Transitional Fossils:
Transitional fossils are fossils that indicate intermediate forms between
two distinct groups of organisms. These fossils bridge the evolutionary
gap between 2 different types of organisms, and frequently show
conserved (unchanged) as well as derived (changed) traits. In other
words, the fossils show some skeletal adaptations similar to the
organisms that existed before them (ancestors), and some similar to
those organisms that have evolved since them (descendants).
The Transition: Quadrupedal to Bipedal Primates
The Transitional Fossil: Lucy; Astralopithecus afarensis
*Use Our Class Website “Resources” to View & for Passwords to Access the
PBS Learning Media Website
Please go to at least 2 interactives, 4 videos, and both articles, to choose your
resources.
Choose 1 interactive, 1 video, & 1 article OR
2 videos and 1 article that you will use as a citation and resource for your work.
The Interactives:
Fossil Evidence
Comparative Skeleton
Origins of Bipedalism
Who’s Who in Human Evolution
Riddle of the Bones
Origins of Humankind
The Videos:
Evolving Ideas: Did Humans Evolve?
Fossil Evidence of Bipedalism
Walking Tall
Finding Lucy
Laetoli Footprints
Becoming a Fossil (A. afarensis)
The Articles:
Quadrupedal to Bipedal Primates.
The Transforming Leap, from Four Legs to Two.
Images & Documents:
Laetoli Trackways Diagram
Hominid Fossil Data Sheet
Citation 1
Bipedalism:
Name the Transitional Fossil this resource looks at.
When did that fossil live, or when was it made by a living organism (mya) millions of
years ago)?
What are the adaptations or structures visible in the fossil record of this fossil?
Which 2-3 structures have remained unchanged from the common ancestor
of apes and humans?
Please describe each
1
2
3
Which 2-3 structures have changed from the common ancestor and show a
more bipedal adaptation?
Please describe each
1
2
3
Does this fossil show further information other than evidence of skeletal
adaptations?
What was life like for quadrupedal ancestors of apes and humans? How were their
quadrupedal bodies well suited to the environment in which they lived?
Why might bipedalism have been an advantage in early hominids?
Describe 2-3 advantages described in this resource for being bipedal
1
2
3
Describe changes in the environment in which bipedal primates may have been well
adapted to survive.
How does this fossil or fossil evidence support Darwin’s idea of common ancestory?