Lucy (Australopithecus)

Lucy

Catalog number	AL 288-1
Common name	Lucy
Species	Australopithecus afarensis
Age	3.2 million years[1]
Place discovered	Afar Depression, Ethiopia
Date discovered	November 24, 1974 (1974-11-24)
Discovered by	Donald Johanson Maurice Taieb Yves Coppens Tom Gray[2]

Lucy is the common name of AL 288-1, several hundred pieces of bone representing about 40% of the skeleton of an individual Australopithecus afarensis. The specimen was discovered in 1974 at Hadar in the Awash Valley of Ethiopia's Afar Depression. Lucy is estimated to have lived 3.2 million years ago.^[1][3] The discovery of this hominid was significant as the skeleton shows evidence of small skull capacity akin to that of apes and of bipedal upright walk akin to that of humans, providing further evidence supporting the view that bipedalism preceded increase in brain size in human evolution,^[4][5] though other findings have been interpreted as suggesting that Australopithecus afarensis was not directly ancestral to humans.^[6] In 1994, a new hominid, Ardi, was found, pushing back the earliest known hominid date to 4.4 million years ago, although details of this discovery were not published until October 2009.^[7]

Discovery

Side view of Lucy replica

French geologist Maurice Taieb discovered the Hadar Formation in the Afar Triangle of Ethiopia in 1972. He then formed the International Afar Research Expedition (IARE), inviting three scientists from three countries to co-direct the research. These were Donald Johanson, an American anthropologist, and Founding Director of the Institute of Human Origins of Arizona State University; the famous British archaeologist Mary Leakey; and Yves Coppens, a French born paleontologist now based at the Collège de France. An expedition was formed with four American and seven French participants, and in the autumn of 1973 the team surveyed Hadar for fossils and artifacts related to the origin of humans.^[8]

In November 1973, near the end of the first field season, Johanson noticed a fossil of the upper end of a shinbone, which had been sliced slightly at the front. The lower end of a femur was found near it, and when he fitted them together the angle of the knee joint clearly showed that this fossil, reference AL 129-1, was an upright walking hominid. The fossil was over three million years old, much older than any others known at the time. The site lay about 2.5 kilometres (1.6 mi) from the site where they subsequently found "Lucy".^[9][10]

The team returned for the second field season in the following year and found hominid jaws. Then, on the morning of November 24, 1974, near the Awash River, Johanson abandoned a plan to update his field notes and joined graduate student Tom Gray to search Locality 162 for bone fossils.^[11]

Both Donald Johanson and Tom Gray spent two hours on the increasingly hot arid plain, surveying the dusty terrain, then Johanson decided on a hunch to make a small detour on their way back to their vehicle to look at the bottom of a small gully that had been checked at least twice before by other workers. At first sight there was nothing immediately visible, but as they turned to leave, a fossil caught Johanson's eye: an arm bone fragment lying on the slope. Near it lay a fragment from the back of a small skull. They noticed part of a femur (thigh bone) a few feet (around 1 m) away. As they looked further, they found more and more bones on the slope, including vertebrae, part of a pelvis, ribs, and pieces of jaw. They marked the spot and returned to camp, excited at finding so many pieces apparently from one individual hominid.^[2][12]

Cast of Lucy in Mexico

In the afternoon, everyone on the expedition was at the gully, sectioning off the site and preparing for careful collection which eventually took three weeks. That first evening they celebrated at the camp, staying up all night, and at some stage during the evening the fossil AL 288-1 was nicknamed Lucy, after the Beatles song "Lucy in the Sky with Diamonds", which was being played loudly and repeatedly on a tape recorder in the camp.^[3]

Over the next three weeks, several hundred pieces or fragments of bone were found, with no duplication, confirming their original speculation that they were from a single skeleton. As the team analyzed the fossil further, they calculated that an amazing 40% of a hominid skeleton had been recovered, an astounding feat of anthropology. Usually, only fossil fragments are discovered; rarely are skulls or ribs found intact. Johanson considered it was female, based on the one complete pelvic bone and sacrum indicating the width of the pelvic opening.^[3] Lucy was only 1.1 m (3 ft 7 in) tall,^[13] weighed 29 kg (64 lb) and looked somewhat like a Common Chimpanzee, but although the creature had a small brain, the pelvis and leg bones were almost identical in function to those of modern humans, showing with certainty that these hominids had walked erect.^[14] Under an agreement with the government of Ethiopia, Johanson brought the skeleton back to Cleveland where it was reconstructed by Owen Lovejoy. It was returned to Ethiopia according to agreement some 9 years later. Lucy as a fossil hominid captured public notice, becoming almost a household name at the time.

Further discoveries of A. afarensis specimens occurred during the 1970s, giving anthropologists a much better appreciation of the range of variability and sexual dimorphism of the species.

Age estimates

The fossil was dated reliably in 1990–1992 by applying the argon-argon radiometric dating method to the volcanic ash surrounding Lucy. Initial attempts were made in 1973 and 1974 to estimate the age of the fossil using the potassium-argon radiometric dating method in James Aronson's laboratory at CWRU (now moved to Dartmouth). These attempts, made by Maurice Taieb and Aronson, were hindered by the scarcity of datable crystals, the fact that the volcanic rocks in the area of concern were chemically altered or reworked, and the complete absence of purnice clasts at Hadar. Lucy's skeleton occurs in the part of the Hadar sequence that accumulated with the fastest rate of deposition which partly accounts for her excellent preservation, with the older ash being about 18 m below the fossil and the younger ash only 1 m below, and closely indicating her age of deposition.

Fieldwork at Hadar was suspended in the winter of 1976–1977 and resumed in 1990;in the mean time, the more precise argon-argon technology had been improved by Derek York from the University of Toronto. In 1990–1992, two suitable samples of ash found by Aronson and Robert Walter were argon-argon dated by Walter at 3.22 and 3.18 million years in the IHO's geochronology laboratory.^[15]

Notable characteristics

Postcranial

Lucy skeleton reconstruction. Cleveland Museum of Natural History

One of Lucy's most striking characteristics is a valgus knee,^[16] which indicates that she normally moved by walking upright. Her femoral head was small and her femoral neck was short, both primitive characteristics. Her greater trochanter, however, was clearly derived, being short and human-like rather taller than the femoral head. The length ratio of her humerus to femur was 84.6% compared to 71.8% for modern humans and 97.8% for Common Chimpanzees, indicating that either the arms of A. afarensis were beginning to shorten, the legs were beginning to lengthen, or both were occurring simultaneously. Lucy also had a lumbar curve, another indicator of habitual bipedalism. Lucy likely had non-pathological (physiologic) flat feet, not to be confused with pes planus, though other afarensis individuals appear to have had arched feet.^[17]

Pelvic girdle

Johanson recovered Lucy's left innominate bone and sacrum. Though the sacrum was remarkably well preserved, the innominate was distorted, leading to two different reconstructions. The first reconstruction had little iliac flare and virtually no anterior wrap, creating an ilium that greatly resembled that of an ape. However, this reconstruction proved to be faulty, as the superior pubic rami would not have been able to connect if the right ilium was identical to the left. A later reconstruction by Tim White showed a broad iliac flare and a definite anterior wrap, indicating that Lucy had an unusually broad inner acetabular distance and unusually long superior pubic rami. Her pubic arch was over 90 degrees, similar to modern human females. Her acetabulum, however, was small and primitive.

Cranial specimens

The cranial evidence recovered from Lucy is far less derived than her postcranium. Her neurocranium is small and primitive, while she possesses more spatulate canines than apes. The cranial capacity was about 375 to 500 cc.

Other findings

A study of the mandibular structure of a number of specimens of Au. Afarensis indicated that Lucy's jaw was rather unlike other hominins, having a more gorilla-like appearance.^[18] Rak et al. consider that this mandible structure arose "independently in gorillas and hominins", but that Au. Afarensis is therefore "too derived to occupy a position as a common ancestor of both the Homo and robust australopith clades".^[6]

Exhibitions

Lucy is preserved at the National Museum of Ethiopia in Addis Ababa. A plaster replica is displayed instead of the original skeleton. A cast of the original skeleton in its reconstructed form remains on display at the Cleveland Museum of Natural History.^[19] A diorama of Australopithecus afarensis and other human predecessors showing each species in its habitat and demonstrating the behaviors and capabilities that scientists believe it had is displayed in the Hall of Human Biology and Evolution at the American Museum of Natural History in New York City. A cast of Lucy's skeleton as well as a reconstruction of Lucy is on display at The Field Museum in Chicago in their Evolving Planet exhibition.

US tour

A six-year exhibition tour of the United States, titled Lucy’s Legacy: The Hidden Treasures of Ethiopia, features the Lucy fossil as well as over 100 artifacts from ancient times to the present, is currently underway. The tour was approved by the Ethiopian government and organized in collaboration with the Houston Museum of Natural Science, where it had been on display from August 31, 2007 until September 1, 2008.^[20] An undisclosed proportion of the proceeds from the tour is to go toward modernizing Ethiopia's museums.^[21] The U.S. Department of State also approved the tour. There was controversy in advance of the tour over concerns about the fragility of the specimens, with various experts including paleoanthropologist Owen Lovejoy and anthropologist and conservationist Richard Leakey publicly stating their opposition. The Smithsonian Institution and Cleveland Museum of Natural History were among museums declining to host the exhibits.^[22] The fossil's discoverer Don Johanson stated that although he was somewhat uneasy about the possibility of damage, he did not oppose exhibiting Lucy as it will help to raise awareness of human-origins studies. The museum is making arrangements for the exhibits to be shown at as many as ten other museums. The exhibit was shown at the Pacific Science Center in Seattle, Washington where it was displayed from October 4, 2008 - March 8, 2009.^[21] In September 2008, between the exhibits in Houston and Seattle, the fossils were taken to the University of Texas at Austin for 10 days to complete the first ever high resolution CT scan of the fossil.^[23]

Lucy has been open at Discovery Times Square Exposition, a new facility located in New York City since June 24, 2009. The Australopithecus afarensis was on display until October 25, 2009.^[24] In New York, the exhibition will include Ida (Plate B), the other half of the recently announced Darwinius masilae fossil.^[25]

See also

• List of human evolution fossils

References

1. ^ ^{a b} "Mother of man - 3.2 million years ago". BBC Home. http://www.bbc.co.uk/sn/prehistoric_life/human/human_evolution/mother_of_man1.shtml. Retrieved 2008-10-10. 
2. ^ ^{a b} "Institute of Human Origins". http://www.asu.edu/clas/iho/lucy.html. Retrieved 2007-08-30. 
3. ^ ^{a b c} Johanson 1981, p. 22
4. ^ Hadar. (2008). In Encyclopædia.
5. ^ Stephen Tomkins (1998). The Origins of Humankind. Cambridge University Press. ISBN 0521466768. 
6. ^ ^{a b} Rak, Y.; Ginzburg, A.; Geffen, E. (2007). "Gorilla-like anatomy on Australopithecus afarensis mandibles suggests Au. Afarensis link to robust australopiths". Proceedings of the National Academy of Sciences 104 (16): 6568–6572. Bibcode 2007PNAS..104.6568R. doi:10.1073/pnas.0606454104. PMC 1871826. PMID 17426152. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1871826.  edit
7. ^ http://sciencenow.sciencemag.org/cgi/content/full/2009/1001/1
8. ^ Johanson 1981, pp. 154–158
9. ^ Letter from Donald Johanson, August 8, 1989 Lucy's Knee Joint
10. ^ Johanson 1981, pp. 159–163
11. ^ Johanson 1981, p. 18 (Note that the book shows the discovery date as November 30, 1974)
12. ^ Johanson 1981, pp. 20–21
13. ^ Jungers, W.L. (1988). "Lucy's length: Stature reconstruction in Australopithecus afarensis (A.L.288-1) with implications for other small-bodied hominids". American Journal of Physical Anthropology 76 (2): 227–231. doi:10.1002/ajpa.1330760211. PMID 3137822. 
14. ^ Johanson 1981, pp. 20–22, 184–185
15. ^ Walter, Robert C. (1994). "Age of Lucy and the First Family". Geology (GSA Publications) 22 (January): 6–10. http://geology.gsapubs.org/content/22/1/6.abstract?sid=ce1fb3b0-3e97-4b33-95fa-795e10ba1630. 
16. ^ Stern, Jack T. Jr. and Randall L. Susman (1983), The Locomotor Anatomy of Australopithecus afarensis, Journal of Physical Anthropology, 60:279-317.
17. ^ DeSilva, J. and Zachary Throckmorton (2010), Lucy's flat feet: the relationship between the ankle and rearfoot arching in early hominins, PLoS ONE, 5:12:e14432.
18. ^ Ferguson, W. W. (1989). "Critique of ‘Australopithecus afarensis’ as a single species based on dental metrics and morphology". Primates 30 (4): 561–569. doi:10.1007/BF02380881.  edit
19. ^ "Permanent Exhibits." www.cmnh.org. 3 January 2009.
20. ^ "Lucy’s Legacy: The Hidden Treasures of Ethiopia". Houston Museum of Natural Science. 2008. http://www.hmns.org/exhibits/special_exhibits/lucy.asp?r=1. Retrieved 2008-07-15. ^{[dead link]}
21. ^ ^{a b} Jim Kennett (August 31, 2007). "Bloomberg.com: Canada". Lucy's Ancient Bones Visit Houston Museum as Scientists Fret. http://www.bloomberg.com/apps/news?pid=20601082&sid=a7j_9OLhOJUI&refer=canada. Retrieved 2007-09-11. 
22. ^ Stefan Lovgren (November 1, 2006). ""Lucy" Fossil Tour Sparks Controversy Among U.S. Museums". National Geographic News. http://news.nationalgeographic.com/news/2006/11/061101-lucy-tour.html. Retrieved 2007-09-11. 
23. ^ University of Texas at Austin Office of Public Affairs (February 6, 2009). "Researchers Complete First CT Scan of Ancient Human Ancestor Lucy". University of Texas at Austin. http://www.jsg.utexas.edu/news/rels/020609.html. Retrieved 2009-02-06. 
24. ^ "Lucy’s Legacy: The Hidden Treasures of Ethiopia". Houston Museum of Natural Science. 2009. http://lucyexhibition.hmns.org/about-the-exhibit.aspx. Retrieved 2009-06-04. 
25. ^ "Famous Fossil to go on display in Times Square". USA Today. 2009. http://blogs.usatoday.com/sciencefair/2009/06/famous-fossils-to-go-on-display-in-times-square.html. Retrieved 2009-06-18. 

Further reading

• Johanson, Donald; Edey, Maitland (1981). Lucy, the Beginnings of Humankind. St Albans: Granada. ISBN 0-586-08437-1. 
• Lovgren, Stefan. ""Lucy" Fossil Tour Sparks Controversy Among U.S. Museums", National Geographic News, November 1, 2006. Accessed August 16, 2007.
• Johanson, Donald C., and Kate Wong. Lucy's Legacy. N.p.: Crown Publishing, 2009. Print.

External links

• Institute of Human Origins
• "Becoming Human: Paleoanthropology, Evolution, and Human Origins", a documentary hosted by Donald Johanson
• "New Link In Human Evolution Discovered", facial reconstruction of Lucy, an Agence France-Presse photo published by the Taipei Times, May 8, 2006. Accessed September 11, 2007.
• "BBC - Science & Nature - The evolution of man". Mother of man - 3.2 million years ago. http://www.bbc.co.uk/sn/prehistoric_life/human/human_evolution/mother_of_man1.shtml. Retrieved 2007-11-01. 
• "Hall of Human Origins : American Museum of Natural History". History of Human Evolution: Lucy. http://www.amnh.org/exhibitions/permanent/humanorigins/history/humans5.php. Retrieved 2008-02-28. 
• "PREMOG - Research". How Lucy walked. Primate Evolution & Morphology Group (PREMOG), the Department of Human Anatomy and Cell Biology, the School of Biomedical Sciences at the University of Liverpool. 18 May 2007. Archived from the original on 2007-10-25. http://web.archive.org/web/20071025040650/http://www.liv.ac.uk/premog/premog-research.htm#backevidence. Retrieved 2007-11-01. 
• Thorpe S.K.S.; Holder R.L., and Crompton R.H. (24 May 2007). "PREMOG - Supplementry Info". Origin of Human Bipedalism As an Adaptation for Locomotion on Flexible Branches. Primate Evolution & Morphology Group (PREMOG), the Department of Human Anatomy and Cell Biology, the School of Biomedical Sciences at the University of Liverpool. Archived from the original on 2007-07-17. http://web.archive.org/web/20070717191040/http://www.liv.ac.uk/premog/premog-sup-info-SCIENCE.htm. Retrieved 2007-11-01. "Based on computer simulations of the mechanics of motion in fossil human ancestors such as the famous 'Lucy' skeleton, our research group has long argued that early human ancestors would have walked upright, rather than semi-crouched, as the old 'up from the apes' view has suggested But we have not been able to say where such upright walking originated. Now, research on the orang utan, suggests that upright walking may have been a basic element of the lifestyle of the earliest ancestors of modern apes, including humans, which would have been tree-dwelling specialists on ripe fruit, living among the fine branches of tropical forest trees." 
• University of Texas's eLucy.org website Enables visitors to view bones and bone casts, and learn more about human origins and evolution. Activities and lessons are provided to encourage additional study.
• National Public Radio "Science Friday" interview with Dr. Donald Johanson titled "Lucy's Legacy" originally aired on 6 Mar 2009