Investigating Human Evolution

Using skull fossils to examine evolutionary changes in human ancestors.

Fossils as evidence for evolution

We will be using real fossil scans for this investigation, like those from this African Fossils or this Morphosource database to look at fossils from organisms from all over the U.S. Fossil databases allow scientists to compare fossil records from all over the world.

Pre-lab Questions

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1. What information can be gathered from skull size?

Pre-lab Questions

I can infer that…

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2. We will be taking quantitative measurements of the skulls of fossils of various species from the primate family. How do you think the skulls of primates have changed over time?

Zygomatic Bone

(cheekbone)

Parietal Bone (skull)

3. The skeleton represents the modern human. The species in the pictures were alive thousands or millions of years ago (mya). Arrange the pictures around the skeleton based on how closely you think they are related to the to each other and to the modern human based on skull shape.

Observing Skulls of Human Ancestors

In this investigation you will measure skull fossils from 3D scans of hominids and compare the measurements to modern humans. Make sure to measure consistently on the 3D fossil scans for the two measurements.

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SKULL WIDTH

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• Measure from one side of the head to the other
• Measure the width above the eyebrow

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CHEEKBONE WIDTH

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• Measure from one side of the face to the other
• Measure at the cheekbone level

SKULL WIDTH

CHEEKBONE WIDTH

Observing Skulls of Human Ancestors

Use the ruler on each slide. Move the ruler to the 3D fossil images and record the width on the slides and on this Skull Data Analysis Google sheet to be able to graphically represent the data.

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• Make sure that you do not change the size of the ruler in order to gather consistent measurements.
• Move the ruler by clicking and dragging it.

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SKULL WIDTH

CHEEKBONE WIDTH

Observing Skulls of Human Ancestors

In order to compare the data for the skull measurements, you will calculate a ratio so that the the quantitative data can be analyzed without the size of the 3D scan image and the skull fossil impacting the quantitative comparison.

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• The ratio will allow for you to compare how large the skull is in comparison to the cheekbones.
• Divide the width of the SKULL BY the CHEEKBONE width

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SKULL to CHEEKBONE Ratio = SKULL Width .

CHEEKBONE Width

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SKULL WIDTH

CHEEKBONE WIDTH

01. Pan troglodytes

Skull Width *10* cm

Cheekbone Width*14* cm = *0.71*

*Answers will vary*

Skull Width: ** cm

Cheekbone Width: ** cm

QUANTITATIVE MEASUREMENTS

PROCESS DATA- Skull to Cheekbone Ratio

QUALITATIVE OBSERVATIONS

02. Australopithecus afarensis

Skull Width *10* cm

Cheekbone Width*17.5* cm = *0.57*

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Skull Width: ** cm

Cheekbone Width: ** cm

QUANTITATIVE MEASUREMENTS

PROCESS DATA- Skull to Cheekbone Ratio

QUALITATIVE OBSERVATIONS

03. Australopithecus (Paranthropus) aethiopicus

Skull Width *11* cm

Cheekbone Width*19* cm = *0.58*

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Skull Width: ** cm

Cheekbone Width: ** cm

QUANTITATIVE MEASUREMENTS

PROCESS DATA- Skull to Cheekbone Ratio

QUALITATIVE OBSERVATIONS

04. Homo erectus

Skull Width *13* cm

Cheekbone Width*16.5* cm = *0.79*

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Skull Width: ** cm

Cheekbone Width: ** cm

QUANTITATIVE MEASUREMENTS

PROCESS DATA- Skull to Cheekbone Ratio

QUALITATIVE OBSERVATIONS

05. Homo neaderthalensis

Skull Width *13* cm

Cheekbone Width*15* cm = *0.87*

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Skull Width: ** cm

Cheekbone Width: ** cm

QUANTITATIVE MEASUREMENTS

PROCESS DATA- Skull to Cheekbone Ratio

QUALITATIVE OBSERVATIONS

06. Homo sapiens

Skull Width *12.5* cm

Cheekbone Width*14.5* cm = *0.86*

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Skull Width: ** cm

Cheekbone Width: ** cm

QUANTITATIVE MEASUREMENTS

PROCESS DATA- Skull to Cheekbone Ratio

QUALITATIVE OBSERVATIONS

Data Analysis of Skulls

Record your measurements in the Skull Data Analysis Google sheet. Follow the directions in the sheet to graph the SKULL : CHEEKBONE ratio in a Bar Chart. Copy and paste your graph in the space below.

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Data Analysis Questions

1. Why is it useful to calculate a cranial measurement ratio using the skull and cheekbone measurements?

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• What are the trends in the cranial measurement ratio in terms of the species and your qualitative observations?

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2-4 mya

2.5 mya to 40,000 ya

Evolved 200,000 ya

Genus Australopithicus

Genus Homo (Hominids)

Homo sapiens

Quantitative & Qualitative Comparison

Post-lab: Comparing Human Ancestors

Use the links on the following page to obtain more data and information about each of the species. Use this information to answer the post-lab questions.

02. Australopithecus afarensis

01. Pan troglodytes

05. Homo neanderthalensis

06. Homo sapiens

03. Australopithecus (Paranthropus) aethiopicus

04. Homo erectus

3.9-2.9 mya

Extant- current version of chimpanzee

400,000-40,000 ya

200,000 ya-present

2.7-2.3 mya

1.89 million to 110,000 thousand ya

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Post-lab Questions

• After reading about the species, suggest reasons that Australopithecus afarensis may have gone extinct.

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• Based on the quantitative data of the skull measurements and the readings, which species is more closely related to Homo sapiens?

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• What evolutionary changes did the genus Homo have in comparison to the genus Australopithecus?

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Locations of Human Ancestors

Homo erectus

Homo neanderthalensis

Australopithecus afarensis

Paranthropus aethiopicus

This map shows where the ancestors of humans were located, based on the discoveries of fossil remains

Post-lab Questions

4. Consider the locations of the species on the map. Explain how environmental pressures may have played a role in natural selection that lead to the extinction of the genus Australopithecus and the speciation that gave rise to the genus Homo.

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5. Homo erectus and Homo neanderthalensis were found in many more locations spanning multiple continents. Which traits in their gene pool would lead to better fitness for this lifestyle compared to other primates.

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Now that you have obtained quantitative observations and learned the names and timelines for these fossils, arrange the pictures around the skeleton based on how closely you think they are related to the to each other and to the modern human based on skull shape. The skulls are ordered from left to right in the number order from slide 21.

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Resources

Human Evolution Teaching Materials Project

Lesson ideas and 3D files, including .STL files are available.

Thanks!

Do you have any questions?

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senelson@henrico.k12.va.us

Henrico High School

Henrico County Public Schools

Please keep this slide for attribution

CREDITS: This presentation template was created by Slidesgo, including icons by Flaticon, and infographics & images by Freepik

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Introduction

CONTRIBUTOR:

Toshisada Nishida

TITLE

Chimpanzee

PUBLISHER

Encyclopædia Britannica

DATE PUBLISHED

March 16, 2020

URL

https://www.britannica.com/animal/chimpanzee

ACCESS DATE

December 08, 2020

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Sources

https://humanorigins.si.edu/evidence/human-fossils/species

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https://pixabay.com/vectors/ruler-measure-length-meter-cm-146428/

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452,021

Despite being red, Mars is actually a cold place full of iron oxide dust

Process

Earth is the planet where we live on

Mercury is the smallest planet

Saturn is a gas giant and has several rings

Venus is the second planet from the Sun

01.

02.

03.

04.

Overview Diagram

Jupiter

Mars

Mercury

Saturn

Saturn is a gas giant and has several rings

Mercury is the closest planet to the Sun

Despite being red, Mars is a cold place

Percentages

Babies

New-born babies have around 305 bones

Adult

The skeleton of an adult consists of 206 bones

40%

60%

Exercise

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Mercury is the closest planet to the Sun

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Despite being red, Mars is actually a cold place

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Venus is the second planet from the Sun

Alternative Resources

Resources

VECTOR

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• Human skeleton template
• Colorful human elements vector

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PHOTO

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• Detail of an x-ray of lungs