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The skull of Australopithecus sediba. Picture by Brett Eloff, courtesy of Lee Berger and the University of the Witwatersrand

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.

The outline of a mastodon skeleton, found at a pre-Clovis site in Washington, indicating where a spear hit the animal. Image courtesy of the Center for the Study of First Americans, Texas A&M University

Sometime near the end of the Pleistocene, a band of people left northeastern Asia, crossed the Bering land bridge when the sea level was low, entered Alaska and became the first Americans. Since the 1930s, archaeologists have thought these people were members of the Clovis culture. First discovered in New Mexico in the 1930s, the Clovis culture is known for its distinct stone tools, primarily fluted projectile points. For decades, Clovis artifacts were the oldest known in the New World, dating to 13,000 years ago. But in recent years, researchers have found more and more evidence that people were living in North and South America before the Clovis.

The most recently confirmed evidence comes from Washington. During a dig conducted from 1977 to 1979, researcher uncovered a bone projectile point stuck in a mastodon rib. Since then, the age of the find has been debated, but last month in the journal Science, Michael Waters of Texas A&M University and colleagues announced a new radiocarbon date for the rib: 13,800 years ago, making it 800 years older than the oldest Clovis artifact. Other pre-Clovis evidence comes from a variety of locations across the New World. Here’s a brief tour of some of the most important sites:

Ayer Pond, Orcas Island, Washington: While digging in a wetland in 2003, workers discovered the bones of ancient bison, later radiocarbon-dated to about 13,800 years ago. Cuts on the bones and other signs of butchering indicate humans were in the area at that time. The researchers speculate that the hunters dismembered the bison on top of a frozen pond, leaving the carcass behind to fall to the pond’s bottom when the ice thawed.

Debra L. Friedkin site, Texas: An excavation at this site yielded 15,528 artifacts dating from 13,200 to 15,500 years ago. Named the Buttermilk Creek Complex, these small, lightweight tools—an indicator that the artifacts were designed to be carried around a lot—do not resemble Clovis tools, the researchers reported earlier this year in Science. But they may be the type of artifacts which later developed into Clovis tools.

Monte Verde, Chile: One of the first challenges to the Clovis theory came from southern Chile. In the 1970s, archaeologists discovered the remains of a campsite that dated to about 14,000 years ago, but the age was contested. In 2008, researchers obtained new radiocarbon dates from seaweed associated with stone tools at the site, placing humans in Chile as early as 14,200 years ago.

Paisley Caves, Oregon: So far, all of the pre-Clovis sites lack human bones; the case for a human presence is based solely on the discovery of artifacts and butchered bones. The Paisley Caves in Oregon, however, contain a type of human remains: fossilized poop, or coprolites if you want to be more scientific (and polite). Fourteen coprolites at the caves resembled human coprolites based on size, shape and other physical features. DNA from the samples confirmed their human origin. Radiocarbon dating indicates people left the specimens behind between 14,000 and 14,270 years ago. Canid DNA in the coprolites suggests early Americans may have eaten dogs, wolves or foxes; alternatively, such animals later came by and urinated on the dung.

Meadowcroft Rockshelter, Pennsylvania: Just an hour’s drive from Pittsburgh, Meadowcroft may be the oldest site of human habitation in the New World. The first artifacts were found in the 1950s, and subsequent excavations unearthed small stone blades, flakes and a projectile point that date to as many as 15,200 years ago. Some researchers think humans first called the rockshelter home even earlier, about 16,000 years ago. To imagine what life was like for America’s earliest immigrants, you can take a tour of Meadowcroft, which is open to the public May through October.