Flashcards for Early Hominin Evolution
Topic 2:  Analysis of Early Hominins
(14 cards)

Select the "Next Card" button to see a card. Select it again to view the answer.
"Delete Card" allows you to eliminate a card from the stack during this session.
Copyright © 2004-2012 by Dennis O'Neil. All rights reserved.

The genus of early hominins that was most likely the immediate ancestor of humans.


The group of australopithecine species that was least likely to have been an ancestor of humans. This group lived at the same time as the first humans.   (gracile or robust)

robust australopithecines

The term for the bones of the hip region.

pelvis or pelvic girdle

The kind of environment in which bipedal locomotion probably evolved. Bipedalism was very likely an adaptation to living in this kind of environment—it provided advantages for survival.

mixed woodland and grassland environment

The bony arch extending horizontally on either side of the face just below the eyes on primates and many other vertebrates. The major jaw muscles pass under these arches on their way up to the temporal areas of the skull for attachment.

zygomatic arch

A species of early australopithecines that lived about 3.7-3.0 million years ago in East Africa. Skeletally, they were still somewhat transitional from early Pliocene apes. This can be seen in their legs which were relatively shorter than those of the later australopithecines. They also had slender curved fingers reminiscent of chimpanzees. As a result of these anatomical characteristics, it has been suggested that they were less efficient bipeds and more efficient tree climbers than the later australopithecines. Some of the males had small sagittal crests.

Australopithecus afarensis

The earliest known australopithecine species. They lived 4.2-3.9 million years ago in East Africa. Little is known about them due to the scarcity of their fossils. However, they apparently were a transitional species descended from Ardipithecus ramidus or an even earlier ape ancestor near the beginning of the Pliocene Epoch. They probably were only partially bipedal and still efficient tree climbers.

Australopithecus anamensis

A term applied to the early australopithecines and the earliest humans. It means graceful, slender, and delicate and is used to describe the body characteristics (especially bones) of these species.


A species of australopithecine that lived about 3.3-2.5 million years ago in both East and South Africa. Skeletally, they were less ape-like than earlier species of australopithecines but were still usually small and light in frame. This was one of the last gracile australopithecine species.  It was also the first one to be discovered.

Australopithecus africanus

A super-robust East African species of early hominids that lived about 2.4-1.4 million years ago. They were more massive and beefy-looking than Australopihecus robustus. While they were only a few inches taller, they averaged 20 pounds heavier. Like their South African cousins, they had prominent sagittal crests and very large grinding teeth with thick enamel. This suggests a similar diet of hard vegetable foods.

Australopithecus boisei

The earliest known robust species of early hominins--it lived about 2.5 million years ago. So far, this species has been found only in East Africa. Since it had a smaller brain than the other robust species and it was early, it is thought to be a transitional form from one of the gracile species that came before. It had a very large sagittal crest.

Australopithecus aethiopicus

A South African robust species of early hominins that lived about 2.0-1.5 million years ago. Like Australopithecus boisei, their teeth appear to have been adapted to eating tough, fibrous vegetable foods. This is indicated by their strong jaws and very large molar and premolar teeth with thick enamel. Microscopic wear patterns on their teeth indicate that they regularly ate foods such as hard nuts and seeds. They also had pronounced sagittal crests, though not as large as boisei.

Australopithecus robustus
The genus of all human species.

The genus that was most likely the immediate ancestor of humans.