December 12, 2012
South Africa plays a central role in the history of paleoanthropology. Anthropologists and other scientists of the 19th and early 20th century balked at the possibility that Africa was humankind’s homeland—until an ancient hominid was unearthed in South Africa in 1924. Since then, Africa has become the center of human evolution fieldwork, and South Africa has produced a number of iconic hominid fossils and artifacts. Here is a totally subjective list of the country’s most important hominid discoveries.
Taung Child: In 1924, anatomist Raymond Dart pried a tiny fossilized partial skull and brain from a lump of rock. The bones were the remains of a child. The youngster looked like an ape, but Dart also recognized some human qualities. He decided he had found a human ancestor that was so ancient it was still ape-like in many ways. (Later, scientists would determine the bones were nearly three million years old). Dart named the hominid Australopithecus africanus. The Taung Child, known by the name of the place where the fossils came from, was the first australopithecine ever discovered—and the first early hominid found in Africa. After the discovery, anthropologists who were searching for humanity’s origins in Europe and Asia switched their attention to Africa.
Mrs. Ples: Throughout the 1930s and 1940s, paleontologist Robert Broom led the efforts to find hominids in South Africa. He scoured the region’s limestone caves and quarries—the Taung Child came from a quarry—and was well rewarded for his efforts. Of the numerous fossils he uncovered (sometimes with the help of dynamite), his most influential find was a roughly 2.5-million-year-old skull of an adult female hominid now known as Mrs. Ples. Unearthed in 1947 at a site called Sterkfontein, the skull was well preserved and displayed the same mix of ape and human features seen in the Taung Child. Finding an adult version of A. africanus helped convince skeptics that the species was an ancient human ancestor. Some anatomists had thought Taung was just an ape and would have developed more pronounced ape-like features, and lost its human-like traits, as it grew up. Instead, Mrs. Ples showed that the species retained its mix of human and ape traits throughout life.
STS 14: Another one of Broom’s key finds is a set of well-preserved post-cranial bones that includes a pelvis, partial spine, ribs and upper thigh. Like Mrs. Ples, these fossils were found in 1947 at Sterkfontein and date to about 2.5 million years ago. The bones are officially known as STS 14 (STS refers to Sterkfontein) and presumably belonged to an A. africanus individual. The shape of the pelvis and spine are remarkably modern, and the find was some of the first evidence that early human ancestors walked upright on two legs.
SK 48: In addition to finding a trove of A. africanus specimens, Broom, along with his many assistants, discovered a new hominid species: Paranthropus robustus. The first hints of the species came in 1938 when Broom acquired a jaw fragment and molar that were much larger and thicker than any fossils belonging to A. africanus. Broom collected more of the unusual fossils and then hit the jackpot in 1950. A quarry worker found a nearly complete skull of an adult hominid that had giant teeth and a flat face. The fossil is officially called SK 48 (SK refers to the cave of Swartkrans where the skull was found). The collection of fossils with big chompers, which the hominids used to chew tough foods, was given the name P. robustus, which lived in South Africa about 1.8 million to 1.2 million years ago.
Little Foot: In the early 1990s, anthropologist Ron Clarke of South Africa’s University of the Witwatersrand found four small australopithecine foot bones at Sterkfontein. Later, Clarke and his colleagues discovered a nearly complete skeleton embedded in limestone that belonged to the foot. The researchers are still carefully chipping away at the rock to release the skeleton, dubbed Little Foot, but they have already noted that the individual has some characteristics not seen in any other known species of Australopithecus. But since the bones haven’t been fully studied and shared with other scientists, it’s hard to know where the hominid sits in the family tree, Science reported last year. It’s also hard to know exactly how old it is. Clarke’s team places the fossils at 3.3 million years old while other groups using different dating methods say Little Foot is more like 2.2 million years old. Science reported that Little Foot was expected to be fully liberated from its rocky enclosure sometime this year. As far as I know, that hasn’t happened yet.
Australopithecus sediba: The most recent major hominid fossil discovery in South Africa occurred in 2010. Lee Berger of the University of the Witwatersrand led a team that found two partial hominid skeletons at Malapa Cave. Dating to nearly two million years ago, the skeletons indicate that these hominids had their own unique style of walking and spent time both on the ground and in trees. X-ray scans of one of the skulls reveals that some aspects of the brain were more modern than in previous species. Berger and his colleagues therefore think the species, which they named A. sediba, could have given rise to the genus Homo.
Origins of Modern Behavior: Fossils aren’t the only major human evolution discoveries from South Africa. Several coastal cave sites have been treasure troves of artifacts that reveal when and how sophisticated behavior and culture emerged in early populations of Homo sapiens. There have been too many of these discoveries to single any one out. Some of these finds—such as red pigments used 164,000 years ago and shell beads dating to 77,000 years ago—are among the earliest evidence for symbolic thinking in our ancestors. Other artifacts, like 71,000-year-old projectile weapons, indicate early humans could construct complicated, multipart tools that require a lot of planning and foresight to make.
December 3, 2012
It can be hard to find gifts for lovers of human evolution. They aren’t as easy to find as, say, dinosaur gifts. So I spent some time cruising the Internet looking for some unusual and unique options for the holidays this year. Here’s what I found.
Something to read:
Over the last year, several books on how modern humans took over the world were published. Lone Survivors by anthropologist Chris Stringer weaves archaeology with genetics to explain why Homo sapiens became the last hominid left on Earth. The Last Lost World by father-and-daughter duo Stephen and Lydia Pyne considers how hominids evolved during the ice ages of the Pleistocene epoch and how scientists’ understanding of this period, lasting some 2.6 million to 11,700 years ago, has changed over time. Anthropologist Ian Tattersall takes an even broader look at the rise of humans, surveying the last 8 million years or so of human evolution in Masters of the Planet. In Homo Mysterious psychologist David Barash examines a number of evolutionary puzzles, including why humans have big brains and why women tend to live longer than men.
If you’re shopping for an uber-hominid fan, consider this simple “I Heart Hominids” bumper sticker, or maybe human evolution decals to jazz up a boring lapotop. I’m hoping for a hominid skull to put in my office: made out of chalkboard, they come in various species and colors. Candle lovers might be intrigued by this unusual candle holder. And who wouldn’t want a Neanderthal piñata?
Some hominid gifts can be fun and practical. Need a bag to carry groceries? How about this “I Love Lucy” cotton tote with a picture of the Lucy skeleton. It comes in several different sizes. Or maybe your loved one would like a pewter key chain of a Paranthropus boisei or Homo erectus skull, which a reader of last year’s Hominid Hunting holiday gift guide suggested. These colorful glass coasters are also useful.
Something to hang on the wall:
I think I’ve said this before–the Taung Child is my favorite hominid fossil. If you know someone else who really digs the specimen, check out this framed drawing of the skull. These woodcut prints of hominid skulls are another good way to spruce up an empty wall. A Bigfoot skeptic (or a believer with a sense of humor) might like this print from Society 6.
Last year, the big ticket items in my gift guide were hominid fossil reproductions. This year, you can give someone his/her genome. With only a sample of saliva, the genetics company 23andMe analyzes an individual’s complete set of DNA to trace the geographic origins of that person’s forefathers and to look for Neanderthal ancestry.
What would you like for the holidays?
November 19, 2012
Lucy and Ardi are the poster children of human evolution. But these famous fossil skeletons may never have been found if it weren’t for Louis and Mary Leakey’s pioneering efforts. The pair made several discoveries at Tanzania’s Olduvai Gorge in the 1950s and 1960s that inspired other anthropologists to come to East Africa in search of human ancestors. Here’s a look at some of the most important hominid fossil finds from Tanzania.
The Nutcracker Man (OH 5): The Leakeys’ first major discovery at Olduvai Gorge occurred in 1959. Mary found the roughly 1.8-million-year-old skull of a hominid with a flat face, gigantic teeth, a large crest on the top of its head (where chewing muscles attached) and a relatively small brain. They named the species Zinjanthropus boisei (now known as Paranthropus boisei). Nicknamed the Nutcracker Man, the species was too different from modern people to be the direct human ancestor that Louis had been hoping to find. But the discovery captured public interest in human evolution, and the Leakeys went on to unearth many more hominid fossils at Olduvai. OH 5 is the fossil’s official catalog name, meaning Olduvai Hominid Number 5.
Johnny’s Child (OH 7): The next big Leaky discovery came in 1960. Mary and Louis’ son, Johnny, found a lower jaw about 300 yards away from where the Nutcracker Man was discovered. The bone came from a young hominid; thus, the fossil was nicknamed Johnny’s Child. At the same spot, the Leakeys also dug up some hand bones and skull fragments. Using these skull fragments, the Leakeys and their colleagues estimated the roughly 1.8-million-year-old hominid’s brain size: 680 cubic centimeters. That was significantly bigger than the size of the average australopithecine brain, about 500 cubic centimeters. The hand bones revealed that the hominid had a “precision grip,” when a fingertip presses against the tip of the thumb. This movement allows for fine manipulation of objects, such as turning a key in a door or threading a needle. The precision grip led the Leakeys to conclude that this hominid was the one who made the stone tools found at Olduvai. Because of the tool-making and the big brain, the Leakeys decided OH 7 represented the earliest member of the genus Homo: Homo habilis (meaning Handy Man).
OH 8: Also in 1960, the Leakeys’ team discovered a well-preserved fossil foot belonging to H. habilis. The bones indicate the hominid had modern-looking foot arches, suggesting the species walked like modern people do. Tooth marks on the specimen’s ankle reveal the hominid had been a crocodile’s lunch.
OH 9: At the same time the Leakeys unearthed the first examples of H. habilis, they also recovered the skull cap of a more recent hominid dating to about 1.4 million years ago. At 1,000 cubic centimeters, the specimen’s brain was much bigger than that of H. habilis. The skull had thick brow ridges and a low, sloped forehead—key features linking the fossil to the species Homo erectus.
Twiggy (OH 24): Discovered in 1968 by Peter Nzube, Twiggy is a skull belonging to an adult H. habilis dating to roughly 1.8 million years ago. Although OH 24 is the most complete H. habilis skull from Olduvai Gorge, it was found crushed completely flat (and therefore named after the slender British model of the same name). Paleoanthropologist Ron Clarke reconstructed what the skull would have looked like, but it’s still fairly distorted.
LH 4: In the 1970s, after Louis died, Mary began excavations at Laetoli, about 30 miles from Olduvai Gorge. The fossils she was finding there were much older than the bones she and Louis had discovered at Olduvai. In 1974, for example, her team unearthed a lower jaw with teeth dating to 3.6 million years ago. It was cataloged as Laetoli Homind 4, or LH 4. Around the same time, anthropologists at the site of Hadar in Ethiopia were also finding hominid fossils dating to more than 3 million years ago, including the famous Lucy skeleton. At first, no one was sure what to call these older fossils. After analyzing both the Hadar and Laetoli specimens, anthropologists Tim White and Donald Johanson (Lucy’s discoverer) concluded that all of the fossils represented one species that they called Australopithecus afarensis. They chose LH 4 as the species’ type specimen, or the standard representative of the species. Mary did not approve. She didn’t believe the fossils from Laetoli were australopithecines. But under the rules of taxonomy, once a type specimen is designated, it’s forever associated with its species name. (For more on the controversy, see Johanson’s book Lucy.)
Laetoli Footprints: In 1978, one of Mary’s team members, Paul Abell, made the most famous discovery at Laetoli: He found the trail of about 70 fossilized hominid footprints. Based on the footprints’ age, 3.6 million years, anthropologists think they were made by an A. afarensis group. The footprints reveal this early hominid had a very modern way of walking. The big toe was in line with the other toes, not off to the side like an ape’s big toe. And the prints reveal the walkers had arches, unlike the flat feet of an ape. The footprints also suggest A. afarensis had a modern gait.
November 14, 2012
The nearly 2-million-year-old Paranthropus boisei was the cow of the hominid family. Unlike other human cousins, the species was a fan of dining on grasses. But it turns out it wasn’t the only, or even the first, hominid grazer. Australopithecus bahrelghazali was munching on grasses and sedges at least 1.5 million years before the origin of P. boisei, a new study in the Proceedings of the National Academy of Sciences suggests. The findings may mean early hominids were capable of consuming a wide variety of foods and colonizing new environments.
But before we discuss how scientists figured out A. bahrelghazali‘s diet, and why that matters, we need to address a far more pressing question: Who the heck was A. bahrelghazali?
In 1993, researchers in Chad unearthed a 3.5-million-year-old hominid lower jaw fragment and a few attached teeth. Based on the fossils’ age, many paleoanthropologists think the bones belonged to Australopithecus afarensis. But the specimen was found more than 1,500 miles farther west than any other A. afarensis bones, and subtle differences in the size and shape of the fossils led the discoverers to conclude they had found a new species. They named it A. bahrelghazali after the Bahr el Ghazal valley in Chad where the bones were recovered. Since then, researchers haven’t found any other A. bahrelghazali fossils and its species’ status remains controversial.
With just a jaw and teeth, there’s not too much scientists can say about what A. bahrelghazali looked like or how it lived its life. But, fortunately, diet is something that can be gleamed from these fossils. Analyzing the teeth’s chemistry is one way to assess what the species ate. This is possible because the carbon found in plants comes in two versions, or isotopes, called C3 and C4. Trees and other forest plants are rich in C3; grasses, sedges and other grassland plants have an abundance of C4. When an animal eats these plants—or eats other animals that eat these plants—the different carbon isotopes get incorporated into the individual’s teeth, serving as a record of what it once ate. Previous work on P. boisei has shown that C4 plants made up as much as 77 percent of that hominid’s diet.
In the new study, Julia Lee-Thorp of Oxford University and colleagues come to a similar conclusion for A. bahrelghazali, that the species mainly ate C4 plants, probably grasses and sedges. And like modern baboons that live on savannas, the hominid probably ate different parts of these plants, including underground tubers and bulbs. This diet is not surprising given the type of habitat A. bahrelghazali lived in. Based on the other types of animals found near the hominid, the researchers say A. bahrelghazali made its home in an open grassland, with few trees, near a lake. So forest foods weren’t really a dining option.
The results mean that by 3.5 million years ago hominids were probably already “broad generalists” capable of eating a variety of foods depending on what was locally available, the researchers say. (The younger Australopithecus sediba,which lived roughly 2 million years ago, demonstrates some of the stranger foods that hominids could eat: The South African species liked to eat wood—a dietary preference not seen in any other hominid.) Being a food generalist may have allowed A. bahrelghazali to explore new environments and leave behind the forests that earlier hominids, such as Ardipithecus ramidus, and their ancestors resided in.
October 1, 2012
“Becoming Human” is a series of posts that periodically examines the evolution of the major traits and behaviors that define humans, such as big brains, language, technology and art.
For decades, anthropologists believed the ability to use tools separated modern humans from all other living things. Then scientists discovered chimpanzees use rocks to hammer open nuts and twigs to fish out termites from mounds. And then they learned tool use wasn’t even limited to apes. Monkeys, crows, sea otters and even octopuses manipulate objects to get what they want. Yet there’s no denying humans have taken technology to a completely different level. Given that our high-tech tools are one of our defining features, you’d think anthropologists would know when hominids began modifying stones to make tools and which species was the first to do so. But there’s still much to be learned about the origins of stone tools.
The oldest-known type of stone tools are stone flakes and the rock cores from which these flakes were removed. Presumably used for chopping and scraping, these tools are called Oldowan, named for Tanzania’s Olduvai Gorge, where they were first recognized. Louis Leakey first found roughly 1.8-million-year-old tools in the 1930s. But it wasn’t until the 1950s that he found hominid bones to go along with the Stone Age technology. In 1959, Leakey’s wife, Mary, discovered the species now known as Paranthropus boisei. With its giant teeth, massive jaws and relatively small brain, the hominid didn’t look very human, but the Leakeys concluded P. boisei had to be the site’s toolmaker—until the 1960s, when they found a slightly larger-brained hominid called Homo habilis (meaning “the handy man”). This more human-like hominid must have manufactured the tools, the Leakeys thought. But P. boisei and H. habilis overlapped in time (roughly 2.4/2.3 million years ago to 1.4/1.2 million years ago), so it’s been hard to definitively rule out the possibility that both types of hominids were capable of making stone tools.
It turns out neither species is probably eligible for the title of earliest toolmaker. In the 1990s, archaeologists recovered even older Oldowan tools at the Ethiopian site called Gona, dating to 2.6 million to 2.5 million years ago. Identifying the toolmaker is tricky because no fossils have been found in association with the artifacts, and there weren’t many hominid species present in East Africa during this time period to pick from. Paranthropus aethiopicus is one possibility. But so far only one skull and a few jaws of the species have been found in one area of Kenya, so not much is really known about the hominid.
A better choice might be Australopithecus garhi. The species was discovered at a site about 55 miles south of Gona, in association with animal bones that display the characteristic markings of butchering—indirect evidence of tool use. Again, not much is known about A. gahri, as scientists have only found one skull, some skull fragments and one skeleton that is tentatively considered part of the species.
Even these tools, however, are probably not the oldest stone tools, say Sileshi Semaw, director of the Gona Paleoanthropological Research Project, and the other researchers who found the Gona artifacts. The tools at this site are so well made, requiring such precision, that the anthropologists suspect that by 2.6 million years ago hominids had been making stone tools for thousands of years.
In 2010, a group of archaeologists claimed the origins of stone tools went back another 800,000 years. Shannon McPherron of the Max Planck Institute for Evolutionary Anthropology in Germany and colleagues announced they had discovered signs of butchering at another Ethiopian site, dating to 3.39 million years ago. The rib from a cow-sized hoofed mammal and the leg fragment from a goat-sized mammal contained microscopic scratches indicative of cutting and scraping to remove flesh and pounding to break open a bone to retrieve marrow. The only hominid species around at that time was Australopithecus afarensis, Lucy’s species. McPherron’s team suggested tools have not yet been found with Lucy’s kind because early tool use was probably not as extensive as it was later on. So hominids were probably making fewer tools and thus leaving behind fewer artifacts for scientists to unearth.
The case for 3.39-million-year-old stone-tool manufacturing is controversial. McPherron and colleagues acknowledge that hominids didn’t necessarily make tools to butcher their prey; they could have used naturally sharp rocks. Other researchers doubt any butchering even happened at all. Manuel Domínguez-Rodrigo of Complutense University of Madrid in Spain and colleagues say the cut marks may actually be trampling damage or scratches from the abrasive sediments the bones were buried in. Further research is needed to confirm the marks were actually made by hominids.
Although the exact timing of when hominids began making stone tools is still unsettled, at least one thing is clear: Big brains weren’t required to make simple stone tools. The evolution of bigger brains comes at least a million years after our ancestors invented the Oldowan toolkit.