The Genus Homo Study Guide

The Genus Homo 1. Understand the biological and cultural features of the earliest species of Homo. Key hominin fossil discoveries announced in 2015 included, first, a jaw fragment found in Ethiopia dating back to 2.8 million years ago, that appears to be the earliest known member of the genus Homo, and second, finds at South Africa’s Rising Star cave of more than 1,500 bone, representing at least 15 individuals, which have been assigned to a new species, H. naledi. Based on their mix of primitive and modern features, these fossils, originally undated, could have been between 3 and 2 million years ago. Four hominin species coexisted in Africa around 2 million years ago. They were Paranthropus (2.4-1.0 million years ago), H. rudolfensis (2.4?-1.78 million years ago), H. habilis (2.8?-1.44 million years ago), and H. erectus (1.9-0.5? million years ago). Compared with the austrolopiths, dental, facial, and cranial robustness was reduced in early H. habilis and H. erectus. H. erectus extended the hominin food quest to the hunting of large animals and was the first hominin to achieve modern body size and form. H. erectus's average cranial capacity doubled the austrolopith average. Tool complexity and archaeological evidence for cooperative hunting suggest a long period of enculturation and learning. H. erectus extended the hominin range beyond Africa to Asia and Europe. 2. Recall the adaptive strategies of H. erectus and the role they played in its expansion out of Africa and into most parts of the Old World. Hominins migrated out of Africa in multiple waves, and the first to expand was H. erectus between 2 and 1 million years ago. H. erectus initiated the expansion of hominins beyond Africa. Small groups broke off from larger ones and moved a few miles away. They foraged new tracts of edible vegetation and carved out new hunting territories. Through population growth and dispersal, H. erectus gradually spread and changed. Fueling this expansion was commitment to an essentially human lifestyle based on hunting and gathering. The main Lower Paleolithic toolmaking tradition used by H. erectus was the Acheulean. Archaeological evidence for tools illustrating such a mental template confirms a cognitive leap between earlier hominins and H. erectus. a. More sophisticated tools helped H. erectus expands its range b. Biological changes also increased hunting efficiency c. Rugged, but essentially modern skeletons, permitted long-distance stalking and endurance during the hunt d. The body was much larger and longer-legged than those of previous hominins, permitting longer-distance hunting of the large prey e. Increased cranial capacity has been a trend in human evolution f. Language was an additional advantage —> archaeological evidence confirms the cooperative hunting of large animals and the manufacture of complicated tools g. Fire was a part of the history of H. erectus h. As hominins became more carnivorous, they expanded their home ranges in accordance with those of the animals they hunted i. Meat-rich diets provided higher-quality protein and fat as fuel; once hominins developed stronger bodies, they could (and had to) spread out 3. Describe the Middle Pleistocene hominins, including when and where they lived, and how they are related to H. erectus and the Neandertals. (781,000-126,000 B.P.); Throughout the Pleistocene epoch, several ice ages occurred. Hominin fossils found in association with animals known to occur in cold or warm climates permit us to date them to a glacial or interglacial period. The species name H. heidelbergenesis is commonly used to refer to a group of Middle Pleistocene hominins that lived in Europe, Asia, and Africa between roughly 850,000 and 200,000 B.P. H. heidelbergenesis overlaps with when H. erectus was alive, but occurs right before the beginning of the Neandertals. Some of the earliest likely members of H. heidelbergenesis come from Northern Spain’s Atapuerca Mountains. 4. Describe the Neandertals, including when and where they lived, how they are related to other species of Homo, and how they adapted to a cold region. Neandertals were first discovered in western Europe. The first one was found in 1856, and scientists had trouble interpreting the discovery because even though it was clearly human, it was different enough from modern Europeans to be considered abnormal. There have been numerous subsequent discoveries of Neandertals in Europe, the Middle East, and extending eastward to central Asia and even Siberia. By 75,000 B.P., Neandertals faced extreme cold as the Wurm glacial began. To deal with this new environment, they made more elaborate tools, and hunted reindeer, mammoths, and woolly rhinos. The Neandertals were stocky, with large trunks relative to limb length (a phenotype that minimizes surface area and thus conserves heat). Another adaptation to extreme cold was the Neandetal’s face, which has been likened to an H. erectus face that has been pulled forward by the nose. The massive nasal cavities of Neandertals suggest that they had long, broad noses which were beneficial for warming and moistening the air. They had huge front teeth, which probably did many jobs later done by tools. The front teeth show heavy wear, suggesting that they were used for varied purposes, including chewing animal hides to make soft winter clothing. a. The current prevailing view proposes that H. heidelbergenesis split into separate groups: one ancestral to the Neandertals, and the other ancestral to AMHs, who first reached Europe around 45,000 B.P. b. The bones and skull of Neandertals were generally more rugged and had greater sexual dimorphism than those of AMHs c. Unlike Neandertals, AMHs were tied into regional social networks 5. Describe who the Denisovans were and how they were related to the Neandertals. The Denisovans are identified as distant cousins to Neandertals. They got their name from Denisova, a cave in Southern Siberia where their traces have been found. One of the traces found in the cave was a molar of a child, and the child is estimated to have lived between 150,000 and 100,000 years ago. Following a complete extraction of the Denisovan genome, the DNA suggests that the split between Denisovans and Neandertals happened around 400,000 years ago. The Neandertals spread to the west, while the Denisovans headed east. 6. Explain the DNA links between Neandertals, Denisovans, and anatomically modern humans. Based on ancient DNA analysis, the common ancestor of the Neandertals, Denisovans, and AMHs lived between 765,000 and 550,000 B.P. The descendants of that common ancestor split into two lineages between 473,000 and 445,000 B.P. One lineage was jointly ancestral to Neandertals and Denisovans, while the other led to AMHs. Inbreeding in Europe between Neandertal ancestors and very early AMH emigrants from Africa sometime before 270,000 B.P. contributed AMH mtDNA to the Neandertal gene pool. That AMH mtDNA eventually replaced ancestral Neandertal mtDNA, which explains why Neandertal mtDNA resembles modern mtDNA more than it does either Denisovan mtDNA or the mtDNA extracted from 430,000 year old Neandertal-like fossils found in the Spanish cave of Sima de los Huesos. 7. Recall the characteristics of Homo floresiensis. The discovery of bones and tools of a group of tiny primitive humans who inhabited the Liang Bua cave on Flores, an Indonesian island 370 miles east of Bali. H. floresiensis dates back 700,000 years. At 3.5 feet tall, these tiny hominins lived, hunted, and gathered, on Flores until at least 60,000 B.P. One of their most surprising features is a very small skull, slightly than a chimpanzee average. The lower limbs and feet were apelike, and the big toe was stubby like a chimp’s. Their feet were large, more than 7.5 inches, and these promotions, similar to African apes, had never been seen before. H. floresiensis must have been influenced by the same evolutionary forces that reduced the size of the elephants. There is evidence that AMHs reached Flores by 46,000 B.P., and their arrival may have ultimately hastened the extinction of the tiny hominins. 8. Define the following terms (and provide any examples from the text and lecture): a. Acheulean- lower Paleolithic tool tradition associated with H. erectus b. AMHs- anatomically modern humans c. Glacials- major advances of continental ice sheets in Europe and North America d. H. erectus- a highly successful form of early human, expanded from Africa into Eurasia by 1.77 million years ago (1.9-0.5 million years ago) e. H. habilis- an early hominin species (2.8?-1.44 million years ago) that was first discovered by L.S.B. and Mary Leakey in 1960; named habilis, meaning “able”, for their presumed ability to make tools f. H. heidelbergensis- a hominin group that lived in Europe, Africa, and Asia from about 850,000 to about 200,000 B.P. g. Interglacials- extended warm periods between glacials h. Mousterian- a middle Paleolithic toolmaking tradition associated with Neandertals i. Neandertals- distinctive hominin group that inhabited Europe and the Middle East from 130,000 to 39,000 B.P. j. Paleolithic (Upper, Middle, Lower)- Old Stone Age, including lower (early), middle, and upper (later) k. Mesolithic- the middle part of the Stone Age, between the Paleolithic and Neolithic eras l. Pleistocene- main epoch (2.6 million years ago to 10,000 B.P.) of evolution of Homo