September 10, 2012
Indonesia is the overlooked birthplace of professional paleoanthropology. In Europe in the mid-19th century, scientists discovered an extinct hominid species for the first time: Neanderthals. Actually, it’s more accurate to say Neanderthal fossils were found by lay people who then brought them to the attention of well-known anatomists. It wasn’t until 1890 that a researcher went into the field looking for hominid bones. Eugene Dubois, a Dutch medical doctor, traveled to Indonesia, then a Dutch colony, in search of human ancestors. In 1891, he discovered Homo erectus fossils and made hominid hunting a proper endeavor—and made Asia a destination for paleoanthropologists.
Trinil: Dubois’ discoveries occurred near the village of Trinil in central Java. His first find was a skullcap, now known to date to 700,000 to 1 million years ago. The skull looked humanlike, but it had thick bones, heavy browridges and a low, sloping forehead. A year later, in 1892, Dubois recovered a nearly complete thigh bone that looked almost modern. He decided the bones belonged to an extinct species that was a “missing link” between apes and humans. He named the species Pithecanthropus erectus (“erect ape man”). Sometimes called Java Man, the species today is called Homo erectus.
Ngandong: Dutch researchers discovered more H. erectus fossils, representing 15 individuals, in Java in the 1930s near the village of Ngandong on Java’s Solo River. Until recently, paleoanthropologists thought the Ngandong bones represented a very recent H. erectus population. Thought to be perhaps as young as 30,000 to 50,000 years ago, these hominids could have been contemporaries of Neanderthals and modern humans living in Europe and West Asia. But more recent fieldwork and dating analyses suggest the Ngandong hominids lived much earlier, sometime between 143,000 and 546,000 years ago.
Mojokerto: In 1936, an assistant working with the Dutch Geological Survey unearthed a partial skullcap of a two- to three-year-old child in eastern Java. Team member Ralph von Koenigswald, a German paleontologist, recognized the skull as belonging to an early hominid, H. erectus. Although the exact location, and therefore age, of the fossil has been questioned in recent years, scientists generally think the Mojokerto skull dates to about 1.8 million years ago. That makes it one of the oldest hominid bones ever found outside Africa.
Sangiran: Between 1937 and 1941, von Koenigswald found additional H. erectus fossils at the site of Sangiran in central Java. The finds included three partial skulls, partial jaws and dozens of isolated teeth. These fossils, dating to more than one million years ago, helped confirm the validity of the species status of H. erectus. Today, tourists can visit the fossil site, which is home to ongoing excavations as well as a museum.
Flores: Indonesia’s most recent hominid discovery was a big shocker. In 2004, a group of researchers from Indonesia and Australia announced they had found an unusual collection of fossils on the Indonesian island of Flores. The bones belonged to a small-brained hominid that stood less than four feet tall and weighed less than 70 pounds—yet some of the fossils were just 17,000 years old. The researchers decided the “Hobbit” belonged to a new species, Homo floresiensis. Once the species’ ancestor, perhaps H. erectus, arrived on the island, the hominid evolved to be smaller as an adaptation to living on a small island. Critics, however, say the Hobbit is actually a modern human with some kind of growth disorder.
August 27, 2012
In 2009, paleoanthropologists working in a cave in Laos unearthed skull bones and teeth belonging to a modern human. Dating to between 46,000 and 63,000 years ago, the bones may be the earliest fossil evidence of Homo sapiens in mainland Southeast Asia, researchers reported last week in Proceedings of the National Academy of Sciences.
The fossils—a partial skull, jaw fragments and teeth—were found in Tam Pa Ling (Cave of the Monkeys). Several physical features indicate the individual was human, including a lack of browridges, a widening of the skull behind the eyes and smaller teeth relative to earlier hominids. The third molar was just surfacing, suggesting the individual was a young adult.
No artifacts were found with the bones, which appear to have washed into the cave. Radiocarbon and luminescence dating (a measure of the last time something was heated or exposed to sunlight) of charcoal and sediments directly above and below the fossils indicate the bones were deposited in the cave 46,000 to 51,000 years ago, making that a minimum age of the bones. Dating a piece of the skull with uranium dating shows the the fossils are no older than 63,000 years. (The University of Illinois has several pictures of the fossils and cave site.)
The discovery is important because scientists haven’t found too many human fossils in eastern Asia dating to between 120,000 and 40,000 years ago, even though genetic evidence and stone tools suggest people must have been in the area. “There are other modern human fossils in China or in Island Southeast Asia that may be around the same age, but they either are not well dated or they do not show definitively modern human features,” team leader Laura Shackelford of the University of Illinois at Urbana-Champaign said in a press release. “This skull is very well dated and shows very conclusive modern human features.”
Other early modern human fossils in East Asia include skull fragments found in 1976 at the Xujiayao site in northeastern China. Based on the age of rhinoceros teeth found in the same location, the bones have been dated to 104,000 to 125,000 years ago, but some researchers have questioned whether the human fossils were really found in the same geologic layer as the rhino remains. There’s also a partial lower jaw from Zhirendong in southern China that’s been clearly dated to about 100,000 years ago, but some experts question whether it’s really from a modern human. In 2010, I reported on the discovery of a 67,000-year-old toe bone found in the Philippines. The fossil belongs to the genus Homo, but a single foot bone is not enough to determine the exact species.
Finding the physical remains of modern humans is important in clarifying the history of human migration into this part of the world, especially now that we know other hominids lived in eastern Asia at the end of the Pleistocene. The tiny Hobbit lived in Flores as recently as 17,000 years ago. And last year scientists learned that the Denisovans, a hominid species known only from DNA recovered from a finger bone and tooth, must have lived in Asia at the same time as modern humans: Genetic evidence from modern Southeast Asians, Australian Aborigines, Melanesians and other people of Oceania suggests humans and Denisovans interbred.
But it’s hard to find hominid fossils in Southeast Asia. The warm, wet environment inhibits fossil preservation, which probably explains why so many fossils in the area have been found in cooler, drier caves. Let’s hope this latest discovery spurs other anthropologists to start searching for more fossils to fill in the East Asian gap in early modern human history.
July 17, 2012
A hundred years ago, archaeologists thought Native Americans came to North America only 5,000 years ago. That belief changed in the 1920s and 1930s as researchers started finding stone projectile points associated with the fossils of mammoths and giant bisons—animals that went extinct more than 10,000 years ago. For decades, the oldest known points dated to 13,000 years ago. Called Clovis points, they contained characteristic “flutes,” or long, concave grooves, where a spear locked into place.
More recent evidence reveals humans reached the New World, via the Bering Strait, by at least 15,000 years ago. These early Americans weren’t making Clovis points. Last week, archaeologists announced in Science another example of pre-Clovis technology.
The tools come from Oregon’s Paisley Caves. Dennis Jenkins of the University of Oregon and colleagues determined people were living in the area by at least 14,000 years ago based on the radiocarbon dates of human coprolites (fossilized dung) found in the cave. They also found projectile points of the same age or slightly older than Clovis points. Known as the Western Stemmed Tradition, these points are narrower, lack flutes and require a different chipping method to make than Clovis points.
The team suggests the Clovis and Western Stemmed points probably developed independently from an even earlier tool technology, with the Clovis originating in the Plains and Southeast and the Western Stemmed arising in the West. This fits with a discovery reported last year in Science. At the Debra L. Friedkin site in central Texas, archaeologists recovered more than 16,000 artifacts dating to 13,200 to 15,500 years ago. Among the artifacts were blades and two-sided flakes that Clovis tools could have evolved from, the researchers suggested. (A study published online in the Journal of Archaeological Science, however, challenges those dates and even argues that the artifacts may actually be Clovis tools.)
In other early American news, a team led by David Reich of Harvard Medical School reconstructed the ancestry of Native Americans living in North and South America. They reported their findings last week in Nature. Based on a genetic analysis of 52 modern Native American groups and 17 Siberian groups, the researchers concluded the majority of Native Americans descend from a single Siberian population. Arctic people who speak Eskimo-Aleut languages also inherited about half of their genetic material from a second wave of Siberian immigrants. Members of a third migration contributed to the gene pool of Na-Dene-speaking Chipewyans of Canada. Finding multiple migrations complements previous genetic, archaeological and linguistic studies.
Of course, that doesn’t mean there were only three migrations to the New World. The researchers only looked at the ancestry of living Native Americans. There could be early migrating groups that didn’t leave behind living descendants. That’s something we may never know.
July 9, 2012
The 2003 discovery of the diminutive Homo floresiensis, better known as the Hobbit, on the Indonesian island of Flores was a shock. Anthropologists never expected to find a 3-foot, 6-inch-tall hominid living in Southeast Asia at the same time as modern humans, as recently as 17,000 years ago. Aside from the controversy over the hominid’s true identity—a diseased Homo sapiens or a member of its own species—another intriguing question was how the ancestors of the Hobbits got to Flores.
One possibility is that the Hobbits’ forefathers sailed over on a raft. Or their arrival might have been an act of nature: A powerful storm or tsunami could have washed a small group of hominids out to sea, and then floating vegetation carried them to Flores. That idea sounds implausible, but it’s also an explanation for how monkeys reached South America.
Scientists will probably never know for certain what the Hobbit’s ancestors went through to get to Flores. Such ancient wooden boats are unlikely to be preserved and there’s no way to prove it was a freak accident.
But recently a pair of researchers offered a novel way of assessing the issue. Ecologist Graeme Ruxton of the University of St. Andrews in Scotland and biologist David Wilkinson of Liverpool John Moores University in England simulated population growth over time of planned colonizations versus accidental castaways to see which scenario could lead to successful inhabitations of an island. They reported their results in the Journal of Human Evolution.
The premise of the model is that a group of hominids reach an island. The hominids mate monogamously and each year there is a set probability that a female of a certain age will give birth. There’s also a given probability that individuals in the population will die, based on age and sex.
For the scenario of a planned trip at sea aboard a raft, Ruxton and Wilkinson assumed colonists were sailing as groups of families. So the founding populations in this model had an equal number of adult males and adult females. Ruxton and Wilkinson ran their simulations using different group sizes for a founding population. After running each scenario a thousand different times, they concluded such populations could be successful—defined as lasting 500 years or reaching 500 individuals. The likelihood of success increased with founding population group size, reaching a success plateau at groups of just 20.
To simulate an accidental island arrival due to a storm or tsunami, the pair changed one of their starting assumptions. Instead having an equal number of adult males and adult females at the onset, they assumed the sex ratio was random. No one plans to be washed out to sea, after all. Under this scenario, colonizations were 50 percent less likely to succeed compared to the planned trips aboard a boat. But with slight modifications, that number went up. By adding a 2 percent chance that one to four additional castaways might reach the island each year for the first 400 years, Ruxton and Wilkinson found that unintentional colonizations were as likely to succeed as planned ones. These newcomers increased a stranded population’s chance of long-term viability by introducing new genes to the island and/or balancing out skewed sex or age ratios.
Although the chance of different storms washing different groups of hominids to the same island sounds as likely as lightning striking twice, it may not be that far-fetched. Ruxton and Wilkinson point out ocean currents and wind patterns can lead floating objects to the same place over and over again.
So what does all of this computation really tell us? On the one hand, the models are only as useful as the assumptions Ruxton and Wilkinson used to build them. If the hominids didn’t mate monogamously, for example, then the pair’s conclusions may not be valid. But putting such concerns aside, the results indicate that both rafting and accidental ocean dispersals are possible explanations for the Hobbits’ inhabitation of Flores. Therefore, the researchers warn, a hominid’s presence on an island isn’t necessarily evidence of some kind of sailing technology.
Today, humans live on tens of thousands of islands—even if they didn’t necessarily mean to.
June 11, 2012
This month, Smithsonian looks at the origins of the chicken, tracing the domesticated version of the bird to either India or Southeast Asia. The magazine has also explored the beginnings of the house cat in the Near East. Here’s a brief look at where other domesticated animals got their start.
Dog: Descended from the grey wolf, the dog became man’s best friend tens of thousands of years ago. The earliest known dog fossils come from a site in Belgium dating to more than 31,000 years ago. But a 2010 genetic study suggests modern dogs probably come from the Middle East: Dog DNA best matches the DNA of wolves from that part of the world. Although dog fossils date to as many as 31,000 years ago, the most ancient dog breeds around today—such as the Afghan hound, Siberian husky, chow chow and Shar Pei—are no more than a few thousand years old. And most modern dog breeds are only a couple of hundred years old, originating during the Victorian era of the 19th century.
Goat: Modern goats stem from six maternal genetic lineages, but most of today’s farm goats arose from just two domestication events: one in southeastern Turkey 10,500 years ago and another in the southern Zagros Mountains and Central Iranian Plateau almost 10,000 years ago. A 2008 genetic study of domesticated goats and their ancestor, the bezoar, indicates almost all of today’s goats (perhaps as many as 90 percent, according to one study) descend from those that originated in Turkey.
Sheep: Along with goats, sheep were among of the first hoofed animals to be domesticated, about 11,000 years ago. The animals were originally bred for their meat, and it wasn’t until about 5,000 years ago that they were also raised for wool. Archaeological and genetic evidence points to the Fertile Crescent as the original home of sheep. But researchers have discovered at least five distinct genetic lineages, indicating the animals were probably domesticated several times from various wild sheep ancestors such as the mouflon.
Cow: Domesticated cattle come in two main varieties: Taurine cattle are the common dairy and beef cattle found in Europe, North America and other cool environments. Zebu, or humped cattle, are found in warmer, tropical climates. The Taurine evolved from wild ox somewhere in the Fertile Crescent about 10,000 years ago. Research published earlier this year estimates the original population consisted of just 80 female oxen—a sign that the domestication occurred in a restricted region of the Middle East. European wild ox contributed to the cattle gene pool later, when farmers brought cattle to the continent from the Middle East. Zebu cattle can be traced back to the Indus Valley of India.
Pig: Humans domesticated pigs from wild boars several times in several different places. The earliest evidence comes from Cyprus, where fossils reveal that humans brought wild boars to the island by 12,000 years ago. Full-fledged pigs appear in the Fertile Crescent by 9,000 years ago. Genetic evidence indicates pigs also arose separately in East Asia, Southeast Asia, India and Europe. In Europe, however, the first pigs were migrants that came over with farmers from the Middle East. Later, these foreign pigs were replaced by home-grown pigs domesticated from local European boars.
Horse: Last month, researchers reconstructing the population genetics of horses confirmed humans first tamed the equines somewhere in the western part of the Eurasian Steppe. The earliest fossil evidence comes Kazakhstan when the area was inhabited by people of the Botai culture. Horse teeth dating to 3,500 B.C. show the characteristic damage that develops from biting a harnessing bridle. And chemical analyses of fatty acid residues on pottery indicate the Botai were consuming horse milk.
Donkey: The domestication of the donkey allowed people to develop mobile forms of pastoralism, enabled long-distance trade and aided in the rise of early Egypt. Modern donkeys belong to one of two distinct genetic groups, implying the animal was domesticated twice. DNA points to both events happening around 5,000 years ago in Northeast Africa. Last year, researchers determined one group descends from the Nubian wild ass. Scientists had thought the Somali wild ass was the ancestor of the second donkey clan, but DNA shows that’s not possible. Scientists have yet to pinpoint the form that gave rise to this donkey group.