Australopiths
"Australopith" is a term used for a number of similar species. Most of these species are included in the genus Australopithecus - hence the term "Australopith" - but others are in the genus Paranthropus. Some researchers put all of these species into the genus Australopithecus, and therefore refer to the whole group as "Australopithecines". I will probably slip up and use that term in class, since it's actually more common.
The Australopiths came in three forms:
Early Australopiths, from 5-3mya, all of which are members of the genus Australopithecus
Later Australopithis, from 3-1mya, which came in two flavors:
Gracile - Australopiths with smaller skulls and muscle attachments, members of the genus Australopithecus or Kenyanthropus
Robust - Australopiths with larger skulls and muscle attachments, members of the genus Paranthropus
General Characteristics of Early Australopiths
We have many thousands of fossils, including some complete skeletons (like the famous Lucy). These are the first really well known hominin species, and they are definitely hominins. They arre fully bipedal, well after split with apes, so unlike the fragmentary Basal Hominin fossils, there is not doubt that these Early Australopiths are not a species of last common ancestor with the chimps, or a chimp ancestors. These are members of our own lineage.
Similarities between Early Australopiths and Basal Hominins:
Found in East and Central Africa
The only countries to yield evidence of Early Australopthis are Chad, Ethiopia, Kenya, and Tanzania
None yet found in other regions
Lived in mixed forest/grassland areas
We do not find their fossils in totally open areas without trees
However, they are not found in dense forest, either. This is more evidence they lived in open environments than with Basal Hominins.
Chimp-sized brain
Well-developed climbing ability
Long, strong hands with curved fingers, like an ape, for grabbing.
Arms much longer relative to body size than ours
Differences between Early Australopiths and Basal Hominins (derived traits):
fully bipedal
pelvis much more like ours (still not identical, but recognizably human)
foot much more like ours (same as above)
shape of foot and pelvis, combined with the long arms and hands, suggests these individuals were fully adapted to both bipedal walking and climbing
skull more robust
bone is thicker
heavier muscle attachments on the skull
face not as flat (it is more prognathic)
teeth more robust (bigger, wider, and with thicker molar enamel, for chewing hard foods)
overall, ironically, the skulls are more chimp-like than those of our last common ancestor with the chimp. This probably suggests similar dietary adaptations for heavy chewing
hand looks more like ours (although see above about the long, curved fingers)
hand includes a muscle found only in humans that allows for strong opposition of thumb
fingers and thumbs oppose more finely (fingers not as long as chimp), allowing for finer manipulation and throwing of objects
Species of Early Australopiths:
Fossils assigned to this species date from 3.6-3.0mya
We have thousands of specimens of A. afarensis, found at a variety of archaeological sites, including:
Alllia Bay, in Kenya
Omo, Hadar, and Dikika in Ethiopia
Laetoli in Tanzania
The fossils are found in what was (at the time) a mixed woodland to dry savannah
Some traits of the species:
diastema in upper tooth row
significant sexual dimorphism
curved toes (as well as fingers) suggest climbing still important
Australopithecus bahrelghazali
Fossils assigned to this species date from 3.1-3.4mya (based on biochronology)
This species designation is based on a single mandibular fragment, and some researchers have put it into the category Australopithecus afarensis. The fragment came from the site Bahr el-ghazal, in Chad, and was discovered by Michele Brunet.
The environment at the time would have been significantly wetter and more forested than today
Some traits of the species (compared to Australopithecus afarensis:
more vertical interior of the mandible
premolars have different root structure and thin enamel
Fossils assigned to this species date from 4.2-3.8mya
We have 80 or more specimens of A. anamensis, found at a variety of archaeological sites, including:
Kanapoi, Allia Bay, and Lake Turkana, in Kenya (discovered by Maeve Leakey in 1994)
Aramis and Asa Issie, in Ethiopia (discovered by Tim White)
fossils from the site of Waranso-Mille, Ethiopia, dating to 3.8-3.6mya that look intermediate between A. anamensis and A. afarensis (discovered by Yahannes Haile-Selassie in 2010)
The fossils are found in what was (at the time) a relatively wooded habitat (particularly at the site of Asa Issie), or in more mixed woodlands and grasslands habitats, in Kenya
Some traits of the species:
larger canines than other Australopiths
General Characteristics of Late Australopiths
After the Early Australopiths, the genus diversifies (undergoes adaptive radiation). A variety of Australopiths lived at the same time, in different niches, between 3-1mya. We devide these species into the Robust and Gracile Australopiths. These two groups were probably divided by their diet. Gracile Australopiths were probably the ancestors to members of the genus Homo (unless Homo developed directly from Early Australopiths).
Similarities between Late Australopiths and Early Australopiths:
still small-brained, like a chimp (note this reflects millions of years without much brain growth
fully bipedal and yet fully capable of climbing
pelvis and foot like ours (even more like ours than the Early Australopiths)
long arms and long curving fingers
skull still robust
heavy muscle attachments
face projects (prognathic)
big, strong teeth
Differences between Late Australopiths and Early Australopiths (derived traits):
found in a wider variety of places, especially South Africa (Remember, though, that the locations of these fossils are not an exhaustive list of where the animals themselves lived. The fossilization environment, surface exposure, and political situation for paleoanthropologists are all factors that determine whether or not we know about ancient hominin populations in particular areas.)
usually found in more open environments - more grassland, less forest
more extreme sexual dimorphism, perhaps suggesting a gorilla-like social organization (one-male/multi-female)
more species variation
Robust Species (Genus Paranthropus)
heavily built, with extremely large muscle attachments for heavy chewing
jaws, cheek teeth, and face very large
body same as gracile species, only skull heavier
diet may have been gorilla-like, with constant eating of hard plant foods, like seeds and nuts
Gracile Species (Genus Australopithecus or Kenyanthropus)
lightly built skulls relative to robust species (still heavier and more robust than basal hominins or modern humans)
thinner bone with less pronounced muscle attachments than robust species (but again, heavier than basal hominins or modern humans)
smaller teeth than robust species (yet again, heavier than basal hominins or modern humans)
diet more omnivorous than robust species, with a mixture of fruits, leaves, and meat. Probably frequently scavenged meat.
Species of Robust Late Australopiths:
There is only one major specimen assigned to this species, "the black skull" and it dates 2.5mya
The only P. aethiopicus specimens we have are from Kenya, the sites of West Turkana and Omo. They were discovered by Alan Walker in 1985.
Some traits of the species:
Massive face, jaws, and teeth
largest sagittal crest of any known hominin
Large number of specimens, dating from 1.8-1mya
All P. robustus specimens are from South Africa, the sites of Swartkrans and Kromdraai. The species was first discovered by Robert Broom in 1937.
Some traits of the species:
small size (only 4 feet tall and less than 100 lbs)
massive face is flat or dish-shaped
large supraorbital torus
major sexual dimorphism
relatively small front teeth, massive grinding molars
fossils date from 2.2-1.3mya
P. bosei is found in East Africa, at the sites of Koobi Fora, Olduvai, and Omo (Kenya and Ethiopia). The first fossil, named "Zinj", was discovered by Mary Leakey in 1959.
Some traits of the species:
Face and molars even more massive than other robust australopiths
extreme sexual dimorphism, with males twice the size of females
dietary studies have shown it ate roots, tubers, and seeds, but not leaves
Species of Gracile Late Australopiths:
This is one of the better-represented species, with a huge number of fossils dating from 3-2.2mya
A. africanus is a South African species, found at the sites of Taung, Sterkfontein, and Makapansgat. It was first discovered by Raymond Dart in 1924.
Some traits of the species:
slightly larger body than A. afarensis
brain small by modern human standards, but about 25% larger than a chimpanzees
small body size (4-4.5 ft tall, weighing less than 100 lbs)
larger molars than earlier australopiths (but not as large as robust australopiths).
face less prognathic than earlier australopiths
smaller canines and diastema compared to earlier australopiths
Kenyanthropus platyops
Only two fossil specimens have been assigned to Kenyanthropus platyops, and these date to 3.5-3.2mya
The fossils were found at the site of Lomekwi in Kenya, by Maeve Leakey in 1999. More than thirty skull and teeth fragments were found at the site, but only two have been designated K. platyops. The others are not assigned to any species.
Some traits of the species:
small auditory meatus
chimp-sized brain
tall, vertical cheek bones
unusually flat face
small molars (appears to have a different diet from other australopiths)
small supraorbital torus
except for the small brain, shares many traits with Homo rudolfensis, and early member of the genus Homo
Fossils assigned to this species were discovered in Ethiopia, at the site of Bouri, by Berhane Asfaw and Tim White in 1996. They dated to 2.5mya
Some traits of the species:
prognathic face
extremely large teeth, more like those of a robust australopith, and in fact larger than most of them
sagittal crest
yes other aspects of skull are more in line with gracile australopiths
Two full skeletons of A. sediba have been published, and more have been discovered and await publication. They date to 1.9-1.75mya
The species was discovered at Malapa Cave in 2008 by Lee Berger (actually by his 9-year old son)
Some traits of the species:
small brain, but with less post-orbital constriction
body that looks mostly like A. africanus
teeth, maxilla, and jaws look a lot like early members of the genus Homo
may be part of the evolution into the genus Homo