1. IB Biology Option D D3 Human Evolution Jason de Nys IB Biology Option D D3 Human Evolution Jason de Nys All syllabus statements ©IBO 2007 All images CC or public domain or link to original material. http://commons.wikimedia.org/wiki/File:Human-evolution.jpg http://commons.wikimedia.org/wiki/File:LB1_skull.jpg

2. D.3.1 Outline the method for dating rocks and fossils using radioisotopes, with reference to 14 C and 40 K. 14 C is a naturally occurring isotope of carbon with a half life of 5730 years It is constantly being made in the atmosphere when cosmic rays cause neutrons to fuse with nitrogen nuclei and “kick out” protons http://en.wikipedia.org/wiki/File:Carbon_14_formation_and_decay.svg 14 C production is in equilibrium with its decay to 12 C The 14 C is incorporated in carbon dioxide which is then taken up by plants. In the end all living things have the same ratio of 14 C to 12 C When an organism dies it no longer takes in 14 C. So over time the ratio of 14 C to 12 C changes. This is measurable and can be used to estimate age. The limit for accurate determination of age is about 50,000y Formation Decay

3. 40 K is an isotope with a half life of 1.3 X 10 9 y It decays to 40 Ar. When 40 K is released from a volcano in lava all of the argon gas is driven off. So brand new rocks effectively have a ratio 40 K: 40 Ar of 100:0 Over time the lava may be weathered and eroded and incorporated into sedimentary rocks. The measured ratio of 40 K to 40 Ar can be used to date rocks over one million years old with an accuracy of around 50000 years

5. D.3.2 Define half-life. Simulation of many identical atoms undergoing radioactive decay, starting with either four atoms (left) or 400 atoms (right). The number at the top indicates how many half-lives have elapsed http://en.wikipedia.org/wiki/File:Halflife-sim.gif The time it takes for half of a radioactive isotope to decay

6. What is the half life for each of the isotopes represented by these curves? http://en.wikipedia.org/wiki/File:Plot-exponential-decay.svg

7. 3.420.130.7 ?.??

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

9. D.3.4 Describe the major anatomical features that define humans as primates. http://www.flickr.com/photos/johnkay/5901639745/ http://www.flickr.com/photos/shannonkringen/5466678956/ http://www.flickr.com/photos/grendelkhan/1160017887/ human gibbon gorilla Grasping pentadactyl limbs

10. http://www.flickr.com/photos/patries71/3038074728/ http://www.flickr.com/photos/tambako/5289604279/ http://www.flickr.com/photos/kevenlaw/2260970300/ http://www.flickr.com/photos/pezz/447411079/ http://www.flickr.com/photos/maessive/62526827/ Binocular Vision

11. http://www.flickr.com/photos/21185968@N00/3760968061/ http://www.flickr.com/photos/tomitapio/4566585948/ http://www.flickr.com/photos/aechempati/5419119893/ http://www.flickr.com/photos/tambako/4561359690/sizes/l/in/photostream/ Reduced snout leading to reduced olfaction vs. Squirrel Doggie Monkey Human

12. http://www.flickr.com/photos/philman/2755063715/ http://www.flickr.com/photos/patries71/3149890871/ http://www.flickr.com/photos/mugley/3280473929/ http://www.flickr.com/photos/plasticbrain/4243519977/ Generalised Dentition Human Baboon Gorilla Moo Cown

13. 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

14. 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.

15. http://commons.wikimedia.org/wiki/File:Ardi.jpg http://commons.wikimedia.org/wiki/File:Australopithecus_afarensis_reconstruction.JPG http://commons.wikimedia.org/wiki/File:Australopithecus_africanus_face1_(University_of_Zurich).JPG http://commons.wikimedia.org/wiki/File:Homo_habilis-KNM_ER_1813.jpg http://commons.wikimedia.org/wiki/File:Broken_Hill_Skull_(Replica01).jpg http://commons.wikimedia.org/wiki/File:Homo_sapiens_neanderthalensis.jpg http://www.flickr.com/photos/53898309@N00/2211288333/ Ardipithecus ramidus Australopithecus africanus Australopithecus afarensis Homo habilis Homo erectus Homo neanderthalensis Homo sapiens Skulls not to scale

16. 1. Gorilla 2. Australopithecine 3. Homo erectus 4. Neanderthal (La-Chapelle-au-Seine) 5. Steinheim Skull 6. Modern human http://commons.wikimedia.org/wiki/File:Craniums_of_Homo.svg

17. 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.

18. http://pandasthumb.org/archives/2006/09/fun-with-homini.html Homo sapiens Pan troglodytes (chimpanzee) http://commons.wikimedia.org/wiki/File:Human_and_chimp_brain.png

19. The jaw has developed from a U into a V shape. Teeth have generally reduced in size. (Chimpanzee provided for comparison)

20. 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. http://www.flickr.com/photos/docsearls/5500125757/ http://en.wikipedia.org/wiki/File:Western_Lowland_Gorilla.jpg http://www.flickr.com/photos/cskk/2709688102/

21. 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

22. Neoteny, also called juvenilisation or pedomorphism, is the retention, by adults in a species, of traits previously seen only in juveniles. (Wikipedia) 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

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

24. http://en.wikipedia.org/wiki/Human_evolution

26. Note that according to this interpretation of the fossil record Homo sapiens is not descended from Homo erectus or Homo neanderthalensis. However, some postulate that Homo sapiens may have hybridised with Homo neanderthalenis. This could have contributed to the disappearance of the neanderthals in much the same way that indigenous animals like dingos are in danger of extinction due to breeding with domestic dogs. http://en.wikipedia.org/wiki/File:Humanevolutionchart.png

27. TOK Read the article on Wikipedia about Homo floresiensisHomo floresiensis Discovered in 2004 on the Indonesian island of Flores, it has stirred up controversy in the palaeoanthropological world. Is it a separate species or is it the remains of diseased Homo sapiens. You be the judge! Short PBS video

28. D.3.7 Discuss the incompleteness of the fossil record and the resulting uncertainties about human evolution. 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 fossilised 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.

29. Skulls and teeth are usually the parts of the ancestral hominids that survive to be fossilised and found Therefore there is a lot of conjecture as to where they all fit in the family tree. Hypotheses are often overturned by new discoveries that rewrite the relationships between the species. http://www.flickr.com/photos/brentdanley/2205021283/

30. http://www.flickr.com/photos/prfr/3196435827/ 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.

31. 1850 http://en.wikipedia.org/wiki/Transitional_fossil

32. 1900 http://en.wikipedia.org/wiki/Transitional_fossil

33. 1950 http://en.wikipedia.org/wiki/Transitional_fossil

34. 2002 http://en.wikipedia.org/wiki/Transitional_fossil

35. Despite the fossil evidence we have so far, there are still large gaps in our knowledge We have no fossil for the last common ancestor of humans and chimpanzees It is believed to have lived 6-8 million years ago Find out how this estimate was determined http://www.flickr.com/photos/owenbooth/126288240/

36. 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 Wamth Protection Greater behavioural flexibility (less reliance on instinct and better able to learn and pass on knowledge necessary to adapt to an environment) http://madsenworld.dk/anigif/light/flames.gif http://commons.wikimedia.org/wiki/File:Miscellaneous_stone_tools.jpg

37. 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 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. http://www.flickr.com/photos/superbomba/2288271254/

38. The solution to this energy crisis was to swap a diet of these: http://www.flickr.com/photos/heydrienne/22080973/

39. 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

40. D.3.9 Distinguish between genetic and cultural evolution. Well gosh, we know all about genetic evolution by now! In this context it 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

41. D.3.10 Discuss the relative importance of genetic and cultural evolution in the recent evolution of humans. TOK Read this article: Are We Still Evolving? What do you think of the arguments for and against this proposition?

42. 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. The cultural evolution has spanned millions of years in three major stages: the nomadic (hunting), agricultural (settled), and industrial ages. http://www.flickr.com/photos/wallyg/415498335/

43. BBC Website Further information: Excellent site!