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.
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.
April 2, 2012
Lucy wasn’t alone. A new fossil foot unearthed in East Africa comes from an unknown hominid species that lived at the same time and in the same region as Lucy‘s species, Australopithecus afarensis. Lucy and her neighbors were both capable of walking upright on two legs, researchers say. But while Lucy spent most of her time on the ground, the newly discovered species was more adept at moving around in the trees.
“This find alters our understanding of the evolution of bipedalism because it shows that there was more diversity than previously recognized in the ways that early [hominids] moved around their environments,” says Brian Richmond, a paleoanthropologist at Smithsonian’s Human Origins Program and George Washington University.
The new discovery—eight bones from the front part of a right foot—comes from Ethiopia’s Woranso-Mille site and dates to 3.4 million years ago. This coincides with the period when Australopithecus afarensis lived in this part of Africa, about 3.0 million to 3.9 million years ago. The analysis of the bones was led by Yohannes Haile-Selassie, curator of physical anthropology at the Cleveland Museum of Natural History, and Bruce Latimer, a physical anthropologist at Case Western Reserve University in Ohio.
The researchers determined that the foot possesses features indicative of bipedal walking, such as certain joints seen in modern humans that allow the toes to push off the ground and propel the foot forward during upright walking. But the foot also appears apelike: Its opposable, grasping big toe suggests the unnamed species was a good tree climber and probably spent much less time on the ground than Lucy and later hominids, the researchers reported last week in Nature.
Haile-Selassie and his colleagues can’t give the species a name based on the scant fossil evidence. But the foot does resemble an even earlier hominid, the 4.4-million-year-old Ardipithecus ramidus, which also had an opposable big toe. Perhaps some species of Ardipithecus survived until this time.
Regardless of who the foot belonged to, it seems two types of hominids were around during this relatively early period in human evolution—and it means the evolution of bipedalism was probably more complicated than scientists suspected. For decades, the question has been what factor led the ancestors of hominids to walk upright. Now anthropologists also have to consider what factor(s) led to the origin of different styles of bipedalism.
March 28, 2012
Last December, I described one of the long-standing mysteries in the history of human evolution: the missing Peking Man fossils. Now a new lead has brought anthropologists to the fossils’ possible location. The only problem is that the spot is covered by an asphalt parking lot.
The Peking Man fossils are a set of 200 Homo erectus fossils excavated from China’s Zhoukoudian cave site during the 1920s and 1930s. During World War II, Chinese authorities packed up the fossils to send them to the United States for safekeeping. The bones were supposed to be transported to a U.S. Marine base and then shipped off. Instead, the fossils vanished, and no one really knows what happened to them.
A break in the case came in April 2010. Paul Bowen, the son of former U.S. Marine Richard Bowen, emailed paleoanthropologist Lee Berger of the University of the Witwatersrand in South Africa. Bowen claimed his father had dug up a box of bones while stationed in the port city of Qinhuangdao (formerly called Chingwangtao) in 1947, during China’s Nationalist–Communist Civil War. In his email, the younger Bowen describes what his father told him:
Day after day the war there was getting hotter and closer. Peitaiho, south of us, was mostly overrun. … The city of Chinwangtao was now under siege by the Communist 8th Route Army with Nationalist gun-boats shelling them over our camp. One day a group of them asked us to surrender, saying that they had 250,000 men. To prove the point, that night thousands of fires were lit by them on the adjacent hills and high ground. It looked like Christmas time. From that time on we started digging fox holes at night and napping during the day. I had a 30 caliber machine gun and our lieutenant would, from time to time, change our crossfire. In this nightly digging process we dug a lot of holes. In one of them we found a box that was full of bones. At night it gave us a little scare and we filled in that hole and dug another. Shortly after this we evacuated the area, went back to Tientsin, and then back to the United States with the First Marine Division colors.
Berger used Bowen’s story to investigate further. Working with Wu Liu and Xiujie Wu, both of China’s Institute for Vertebrate Paleontology and Paleoanthropology in Beijing, Berger went to Qinhuangdao in November 2010 to locate the site of the U.S. Marine base where Bowen was stationed. The area is now an industrial hub with numerous warehouses. The most likely site where Bowen found the bones, which the team located based on Bowen’s descriptions and with the help of a local historian, is now a large parking lot, the researchers report in the South African Journal of Science. (National Geographic has pictures of what the area looks like today.)
Berger and his colleagues did not excavate the area. But if the bones were buried there, and if they survived the parking lot’s construction, researchers may find them one day. The area is expected to undergo a large redevelopment sometime soon. And, Berger and his colleagues say, local officials at the Cultural Heritage Office have agreed to monitor any excavations in case the bones turn up.
March 21, 2012
Last week, an international group of researchers reported the discovery of fossils belonging to a strange population of hominids that lived in southwestern China as recently as 11,500 years ago, at the end of the Pleistocene Epoch. The fossils resemble modern humans in many ways but possess some unusual characteristics. The traits may be evidence that Homo sapiens were more diverse in the past—or a sign that scientists have uncovered a new species.
Anthropologist Darren Curnoe of the University of New South Wales in Australia led the analysis of the fossils, detailed in the journal PLoS ONE. The bones—a partial skull, skull cap, jaws and teeth—came from Longlin Cave in Guangxi Province and Malu Cave in Yunnan Province, and date to 11,500 to 14,300 years ago. In comparing the Chinese bones with those of recent humans, H. sapiens living during the Pleistocene, Neanderthals and Homo erectus, the researchers concluded the Chinese fossils have a unique mix of modern features and traits rarely, if ever, seen in recent and Pleistocene humans, such as a very broad face and a protruding jaw.
The most dramatic interpretation of the fossils is that they represent a newly discovered species that lived alongside modern humans in East Asia until very recently. Anthropologist Chris Stringer of the Natural History Museum in London thinks that’s a feasible idea. In fact, the fossils could be the remains of the mysterious Denisovans, Stringer told New Scientist. Scientists discovered the Denisovans a few years ago while analyzing DNA recovered from a finger bone found in a Siberian cave that dated to 30,000 to 48,oo0 years ago. The DNA didn’t align with that of modern humans or Neanderthals, the only species known to inhabit the area at the time. Since then, scientists have been looking to match a face to the DNA. This idea will be confirmed only if the researchers manage to retrieve DNA from any of the Chinese fossils.
A less headline-worthy explanation is that these hominids were members of an early, unknown migration of H. sapiens out of Africa. (Genetic evidence indicates there were at least two migrations into Eurasia: one at 60,000 to 70,000 years ago and another at 30,000 to 40,000 years ago.) Once these people settled in East Asia, they somehow remained isolated from other human populations for thousands of years and eventually died out without leaving behind descendants. Under this scenario, the population’s unusual features suggest our species was more diverse thousands of years ago than it is today. This possibility is supported by other fossils found in Africa. Curnoe and his colleagues describe H. sapiens fossils found in East, South and North Africa, dating from 12,000 to 100,000 years ago, that possess a mix of modern and more primitive traits.
This situation reminds me of the search for the earliest modern humans. Many of these fossils also retained primitive features, which has made it difficult for anthropologists to decide which ones are truly modern humans and which ones aren’t. Likewise, anthropologists now have to determine whether modern humans could have been more diverse near the end of the Pleistocene than they had previously thought or whether more hominid species were living back then than they had previously expected.