IB Biology Option D D3 Human Evolution.

IB Biology Option D D3 Human Evolution

D.3.1 Outline the method for dating rocks and fossils using
radioisotopes, with reference to 14C and 40K. 14C is a naturally occurring isotope of carbon with a half life of 5730 years. Constantly being made in the atmosphere when cosmic rays cause neutrons to fuse with nitrogen nuclei and “kick out” protons Formation Decay Carbon dating – Mr. Andersen

radioisotopes, with reference to 14C and 40K. 14C production is in equilibrium with its decay to 12C The 14C is incorporated in carbon dioxide which is then taken up by plants. In the end all living things have the same ratio of 14C to 12C When an organism dies it no longer takes in 14C. So over time the ratio of 14C to 12C changes. This is measurable and can be used to estimate age. The limit for accurate determination of age is about 50,000y

radioisotopes, with reference to 14C and 40K. 40K is an isotope with a half life of 1.3 X 109 y 40K decays to 40Ar. When 40K is released from a volcano in lava all of the argon gas is driven off. So brand new rocks effectively have a ratio 40K: 40Ar of 100:0 Over time the lava may be weathered and eroded and incorporated into sedimentary rocks. The measured ratio of 40K to 40Ar can be used to date rocks over one million years old with an accuracy of around years

When to use which isotope? Rocks
D.3.1 Outline the method for dating rocks and fossils using radioisotopes, with reference to 14C and 40K. When to use which isotope? Rocks - K-40 - For older samples, over 100,000 years old Fossils - C-14/C-13/C-12 - For young samples, from 1000 to 100,000 years old - Lots C14 recent death; little C14, old!

D.3.2 Define half-life. Half-life = The time it takes for half of a radioactive isotope to decay What is the half life for each of the isotopes represented by these curves?

D.3.2 Define half-life. 3.42 0.13 0.7 ?.??

D.3.3 Deduce the approximate age of materials based on a
simple decay curve for a radioisotope. Play the game

Grasping pentadactyl limbs
D.3.4 Describe the major anatomical features that define humans as primates. human gibbon gorilla Grasping pentadactyl limbs Did Humans Evolve? (PBS)

D.3.4 Describe the major anatomical features that define
humans as primates. Binocular Vision

Reduced snout leading to reduced olfaction
D.3.4 Describe the major anatomical features that define humans as primates. Monkey Reduced snout leading to reduced olfaction Monkey Squirrel vs. Doggie Human

Generalized Dentition
D.3.4 Describe the major anatomical features that define humans as primates. Human Baboon Gorilla Generalized Dentition Moo Cown

D.3.4 Describe the major anatomical features that define
humans as primates. Others: Forelimbs able to twist Clavicle allows wide range of arm movement (re. the above two points: if you have a gentle and patient pet dog, give it a rub on the tummy and then move it’s forelegs, they really only move in one plane) Slower reproduction - long gestation - usually one offspring at a time Larger skull – relative to body size Large brain – more complex, more folds Better visual acuity – more of the photoreceptors have their own sensory neurons Social dependency

D.3.5 Outline the trends illustrated by the fossils of Ardipithecus
ramidus, Australopithecus including A. afarensis and A. africanus, and Homo including H. habilis, H. erectus, H. neanderthalensis and H. sapiens.

Ethiopia; similar to chimpanzee
D.3.5 Outline the trends illustrated by the fossils of: approximate dates distribution Ardipithecus ramidus 5.8 mya – 4.4 mya Ethiopia; similar to chimpanzee Australopithecus: A. afarensis 4 mya – 2.5 mya Eastern Africa; “Lucy” A. africanus 3 mya - <2.5 mya Southern Africa Ardipithecus ramidus lived approx. 5.8 million to 4.4 MYA in Ethiopia Believed to be very close to split between the line that led to human-like organisms and line that led to chimpanzee-like organisms Most fossils of this species are teeth so difficult to be sure about physical features Probably similar to chimpanzees but canines were more hominid-like Possibly bipedal

Europe, India, China, Indonesia, Africa
D.3.5 Outline the trends illustrated by the fossils of: Homo: H. habilis 2.4 mya – 1.6 mya Olduvai Gorge (Tanzania), Kenya, Ethiopia, South Africa; simple stone tools, fire, cave-dwelling H. erectus 1.8 mya – 100,000 ya Europe, India, China, Indonesia, Africa H. neandertha-lensis 200,000 – 30,000 ya Europe, Western Asia; larger brain than modern human!  H. sapiens 140,000 – 70,000 ya Africa, Europe, Asia; cave paintings; tool technology/weapons

THE HOMINIDS http://humanorigins.si.edu/resources/multimedia/videos
What does it mean to be human? (Smithsonian National Museum of Natural History)

Australopithecus afarensis
3.9 – 2.9 Mya Climate changing. Antarctic ice cap advance 5 Mya Distribution: Ethiopia, Kenya, Tanzania Cranial capacity: 380 – 450 cm3 Height: 1.07m Bipedal (footprints 3.6 Mya old) /climber U-shaped dental arcade but reduced canines Arboreal / terrestrial herbivore Australopithecus afarensis is one of the longest-lived and best-known early human species—paleoanthropologists have uncovered remains from more than 300 individuals! Found between 3.85 and 2.95 million years ago in Eastern Africa (Ethiopia, Kenya, Tanzania), this species survived for more than 900,000 years, which is over four times as long as our own species has been around. It is best known from the sites of Hadar, Ethiopia (‘Lucy’, AL 288-1 and the 'First Family', AL 333); Dikika, Ethiopia (Dikika ‘child’ skeleton); and Laetoli (fossils of this species plus the oldest documented bipedal footprint trails). Similar to chimpanzees, Au. afarensis children grew rapidly after birth and reached adulthood earlier than modern humans. This meant A. afarensis had a shorter period of growing up than modern humans have today, leaving them less time for parental guidance and socialization during childhood. Au. afarensis had both ape and human characteristics: members of this species had apelike face proportions (a flat nose, a strongly projecting lower jaw) and braincase (with a small brain, usually less than 500 cubic centimeters -- about 1/3 the size of a modern human brain), and long, strong arms with curved fingers adapted for climbing trees. They also had small canine teeth like all other early humans, and a body that stood on two legs and regularly walked upright. Their adaptations for living both in the trees and on the ground helped them survive for almost a million years as climate and environments changed. © 2008 Paul Billiet ODWS

Australopithecus africanus (Southern Ape of Africa)
3 – 2.25 Mya Cooling of climate reduced rainfall Further advance of Antarctic ice Development of scrubland and savannah Forest cover retreats Au. africanus was anatomically similar to Au. afarensis, with a combination of human-like and ape-like features. Compared to Au. afarensis, Au. africanus had a rounder cranium housing a larger brain and smaller teeth, but it also had some ape-like features including relatively long arms and a strongly sloping face that juts out from underneath the braincase with a pronounced jaw. Like Au. afarensis, the pelvis, femur (upper leg), and foot bones of Au. africanus indicate that it walked bipedally, but its shoulder and hand bones indicate they were also adapted for climbing, © 2008 Paul Billiet ODWS

Australopithecus africanus (Southern Ape of Africa)
Distribution: Southern and Eastern Africa Cranial capacity: 500 cm3 (Chimp = 400cm3) Bipedal 20 – 35 kg Rounder skull Parabolic dental arcade Longevity: 40 years maximum Scavenger of bone marrow/ brain cases Used simple tools © 2008 Paul Billiet ODWS

Homo habilis - the handy man
Mya E. Africa Scavenging significant part of the diet Cranial capacity: 600 – 800 cm3 Height: 1.20 – 1.35m Simple fashioned tools – choppers © 2008 Paul Billiet ODWS

Homo erectus – the upright man
1.8 to 0.5 Mya 0.9 Mya beginning of the Pleistocene ice age Oscillations between cold and warm periods Spread out of Africa (1.6Mya) throughout the old world Scavenging to hunting Use of a home base Pleistocene is characterized by the alternate appearance and recession of northern glaciation, the appearance and worldwide spread of hominids, and the extinction of numerous land mammals, such as the mammoths, mastodons, and saber-toothed tigers © 2008 Paul Billiet ODWS

Homo erectus – the upright man
Cranial capacity: 850 – 1100 cm3 (H. sapiens = 1350 cm3) Use of fire Height 1.55 to 1.8m Extended childhood 1st molar at 4.6 years old (H. sapiens = 5.9y) Greater longevity  52 years Speech? (Brain says: yes; spine says: no) Improved tools: Hand axes What is all this fuss about Broca's area and how does it relate to speech in Homo erectus? Broca's area, the new, deeper speech center, apparently creates a bulge in the surface of the brain. This bulge is the classical Broca's area but the bulge is due to the deeper speech center which as Walker and Shipman said, lies like a cat under the bed clothes. This bulge leaves an impression on the inside of your skull. Since skulls are fossilized, the earliest appearance of this bulge on the interior of the skull can be noted. Apes do not have a Broca's bulge.(Dean Falk, Comments, Current Anthropology, 30:2, April, 1989, p ) The earliest occurrence of Broca's bulge on the interior of the skull occurs in KNM-ER 1470 a 1.9 million year old Homo habilis. All Homo erectus' like modern man, have Broca's bulge imprinted onto the interior of the skull. This is something that no australopithecus nor ape possesses. There is another feature which is required for modern speech. It is the cranial flexion at the base of the skull. Jeff Laitman has shown that the cranial flexion was non-existent in Australopithecus, "substantial“ in erectus and fully developed with Neanderthal and modern humans. Erectus had a brain the size of a one-year-old modern human. The face of Homo erectus was not that different from its forebearers. It still had protruding jaws, no chin, thick brow ridges, and a long low skull. Its teeth were smaller than those of Homo habilis. This species grew to be up to 6 feet and they were slender which gave them ample surface area for sweating, an advantage in the tropics. Their hips were narrower than those of other hominids; this gave them great speed. They also had robust bones which helped them through a physically-demanding life. The hole in a vertebra, smaller than that of a modern humans, carried a spinal cord which was probably too small for true speech. Since Homo erectus was a meat-eater it did not need the powerful jaws that Homohabilis and earlier forms would have needed for grinding coarse vegetation. © 2008 Paul Billiet ODWS

Homo neanderthalensis (our distant cousins?!)
to years ago Europe, Middle East, into Central Asia Evolved from H. erectus populations perhaps via H. heidelbergensis, then became extinct Adapted to the ice-age conditions of temperate zone Large nose may have warmed cold air The enigma of its extinction is not explained Neandertals appeared approximately 200,000 – 30,000 years ago first discovered in Neander Valley in Germany lived throughout Europe and western Asia short, sturdy builds, faces projected slightly, chins and foreheads receded, had heavy brow ridges and jaw bones, brains (1600 cm3) and front teeth were larger than modern humans © 2008 Paul Billiet ODWS Meanderthal

Homo neanderthalensis (our distant cousins?!)
Cranial capacity: 1400 cm3 (H. sapiens = 1350 cm3) Brow ridge, long low skull Height: 1.67m Stocky build Improved sophisticated tools Sometimes buried their dead Made simple jewelry much debate exists about whether the Neandertals are a separate species from modern humans or a race of Homo sapien many researchers believe that anatomical differences between Neandertals and modern humans indicate that they were separate species – Homo neanderthalensis and Homo sapien tools included oldest known spear points (known as Mousterian tools) – more sophisticated than those of H. erectus existence of skeletons of elderly Neandertals and of Neandertals with healed fractures demonstrates that they cared for aged and the sick – indication of advanced social cooperation had rituals and buried their dead © 2008 Paul Billiet ODWS

Homo sapiens – Modern Human
From years ago to present Originating in Southern Africa then went worldwide Reached Europe about years ago Cooling of the climate during the last glacial period from about a led to their predominance over other species (e.g. H. neanderthalensis) Omnivore Alters environment Domestication of species, farming Archaic Homo sapiens appeared about 800,000 years ago descendants of Homo erectus or Homo ergaster that lived in Africa, Asia, and Europe they overlapped both Homo erectus populations and the later appearing Neandertals some researchers classify archaic Homo sapiens as a separate species, Homo heidelbergensis © 2008 Paul Billiet ODWS

Homo sapiens – Modern Human
Cranial capacity: 1350 cm3 (range 1000 to 2000 cm3) 20% of the body’s energy consumption for 5% of body mass Speech Art Extensive tool kit including new materials (bone, ivory, antler) Symbolic thought 1st molar tooth 5.9 years old Longevity 66 years © 2008 Paul Billiet ODWS

Australopithecus africanus Australopithecus afarensis
**Skulls not to scale Ardipithecus ramidus Australopithecus africanus Australopithecus afarensis Homo neanderthalensis Homo habilis Homo erectus Homo sapiens

Homo erectus Australopithecine Gorilla Modern human Neanderthal 29

From the previous two slides you can see:
D.3.5 Outline the trends illustrated by the fossils of Ardipithecus ramidus, Australopithecus including A. afarensis and A. africanus, and Homo including H. habilis, H. erectus, H. neanderthalensis and H. sapiens. From the previous two slides you can see: enlargement of the brain case shortening of the face loss of brow ridges You can’t really see it but the hole in the bottom of the skull where the spinal cord exits the brain (foramen magnum) is further forward in modern humans. This distributes the weight of the head over the spine so that modern humans do not need huge necks muscles.

ramidus, Australopithecus including A. afarensis and A. africanus, and Homo including H. habilis, H. erectus, H. neanderthalensis and H. sapiens. Homo sapiens Pan troglodytes (chimpanzee)

ramidus, Australopithecus including A. afarensis and A. africanus, and Homo including H. habilis, H. erectus, H. neanderthalensis and H. sapiens. The jaw has developed from a U into a V shape. Teeth have generally reduced in size. (Chimpanzee provided for comparison)

ramidus, Australopithecus including A. afarensis and A. africanus, and Homo including H. habilis, H. erectus, H. neanderthalensis and H. sapiens. Human hands are adapted for grasping and fine manipulation. In contrast gorillas have short fingers for knuckle walking and gibbons have elongated fingers and reduced thumbs for brachiating.

Skeleton, locomotion and posture
D.3.5 Outline the trends illustrated by the fossils of Ardipithecus ramidus, Australopithecus including A. afarensis and A. africanus, and Homo including H. habilis, H. erectus, H. neanderthalensis and H. sapiens. Skeleton, locomotion and posture Human knees aligned under the body’s centre of gravity because femurs are angled inwards. Human legs straighten completely when walking. Human spine has additional curves to keep centres of mass of head and trunk aligned for bipedalism. Big toe not opposable in humans, which allows for an arched foot. Ratio legs:arms greater for humans than other apes Human pelvis broader

ramidus, Australopithecus including A. afarensis and A. africanus, and Homo including H. habilis, H. erectus, H. neanderthalensis and H. sapiens. Neoteny, also called juvenilization or pedomorphism, is the retention, by adults in a species, of traits previously seen only in juveniles.

Some human characteristics thought to be a result of Neoteny:
D.3.5 Outline the trends illustrated by the fossils of Ardipithecus ramidus, Australopithecus including A. afarensis and A. africanus, and Homo including H. habilis, H. erectus, H. neanderthalensis and H. sapiens. Some human characteristics thought to be a result of Neoteny: Lack of body hair Small teeth and reduced numbers of teeth Prolonged growth period Long life span Flat face and thin skull bones Lactase production in adults Epicanthic eye fold Small nose Longer trunk relative to arms and legs 36

D.3.6 State that, at various stages in hominid evolution,
several species may have coexisted. Doesn’t necessarily mean they lived together/near each other...just means fossils present at same time A. afarensis & A. africanus ~ 3mya A. africanus & H. habilis ~2mya H. neanderthalensis, H. erectus, and H. sapiens ~100,000 yrs ago

THE CHANGING TREES OF HUMAN EVOLUTION
© 2008 Paul Billiet ODWS

1960 Up the ladder The idea that one species smoothly evolves from one into another is regarded today as an oversimplification Unfortunately it is a very persistent view that continually resurfaces in cartoons Australopithecus Homo erectus Homo sapiens Public Domain Images © 2008 Paul Billiet ODWS

Branching out Homo sapiens Homo erectus Homo habilis Australopithecus africanus A. robustus A. boisei Australopithecus afarensis “Lucy” Added 1974 The 1960s and 1970s were a fertile period for fossil hunting in Africa The idea developed that more than one hominid species existed at the same time developed © 2008 Paul Billiet ODWS

Australopithecus afarensis
Changing status As more specimens were found a clearer idea developed of the relationships between them Homo sapiens Homo erectus Homo habilis A. africanus A. robustus A. boisei Australopithecus afarensis © 2008 Paul Billiet ODWS

2001 From a tree to a bush Homo sapiens Homo neanderthalensis
? 1 Ma 2 Ma 3 Ma 4 Ma Homo sapiens Homo erectus Homo habilis A. africanus P. robustus Paranthropus boisei Australopithecus afarensis Australopithecus anemensis Ardipithecus ramidus P. aethiopicus Homo rudolfensis H. ergaster H. heidelbergensis Homo neanderthalensis A. garhi © 2008 Paul Billiet ODWS

2003 DEEPER ROOTS ? 1 Ma 2 Ma 3 Ma 4 Ma 5 Ma 6 Ma 7 Ma
Homo sapiens Homo erectus Homo habilis A. africanus Paranthropus robustus Paranthropus. boisei Australopithecus afarensis Australopithecus anemensis Ardipithecus ramidus P. aethiopicus Homo rudolfensis H. ergaster H. heidelbergensis Homo neanderthalensis A. garhi Orrorin tugensis Gorilla gorilla Sahelanthropus tchadensis “Toumai” Pan trogolodites © 2008 Paul Billiet ODWS

D.3.6 State that, at various stages in hominid evolution,
several species may have coexisted.

D.3.7 Discuss the incompleteness of the fossil record and the
resulting uncertainties about human evolution. Reasons for the incompleteness of the fossil record: fossils only form when buried under sediment before decomposition occurs; animal bodies are usually eaten by detrivores, decomposed by bacteria, or broken down chemically of remains fossilized, most remain buried in sediment/ remain unfound; Measurements imprecise b/c age differences of organisms at death (juvenile  adult) It isn’t easy to create a collection of fossils that clearly show the change of species from one to another. Fossils rarely result when an animal dies for the following reasons: Decomposition is usually rapid; soft body parts are rarely fossilized Scavengers usually break up skeletons and even chew up bones The conditions have to be just right for fossilisation to occur. Only a tiny, tiny, tiny fraction of all of the fossils in existence have been found. TOK: Paleoanthropology is an example of the diverse aspects of science, in that it is a data-poor science with largely uncontrollable subject matter. Paradigm shifts are more common in a data-poor science. The discovery of small numbers of fossils has caused huge changes in theories of human evolution, perhaps indicating that too much has been constructed on too little. Conversely, discoveries such as those made in Dmanisi, Georgia, provide examples of falsification of earlier held positions indicating why paleoanthropology can be considered a science.

resulting uncertainties about human evolution. Reasons for the incompleteness of the fossil record: hominid fossils that have been found may or may not be representative of hominid history; hominid fossils that have been found are usually partial, and the remainder of the organism must be inferred/ inferences may or may not be correct; only hard parts of individuals fossilize, leaving many questions concerning the rest of the individual’s phenotype; It isn’t easy to create a collection of fossils that clearly show the change of species from one to another. Fossils rarely result when an animal dies for the following reasons: Decomposition is usually rapid; soft body parts are rarely fossilized Scavengers usually break up skeletons and even chew up bones The conditions have to be just right for fossilisation to occur. Only a tiny, tiny, tiny fraction of all of the fossils in existence have been found. TOK: Paleoanthropology is an example of the diverse aspects of science, in that it is a data-poor science with largely uncontrollable subject matter. Paradigm shifts are more common in a data-poor science. The discovery of small numbers of fossils has caused huge changes in theories of human evolution, perhaps indicating that too much has been constructed on too little. Conversely, discoveries such as those made in Dmanisi, Georgia, provide examples of falsification of earlier held positions indicating why paleoanthropology can be considered a science.

resulting uncertainties about human evolution. The large gaps in the human evolution fossil record are consistent with punctuated equilibrium The following four slides show how the gaps are filled over time with new discoveries. The graphs plot cranial size against the age of the fossil.

D.3.8 Discuss the correlation between the change in diet and
increase in brain size during hominid evolution. The benefits of a bigger brain include: More complex tools Mastery of fire Cooking Warmth Protection Greater behavioral flexibility (less reliance on instinct and better able to learn and pass on knowledge necessary to adapt to an environment)

increase in brain size during hominid evolution. The cost of having a big brain: Longer gestation period Years of development before young can look after themselves Much more brain development occurs post birth that for any other animal

increase in brain size during hominid evolution. In summary: Big brains are energetically expensive. The mother must take in lots of energy not only during pregnancy, but for a significant time after. Hominids needed to increase their energy uptake. Bigger brain...need more energy! More food in diet or energy & protein-rich food  Hominids! (more meat in diet) Hunting tools, social groups Better diet feeds bigger brain Bigger brain then allows tool development, hunting techniques, etc. Further skills...cooking food  easier to digest, less energy required Problem...Neanderthals had HUGE brains...

increase in brain size during hominid evolution. The solution to this energy crisis was to swap a diet of these:

increase in brain size during hominid evolution. For some chunks of this: The increase in brain size observed in hominid fossils has been closely correlated with an increased intake of meat. A bigger brain made hunting and killing easier

D.3.9 Distinguish between genetic and cultural evolution.
Genetic evolution refers to the genetic changes that have occurred during the evolution of hominids. e.g. increased brain size, spine shape, position of knee Cultural evolution is the changing of ideas held and actions carried out by societies and the transmission of these ideas through social learning from one generation to the next. e.g. the use of fire, agriculture, tools, weapons, religion, beliefs The cultural evolution has spanned millions of years in three major stages: the nomadic (hunting), agricultural (settled), and industrial ages. However, we have not changed biologically in any significant way. We could take a baby from 80,000 years ago, raise it in a modern environment and it would be indistinguishable from other humans in terms of intelligence and social capabilities.

D.3.9 Distinguish between genetic and cultural evolution. Genetic
Inherited, parent to child only Body morphology (e.g. increased brain size, spine shape, position of knee) # chromosomes Biochemicals Cultural Acquired knowledge, passed on to many in the group/family, generation to generation (e.g. the use of fire, agriculture, tools, weapons, religion, beliefs) Language Customs/rituals Art Technology The cultural evolution has spanned millions of years in three major stages: the nomadic (hunting), agricultural (settled), and industrial ages. However, we have not changed biologically in any significant way. We could take a baby from 80,000 years ago, raise it in a modern environment and it would be indistinguishable from other humans in terms of intelligence and social capabilities.

Comparison D.3.9 Distinguish between genetic and cultural evolution.
The product of natural selection The product of learning. the transmission of acquired behaviour characteristics Darwinian Lamarkian Innate not modified during the organism’s life time Learned during the life time Passed on through hereditary information Passed on to kin (family), social group, population, within a generation and between generations Slow change Fast change © 2008 Paul Billiet ODWS

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