“Lucy in the Sky with Diamonds: Primate Evolution”

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In 1974 paleontologist Donald C. Johanson discovered the first Australopithecus afarensis skeleton ever found in Hadar, Ethiopia.  After Johanson and his team worked for hours to collect the remains they had a celebration under the night sky of Ethiopia.  The Beatles song “Lucy In the Sky With Diamonds” played repeatedly through the night.  At some point in the night, the remains were named Lucy.  The name has since stuck.  “After decades of searching, most researchers had concluded that Australopithecus afarensis was the only clearly identified hominid in Africa at that time.” (Balter, 2001)  Johanson’s discovery of Lucy is significant in our understanding of human evolution because she is the oldest, most complete erect-walking human ancestral skeleton found to date.  “From the study of amino acid sequences in proteins, or of nucleotide sequences in DNA, we know that the split between the evolutionary line leading to us and the evolutionary line leading to chimpanzees, our closest living relatives, probably occurred between five and seven million years ago.  The best evidence for the date of Lucy and her kind is the three to three and a half million years ago, so even if Australopithecus afarensis is on the direct line of descent-which is by no means certain-there is still a gap of at least one and a half million years, and perhaps as much as four million years, before we get to our common ancestor.” (Glynn, 2003)

The remains that were discovered have led scientists to recreate what they thought Lucy may have looked like.  They determined that she stood approximately three and half feet tall.  With a mixture of ape and human features—including long dangling arms but pelvic, spine, foot, and leg bones suited to walking upright.  “Recreations based on other Australopithecus afarensis skulls later found nearby reveal an apelike head with a low and heavy forehead, widely curving cheekbones, and a jutting jaw—as well as a brain about the size of a chimpanzee’s.” (National Geographic News, 2006)  She was probably between twenty-five and thirty years old and showed some signs of possible arthritis.  Lucy’s mandible also shows traits of both chimpanzees and modern humans.  Apes’ mandibles show parallel rows of molars as opposed to the wide U-shape of modern human. Lucy’s dentition is a cross between ape and human in that the overall shape is apelike while the canine tooth size resembles that of modern humans.  Lucy’s size gives her away as a female.  “Later fossil discoveries established that Australopithecus afarensis males were quite a bit larger than females.” (National Geographic News, 2006)

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Lucy’s discovered skeleton pieces included several of her bigger bones, in which two of these, the bones of her femur and pelvis, indicated that she was indeed bipedal. (Becoming Human, 2008)   However, a disagreement lies in the question of how she maneuvered on her two feet. One side believes that she walked as modern humans walk today: an erect posture with legs fully extending. The other side believes that she walked slightly differently: a somewhat hunched posture and bent at the knee.

            As Lucy’s skeleton is only forty percent complete, the side that deems the “slightly differently style” states that “critical bones were missing or shaped slightly differently than the same bones in humans today and from this they (the researchers) concluded Lucy walked with bent knees and her upper body bent forward slightly at the hips”. (Becoming Human, 2008)   The “modern style” supporters help illustrate their reasons with an event from the past. About five hundred thousand years before Lucy, footprints of some other two-footed individuals were fossilized. A volcano had erupted and thick ash had covered the surrounding area. These bipedal individuals left their footprints in this ash which became solidified as a result of heat and light rain. “Some scientists claimed the foot prints were almost indistinguishable from those of modern humans, leaving clear impressions of heel and toe, and thus proving Lucy (and the fellow members of her species, Australopithecus afarensis) walked then as we do today”. (Becoming Human, 2008) However, some argue that the footprints did not resemble modern humans’ walking footprint characteristics, with different heel and toe impressions. The controversy is still in debate today.

Lucy was made of some characteristics that resembled humans and other characteristics that resembled chimpanzees. Her kind, Australopithecus afarensis, is believed to be the “earliest common ancestor shared between primates and early humans”. (Gabbo, 2008)   (Even though Lucy shares certain characteristics, she is still labeled as a Hominid, which is an ape that correlates very closely with humans. “In terms of overall body size, brain size and skull shape, ‘Lucy’ resembles a chimpanzee… (but) the way the hip joint and pelvis articulate indicates that ‘Lucy’ walked upright like a human”. (WSU, 2003)   These links illustrated how she came before humans and after apes.

In terms of overall body size, Lucy and the other Australopithecus afarensis were sexually dimorphic, meaning that the females were smaller than the males. Lucy herself stood about 3 feet, 6 inches and weighed about 60 pounds. In her mouth, her teeth were more similar to modern human dentures though. “The canine teeth are much smaller than those of modern apes, but larger and more pointed than those of humans, and shape of the jaw is between the rectangular shape of apes and the parabolic shape of humans”. (Talk Origins, 2004)  Whereas the jaws on apes protrude greatly, the jaws of Lucy and Australopithecus afarensis protrude less (and for humans even less of a protrusion). Lucy appears to be the “middle man” between apes and humans again.

DeWaal once commented that “the most significant difference between Lucy and modern chimpanzees is found in their hips, not their craniums”. (Terrie, 2002)   Even though Lucy had the comparable skull of a chimpanzee, her hips resembled that of a human. As stated above, the hip joint and pelvis articulate indicates that Lucy walked upright like a human. But being able to walk upright doesn’t earn the scientific, phylogenetic designation of human- we designate all human species by the genus “Homo” as in our binomial, Homo sapiens. These first human ancestors weren’t human enough to be considered part of our genus, and instead are called, Australopithecus.  The pelvis itself was one of the determining factors in establishing the theory that Lucy was a female. More so however, the pelvis illustrates that bipedalism was present. Bipedal beings have their feet closer together as opposed to quadruped creatures; this is done so to keep a relative center of gravity. The femurs are angled in from the joint of the hip which creatures a curve-like appearance and the tibia continues straight down. The angled femurs with the knee joint produce the “weight bearing axis” which chimps do not exhibit as their femur comes straight out of their hip opening. (Terrie, 2002)  Here Lucy displays another comparable characteristic related to human beings.

About forty years ago, researchers were having a chicken vs. the egg dispute: Did developing larger brains or transitioning from a four to two footed walking style come first? Lucy’s pelvis and leg skeletal pieces concluded that it was the latter. Bipedalism beat the brains. UW’s Kramer stated, “There was no question that we were bipedal millions of years before our brains got big” and as such, it is currently thought that bipedalism created a pathway to bigger brains as follows:

o   “Standing up freed our hominid hands to eventually allow for tool use.

o   Tool use led to greater success in hunting or otherwise acquiring meat in the diet.

o   A diet rich in meat provided more of the basic biochemical building blocks needed for brain development.

o   Someone, at some point, learned how to use fire. Someone started talking. Someone started writing”. (Paulson, 2008)

In essence, thanks to only walking on two feet led to being able to write novels of the greatest kind.


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“Lucy in the Sky with Diamonds: Primate Evolution”. (2017, Feb 01). Retrieved from


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