14 | A NCIENT BONES The upper jawbone found by a Bavarian soldier in Pikermi and now in the collection of the Bavarian State Collection for Palaeontology and Geology in Munich. It was used by Johann Andreas Wagner in 1839 to document a species he named Mesopithecus pentelicus. An almost complete skull of Mesopithecus pentelicus THE GREEK ADVENTURE | 17 Detail of bone fragments from Pikermi. Embedded in the fine-grained red sedimentary rock is a chaotic assemblage of bones, primarily from horses, antelopes, and giraffes. 30 | A NCIENT BONES the root tips of the two premolars fuse into a single power- ful root. In many of us, you can tell that the pencil-shaped roots have fused together because there is more than one root canal. The molars of great apes and humans are not the same shape, because they have different demands made on them when the animals are chewing. Different diets mean great apes and hominins (Hominini) have developed differently shaped teeth. (Hominin or Hominini is the term paleoanthro- pologists use for our species and for all our extinct ancestors who lived later than the common ancestor of humans and chimpanzees.) DiGrafikfferen 1.1-b:ces in Unterschiede DeDifferencesntition an Menschenaffd T ooin thDentition Rooen-Menschts and Toothin Bezahnung Roots Lower jaw of a modern human Molars Premolars Human Canines premolar Incisors with a single root Lower jaw of a chimpanzee Molars Premolars Chimpanzee Canines premolar with a Incisors double root 32 | A NCIENT BONES between 5.8 million and 2 million years old. But when exactly had Graecopithecus lived? CT-Scan of the Lower Jawbone of Graecopithecus freybergi Root canals Roots Comparison: Premolar with partially cross section of lower jaw fused roots p3 p3 p4 p4 m1 m1 m2 m2 m3 m3 SahelanthropusGraecopithecus Inner view Outer view 34 | A NCIENT BONES calcite had formed above the sediment, as they had done in the finds from Pikermi that the Bavarian soldier thought were filled with diamonds back in 1838. The Earth’s Magnetic Field and the Principles of Paleomagnetism Earth’s magnetic field Earth's magnetic field showing normal polarity showing reverse polarity Geographic North Pole Geographic North Pole Magnetic Magnetic South North Pole Pole N S S N Magnetic Magnetic South Pole North Pole Geographic South Pole Geographic South Pole Reverse Normal Pattern Magnetized oceanic crust S N N S N S S N Lithosphere Magma rises and cools. The prevailing direction of the Earth’s magnetic field is encoded in rocks as they form. MAGNETOMETERS AND MICROTOMOGRAPHY | 35 The alignment of the sediment surface gave us the infor- mation we needed to reconstruct the exact orientation of the giraffe bones in the sediment. Using these fossil levels, we could deduce the Earth’s magnetic field at the time the fossils in Pyrgos were deposited. How a Fossil Level Works 1. Hollow bone 3 cm Above: Cross-sections of two girae bones from Pyrgos with crystals 2. Bone half-filled with sediment The crystal/sediment boundary marks the and water horizontal level in ancient times. Left: The formation of the paleo-horizontal line 3. Hardening of the sediment: crystals of calcite form in the hollow space. We combined the paleomagnetic data from Pyrgos, Pi- kermi, and Azmaka with data harvested from three other chronological techniques. We could then date the Graecopithe- cus fossils and the other Pyrgos finds fairly accurately: they were 7.175 million years old.9 The premolar from Bulgaria 58 | A NCIENT BONES into lesser apes—gibbons and siamangs (Hylobatidae)—and great apes (Hominidae). Great apes include all great apes living today and humans and their extinct ancestors. First, the orangutans (Ponginae) split from the lineage leading to gorillas, chimpanzees, and humans (Homininae). Then the gorillas (Gorillini) split off, and finally, the chimpanzees and bonobos (Panini), leaving the human line (Hominini). Over millions of years, early hominins (prehumans) evolved into species of early Homo (early humans), and ultimately into us: Homo sapiens. The Evolutionary Development and Diversification of Apes and Humans Gibbons Orangutans Gorillas Bonobos Chimpanzees Humans Panini Hominini 1.5–2.5 Gorillini 7–13 Ponginae 9–18 Hylobatidae Homininae 13–>20 Hominidae (Great apes) >20 Time of split in millions years Hominoidea (Apes) The search for our roots, therefore, reaches way back into the evolutionary history of primates. The changes in body shape of the different species, which evolved as they settled in new habitats and adapted to changes in climate, are the cornerstones of human evolutionary history. 64 | A NCIENT BONES stretch of the southern edge of Europe rose as the ocean floor of Tethys slid beneath it, throwing up the European mountain ranges of the Pyrenees, the Apennines, the Alps, the Dinarides, and the Balkans. The Old World, as seafarers called Afro-Eurasia at the beginning of the modern era, was coming together. And in a future only a few million years away from our present, the Mediterranean will eventually disappear completely, buried under new mountain ranges, and a new supercontinent will be formed. The Paleogeographic Evolution of the Earth Glaciers Deserts 100 million years ago Vegetation Eurasia NortNo th AmeAmmerica North Atlantic Pacific Tethys South Africa AmericA a India South Auststrraalia Atlantic AAntarctica 50 million years ago North Europe America Asia North Pacific Atlantic Africa Indiandia Southth America Indian South Ocean Atlantic Australia Antarctica 14 million years ago NNorth Europeo Asia America North Atlantic Indiaa Pacific Africa South Ammericme a Indian South Ocean Atlantic AustrA raalil a Antarcctica 18,000 years ago (the last glacial period) Euroopee NortNorth Asia America North Atlantic Africa Pacific South Indian AAmericAm a South Ocean Atlantic AAustustrraalia AAntarctica into the future Med North editerr rr NorthNor Atlantic ane an M Eurrasia AmericAmemerica ountainsunta Africa South America Pacific South Atlantic Austrstralia Antarctica Glaciers Deserts 100 million years ago Vegetation Eurasia NortNo th AmeAmmerica North Atlantic Pacific Tethys South Africa AmericA a India South Auststrraalia Atlantic AAntarctica 50 million years ago North Europe America Asia North Pacific Atlantic Africa Indiandia Southth America Indian South Ocean Atlantic Australia AntarcticaAFRICAN BEGINNINGS | 65 14 million years ago NNorth Europeo Asia America North Atlantic Indiaa Pacific Africa South Ammericme a Indian South Ocean Atlantic AustrA raalil a Antarcctica 18,000 years ago (the last glacial period) Euroopee NortNorth Asia America North Atlantic Africa Pacific South Indian AAmericAm a South Ocean Atlantic AAustustrraalia AAntarctica into the future Med North editerr rr NorthNor Atlantic ane an M Eurrasia AmericAmemerica ountainsunta Africa South America Pacific South Atlantic Austrstralia Antarctica 70 | A NCIENT BONES soil were moved, leading to the discovery of thousands of fossils,28 including three genera of great apes (Dryopithecus, Anoiapithecus, and Pierolapithecus) from the middle phase of great ape evolution.29 Paleogeography 10 Million Years Ago and Great Ape Finds 1 Dryopithecus 2 Pierolapithecus 3 Danuvius 4 Hispanopithecus 5 Rudapithecus 6 Ouranopithecus 3 5 7 Oreopithecus 1 1 8 Graecopithecus Iberia Paratethys 8 9 Sahelanthropus 7 6 10 Trachilos footprints 1 2 4 Anatolia 8 10 Mediterranean Africa Arabia 9 Fat Reserves for Lean Times During the middle phase of great ape evolution, deciduous trees such as oaks and beeches were crowding out their tropical counterparts in many parts of Europe and Asia. At the same time, animals that flourished in the heat, such as crocodiles, snakehead fish, and chameleons, were also disap- pearing. It took time for the apes from Africa to adjust to the new vegetation of Eurasia, and they found themselves fac- ing considerable challenges. For example, unlike in Africa, PROGRESS IN EUROPE | 77 Geological Epochs and Important Genera of Hominoids s ear y f o s ds h Africa Europe ons o i oc er Tarantian Milli P Ep y e Chibanian n e oc t Calabrian s i e uaternar l Q Homo Homo P Gelasian olution Piacenzian e d phase n e Australopithecus oc eat ape ev Pli Zanclian 5 Ardipithecus The thir of gr Orrorin Trachilos footprint Messinian Sahelanthropus Graecopithecus Ouranopithecus Hispanopithecus n Tortonian Rudapithecus 10 olutio ond phase of Danuvius eat ape ev gr e Pierolapithecus The sec en Dryopithecus g Serravalian Neo e n Kenyapithecus Kenyapithecus e oc i M 15 Langhian Afropithecus olution Burdigalian eat ape ev Ekembo The first phase of gr 20 Aquitanian Paleogene 102 | A NCIENT BONES angle slightly inward so the knees end up directly beneath the body’s center of gravity. Upright Gait The human foramen magnum (the hole at the base of the skull through which the spinal cord passes) is centered under the skull. This balances the head more eciently over the neck. The human spine is S-shaped and acts like Great apes need strong neck muscles, because the a spring when we walk foramen magnum is located at the back of the skull upright. above the neck In humans, the upper ribcage is wide, allowing the shoulder blades to move backward, which frees up the arms. The human The longer shoulder blades of great thighbone is long apes lie to each side of their narrow and straight. upper ribcage, which makes it easier The knee, when for them to move their arms when they straightened, is are walking on all fours. below the body’s center of gravity. In great apes, the knee is always bent and oset from the body’s center of gravity. The thighbone is short and curved. The human pelvis is shallow, wide, and bowl-shaped. The lumbar spine bends, which leads to flexible hips and strong Humans have a compact walking foot. The back muscles so the upper body can be ball of the foot is pronounced and the big toe held upright. is elongated and aligns with the other toes.