Biology > Fossil Records from the Australopithecus to the Homo Sapiens

Trace the fossil record form Australopithecus to Homo sapiens. Include in your answer the time frame for these fossils and the physical changes which represent the evolution of the hominid lineage.

 

The evolutionary design of man has intrigued humans for many years. Anthropologists have traveled the world to search for fossil evidence to learn who we have evolved from. Human evolution began roughly 5-10 million years ago when the human line split from the apes. Scientists and anthropologists slowly have tried to put the facts together that fossil records gave them to give us an idea of our evolutionary line.

Our farthest ancestor is believed to be Austrapithecus afarensis, which existed between 3.9 and 3.0 million years ago. Afarensis had an apelike face with a sloping forehead, a bony ridge over the eyes, a flat nose, and chinless lower jaw. They had protruding jaws with large back teeth, and their skull capacity ranged from 350 to 500 cm3. It was between 3’6” and 5’ tall. Its build was about the same as the modern human but its head and face were proportionately much larger. The most well known member of the species is Lucy, who shows that at 3 million years ago hominids were completely bipedal. Long and curved fingers and toes show that they were also well adapted for climbing trees.

Australopithecus africanus was the first australopithecine species to be discovered. Australopithecus africanus fossils have been dated back to the time period between 2.4 and 3 million years ago. The skull volume ranged between 420 and 500cm3 and its body size was a little greater that A. afarensis. The fossil records show that this hominid was a biped and they were still slightly suited for trees. The brain was not advanced enough for speech. The molars were a little larger than in afarensis and much larger than modern human since they ate plants that were hard to chew. The shape of the jaw was more like of the human. A. africanus has a slight peak on the top of the cranium and ridges over the eyes.

Other hominid species; like A. robustus, A. aethiopicus, A. boisei, developed on a different lineage than the Homo line. Their bones were thicker and more robust than species on the Homo line. They co-existed at about the same time as Homo habilis and their stream died out at around the time of Homo erectus.

Homo habilis existed between 2.4 and 1.5 million years ago. Homo habilis is translated as “the human with ability” also called the “handy man” because tools were found with his fossil remains. The brain size in earlier fossil specimens was about 500cc but rose to 800cc toward the end of the species life period. The brain shape of Homo habilis shows evidence that some speech had developed. This hominid was about 5’ tall and weighed about 100 pounds.

Homo erectus lived between 1.8 million and 300,000 years ago. They were the first “human”. The skull capacity in these hominids jumped in early examples to 900cm3, toward the end of its reign its brain was almost the same size as modern man, at about 1200cm3. Homo erectus developed tools, weapons and fire and probably cooked his food. They were hunting for food, definitely had speech, and also had a very efficient walking style. Only his head and face was different from modern man. Home erectus had a long low skull, massive jaws with big molars, thick brow ridges and had no chin. This hominid was the first to spread across the world by 800,000 years ago to China and about 500,000 years ago to Europe.

Homo sapiens evolved in Africa about 200,000 to 100,000 years ago and during their spread around the world, they replaced other hominids. There were several different types of this species; Homo sapiens archaic, Homo sapiens neandertalensis and Homo sapiens sapiens.

Archaic Homo sapiens appeared about 500,000 years ago. Their brain averaged about 1200cm3, their skulls were more rounded with smaller features, much smaller molars and brow ridges than previous species.

The best known Homo sapiens are the Neandertals. They coexisted with Archaic Homo sapiens and early Homo sapiens sapiens. They lived in Europe between 150,000 and 35,000 years ago. Some scientists theorize that Homo sapiens sapiens killed the Neandertals off, or interbreed with them. Their brain size was about 1450cm3. The head was longer and lower, and their nose was different than modern man. Neandertals were about 5’6” tall with very heavy skeleton that showed the signs of massive muscles.

Our own species, Homo sapiens sapiens first appeared about 120,000 years ago. Cro-Magnon man is an example of modern human, which lived between 35,000 and 10,000 years ago in Europe. His tools are very sophisticated and their cave paintings are very advance too. Modern humans have an average brain size of about 1350cm3, sharply rising forehead, prominent chin, small eyebrow ridges or none, and a very slender skeleton.

Many years of work have gone into the process of constructing our evolutionary history. There are still many holes left to be filled and the species that have been discovered rely on little fossil evidence. The lines separating each species overlaps and the lifestyle of each species are arbitrary determined from Australopithecus to Homo sapiens.

 

 

References:

http://www.stanford.edu/~harryg/protected/chp20.htm

http://www.bruceowen.com/worldprehist/3250s03.htm

Conrad Phillip Kottak: Anthropology

 

 

 

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