Australopithecus afarensis Johanson & White 1978

Nickname: Lucy's species Where Lived: Eastern Africa (Ethiopia, Kenya, Tanzania) When Lived: Between about 3.85 and 2.95 million years ago Australopithecus afarensis is one of the longest-lived and best-known early human species—paleoanthropologists have uncovered remains from more than 300 individuals! Found between 3.85 and 2.95 million years ago in Eastern Africa (Ethiopia, Kenya, Tanzania), this species survived for more than 900,000 years, which is over four times as long as our own species has been around. It is best known from the sites of Hadar, Ethiopia (‘Lucy’, AL 288-1 and the 'First Family', AL 333); Dikika, Ethiopia (Dikika ‘child’ skeleton); and Laetoli (fossils of this species plus the oldest documented bipedal footprint trails). Similar to chimpanzees, Au. afarensis children grew rapidly after birth and reached adulthood earlier than modern humans. This meant A. afarensis had a shorter period of growing up than modern humans have today, leaving them less time for parental guidance and socialization during childhood. Au. afarensis had both ape and human characteristics: members of this species had apelike face proportions (a flat nose, a strongly projecting lower jaw) and braincase (with a small brain, usually less than 500 cubic centimeters -- about 1/3 the size of a modern human brain), and long, strong arms with curved fingers adapted for climbing trees. They also had small canine teeth like all other early humans, and a body that stood on two legs and regularly walked upright. Their adaptations for living both in the trees and on the ground helped them survive for almost a million years as climate and environments changed.

Height: Males: average 4 ft 11 in (151 cm); Females: average 3 ft 5 in (105 cm) Weight: Males: average 92 lbs (42 kg) ; Females: average 64 lbs (29 kg)

This species may be a direct descendant of Au. anamensis and may be ancestral to later species of Paranthropus, Australopithecus, and Homo.

Year of Discovery: 1974 The species was formally named in 1978 following a wave of fossil discoveries at Hadar, Ethiopia, and Laetoli, Tanzania. Subsequently, fossils found as early as the 1930s have been incorporated into this taxon.

Au. afarensis had mainly a plant-based diet, including leaves, fruit, seeds, roots, nuts, and insects… and probably the occasional small vertebrates, like lizards. How do we know what Au. afarensis ate? Paleoanthropologists can tell what Au. afarensis ate from looking at the remains of their teeth. Dental microwear studies indicate they ate soft, sugar-rich fruits, but their tooth size and shape suggest that they could have also eaten hard, brittle foods too – probably as ‘fallback’ foods during seasons when fruits were not available.

AL 288-1 Nickname: Lucy Site: Hadar, Ethiopia Date of discovery: 1974 Discovered by: Donald Johanson and Maurice Taieb Age: About 3.2 million years old Species: Australopithecus afarensis At home in two worlds: Lucy is arguably the most famous of all early human individuals due to her age and relative completeness. Partial skeletons like hers allow us to learn much more about early human body size, shape, and locomotion than more fragmentary and sparse remains. Her long arm bones and the crest created by muscles that attach to her upper arm bone (humerus) are evidence of a powerful chest and strong upper arm muscles necessary for tree climbing. Her short, broad pelvis also held her body upright while angled-in thigh bones kept her body weight directly above her knees while in stride, both requirements for walking efficiently on two legs. Lucy’s compact feet were capable of supporting her full body weight as she walked upright, but her long, curved toe bones resemble that of a tree-climbing ape. Because Lucy could walk upright on the ground and climb trees, she and other members of her species were able to use resources from woodlands, grasslands, and other diverse environments. Lucy was nicknamed the night she was discovered while Johanson’s team celebrated to the Beatles’ hit “Lucy in the Sky with Diamonds.” Her Ethiopian name ‘Dinenesh’ is the Amharic term for ‘You are beautiful.' DIK-1-1 Nickname: Dikika Child Site: Dikika, Ethiopia Date of discovery: 2000 Discovered by: A team led by Zeresenay Alemseged Age: About 3.3 million years old Species: Australopithecus afarensis The fossilized remains of this 3 year-old early human child are often referred to as belonging to ‘Lucy’s baby' since she was found only a few miles south from where Lucy was found Lucy over two decades earlier, even though the child's fossil is actually 100,000 years older than famous Lucy. She is nicknamed ‘Selam’ after the Amharic (Ethiopia’s official language) word for ‘peace,’ and is the most complete early human child known up until Neanderthal times. Prior to Selam’s discovery, researchers knew very little about early human growth patterns as the early human fossil record consists of few children. Because Selam’s baby teeth erupted in a pattern similar to a three-year-old chimpanzee’s, researchers now know A. afarensis children shared a chimpanzee’s fast growth rate. But her brain size indicates that a human growth rate was evolving. CT-scans of her skull show small canine teeth forming in the skull, telling us she was female. Her partial skeleton is made up of a nearly complete skull and torso, and several limb bones---her legs indicate she could walk upright, but other skeletal features showed she could also climb trees. The hyoid bone beneath her neck looks ape-like, and her gorilla-like collarbone and long, curved fingers show significant tree-climbing. Laetoli Footprint Trails Date of discovery: 1978 Discovered by: Mary Leakey and Paul Abell Age: About 3.6 million years old Species: Australopithecus afarensis Site: Laetoli, Tanzania The footprints of our predecessors The Laetoli footprints were most likely made by Australopithecus afarensis, an early human whose fossils were found in the same sediment layer. The entire footprint trail is almost 27 m (88 ft) long and includes impressions of about 70 early human footprints. 3.6 million years ago in Laetoli, Tanzania, two early humans walked through wet volcanic ash. When the nearby volcano erupted again, subsequent layers of ash covered and preserved the oldest known footprints of early humans. Team members led by paleontologist Mary Leakey stumbled upon animal tracks cemented in the volcanic ash in 1976, but it wasn’t until 1978 that Paul Abell joined Leakey’s team and found the 88ft (27m) long footprint trail referred to now as “The Laetoli Footprints,” which includes about 70 early human footprints. The early humans that left these prints were bipedal and had big toes in line with the rest of their foot. This means that these early human feet were more human-like than ape-like, as apes have highly divergent big toes that help them climb and grasp materials like a thumb does. The footprints also show that the gait of these early humans was "heel-strike" (the heel of the foot hits first) followed by "toe-off" (the toes push off at the end of the stride)—the way modern humans walk. The close spacing of the footprints are evidence that the people who left them had a short stride, and therefore probably had short legs. It is not until much later that early humans evolved longer legs, enabling them to walk farther, faster, and cover more territory each day. How do we know these are early human footprints? The shape of the feet, along with the length and configuration of the toes, show that the Laetoli Footprints were made by an early human, and the only known early human in the region at that time was A. afarensis. In fact, fossils of A. afarensis were found nearby to the footprints and in the same sediment layer, telling scientists that A. afarensis was in the area at the same time the footprints were left.

We don’t know everything about our early ancestors—but we keep learning more! Paleoanthropologists are constantly in the field, excavating new areas, using groundbreaking technology, and continually filling in some of the gaps about our understanding of human evolution. Below are some of the still unanswered questions about Au. afarensis that may be answered with future discoveries: 1. A fossil similar to Au. afarensis and dating to 3.5 million years ago has been found in Chad—did this species extend so far into central Africa? 2. We know Au. afarensis were capable of walking upright on two legs, but they would have walked differently than modern humans do today; so, what did their bipedal locomotion look like? 3. Did Au. afarensis usually walk upright like modern humans, or did they spend more time climbing trees like other living African apes? 4. The species Au. afarensis existed through a period of environmental fluctuation yet showed no adaptations to the changing environment—why? Was it because they were able to migrate to where their usual food sources were located? Or were their food sources somehow unaffected? 5. Au. afarensis shows strong sexual dimorphism in that the body sizes between males and females are quite different; however, sexual dimorphism in other primates is usually characterized by size differences in bodies and teeth. Fossil evidence shows that male Au. afarensis individuals had canine teeth comparable in size to those of females. Did male dominance in Au. afarensis individuals not include the need to bear large canine teeth, as it does in many other male primates? 6. The teeth and jaw of Au. afarensis are robust enough to chew hard foods, but dental microwear studies show Au. afarensis individuals ate soft foods like plants and fruit instead. While most scientists think that Au. afarensis ate hard, brittle foods during tough times when vegetation was not easily found, further microwear studies show that eating hard foods did not coincide with dry seasons of little vegetation. So how do properties of A. afarensis teeth relate to their diet?

An educational site that introduces "Lucy", one of the most famous fossil skeletons of <i>Australpithecus afarensis</i>