First of all it is important to understand what hominins
are. Hominins are all species on our side of the last common ancestor of humans
and living apes. They are commonly characterized by bipedalism.
Bipedalism consists in walking on two legs. They are many hypotheses
to present reasons why hominins would adopt bipedalism:
- Not for speed, but better to walk long distances
- Enabled them to use both hands to hold objects
- Efficient to protect against the heat considering the area covered by the sun when straight up is lower
- Possible climate change and habitat change (going from the jungle to the savanna)
Other characteristics make it possible to identify hominins
are the thick tooth enamel, flat molars and small blunt canines. Early hominins
had flat, projecting faces and larger and smaller molars.
Now we will take a close look at each specie, first let’s
see the timeline of hominin evolution for a better understanding.
Sahelanthropus
tchadensis
Also known as TOUMAI, was discovered in 2011 in Chad, in the
southern Sahara desert. It is estimated to be between 7 and 6 million years old
and their brains were the size of a chimpanzee’s brain. The teeth points to the
idea that it was biped but the brain size doesn’t. Because the rest of the body
was never found, the bipedalism remains a question.
Orrorin tugenensis
Nickname is millennium man, found in Easter Africa, Lived about 6.2 to
5.8 million years ago. His femurs allows for a bipedalism evidence, but they
were the size of chimpanzees and probably were arboreal and terrestrial.
Ardipithecus ramidus
Also known as Ardi, is originally from Ethiopia, ages 4.4 million years ago. About 45% of the bones of the body were found starting in 1994, when it was established as a new species. Ardi has some characteristics similar to chimpanzees such as small ear opening and thin dental enamel and does not look fully adaptable to upright position, but it is now known that Ardi walked on two legs because of the bone structure and pelvis.
Australopithecus anamensis
The material consists of 9 fossils mostly found in 1994, in
Kenya. They existed between 4.2 and 3.9 million years ago it has very similar
qualities to older fossils located on the skull, but some body features similar
to modern fossils with strong evidence of bipedalism.
Australopithecus afarensis
Also known as LUCY, was found in Ethiopia and existed about 3.9
and 3.0 million years ago. Sexually dimorphic, presented a very ape-like face
with protuberant low forehead, flat nose and no chin. Bipedal but due to the
finger shape, it’s possible to say that they spend some time on trees too.
Kenyanthropus platyops
It is aged about 3.5 million years old, found in Kenya, the
skull is mostly complete, but it is distorted.
Taung child
Found in South Africa, it’s believed to be a child between 5
and 6 years old because molars were not fully grown. It is estimated to be 2.5
million years old.
Australopithecus africanus
A bit larger than Lucy, they lived about 3 million years
ago, and were found in several regions of Africa, the brain is a bit larger
than the chimpanzees but similar body size. The teeth are very similar to human’s
teeth.
Paranthropus or robust australopithecines
The
Australopithecines in this category are fully bipedal, originated about 2.7
million years ago. Their common characteristic is big molars and strong jaw musculature,
but bodies and brain are considerably small.
Paranthropus aethiopicus
Is the famous “black
skull” part of the robust
australopithecines, was discovered in Kenya and it is estimated to be 2.5
million years old. The color black happen because it was covered in manganese,
which is grey/metallic element.
This Australopithecus represents a link between Australopithecus and
homos. Found in Ethiopia, also believed to be 2.5 million years old.
Was discovered in South Africa in 2008, it is believed to be the transition
to homo. Two partial skeletons were found, one of them a young boy and the
other one an adult female, dated between 1.78 and 1.95 million years ago. The
elements long arms, rib cage and teeth are very similar to homo which leads to
the conclusion that they are the transition between australopithecine and homo.
Personal Input
It is interesting to me how many ancestors we had before
homo species. Among all the 11 species seen in this blog post there are some I
found particularly interesting. Ardi (Ardipithecus ramidus) is the first one of them. We had the opportunity of watching a
video about her during class. Discovery channel was able to recreate the
environment were Ardi once lived, as well as computed animation of Ardi
herself. I found it interesting that she had a very ape like feet that had a
big toe, but yet she walking on two feet, which means Ardi used her feet to
help grab on trees. I also found it
intriguing the skull of the Taung child. I thought it was interesting the story
of how this skull was found by a miner worker in Taung, South Africa and kept
as part of a collection by the Izod family until anthropologist Raymond Dart
found it and identified the skull as an Australopithecus, not as a chimpanzee. Behind
each bone ever found in an exploration, the whole world gets to meet a part of
our own past.
Additional Information
First additional information is not that serious but very
useful to help remember each of the Australopithecus species. It’s a trivia
game I played, and honestly did not score very well, just because the names
start getting confusing at a certain point. Hopefully you will have a better
luck!
This next link is to a very good website from the American Museum
of Natural History. It has plenty of interesting information about human
origins, tool making and future of our species. I am sharing the link about Lucy
inspired by a “critical thinking question” from our text. This link explains
Lucy’s bones and how they similar to humans and how they are similar to chimps.
This next website I used as reference when searching for
content for the blog. It is very specific in the Australopithecines’ history.
It has some data about average body mass and weight of each species found, map
of specific location bones were found in Africa, it talks about Australopithecines’
diet, natural habitat and possible climate changes during each time period.
This is my last additional information during this blog post.
I found this image of Lucy’s skeleton replica aside of the model of how Lucy
would have looked like, from the Houston Museum and I actually remember walking
in the Museum of Natural Science in Houston and passed this part of the exhibit
and not even stopping to take a look at it. It is sad, but I guess I did not
really know how important these bones are for the history of the humanity. I am
thankful that this class has opened my eyes to this and hopefully I will have
the opportunity to go back there some day and really appreciate the exhibit.
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