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Riddle of the Bones

Intro | How did they move? | What did they look like? | Are they all the same species? | When did they live?

What did they look like?

face of Lucy, more apelike than human

A. afarensis, as depicted in NOVA: "In Search of Human Origins"

Fossils alone may intrigue us, but we still yearn to see "fleshed-out" portraits of our ancient ancestors. Creating these images takes a wealth of scientific insight and a touch of artistic license.

Before attempting to put flesh on the bone, it helps to understand whether an individual was male or female, young or old, tall or tiny. Clues to all of these traits can be found in fossil remains.

Teeth reveal roughly how old a person was at death. In children, molars may not have emerged. In adults, the wear on teeth provides a rough estimate of age, and various diseases may have taken their toll on both teeth and bones. Certain bones of the hands, feet, arms, and legs also indicate age because they develop in sections that fuse together as a child grows.

Fossils for males and females often differ, particularly in a species like Lucy's that is sexually dimorphic: Males are much larger than their mates, and their fossils are marked by deeper muscle scars. The pelvic bones of males and females may also be distinctive; females often have a wider "pelvic inlet" (the bony part of the birth canal) that is adapted for giving birth.

Body size is estimated from weight-bearing bones, including those in the hips. In Lucy's species, Australopithecus afarensis, the average adult male weighed near 110 pounds and stood around 4 feet 11 inches tall. Adult females were relatively petite, weighing roughly 60 pounds and standing only about 3 feet 5 inches tall.

To get a sense of facial characteristics, a well-preserved skull is invaluable. But such skulls are rare. In the early 1980s, anthropologist Tim White pieced together hundreds of fragments from different individuals to form a complete, yet composite skull. In 1992, the discovery by anthropologist Yoel Rak of a fairly complete skull at Hadar validated White's work.

With a forward-jutting jaw, low-sloping forehead, and heavy brow ridge, this creature likely had a face more like a gorilla's than like a human's today.

Taking their cues from the fossils, paleoartists have depicted A. afarensis as decidedly ape-faced. These artists -- whether sculpting in clay or sketching on paper -- rely on a detailed knowledge of anatomy to put muscle and flesh on fossil bones.

For one of his works, sculptor John Gurche started with a cast of the 1992 Hadar skull. Layer by layer, he added muscles of modeling clay and plasticene, using muscle attachment scars on the fossils as a guide. He crafted pockets of fat tissue and salivary glands to fill out the face. He shaped epoxy into nasal cartilage. Finally, he covered his creation in a pliable urethane "skin," inserted acrylic eyes, and added hairs one by one.

Paleoartist Jay Matternes, when working in two dimensions, also painstakingly "layers" muscle, cartilage, and skin onto the fossil skeletons in a series of progressive sketches.

Many traits leave no fossil clues and are left to the discretion of the artist. The size and shape of soft tissue parts, like the tip of the nose, the ears, and the breasts, as well as skin color and hair density, are a matter of artistic license. But stunning portraits by such renowned artists as Gurche and Matternes are by no means flights of the imagination. They are grounded in science, and they provide a glimpse into our distant human ancestry.

Details of the fossil evidence

Lucy: pelvis
The primary clue that Lucy was a female is her wide pelvic opening. Her birth canal is small, though, compared to a modern woman's; Lucy's species gave birth to babies with relatively small brains.

assorted vertebrae

Lucy: vertebrae
A near-complete set of fossil vertebrae (backbones) and an intact upper leg bone show Lucy was roughly three-and-a-half feet tall. Muscle attachment scars on her skeleton suggest she was powerfully built.

Lucy: teeth
An erupted third molar, or wisdom tooth, in Lucy's lower jaw reveals that she reached adulthood before her death. But because her teeth show little wear, she likely did not reach old age.

reconstructed fossil skull

Hadar Skull: various features
With a heavy brow ridge and forward-jutting face, this creature looked more ape-like than human. Judging from the cavity at the back of the skull, it had only a chimp-sized brain. This skull, larger than others for the species and marked by deep muscle scars and larger canine teeth, likely belonged to a male.

teeth in Hadar skull

Hadar Skull: teeth
With much of their original enamel worn off, these teeth likely belonged to an older person. Very heavy wear on the front teeth may be the result of stripping vegetation from branches, as some apes do today.

left footprint

Laetoli Footprints: details of prints
This print is remarkably like one a barefoot human would leave in wet sand. The foot that made this print had a big toe in line with the other toes, rather than set apart, as in a tree-dwelling chimp. It also had an arch between the ball and heel that acted as a shock absorber while walking or running.

fossil teeth

First Family: teeth and various bones
Within this group of 13 people, who may have all died together, there was a wide range in height and heft. Clues from teeth and other bones show that there were four youngsters. But even among the nine adults, body size varied widely. Males were much bigger than females, like male gorillas today who tower over their female counterparts.

First Family: jaws and teeth
The jaws found among the First Family show a mix of human and chimp-like traits. In overall shape, their jaws are more curved than a straight-sided chimp's jaw. Their canines, while pronounced, are hardly ape-like fangs. Large front teeth indicate these creatures could bite open hard fruits. And their back molars have large, flat chewing surfaces, good for grinding vegetation.

-> Find out if all the fossils at the four sites belong to the same species

Intro | How did they move? | What did they look like? | Are they all the same species? | When did they live?

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