Australopithecus Afarensis Skeleton from Ethiopia


考试与评价·高二版 2020年6期

K.Kris Hirst 周晶

Lucy is the name of the nearly complete skeleton of an Australopithecus afarensis (南方古猿法種). She was the first nearly complete skeleton recovered for the species, found in 1974 at the Afar Locality (AL) 228, a site in the Hadar archaeological region on the Afar Triangle of Ethiopia. Lucy is about 3.18 million years old and is called Denkenesh in Amharic, the language of the local people.

Lucy is not the only early example of

A. afarensis   found   at   Hadar:  many  more

A. afarensis hominids (原始人类) were found at the site and the nearby AL-333. To date, over 400 A. afarensis skeletons or partial skeletons have been found in the Hadar region from about a half-dozen sites. Two hundred sixteen of them were found at AL-333; together with AL-288 are referred to as “the First Family”, and they all date between 3.7 and 3.0 million years ago.

What Scientists Have Learned About Lucy and Her Family

The numbers of available specimens of A. afarensis from Hadar (including over 30 crania) have allowed continuing scholarship in several regions concerning Lucy and her family. These issues have included terrestrial (地球的) bipedal (二足的) locomotion; the expression of sexual dimorphism (二态性) and how body size shapes human behavior; and the paleoenvironment (古环境) in which A. afarensis lived and thrived.

Lucy's post-cranium skeleton expresses multiple features related to habitual striding bipedalism, including elements of Lucy's spine, legs, knees, feet, and pelvis (骨盆). Recent research has shown that she didn't move in the same way as humans do, nor was she simply a terrestrial being. A. afarensis may well have still been adapted to live and work in trees at least part-time. Some recent research also suggests the shape of the female's pelves was closer to modern humans and less similar to the great apes.

A. afarensis lived in the same region for over 700,000 years, and during that time, the climate changed several times, from arid to moist, from open spaces to closed forests and back again. Yet, A. afarensis persisted, adapting to those changes without requiring major physical changes.

Sexual Dimorphism Debate

Significant sexual dimorphism; that female animal bodies and teeth are significantly smaller than males—is typically found in species which have intense male to male competition. A. afarensis possesses a degree of postcranial skeletal size dimorphism matched or exceeded only by the great apes, including orangutans and gorillas.

However, A. afarensis teeth are not significantly different between males and females. Modern humans, by comparison, have low levels of male-male competition, and male and female teeth and body size are far more similar. The peculiarity of that is still debated: teeth size reduction may be the result of adapting to a different diet, rather than a signal of less male-to-male physical aggression.

Lucy's History

The central Afar basin was first surveyed by Maurice Taieb in the 1960s; and in 1973, Taieb, Donald Johanson and Yves Coppens formed the International Afar Research Expedition to begin an extensive exploration of the region. Partial hominin fossils were discovered in Afar in 1973, and the nearly complete Lucy was discovered in 1974. AL 333 was discovered in 1975. Laetoli was discovered in the 1930s, and the famous footprints discovered in 1978.

Various dating measures have been used on the Hadar fossils, including Potassium/Argon (K/AR) and geochemical analysis of the volcanic tuffs, and currently, scholars have tightened the range to between 3.7 and 3.0 million years ago. The species was defined, using Hadar and A. afarensis specimens from Laetoli in Tanzania, in 1978.

Lucy's Significance

Lucy and her family's discovery and investigation remodeled physical anthropology, making it a much more rich and nuanced (細微差别) field than before, partly because the science changed, but also because for the first time, scientists had an adequate database to investigate all the issues around her.

In addition, and this is a personal note, I think one of the most significant things about Lucy is that Donald Johanson and Edey Maitland wrote and published a popular science book about her. The book called Lucy, the Beginnings of Humankindmade the scientific chase for the human ancestors accessible to the public.