10.2: The Genus Homo

Learning Objectives

• Compare early Homo species to Au. africanus
• Compare species of Homo

Introduction

The genus Homo first appears around 2.5 million years ago in East Africa. By this time all but one Australopithecus species has become extinct. Paranthropus survives as a contemporary of Homo for almost 1.5 million years.

We see a number of trends in this genus, perhaps the most important being the enlargement of the brain, increase in stature, and the elaboration of technology including stone tools. However, the genus is quite variable. There are many species within Homo including Homo habilis, Homo rudolfensis, Homo erectus, Homo heidelbergensis, Homo neandertalensis, and Homo floresiensis. Some researchers place the early species within the genus Australopithecus, and some refer to the later species as archaic Homo sapiens.

Review Questions

1. Identify the major species within the genus Homo.
2. Which features can we use to separate an australopithecine from a Homo erectus skull?
3. Specify major cranial differences between the H. erectus, H. neanderthalensis, and H. sapiens.
4. What are some broad trends that occurred over the course of Homo evolution? Discuss skull shape, facial morphology, and tooth or jaw proportions using specific examples from the different species, noting how they compare to each other.
5. What changes have occurred to the breadth of the pelvic inlet over hominin evolution? What does this suggest about the social behavior and life history of the different hominin species?

References

Frank, Rebecca. 2019. “Activity 14: The Hominin Fossils: Australopithecines.” In LAVC Anthro 111 Lab Manual, 7th Edition, edited by Frank, Rebecca, Brian Pierson, and Philip Stein.

Paskey, Amanda and AnnMarie Beasley Cisneros. 2019. “Chapter 11: Archaic Homo.” In Explorations: An Open Invitation to Biological Anthropology, edited by Beth Shook, Katie Nelson, Kelsie Aguilera, and Lara Braff. Arlington, VA: American Anthropological Association.

Yoshida-Levine, Bonnie. 2019. “Chapter 10: Early Members of the Genus Homo.” In Explorations: An Open Invitation to Biological Anthropology, edited by Beth Shook, Katie Nelson, Kelsie Aguilera, and Lara Braff. Arlington, VA: American Anthropological Association.

Exercise 1: Genus Homo

We will begin our study of the genus Homo by comparing early species to Au. africanus. For this exercise, you will need skull casts of Au. africanus, H. habilis, and H. erectus. Measure and record the features in the chart, and then answer the questions below.

Paleoanthropologists generally agree that Homo erectus belongs in our genus and represents a significant shift towards adaptations important to our own species. However, there is much variation among specimens that are grouped into H. erectus. Your instructor will let you know which of these fossil representatives to use for the exercise today.

Based on your measurements and comparisons in the table above, what are major differences among Au. africanus, H. habilis, and H. erectus? Do you think H. habilis is more like Australopithecus or Homo?

How do these three species reflect the major environmental pressures of the time periods in which they lived, respectively?

List three features that are changing in the genus Homo due to these selective pressures.

List three features found in H. erectus that are derived, compared to Au. africanus.

Exercise 2: Comparing Species of Homo

In this exercise, you will compare four species of Homo. You will again examine skeletal features of the face. Which features are getting larger? Which are getting smaller? What trends do you notice and what do these changes tell us about the selective pressures and adaptations observed in our genus? Measure and record the features in the chart and then answer the questions below.

Identify three major evolutionary trends that occurred in the genus Homo over the last two million years.

Discuss one of these trends and compare the Homo species using your measurements and observations to illustrate this trend. What are the likely reasons behind the changes that occurred in our genus?

Exercise 3: The Postcranial Skeleton

Hominins are defined largely on the basis of erect bipedalism so it is also important to examine the fossil evidence for locomotion. We will focus on the pelvis for this class, but adaptations of the femur and feet are also extremely important. Examine the pelves from an ape, Australopithecus afarensis, Homo erectus, Homo neandertalensis, and Homo sapiens. Observe and record the features in the chart and then answer the questions.

What differences do you see? Which species look most like modern humans? How have bodies and pelves changed over hominin evolutionary history?

Why is the breadth of the pelvic inlet important? What might it tell us about a species’ social behavior or life history?