Smithsonian.com

Cro-Magnon was one of the first fossils of an ancient human ever discovered. Image courtesy of Wikicommons

Paleoanthropologists agree that modern humans evolved in Africa about 200,000 years ago, yet the fossil evidence for the earliest examples of Homo sapiens is scarce. One problem is the difficulty in recognizing true modern humans in the fossil record: At this time, many of the fossils thought to be early members of our species possess a mix of modern and primitive traits. For some paleoanthropologists, it means our species once had a greater range of physical variation than we do today. For others, it means more than one species of Homo may have lived in Africa at this time, sharing some traits in common.

Despite the challenges of identifying early humans, there are several candidates for the earliest known members of our species. Here’s a look at some of the top contenders.

Omo I and II (195,000 years ago): In 1967, a team led by Richard Leakey discovered possible Homo sapiens fossils in the Kibish Formation near the Omo River in southern Ethiopia. Originally the fossils, Omo I (a partial skull and skeleton) and Omo II (a partial skull), were thought to be 130,000 years old, but a dating reanalysis in 2005 revealed they were much older—195,000 years old, making them the oldest fossils assigned to Homo sapiens. Over the last 45 years, the species status of the fossils has been debated. Researchers largely agree Omo I was a modern human; it had the human hallmarks of a flat face, fully formed chin, high forehead and globular braincase. They are less certain about Omo II, which was more primitive with its thicker, more “rugged” cranial bones and sloped forehead. While some paleoanthropologists say Omo II is too archaic to be one of us, others suggest it’s evidence of the great physical diversity of early modern humans.

Herto fossils (160,000 years ago): Tim White of the University of California at Berkeley and colleagues unearthed three largely complete skulls, two adults and one child, in the Middle Awash region of Ethiopia in 1997. The skulls appear quite modern, the researchers reported in Nature in 2003. But because certain cranial traits are outside the range of modern human variation, the researchers placed the Herto fossils in their own subspecies, Homo sapiens idaltu (idaltu means “elder” in the Afar language of Ethiopia). Cutting and scraping marks on the skulls suggest these early humans engaged in some sort of mortuary practices, as these types of markings are not typical of cannibalism.

Qafzeh and Skhul fossils (~100,000 years ago): In the 1930s, researchers working in the caves of Qafzeh and Skhul in northern Israel found the skeletal remains of at least 30 individuals, a few purposefully buried. Some researchers suggest the fossils represent an early migration of humans out of Africa. But like Omo II, some of the fossils in the collection are difficult to classify. For example, the skull known as Skhul V had thick brow ridges and lacked a chin. The primitive traits in this population might have been the result of interbreeding with Neanderthals, which also lived in the region at this time.

Cro-Magnon 1 (30,000 years ago): OK, this fossil is too young to be a real contender for the oldest member of our species. But I included it on the list for its historical significance. Discovered in France in 1868, the Cro-Magnon 1 skull was one of the first ancient Homo sapiens fossils ever found, demonstrating our species’ great antiquity.

A reconstruction of Gigantopithecus. Image courtesy of Flickr user Sam_Wise

Bigfoot. Sasquatch. Yeti. The Abominable Snowman. Whatever you want to call it, such a giant, mythical ape is not real—at least, not anymore. But more than a million years ago, an ape as big as a polar bear lived in South Asia, until going extinct 300,000 years ago.

Scientists first learned of Gigantopithecus in 1935, when Ralph von Koenigswald, a German paleoanthropologist, walked into a pharmacy in Hong Kong and found an unusually large primate molar for sale. Since then, researchers have collected hundreds of Gigantopithecus teeth and several jaws in China, Vietnam and India. Based on these fossils, it appears Gigantopithecus was closely related to modern orangutans and Sivapithecus, an ape that lived in Asia about 12 to 8 million years ago. With only dentition to go on, it’s hard to piece together what this animal was like. But based on comparisons with gorillas and other modern apes, researchers estimate Gigantopithecus stood more than 10 feet tall and weighed 1,200 pounds (at most, gorillas only weigh 400 pounds). Given their size, they probably lived on the ground, walking on their fists like modern orangutans.

Fortunately, fossil teeth do have a lot to say about an animal’s diet. And the teeth of Gigantopithecus also provide clues to why the ape disappeared.

The features of the dentition—large, flat molars, thick dental enamel, a deep, massive jaw—indicate Gigantopithecus probably ate tough, fibrous plants (similar to Paranthropus). More evidence came in 1990, when Russell Ciochon, a biological anthropologist at the University of Iowa, and colleagues (PDF) placed samples of the ape’s teeth under a scanning electron microscope to look for opal phytoliths, microscopic silica structures that form in plant cells. Based on the types of phyoliths the researchers found stuck to the teeth, they concluded Gigantopithecus had a mixed diet of fruits and seeds from the fig family Moraceae and some kind of grasses, probably bamboo. The combination of tough and sugary foods helps explain why so many of the giant ape’s teeth were riddled with cavities. And numerous pits on Gigantopithecus‘s teeth—a sign of incomplete dental development caused by malnuntrition or food shortages—corroborate the bamboo diet. Ciochon’s team noted bamboo species today periodically experience mass die-offs, which affect the health of pandas. The same thing could have happened to Gigantopithecus.

A Gigantopithecus jaw. Image courtesy of Wikicommons

Further evidence of Gigantopithecus‘ food preferences and habitat was published last November. Zhao LingXia of the Chinese Academy of Sciences and colleagues analyzed carbon isotopes in a sample of Gigantopithecus teeth. Plants have different forms of carbon based on their type of photosynthesis; this carbon footprint is then recorded in the teeth of animals that eat plants. The team determined Gigantopithecus—and the animals living alongside it, such as deer, horses and bears—ate only C3 plants, evidence the ape lived in a forested environment. This work also supports the proposed bamboo diet, as bamboo is a C3 plant.

So what happened to this Pleistocene Yeti? Zhang’s team suggested the rise of the Tibetan plateau 1.6 million to 800,000 years ago altered the climate of South Asia, ushering in a colder, drier period when forests shrank. Other factors could have exacerbated this crisis. Gigantopithecus‘s neighbor, Homo erectus, may have over-hunted and/or outcompeted their larger ape cousin. And at least one dental study indicates Gigantopithecus developed and matured very slowly—a sign they probably had low reproductive rates, which can elevate a species’ risk of going extinct.

Some Bigfoot hunters say Gigantopithecus is alive and well, hiding out in the forests of the Pacific Northwest. Other Sasquatch enthusiasts, however, point out this is unlikely, as Bigfoot is reported to be a swift, agile, upright walker—not a lumbering, 1,200-pound quadruped.

Humans are the only hominids with true chins. Image courtesy of Wikicommons

When you think about what makes modern humans unique, the chin is probably not the first, second or even third thing that comes to mind. Yet this bony protrusion at the end of the lower jaw is not seen in any other hominid species. So what’s a chin good for? Over the years, researchers have thought up a variety of explanations for why we have chins.

Perhaps the most common explanation is that our chin helps buttress the jaw against certain mechanical stresses. Ionut Ichim, a Ph.D. student at the University of Otago in New Zealand, and colleagues suggested in the journal Medical Hypotheses in 2007 that the chin evolved in response to our unique form of speech, perhaps protecting the jaw against stresses produced by the contraction of certain tongue muscles. Others think the chin evolved to safeguard the jaw against forces generated by chewing food. Last year, Flora Gröning, a biological anthropologist at the University of York in England, and colleagues tested the idea by modeling how modern human and Neanderthal jaws withstand structural loads. Their results, which they reported in the American Journal of Physical Anthropology, indicated the chin does help support the jaw during chewing . They suggested the chin may have evolved to maintain the jaw’s resistance to loads as our ancestors’ teeth, jaws and chewing muscles got smaller early on in our species’ history.

A completely different line of reasoning points to sexual selection as the driver of the evolution of the chin. Under sexual selection, certain traits evolve because they are attractive to the opposite sex. Psychological research suggests chin shape may be a physical signal of the quality of a mate. For example, women may prefer men with broad chins because it’s sign that a man has good genes; likewise, a woman’s narrow chin may correlate with high levels of estrogen. Zaneta Thayer, a graduate student at Northwestern University, and Seth Dobson, a biological anthropologist at Dartmouth, examined the sexual selection hypothesis by measuring the chin shape of nearly 200 skulls in a museum collection, representing people from all over the world. The pair discovered that there is a small but distinct difference in chin shape between the sexes, with men having a taller, more pronounced chin. They argued in the American Journal of Physical Anthropology in 2010 that this difference is evidence against explanations that the chin evolved to resist mechanical stress. If chins evolved in response to eating or talking, then there should be no difference in chin shape between the sexes because, presumably, men and women eat and talk the same way.

Maybe the evolution of the chin is more complicated than any one scenario. For example, is it possible the chin initially evolved to handle particular mechanical stresses and was later shaped further by sexual selection? I’d like to see someone test that idea.

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.

A giant bust of Peking Man at Zhoukoudian. Image courtesy of Flickr user Scott SM

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.

For more information, visit the Tanzania Tourist Board and the Ngorongoro Conservation Area websites.

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.

For more information, visit TravelChinaGuide.com and the Heritage Traveller websites.

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?