As 2012 nears its end, one thing stands out as the major theme in human evolution research this year: Our hominid ancestors were more diverse than scientists had ever imagined. Over the past 12 months, researchers have found clues indicating that throughout most of hominids’ seven-million-year history, numerous species with a range of adaptations lived at any given time. Here are my top picks for the most important discoveries this year.
1. Fossil foot reveals Lucy wasn’t alone: Lucy’s species, Australopithecus afarensis, lived roughly 3.0 million to 3.9 million years ago. So when researchers unearthed eight 3.4-million-year-old hominid foot bones in Ethiopia, they expected the fossils to belong to Lucy’s kind. The bones do indicate the creature walked upright on two legs, but the foot had an opposable big toe useful for grasping and climbing. That’s not something you see in A. afarensis feet. The researchers who analyzed the foot say it does resemble that of the 4.4-million-year-old Ardipithecus ramidus, suggesting that some type of Ardipithecus species may have been Lucy’s neighbor. But based on such few bones, it’s too soon to know what to call this species.
2. Multiple species of early Homo lived in Africa: Since the 1970s, anthropologists have debated how many species of Homo lived about two million years ago after the genus appeared in Africa. Some researchers think there were two species: Homo habilis and Homo rudolfensis; others say there was just H. habilis, a species with a lot of physical variation. It’s been a hard question to address because there’s only one well-preserved fossil, a partial skull, of the proposed species H. rudolfensis. In August, researchers working in Kenya announced they had found a lower jaw that fits with the previously found partial skull of H. rudolfensis. The new jaw doesn’t match the jaws of H. habilis, so the team concluded there must have been at least two species of Homo present.
3. New 11,500-year-old species of Homo from China: In March, researchers reported they had found a collection of hominid bones, dating to 11,500 to 14,300 years ago, in a cave in southern China. Based on the age, you’d expect the fossils to belong to Homo sapiens, but the bones have a mix of traits not seen in modern humans or populations of H. sapiens living at that time, such as a broad face and protruding jaw. That means the fossils may represent a newly discovered species of Homo that lived side by side with humans. Another possibility is that the remains came from Denisovans, a mysterious species known only from DNA extracted from the tip of a finger and a tooth. Alternatively, the collection may just reveal that H. sapiens in Asia near the end of the Pleistocene were more varied than scientists had realized.
4. Shoulder indicates A. afarensis climbed trees: Another heavily debated question in human evolution is whether early hominids still climbed trees even though they were built for upright walking on the ground. Fossilized shoulder blades of a 3.3-million-year-old A. afarensis child suggest the answer is yes. Scientists compared the shoulders to those of adult A. afarensis specimens, as well as those of modern humans and apes. The team determined that the A. afarensis shoulder underwent developmental changes during childhood that resemble those of chimps, whose shoulder growth is affected by the act of climbing. The similar growth patterns hint that A. afarensis, at least the youngsters, spent part of their time in trees.
5. Earliest projectile weapons unearthed: Archaeologists made two big discoveries this year related to projectile technology. At the Kathu Pan 1 site in South Africa, archaeologists recovered 500,000-year-old stone points that hominids used to make the earliest known spears. Some 300,000 years later, humans had started making spear-throwers and maybe even bow and arrows. At the South African site called Pinnacle Point, another group of researchers uncovered tiny stone tips dated to 71,000 years ago that were likely used to make such projectile weapons. The geological record indicates early humans made these small tips over thousands of years, suggesting people at this point had the cognitive and linguistic abilities to pass on instructions to make complex tools over hundreds of generations.
6. Oldest evidence of modern culture: The timing and pattern of the emergence of modern human culture is yet another hotly contested area of paleoanthropology. Some researchers think the development of modern behavior was a long, gradual buildup while others see it as progressing in fits and starts. In August, archaeologists contributed new evidence to the debate. At South Africa’s Border Cave, a team unearthed a collection of 44,000-year-old artifacts, including bone awls, beads, digging sticks and hafting resin, that resemble tools used by modern San culture today. The archaeologists say this is the oldest instance of modern culture, that is, the oldest set of tools that match those used by living people.
7. Earliest example of hominid fire: Studying the origins of fire is difficult because it’s often hard to differentiate a natural fire that hominids might have taken advantage of versus a fire that our ancestors actually ignited. Claims for early controlled fires go back almost two million years. In April, researchers announced they had established the most “secure” evidence of hominids starting blazes: one-million-year-old charred bones and plant remains from a cave in South Africa. Because the fire occurred in a cave, hominids are the most likely cause of the inferno, the researchers say.
8. Human-Neanderthal matings dated: It’s not news that Neanderthals and H. sapiens mated with each other, as Neanderthal DNA makes up a small portion of the human genome. But this year scientists estimated when these trysts took place: 47,000 to 65,000 years ago. The timing makes sense; it coincides with the period when humans were thought to have left Africa and spread into Asia and Europe.
9. Australopithecus sediba dined on wood: Food particles stuck on the teeth of a fossil of A. sediba revealed the nearly two-million-year-old hominid ate wood—something not yet found in any other hominid species. A. sediba was found in South Africa in 2010 and is a candidate for ancestor of the genus Homo.
10. Earliest H. sapiens fossils from Southeast Asia: Scientists working in a cave in Laos dug up fossils dating to between 46,000 and 63,000 years ago. Several aspects of the bones, including a widening of the skull behind the eyes, indicate the bones were of H. sapiens. Although other potential modern human fossils in Southeast Asia are older than this find, the researchers claim the remains from Laos are the most conclusive evidence of early humans in the region.
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.
From Fish to Man: Research Reveals How Fins Became Legs
Dec. 10, 2012 — Vertebrates’ transition to living on land, instead of only in water, represented a major event in the history of life. Now, researchers reporting in the December issue of the Cell Press journal Developmental Cell provide new evidence that the development of hands and feet occurred through the gain of new DNA elements that activate particular genes.
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.
Fossil yields theory of life 3.3 million years ago
“She was only 3 years old, but her fossil bones tell a contentious story of ancient prehumans who walked on two feet like us more than 3 million years ago, but climbed trees like her distant ancestors, the great apes.
Her partial skeleton was discovered embedded in the sandstone rocks of Ethiopia’s Afar desert a dozen years ago by Zereseney Alemseged, the noted anthropologist at the California Academy of Sciences. He named her Selam and still works to reconstruct her life.”
Read more here.
A new fossil discovery shows we did not climb out of the trees until much later than once thought.
If you’re on the shorter end of the height spectrum, you know how frustrating it can be to take a stroll with someone who’s tall. At times, you might have to remind your companion to slow down, that your shorter legs can’t keep up. This might have been an even bigger problem for our famous ancestor, Lucy. Within the species Australopithecus afarensis, there was considerable variability in height and limb length, and different members of the species may have had vastly different preferences for walking speeds, new research suggests. How did our ancestors cope with such a dilemma?
The problem really became apparent in 2010 with the discovery of a partial A. afarensis skeleton, nicknamed “Big Man,” in Ethiopia. As his name suggests, the five-foot-tall Big Man was big, at least for an early hominid, and compared to the three-and-a-half-foot-tall Lucy. Big Man’s shin, for instance, was about 50 percent longer than that of Lucy’s—the sort of length difference you see today between a six-year-old child and a six-foot-tall man. But in Lucy and Big Man’s case, both individuals were adults, suggesting there was a large range of heights for A. afarensis. The variation might have been related to sex, with males being significantly taller than females. Or there might have been regional differences in A. afarensis size. Lucy and Big Man were both found in Ethiopia but at different sites.
To understand the walking behavior of Lucy, Big Man and their kind, Patricia Ann Kramer of the University of Washington in Seattle did some experiments with people. In modern humans, the length of the lower leg (or tibia) plays a big role in how much energy a person expends while walking and what his/her preferred speed is. Kramer examined this relationship by measuring the tibia length of 36 children and 16 adults and then placing the volunteers on treadmills to record how much energy they used (measured in terms of oxygen consumption) while walking at different speeds. She discovered that, in general, individuals with longer lower legs have higher “optimal velocities.” That means the speed at which longer-legged people consume the least amount of energy is faster than that of shorter-legged people.
Kramer used the data to create a mathematical equation that related leg length to speed to estimate Lucy’s and Big Man’s optimal velocities based on their tibia lengths. Lucy’s would have been 1.04 meters per second (about 3.4 feet per second) while Big Man’s would have been as much as 1.33 meters per second (about 4.4 feet per second). To put this in perspective, if both individuals walked for an hour at their optimal speeds, Lucy would have covered 3.74 kilometers (2.3 miles) while Big Man would have traversed 4.68 kilometers (2.9 miles), Kramer reports in the American Journal of Physical Anthropology.
Based on two individuals, it’s hard to say how representative these results are for A. afarensis. And even assuming there were big differences in walking speeds, it’s hard to say how it would have affected the behavior of these early hominids. If size differences were sex based, then some members of a group might have had to compromise their preferred walking speed—perhaps females had to walk faster (and thus expend more energy) to keep up with males or maybe males slowed down (also expending more energy) to appease females or maybe both sexes had to adjust their velocities. Another possibility is that males and females spent time away from each other during the day, Kramer says. Among wild chimpanzees, males and females often range separately while searching for food, which might be a consequence of different walking speeds. More studies that examine sex-based ranging patterns in primates might offer more clues to how A. afarensis could have coped. Of course, this variation in height might not have been a problem at all if differences were largely regional.
Although Kramer’s work doesn’t provide any definite answers, it highlights how difficult it is to reconstruct the biology and behavior or our ancestors. It’s clear that A. afarensis walked upright, but we still have a lot to learn about how the early hominid traveled across the East African landscape.
Richard Leakey and Alan Walker observing the skull of the Turkana Boy (1984)
Lucy and Selam’s Species Climbed Trees: Australopithecus Afarensis Shoulder Blades Show Partially Arboreal Lifestyle
ScienceDaily (Oct. 25, 2012) — Australopithecus afarensis (the species of the well-known “Lucy” skeleton) was an upright walking species, but the question of whether it also spent much of its time in trees has been the subject of much debate, partly because a complete set of A. afarensis shoulder blades has never before been available for study.
Neanderthals in Northern Spain Had Knowledge of Plants’ Healing Qualities, Study Reveals
ScienceDaily (July 17, 2012) — An international team of researchers, led by the Universitat Autònoma de Barcelona and the University of York, has provided the first molecular evidence that Neanderthals not only ate a range of cooked plant foods, but also understood its nutritional and medicinal qualities.
Three and a half million years ago was the heyday of Australopithecus afarensis. But Lucy’s species may not have been alone. In 1999, researchers working in West Turkana, Kenya, uncovered a roughly 3.5-million-year-old hominid skull with a face too flat to belong to A. afarensis. The skull’s finders decided it must be a new species, Kenyanthropus platyops.
At the time, anthropologists disagreed over K. platyops‘ identity and place in the human family tree. While some researchers take the species as a sign that there was a diversity of hominid types around during the middle Pliocene epoch, others say the K. platyops skull is not actually a distinct species at all—it’s simply a distorted skull of an A. afarensis.
Where does the debate stand today?
In 2010, some of the original describers of K. platyops—Fred Spoor of the Max Planck Institute for Evolutionary Anthropology in Germany and Meave Leakey of the Koobi Fora Research Project—worked with Koobi Fora’s Louise Leakey to reanalyze the skull. In their new analysis, the team used CT scans of the skull to assess how distorted the fossil really is. Although the skull contains numerous cracks, the shape of the skull and teeth remain largely unaffected by the damage, the researchers reported in Proceedings of the Royal Society B.
With that in mind, Spoor and the two Leakeys compared the physical features of K. platyops to those of A. afarensis and six other extinct hominid species, in addition to modern humans, chimpanzees and gorillas. According to the researchers, the results confirmed that K. platyops was significantly different from other hominid species, mainly in its flat face, forward-facing cheekbones and small molars (over time, the molars got bigger and bigger in the many species of Australopithecus before getting small again in the genus Homo). Thus, the fossil deserves to be in its own species, they concluded.
Of course, one paper never really settles a debate in human evolution. The Smithsonian Human Origins Program, for example, doesn’t include K. platyops in its list of hominid species and categorizes the K. platyops skull as A. afarensis. Many scientists probably won’t be convinced unless more fossils matching K. platyops are found. There are some other fragments of teeth and skull from West Turkana that may belong to the species, but those fossils don’t really shed any further light on the issue.
For those who do accept K. platyops as a distinct hominid, there’s not much to say about the species. Given its age, it’s possible that K. platyops made the famous footprints preserved at Laetoli in Tanzania. The footprints reveal that some sort of hominid with a modern gait was alive at the time. The more popular theory, however, is that A. afarensis was the upright walker at Laetoli.
Regardless of K. platyops‘ status as a species, it’s not the only evidence that more than one type of hominid lived in East Africa alongside Lucy. In April, researchers unearthed a 3.4-million-year-old hominid foot in Ethiopia that retained too many features related to climbing to be the foot of A. afarensis. Who knows—maybe it belonged to K. platyops.
Neanderthals … They’re Just Like Us?
Well, not exactly. But new discoveries have had a surprisingly humanizing effect.
The Neanderthals are both the most familiar and the least understood of all our fossil kin.
For decades after the initial discovery of their bones in a cave in Germany in 1856 Homo neanderthalensis was viewed as a hairy brute who stumbled around Ice Age Eurasia on bent knees, eventually to be replaced by elegant, upright Cro-Magnon, the true ancestor of modern Europeans.
A Neanderthal trove in Madrid
The Lozoya River Valley could help clear up mysteries surrounding extinct species.
The Lozoya River Valley, in the Madrid mountain range of Guadarrama, could easily be called “Neanderthal Valley,” says the paleontologist Juan Luis Arsuaga.
“It is protected by two strings of mountains, it is rich in fauna, it is a privileged spot from an environmental viewpoint, and it is ideal for the Neanderthal, given that it provided the with good hunting grounds.”