December 17, 2012
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.
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 26, 2012
Humans and Neanderthals split from a common ancestor roughly half a million years ago. While many anthropologists will tell you we don’t really know who that common ancestor was, others will say we do: the species Homo heidelbergensis, or something very much like it. An even smaller portion will point to another possibility: a controversial species called Homo antecessor.
H. antecessor, which first came to light in the 1990s, is known almost entirely from one cave in northern Spain’s Atapuerca Mountains. While working at the Gran Dolina site from 1994 to 1996, a team of Spanish researchers found 80 fossils belonging to six hominid individuals that lived roughly 800,000 years ago. The hominids’ teeth were primitive like those of Homo erectus, but aspects of the hominid’s face—particularly the shape of the nasal region and the presence of a facial depression above the canine tooth called the canine fossa—were modern, resembling features of modern people. The unique mix of modern and primitive traits led the researchers to deem the fossils a new species, H. antecessor, in 1997.
In 2008, the researchers expanded the timeline of the species . At another cave site in Atapuerca, Sima del Elefante, scientists unearthed a partial lower jaw, as well as a few dozen stone tools, dating to about 1.2 million years ago. Outside of Spain, the only other potential evidence of H. antessor
fossils are stone tools found at a nearly 800,000-year-old English archaeological site named Happisburgh that might have been made by the species.
H. antessor‘s discoverers—including José Bermúdez de Castro of Spain’s National Museum of Natural Sciences, Juan Luis Arsuaga of the Universidad Complutense in Madrid and Eudald Carbonell of the University of Tarragona—say the species’ similarities with modern people, and its age, make it the best known candidate for the common ancestor of Neanderthals and Homo sapiens. They suggest H. antecessor may have evolved from a population of H. erectus living in Africa more than 1.5 million years ago and then migrated to Europe, journalist Ann Gibbons reported in Science when H. antecessor was first announced. Although the species has yet to be discovered in Africa, an African origin for H. antecessor may be necessary if it was indeed the direct ancestor of modern humans, which all fossil evidence suggests originated in Africa. Furthermore, the researchers say H. heidelbergensis is too similar to Neanderthals to be a direct ancestor of modern humans. Instead, H. antecessor gave rise to H. heidelbergensis, which then gave rise to Neanderthals.
But many anthropologists are not on board with this scenario. One problem is that most of the known H. antecessor specimens represent children, Gibbons reported. Only two of the six individuals found at Gran Dolina are thought to be adults, about 20 years old. Since most of the features tying H. antecessor to modern people were found in juveniles—whose bodies and physical features change as they grow up and go through puberty—it’s possible that H. antecessor adults didn’t really look much like H. sapiens at all. And if that’s the case, then it’s hard to argue the species had an ancestor-descendent relationship with us. The issue won’t be settled until researchers find good examples of complete adult H. antecessor fossils.
September 24, 2012
Neanderthals have a reputation for being dumb brutes. While modern humans (Homo sapiens) were painting cave murals, sculpting tiny figurines and crafting beaded jewelry some 30,000 to 50,000 years ago, Neanderthals weren’t making any art. At least, that’s the way it appears in the archaeological record. Now, a new study of bird fossils suggests our cousins were indeed capable of expressing themselves symbolically—using feathers as personal adornments.
In the last few years, researchers have reported a few archaeological sites with evidence that Neanderthals removed feathers and claws from birds such as raptors, presumably for ornamental purposes. Clive Finlayson of the Gibraltar Museum and his colleagues wanted to see how widespread this behavior was among Neanderthals. They published their findings last week in PLOS One.
To address the question, the team looked at Neanderthals’ association with fossils of raptors (including vultures and eagles) and corvids (including ravens and magpies). They focused on these birds because modern people generally don’t consume them and therefore Neanderthals probably didn’t either. Thus, finding these types of birds at an archaeological site helps exclude the possibility that our cousins were eating them. In searching almost 1,700 sites across Europe and Asia that contain bird fossils, the team noted that species with dark plumage were more common at Neanderthal sites than would be expected by chance alone. So, it seems Neanderthals across their geographic range liked black birds.
Next, the researchers looked at three cave sites on Gibraltar to examine more closely what Neanderthals might have been doing with these birds. The caves date from 57,000 to 28,000 years ago, before modern humans entered the region. The team found 604 avian skeletal pieces, representing at least 124 individual birds. With less than 3 percent of the bones containing the tooth marks of rodents or carnivores, Neanderthals are the likely reason the birds were brought into the caves.
More than half of the bones were wing bones. There’s no reason to expect wing bones to be disproportionately preserved in the fossil record, so this is another sign that Neanderthals were mainly interested in feathers, the researchers say. Furthermore, most of the bones with stone-tool markings are the wing bones. If Neanderthals were butchering the animals for meat, you’d expect to find the most markings on bones connected to fleshy areas, such as the breast bone.
Because soil bacteria rapidly decompose feathers, the researchers conclude our cousins weren’t using feathers as bedding. The only use that makes sense, Finlayson and colleagues argue, is plucking feathers to make headdresses, cloaks or some other adornment.
“Neanderthals, though different in a number of ways from modern humans, had comparable cognitive capacities that included symbolic expression,” the researchers write. Furthermore, they say, any differences in the art or artifacts left behind by the two species was the result of cultural differences, not intellect.
But does the capacity for symbolic expression mean Neanderthals had mental abilities that were on par with modern humans? It depends on who you ask. For decades, symbolism was considered the key cognitive trait that separated modern humans from other hominids. Today, anthropologists think there may be a range of abilities that define the human mind, such as planning for the future and processing disparate chunks of information at the same time (working memory). Until researchers can agree on the core features that characterize human cognition, it will be impossible to determine whether Neanderthal brains were really just like ours.
September 19, 2012
I was intrigued when I saw this headline over at NPR’s 13.7 blog earlier this week: “A Neanderthal-Themed Park for Gibraltar?“ As it turns out, no one’s planning a human evolution Disney World along Gibraltar’s cliffs. Instead, government officials are hoping one of the area’s caves will become a Unesco World Heritage site. Gibraltar certainly deserves that distinction. The southwestern tip of Europe’s Iberian Peninsula, Gibraltar was home to the last-surviving Neanderthals. And then tens of thousands of years later, it became the site of one of the first Neanderthal fossil discoveries.
That discovery occurred at Forbes’ Quarry in 1848. During mining operations, an officer in the British Royal Navy, Captain Edmund Flint, uncovered an adult female skull (called Gibraltar 1). At the time, Neanderthals were not yet known to science, and the skull was given to the Gibraltar Scientific Society. Although Neanderthals were recognized by the 1860s, it wasn’t until the the first decade of the 20th century that anatomists realized Gibraltar 1 was indeed a Neanderthal. Additional Neanderthal discoveries came in the 1910s and 1920s at the Devil’s Tower rock shelter, which appeared to be a Neanderthal occupation site. In 1926, archaeologist Dorothy Garrod unearthed the skull of a Neanderthal child near flaked stone tools from the Mousterian industry. In all, archaeologists have found eight Neanderthal sites at Gibraltar.
Today, excavations continue at Gorham’s Cave and Vanguard Cave, where scientists have learned about the life and times of the most recent populations of Neanderthals. In 2006, researchers radiocarbon dated charcoal to estimate that the youngest Neanderthal populations lived at Gibraltar as recently as 24,000 to 28,000 years before the present. Clive Finlayson, director of the Gibraltar Museum’s Heritage Division, has suggested that Neanderthals persisted so late at Gibraltar because the region stayed a warm Mediterranean refuge while glacial conditions set in across more northern Europe. Ancient pollen data and animal remains recovered from Gibraltar indicate Neanderthals had access to a variety of habitats—woodlands, savannah, salt marshes and scrub land—that provided a wealth of food options. In addition to hunting deer, rabbits and birds, these Neanderthals enjoyed eating monk seals, fish, mussels and even dolphins on a seasonal basis.
As with most things in paleoanthropology, the Neanderthal history at Gibraltar is not settled. Some anthropologists have questioned the validity of the very young radiocarbon dates. Why the Neanderthals eventually died out is also a matter of debate. Further climate change in Europe, competition with modern humans or some mix of both are all possible explanations.