September 26, 2012
By 200,000 years ago, Homo sapiens had emerged somewhere in Africa. By 14,000 years ago, our species had spread to every continent except Antarctica. What happened in between—the pattern of where humans went and when—is still being worked out. To reconstruct the peopling of the world, anthropologists rely on several types of clues.
Fossils: The most obvious way to track our ancestors’ movements is to look for their physical remains. Researchers sketch out travel routes by mapping where the oldest human fossils are found. The earliest Homo sapiens bones outside of Africa come from a cave site in Israel called Qafzeh. Here the skeletons of both adults and children date to as far as 125,000 years ago. This first foray out of Africa didn’t last long. Humans disappeared from the fossil record outside of Africa for many tens of thousands of years, perhaps because the climate became too harsh. Fossils tell us humans made a successful, sustained exodus by at least 50,000 years ago. Human fossils found at Australia’s Lake Mungo site, for example, have been dated to between 46,000 and 50,000 years ago (PDF).
The problem with relying on skeletal remains to map early migrations is that the timing of our ancestors’ travels is only as good as the methods used to date the fossils. Sometimes scientists find bones in places that are not easily dated by geological techniques. And in some areas, fossils aren’t prone to preservation, so there are probably huge gaps in our knowledge of the paths early humans took as they spread around the world.
Artifacts: Archaeologists also look for the items people made and left behind. For example, stone tool discoveries suggest an alternative route out of Africa. For decades, scientists assumed humans left Africa via the Sinai Peninsula, but in the last several years some researchers have favored a “southern” route: leaving from the Horn of Africa, crossing the narrowest part of the Red Sea and entering into southern Arabia. Last year, archaeologists reported finding stone tools in Oman dating to roughly 106,000 years ago. At that time, the Arabian Peninsula was a much more hospitable place than it is today, home to numerous freshwater lakes. As the region became drier, people might have moved east into Asia or returned to Africa.
Of course, when the only remains at an archaeological site are tools, it’s hard to say with absolute certainty who made them. The researchers working in Oman noted that the tools they found in Arabia match the technology of modern humans found in eastern Africa about 128,000 years ago. The team made the case that the tool makers on either side of the Red Sea belonged to the same cultural group—and therefore the same species. But as anthropologists discover more species, such as the Hobbit or the Denisovans, that lived alongside modern humans outside of Africa up until a few tens of thousands of years ago, it becomes harder to say stone tools alone indicate the presence of Homo sapiens.
DNA: Genetic data can help fill in the holes in the human migration story that fossils and artifacts can’t address. Anthropologists collect DNA samples from different ethnic groups around the world. Next, they count up the genetic differences caused by mutations in certain sections of the genome. Groups that are more closely related will have fewer genetic differences, which implies they split off more recently form each other than they did with more distantly related groups. Scientists calculate when in the past different groups diverged from each other by adding up all of the genetic differences between two groups and then estimating how often genetic mutations occurred. Such analyses not only give a sense of when different parts of the world were first inhabited, but they can also reveal more intricate patterns of movement. For example, genetic data suggest North America was colonized by three separate waves of people leaving Siberia across the Bering Strait.
Genetic data are not foolproof, however. The estimated divergence times are only as accurate as the estimated mutation rate, which scientists still debate. In the early days of DNA studies, scientists used either mitochondrial DNA, passed down only by the mother, or the Y chromosome, inherited only from father to son. Neither of these types of DNA presented the full picture of what people were doing in the past, as mitochondrial DNA only tracks maternal lineages while the Y chromosome only follows paternal lines. Today, whole genome sequencing is beginning to allow researchers to trace entire populations.
Languages: Anthropologists use languages in methods analogous to studying DNA; they look for patterns of similarities, or differences, in vocabularies or other aspects of language. Earlier this year, researchers compared different languages within the Indo-European language family to determine where these languages arose. After assessing the relationship between the languages, the researchers considered the geographic ranges where those languages are currently spoken. They concluded that the Indo-European language family originated in what is today Turkey and then spread west into Europe and east into southern Asia as people moved into these areas. But such linguistic analyses may only track relatively recent migration patterns. For example, H. Craig Melchert, a linguist at the University of California, Los Angeles, told Science News that the Indo-European languages can only be traced back about 7,000 years.
December 28, 2011
For this last Hominid Hunting post of 2011, I reviewed recent human evolution research highlights to come up with my picks for the top 10 hominid discoveries of the year. While genetic breakthroughs have hogged the spotlight the past couple of years, good old-fashioned fossil and archaeological finds were front and center in 2011.
10. Earliest Modern Humans in Europe: Paleoanthropologists believe modern humans (Homo sapiens) came to Europe about 43,000 years ago. This date is based on the age of sophisticated stone tools, not human fossils. This year two teams dated European fossils that are in line with the age of the tools: A human upper jaw discovered in southern England in 1927 was dated to 44,000 years ago, and two molars unearthed in Italy were dated to 45,000 years ago. These fossils are the oldest known human remains on the continent.
9. The Arches of Australopithecus afarensis: There’s no doubt that Lucy and her species, Australopithecus afarensis, walked upright. But the degree to which these hominids walked on the ground has been debated. The discovery of a 3.2-million-year-old foot bone confirmed that Lucy and her kind had arched feet and therefore probably walked much like modern people. The researchers who studied the fossil say it indicates Australopithecus afarensis no longer needed to spend much time in the treetops; however, other researchers disagree, saying hominids at this time were still good tree climbers.
8. World’s Earliest Mattress: In a rock shelter in South Africa, archaeologists uncovered a 77,000-year-old mattress composed of thin layers of sedges and grasses, predating all other known mattresses by 50,000 years. Early humans knew how to keep the bed bugs out; the bedding was stuffed with leaves from the Cape Laurel tree (Cryptocarya woodii), which release chemicals known to kill mosquitos and other bugs.
7. Neanderthal Mountaineers: Neanderthals evolved many traits to deal with the cold; for example, their short limbs helped them conserve heat. A mathematical analysis revealed that short limbs may have also helped Neanderthals walk more efficiently in mountainous terrains. Specifically, the fact that Neanderthals had shorter shins relative to their thighs meant they didn’t need to lift their legs as high while walking uphill, compared to modern people with longer legs. “For a given step length, they [needed] to put in less effort,” said lead research Ryan Higgins of Johns Hopkins University.
6. The First Art Studio: Archaeologists working in South Africa’s Blombos Cave discovered early humans had a knack for chemistry. In a 100,000-year-old workshop, they found all of the raw materials needed to make paint, as well as abalone shells used as storage containers—evidence that our ancestors were capable of long-term planning at this time.
5. Australopithecine Females Strayed, Males Stayed Close to Home: In many monkey species, when males reach adolescence, they leave their home to search for a new group, probably as a way to avoid breeding with their female relatives. In chimpanzees and some humans, the opposite occurs: Females move away. Now it appears that australopithecines followed the chimp/human pattern. Researchers studied the composition of strontium isotopes found in the teeth of members of Australopithecus africanus and Paranthropus robustus. An individual consumes strontium through food and it is taken up by the teeth during childhood. Because the isotopes (different forms of the element) in plants and animals vary by geology and location, strontium can be used as a proxy for an individual’s location before adulthood. In the study, the researchers discovered that large individuals, presumably males, tended to have strontium isotope ratios typical of the area where the fossils were found; smaller individuals, or females, had non-local strontium isotope ratios, indicating they had moved into the area as adults.
4. Confirmation of Pre-Clovis People in North America: Since the 1930s, archaeologists have thought the Clovis people, known for their fluted projectile points, were the first people to arrive in the New World, about 13,000 years ago. But in recent years there have been hints that someone else got to North America first. The discovery of more than 15,000 stone artifacts in central Texas, dating to between 13,200 and 15,500 years ago, confirmed those suspicions. Corroborating evidence came from Washington State, where a mastodon rib containing a projectile point was dated this year to 13,800 years ago.
3. Denisovans Left A Mark in Modern DNA: The Denisovans lived in Eurasia sometime between 30,000 and 50,000 years ago. Scientists don’t know what they looked like; the only evidence of this extinct hominid group is DNA extracted from a bone fragment retrieved from a cave in Siberia. But this year, several studies revealed the mysterious population bred with several lineages of modern humans; people native to Southeast Asia, Australia, Melanesia, Polynesia and elsewhere in Oceania carry Denisovan DNA.
2. Out of Africa and Into Arabia: Traditionally, paleoanthropologists have thought modern humans left Africa through the Sinai Peninsula and into the Levant. But some researchers suggest our ancestors took a more southerly route, across the Red Sea and into southern Arabia. This year, several studies provided evidence pointing to this exit strategy. First, a team reported the discovery of 125,000-year-old stone tools in the United Arab Emirates. The researchers suggested humans ventured into Arabia when sea level was lower, making a trip across the Red Sea easier. (Geologists later verified the climate would have been just right at this time.) No fossils were found with the tools, but the scientists concluded they belonged to modern humans rather than Neanderthals or some other contemporaneous hominid. Another study this year complemented the finding: Paleoanthropologists also found stone tools, dating to 106,000 years ago, in Oman. The researchers say the artifacts match tools of the Nubian Complex, which are found only in the Horn of Africa. This connection implies the makers of those African tools, most likely modern humans, made the migration into Oman.
1. Australopithecus sediba, Candidate for Homo Ancestor: Last year, scientists announced the discovery of a new hominid species from South Africa’s Cradle of Humankind—Australopithecus sediba. This year, the researchers announced the results of an in-depth analysis of the 1.97-million-year-old species. They say a mix of australopithecine and Homo-like traits make Australopithecus sediba, or a species very similar to it, a possible direct ancestor of our own genus, Homo.
December 21, 2011
This week Smithsonian introduced the concept of “evotourism,” with 12 sites around the world where visitors can appreciate and learn about evolution. One stop on the tour relates to human evolution: South Africa’s Cradle of Humankind, where the first Australopithecus fossils were discovered.
But there are many other locations where evotourists can marvel at the science and history of human evolution. Here are five additional hominid evotourism destinations.
1. Olduvai Gorge, Tanzania
Its place in hominid history: Some 2,000 miles northeast of the Cradle of Humankind is Africa’s other self-proclaimed Cradle of Mankind, Olduvai Gorge, made famous by Louis and Mary Leakey. In 1959, the husband-and-wife team uncovered a 1.75-million-year-old skull belonging to a species of hominid they dubbed Zinjanthropus boisei, now called Paranthropus boisei. The finding shifted hominid hunters’ interest from South Africa to East Africa, where paleoanthropologists have since found some of the earliest hominids. In the early 1960s, the Leakeys discovered another hominid that once lived at the site, Homo habilis. Dating to about 2.5 million years ago, this species is the earliest known member of the genus Homo. Although it still retained some primitive features, it was the first hominid to have a brain larger than an ape’s. The species’ name means “Handy Man,” referring to the Leakeys’ belief that this hominid made the numerous stone tools found at Olduvai Gorge. These tools are significant in their own right. They are some of the oldest stone tools ever found, and today, archaeologists refer to these types of tools as Oldowan.
What to do there: After touring the Olduvai Gorge Museum, visitors can take guided walks of the hominid site. But the area offers more than just fossils and impressive vistas. The gorge is located within the protected Ngorongoro Conservation Area. The Ngorongoro Crater, the area’s namesake, is a collapsed volcanic crater carpeted with the grasslands of the Serengeti. Tourists can join walking or vehicle safaris, with the chance to glimpse some of the Serengeti’s most famous residents, including lions, baboons, zebras, wildebeest and flamingos.
2. Sangiran, Indonesia
Its place in hominid history: In the 1890s, Dutch anatomist Eugene Dubois discovered the first fossils of Homo erectus (at the time, the species was known as Pithecanthropus erectus), on the island of Java. In fact, it was among the earliest discoveries in the fledgling field of paleoanthropology. Based on the features of the fossils—a modern-looking thigh bone indicating upright walking and a primitive skull cap with thick brow ridges and a sloping forehead—Dubois believed this so-called Java Man was an intermediate form between apes and humans. Starting in the 1930s, German anthropologist Gustav Heinrich Ralph von Koenigswald excavated at Sangiran, not far from where Dubois conducted his work. Von Koenigswald found additional fossils as well as stone tools. These sites in Java, dating to more than a million years ago, are some of the oldest hominid fossil locales outside of Africa.
What to do there: Located in Central Java, about 15 miles south of the city of Solo, Sangiran is a Unesco World Heritage site. The Sangiran Museum offers displays of Java Man fossil replicas as well as real fossils of animals that lived in the area 1.2 million to 500,000 years ago. Tourists can also visit the Sangiran archaeological site, where fossils are still being unearthed, and climb a three-story observation tower to get a more expansive view of the region.
For more information, visit Indonesia’s Official Tourism Website.
3. Zhoukoudian, China
Its place in hominid history: The first and oldest hominid fossils discovered in East Asia were found in the 1920s by paleontologists working at the caves of Zhoukoudian, or Dragon Bone Hill, about 30 miles southwest of Beijing. The fossils were assigned to the species Sinanthropus pekinensis, colloquially called Peking Man. Eventually, anthropologists realized the Sinanthropus fossils in China and the Pithecanthropus fossils in Java belonged to the same species, Homo erectus. The original fossils found in the 1920s through 1930s went missing during World War II, but researchers have since found dozens of other fossils and stone tools. The site is also home to early evidence of the use of fire.
What to do there: With its close proximity to Beijing, Zhoukoudian is easier to get to than many of the other sites on this list, accessible by car or bus. Once there, visitors can see hominid fossils on display at the Zhoukoudian Anthropological Museum, along with the fossils of other animals that coexisted with Peking Man. Tourists can also visit the caves where excavations took place.
4. Lake Mungo, Australia
Its place in hominid history: Located more than 300 miles north of Melbourne, the now-dry Lake Mungo is home to Australia’s oldest human remains. In 1968, geologist Jim Bowler and a group of archaeologists discovered the burnt bones of a woman; six years later, Bowler found the skeleton of an adult man. Known as Mungo Lady and Mungo Man, the fossils have been the center of much debate, with dates for the pair ranging from 28,000 to 62,000 years ago. Today, researchers in Australia think the Mungo people lived about 40,000 years ago—evidence that modern humans arrived in Australia at a very early date. More recently, in 2003, scientists unearthed 500 footprints left behind by humans, other mammals and birds 20,000 years ago.
What to do there: Mungo National Park offers visitors a variety of ways to explore the area’s dry lake beds, sand dunes and grasslands: short hikes, longer driving and bike paths, and tours led by aboriginal park rangers. The park’s visitor’s center has exhibits on the region’s natural history and cultural heritage, and the outdoor Meeting Place has a recreation of the park’s ancient footprints (the real footprints have been covered for their protection and preservation). Several other national parks are within a few hours’ drive of Mungo.
For more information, visit the Mungo National Park website.
5. Lascaux Caves, France
Its place in hominid history: The Vézère Valley in southwestern France is home to 147 archaeological sites and 25 caves adorned with ancient paintings. The most famous cave paintings are those of Lascaux, discovered by a group of teenagers in 1940. The cave paintings depict 100 animal figures, including bison and horses, as well as some human figures.
What to do there: Sadly, tourism has damaged the Lascaux caves paintings. The site opened to the public in 1948, but the arrival of people also brought bacteria, fungi and other microbes that have led to the deterioration of the cave art, and the caves are now closed to the public. However, visitors can tour a replica of the cave and its paintings nearby at Lascaux II. Perhaps an even less intrusive way to see the paintings is through an online virtual tour.
For more information, visit the Lascaux Cave website.
These are just a few accessible locations important to the study of hominid history. What stops would you add to the human evolution world tour? And which would you most like to visit?