Chapter 11: The Origins and Evolution of Early Homo

Homo erectus

Ileret, Kenya. 1.5mya - several dozen footprints have been discovered. Prints are indistinguishable from modern humans. -The footprints show longitudinal arch, big toe is in line with other toes -So, smaller brain, but same locomotion as us! The first cranium (left) is 1.2 myo, has a large browridge and a large area for muscle attachments A slightly younger example from 1 mya is the Daka skull, which resembles H. erectus fossils found in Asia -Some researchers think African H. erectus should be considered a different species, Homo ergaster. Another skull. An interesting and potentially disturbing one. -This cranium, Bodo, dates to 600,000ya from Ethiopia, it's brain size is closer to what we find in us Shows butchering marks on cranium... Ritual or cannibalism? The earliest evidence of cannibalism dates to around 800,000 years ago, but the practice is present in remains associated with several Homo species. -One species from Europe, H. antecessor (1.2 mya - 800,000 ya - which is most likely a lineage of H. erectus), is well-known for evidence of cannibalism found at several sites in Spain. After appearing in Africa, H. erectus quickly spread to Asia and Europe. -The previously mentioned site of Dmanisi dates to 1.77mya, and by 1.2 mya had spread into Europe. -This was a highly adaptable organism

Homo habilis: The First Species of the Genus Homo

Of course, our genus did not appear overnight, and there are transitional fossils dating to 2+mya. They bridge the gap from the Australopithecines . Homo habilis - nicknamed "Handy Man", 1.4-2.5mya Discovered by Louis and Mary Leakey in 1960 Significant increase in the use of stone tools, landscape was 'littered' with Oldowan stone tools, in use between 1.7 and 2.6 mya Named for their discovery in the Olduvai Gorge of Tanzania This species, has a slightly larger braincase and smaller face and teeth than in Australopithecus or older hominin species. But it still retains some ape-like features, including long arms and a moderately- prognathic face. Height: average 3 ft 4 in - 4 ft 5 in (100 - 135 cm) Weight: average 70 lbs (32 kg) Smaller teeth than Australopithecus, enamel still thick and their jaws strong, adaptations to hard foods Dental microwear shows diet was flexible and versatile, but that they did not routinely consume or specialize in eating hard foods like brittle nuts or seeds, dried meat, or very hard tubers Indirect evidence of diet comes from cutmarks on nearby animal remains. Scientists associate these traces of butchery of large animals, direct evidence of meat and marrow eating, with the earliest appearance of the genus Homo, including H. habilis. This is complicated because other hominin species lived at the same time Certainly an early example of Homo, if one at all "Although H. habilis is generally larger than A. africanus, its teeth and jaws have the same proportions. What little evidence there is about its body shape, hands and feet suggest that H. habilis would be a much better climber than undisputed human ancestors. So, if H. habilis is added to Homo, the genus has an incoherent mishmash of features. Others disagree, but I think you have to cherry pick the data to come to any other conclusion."

Homo erectus in Asia

Returning to Indonesia (remember Dubois), and the island of Java. Researchers have found more fossils of H.erectus, including over a dozen partial skulls -This fossil (Sangiran 17) is reminiscent of early fossils from Africa -This is additional evidence for a single H. erectus species.

Homo erectus. Early Homo goes Global

Returning to the idea of one or two early Homo species. In fact, there were probably three species of early Homo coexisting 1.8 - 1 .9 mya Did this species evolve from another, earlier species of Homo or did it evolve from Australopithecus -Most scientists agree that it evolved from an earlier species of Homo Around 1.9 mya ago, early Homo evolved into a hominin with a larger brain, smaller back teeth, and long, human-like legs ;cranial features include large browridges, and long, low skulls. -Unlike earlier hominins, H. erectus left Africa!!! Homo erectus 1.9 - 0.14 mya - Africa, Asia, & Europe. Comparison with Australopithecus, keep in mind that these species coexisted Anatomy & behavior -Larger brain -Small back teeth -Low, long, thick skull -Small chewing muscles -Large browridge -Long legs -Increased body size -Increased tool use Unlike earlier hominins, H. erectus left Africa. They apparently moved out of African fairly quickly, and earliest evidence for this species outside of Africa is found in Dmanisi, Georgia. -A skull (below) and other remains date to 1.77mya. Let's look a bit closer at this species anatomy. The Nariokotome H. erectus skeleton (1.6mya) is remarkably complete, unlike earlier species this skeleton has human-like limb proportions -An 11 year old boy, but he was 5'6" and may have reached 6' as an adult. -Walking would have appeared very human-like -The cranial capacity of the Turkana Boy is exactly between the average chimpanzee and human

Evolution of Homo erectus

We have solid evidence for the sociability of this species, H. erectus live in groups and shared foods. -Consider this skull, from Dmanisi cave, it is an elderly individual whose teeth had fallen out long before his death, resulting in the partial deterioration of his jaw... -Stone tool technology, increased intelligence, and sociability all promoted an increase in food quality and available energy, which in turn fueled the growth of an energetically expensive brain. Brains are only about 2% of the body mass, they eat up 20% of the body's energy! Having a large brain, if nutrients are scarce, could be detrimental and result in selection against it -Large brains can only evolve if there is ample nutrition, which clearly happened with H. erectus; a great example of how culture and biology interact in human evolution -Fire likely played a crucial role in this evolution, allowing our ancestors to inhabit colder climates and allow them to access more nutrients and calories; recent evidence from Wonderwerk cave in South Africa shows H. erectus was using fire by 1 mya, and perhaps has early as 1.5 mya!

what makes our species unique

humans have exceptionally big brains and rely on material culture, turns out that these are useful traits for understanding our genus as well. -although we find stone-tool technology used by Australopithecus genus, it is a combination of stone tool culture, larger brain size, and smaller tooth anatomy that can be used to identify our own genus.

On the trail of first hominins- where to look? Africa or Asia?

in 1887, a young Eugene Dubois, began his search in Indonesia based on his reading of Darwin and Haeckel, the later predicted that a missing link would be discovered in Asia, because of the similarity between humans and orangutans (or so he thought) -Haecklel named his species Pithecanthropus Erectus.

Homo erectus in China

A LOT of fossil evidence for this species comes from China, where evidence has been collected for more than a century, which is why it was once referred to as Peking (北京) Man. -Majuangou - 1.7mya, stone tools and animal bones with cutmarks on them -Gongwangling - 1.2 mya H. erectus skull with a brain size of 800 cc. -Zhoukoudian- a prolific site Zhoukoudian (周口店) - in the 1920s and 1930s, remains of up to 40 individuals, including several nearly complete skulls were discovered; these fossils date to about 750,000 years old -These remains were not washed into these caves, but were places where H. erectus actually lived, we know this because of remains of stone tools and evidence for controlled fire!

Homo rudolfensis

Evidence continues to surface that H. habilis was not the only member of our genus in Africa at the time There is only one really good fossil, from Koobi Fora in the Lake Turkana basin, Kenya, it has a braincase which is considerably above that of H. habilis. Found in Eastern Africa about 1.8-1.9mya, discovered/identified in 1986 H. rudolfensis had larger molars compared to Homo habilis, slightly smaller than robust australopithecines H. rudolfensis didn't have the heavily-built jaw and strong jaw muscle attachments seen in robust australopithecines, these anatomical differences likely indicate a different diet for H. rudolfensis. Returning to the idea of one or two early Homo species. Differences in skull and brain size between two species initially seen as evidence of sexual dimorphism. However, H. rudolfensis had a slighter browridge, larger molars while H. habilis had more modern, smaller teeth; jaw shapes of two species also differed Today, most scientists recognize four species that lived in the Turkana Basin sometime between 2.0 and 1.5 million years ago: Homo rudolfensis, Homo habilis, Homo erectus, and Paranthropus boisei. . In 2012, Meave Leakey published a paper announcing the discovery of three additional fossils from northern Kenya. These new fossils date to between 1.8 and 1.9+ mya.

Homo erectus in Europe

Gran Dolina- one of the oldest sites to yield fossil evidence for Homo erectus in Europe, earliest deposits date to at least 900,000 ya (there is early evidence, but not much) -Fossils from this site and other European locations exhibit anatomical differences when compared with examples from elsewhere, including a wider nose and increased robusticity (cold adaptations)

Homo habilis to Homo erectus

H. erectus was a hunting hominin, a species which ate more meat than previous ones and is identified with the appearance of a new stone tool technology - the Acheulean. -These tools appeared about 1.8mya and remained in use until ~300,000ya. -Lomekwian, Oldowan, and Acheulean tolls comprise the Lower Paleolithic (3.3 mya - 300,000 ya)