.

By analyzing the teeth left behind in the jawbones of these hominins, you will be able to demonstrate not only that these two species have very different dental morphology (i.e. the shape of their teeth), but also that this tooth shape is directly related to their diet.

STEP 1

Hominin Mandible Comparison
To begin, it is important to note which teeth are present in the mandibles (jawbones) of each of the hominin specimens. All hominins have four different types of teeth (including us!). They are:

Incisors: the flat front teeth. Incisors cut food into smaller pieces just like scissors cut paper.
Canines: teeth that tear food apart. They are next to the incisors.
Premolars: the larger, flatter teeth next to the canines. They help grind up the food that we eat.
Molars: the big, flat teeth with sharp ridges found all the way in the back of the mouth. They are perfect for crushing and grinding up food.

All hominin have four incisors, two canines, four premolars, and six molars. They are arranged in the mouth like this:

Human mandible

Sometimes, individuals can lose some of these teeth during their lives. It is also possible for the teeth to be lost over time (i.e. before the fossils were found by the paleoanthropologist but after the individual died). Now, look at both of the two mandibles provided for you. Mark in the table below which teeth are present () and which are missing (x). The teeth are listed from the left side of the dental arcade to the right:

Which of the individuals have more of their teeth present?

STEP 2

Now that you have identified tooth type, it is time for you to measure the different teeth. For each tooth, you will be taking a measurement called the ‘buccolingual width’—it is the measurement of a tooth from the side that your cheek touches (i.e. the part that you can see in the mirror when you smile) to the side that you can touch with your tongue. So ‘bucco-’ refers to the cheek side of the tooth, while ‘lingual’ refers to the tongue side. The measurements will look like this:

Buccolingual Width Measurements

Obtaining Tooth Measurements from the 3D printed casts

Since the teeth are usually symmetrical in the mouth, you only need to measure the eight teeth on the left side of the mandible.

Due to this symmetry, you can say that the hominin dental formula is 2.1.2.3 (2 incisors, 1 canine, 2 premolars and 3 molars). This formula represents one of the four quadrants in the mouth (upper left, upper right, lower left, lower right). If you multiply each tooth type by four you can determine that you as a human have a total of 32 teeth!

Starting in the middle of the dental arcade and working your way towards the back left side, you will get measurements for two incisors (I), one canine (C), two premolars (P), and three molars (M). Remember to take your measurement across the center (i.e. the widest part) of the tooth!

Fill in your measurements in the table below:

STEP 3

In order to account for any mistakes in your measurements, it is important that the data be averaged to ensure that the measurements are as accurate as possible. Add up the measurements of the people around you (i.e. the I1 measurement from Team 1, I1 measurement from Team 2, I1 measurement from Team 3, etc.) and divide by the number of measurements you added together.

Fill in your average measurements in the table below:

• Which teeth have similar measurements (i.e. are the incisors in both species approximately the same size)?
• In which ways do the teeth of these two species look similar?
• Which of the teeth have very different measurements?
• In which ways do the teeth of these two species look different?
• Which species has bigger teeth overall?

In the beginning of this lab you learned the premolars and molars are for crushing and grinding up food. If that is the case:

• Which of these two species would have molars that would be better at grinding up food? (Hint: would it be better to have big teeth if you had to grind up hard foods or would it be better to have small teeth?)

STEP 4

Now it is time to put all of the information you just found out together and determine the diet of H. heidelbergensis and P. boisei.

One of these species ate lots of plants (fruits and leaves) as well a variety of other foods (many of which we still eat today!). They were avid big-game hunters, produced sophisticated stone tools, and had control of fire (Roebroeks and Villa, 2011). All of these skills allowed them to process their foods, thus making it fairly easy to eat.

The other species only had access to extremely tough foods such as grasses, sedges, and tubers. They were not processing their food, and thus it was extremely tough and difficult to eat. They spent a lot time chewing their foods in order to break them down into small pieces.

Based on the measurements of the teeth that you recorded above which diet did

1. heidelbergensis have? How about P. boisei?

STEP 5: Reflections

1. Why do you think it is important for paleoanthropologists to understand the diet of our closest hominin relatives?

2. What might be some problems that paleontologists/paleoanthropologists encounter with this type of analysis? (Hint: when fossils are found, are they usually whole or fragmentary?)

3. Modern humans (i.e. Homo sapiens) have teeth that are very similar in shape and size to those of H. heidelbergensis. Based on what you learned about how the shape and size of teeth reflect diet, answer the following questions:

• What sort of diet do modern human teeth reflect (hard, tough, soft, and/or processed foods)?

• Is that true with what the human diet consists of today?

4. Another adaptation that helps with chewing hard foods is the presence of larger chewing muscle attachment sites on the cranium. One example of this is the presence of a large flange running down the middle of the skull. This is called the sagittal crest and is where the muscles that help you chew hard foods attach to your skull.

Sagittal CrestLook at the following 3D pdfs below. Which cranium do you think belongs to H. heidelbergensis? Which do you think belongs to P. bosiei? Why?

• Boisei Crania | 3DPDF
• Boisei LowerMandible | 3DPDF
• H. Heidelburgensis Crania | 3DPDF
• H. Heidelbergensis Lower Mandible | 3DPDF

STANDARDS

NEXT GENERATION SCIENCE STANDARDS (NGSS)

Biological Evolution: Unity and Diversity
Performance Expectation

Analyze and interpret data from fossils to provide evidence of the organisms and the environments in which they lived long ago. 3-LS4-1

COMMON CORE STATE STANDARDS (CCSS)

CCSS.ELA-Literacy.RST.6-8.1
Cite specific textual evidence to support analysis of science and technical texts.

CCSS.ELA-Literacy.RST.6-8.3
Follow precisely a multistep procedure when carrying out experiments, taking measurements, or performing technical tasks.

RESOURCES & MATERIALS

• PowerPoint: A Comparison of Hominins presented at NSTA 2018, Atlanta.
• For this lab, you will need two hominin mandibles (one belonging to H. heidelbergensis and one belonging to P. boisei). See table below for files
• Measuring implement (calipers or ruler)
• What Does it Mean to be Human? Smithsonian Institution
• How to Print Your own 3D Replicas? Forbes

Suggested Files

Scientific Name	Common Name	Link to Database	Screen Shot
H. heidelbergensis		https://www.morphosource.org/Detail/SpecimenDetail/Show/specimen_id/5560
P. boisei		https://www.morphosource.org/Detail/MediaDetail/Show/media_id/6245

DATABASE TIPS

morphosource.org

Morphosource is an excellent site to find 3D models of fossils. First, you have to create an account (no spam). Second, find your fossils and request permission for download (approval in less than 24 hrs). If the fossil you want does not have STL format, download PLY format and convert to STL.

Convert PLY to STL

1) Download the open source software, MeshLab to convert the files to STL.

2) From MeshLab, import your PLY file, and then export as STL (Use Binary).

KEY ACADEMIC AND/OR SCIENTIFIC LANGUAGE

Mandible: the scientific name for the jaw bone.

Incisors: the flat front teeth. Incisors cut food into smaller pieces just like scissors cut paper.

Canines: teeth that tear food apart. They are next to the incisors.

Premolars: the larger, flatter teeth next to the canines. They help grind up the food that we eat.

Molars: the big, flat teeth with sharp ridges. They are perfect for crushing and grinding up food. They are found all the way in the back of the mouth.

Hominins: a primate of a family that includes humans and their fossil ancestors.

Paleontologist: a scientist who studies fossils.

Paleoanthropologist: a scientist who studies of the origins and predecessors of the present human species using fossils and other remains

Morphology: a branch of biology that deals with the form and structure of animals and plants

PRIOR KNOWLEDGE

• Adaptation, Natural Selection
• Showed videos of how 3D printers, scanners, and 3D software worked
• Allowed them to explore equipment before actually using for assignment