Question

How is Lucy, the A. Afarensis, evidence of evolution?

Answer 1

Lucy was regarded as the oldest known direct ancestor of humans.

Explanation:

Lucy is estimated to be 3 million years old. The fossil evidence discovered in 1973 is that Lucy was a small erect chimp like animal. Scientist have proposed a sequence of replacement of older populations with newer " more fit" populations, starting with Lucy.

Lucy Australopitheus afrarenis is thought to have evolved into Homo habilis, to Homo erectus archaic forms of Homo sapiens to modern humans. Hence the importance of the fossil name Lucy.

A fossil known as KP 271 found at Kanapoi was dated as 4 - 4.5 million years old. However Henry M McHenry of the University of California Davis wrote " The results show that the Kanapoi specimen ( KP 271) dated 4 to 4.5 million years old is indistinguishable from Modern Homo sapiens ( Science 190 31 Oct. 1975 page 428)

The discovery of a fossil thought to be older than Lucy yet more advanced calls into question her importance as evidence of human evolution from more primitive ancestors.

Answer 2

Lucy is famous for revealing a complete skeleton of Australopithecus afarensis, considered to be a direct ancestor of modern Homo sapiens .

Explanation:

The idea that evolution of human could have taken place from ape like creatures came simultaneously with the publication of Darwin's book on natural selection theory. A name for the missing link was even suggested, Pithecanthropus , before discovery of any such fossil (which should be evolutionarily in between ape and man).

By the early years of twentieth century, fossils of java man (from Indonesia) and peking man (from China) were unveiled with much enthusiasm but slowly it was becoming evident that these are fossils fit to be included in Genus Homo-- and that a true missing link between ape and man could have possibly evolved in African grasslands where a variety of ape fossils were getting discovered every year. Now the question was whether apes started walking like men first and became intelligent later or was it the other way around.

Lucy was not the first Australopithecus fossil to be discovered from Africa. Very first one was skull of Taung baby but the discoverer did not earn enough attention from scientific community at the time of discovery (1920s). First fossil declared as a missing link between ape and man was named Zinjanthropus boisei (late 1950s): this is now regarded as a robust Australopithecine- not our direct ancestor.

With the discovery of Lucy (1970s) and its inclusion in genus Australopithecus , story of human evolution became a bit well explained. Anthropologists now accepted that genus Homo evolved in Africa 2 to 3 million years ago, from ape ancestors included in genus Australopithecus .

Now, why Lucy could be considered an evidence of evolution?

1. Lucy actually lived on this earth 3.5 million years ago, as revealed by dating her fossil and today apes like her are all extinct.

2. Attachment of spinal cord to the lowest area of skull proposed erect posture (also true for Taung baby). Her pelvic girdle and leg bones also suggest bipedal habit, though she was very much able to climb trees as suggested by her forelimbs and fingers.

3. Size of brain was close to 500cc, i.e. not larger than the brain of an ape.

Thus Lucy was part of a population of apes in Africa who started walking on their hind legs; thereby their hands became free to explore new opportunities. You may read this for more:

http://www.bbc.com/earth/story/20141127-lucy-fossil-revealed-our-origins