Human Evolution D.3 Chapter 15

D.3.1: Outline a method for dating rocks and fossils using radioisotopes, with reference to 14 C and 40 K Fossils, or the rocks containing fossils can be dated using radioisotopes –When an atom of a radioisotope decays, it changes into another isotope and gives off radiation –Isotopes: different number of neutrons in an element

D.3.1: Outline a method for dating rocks and fossils using radioisotopes, with reference to 14 C and 40 K Radiocarbon dating: the % of surviving 14 C atoms in a sample is measured –Useful in dating samples that are between ,000 years old –C-14 and C-12 are present in living organisms Once an organism dies it no longer takes in C-14 and the existing C-14 decays

D.3.1: Outline a method for dating rocks and fossils using radioisotopes, with reference to 14 C and 40 K Potassium-argon dating: the % of surviving 40 K atoms and daughter 40 Ar atoms are measured –Used to measure the age of rocks –Useful in dating samples older than100,000 years old.

D.3.2: Define half-life The number of years it takes 50% of the sample to decay – 14 C half-life is 5730 years – 40 K half-life is 1.3 billion years # half lives# years passed% original radioisotope remaining % % % %

D.3.3: Deduce the approximate age of materials based on a sample decay curve for a radioisotope To be done in radioactive decay lab

D.3.4: Describe the major anatomical features that define humans as primates Opposable thumbs : allows for grasping hands and feet Long, thin, straight fingers : fine motor skills Fingernails instead of claws Shoulder flexibility (socket) : for greater mobility (swinging in trees) Forward-facing eyes : stereoscopic (3D) vision and depth perception Extensive care of young

D.3.5: Outline the trends illustrated by the fossils of... Approximate datesDistribution Ardipithecus ramidus MYAEthiopia Australopithecus afarensis Lucy MYAEastern Africa Australopithecus africanus MYASouthern Africa Homo habilis MYATanzania, Kenya, Ethiopia, S. Africa Homo erectus 1.8M – 100,000 YAEurope, India, China, Indonesia Homo neanderthalensis 200,000 – 30,000 YAEurope, W. Asia Homo sapiens 140,000 – 70,000 YAAfrica, Europe, Asia

D.3.6: State that, at various stages in hominid evolution, several species may have coexisted Examples: – Homo neanderthalensis and Homo sapiens – A. afarensis and A. africanus

D.3.7: Discuss the incompleteness of the fossil record and the resulting uncertainties about human evolution Incompleteness due to: –Bits and pieces of skulls & skeletons discovered –Discrepancy in the number of fossils found for each species –Estimations in characteristics (cranial capacity) are imprecise due to differences between males, females, and juveniles –Oldest fossils are most difficult to find because they degenerate over time

D.3.7: Discuss the incompleteness of the fossil record and the resulting uncertainties about human evolution Incompleteness results in slightly different timelines of human evolution with different dates and phylogenetic connections between species

D.3.8: Discuss the correlation between the change in diet and increase in brain size during hominid evolution The consequence of a larger brain is the need for more energy –Early hominids were foragers and ate fruit & nuts, and only on occasion meat –As tools became more sophisticated, hunting techniques improved & availability of meat increased Meat in diet + complex tools bigger brain sizes

D.3.9: Distinguish between genetic evolution and cultural evolution Genetic evolution : inherited characteristics –Body morphology (cranial capacity, skull shape, height, robustness) –Number of chromosomes –Biochemicals (blood proteins) These (features of hominids) are passed on through chromosomes.

D.3.9: Distinguish between genetic evolution and cultural evolution Cultural evolution : acquired characteristics –Language (spoken and written) –Customs and rituals (ethnic or religious) –Art (sculpture, pottery, painting) –Technology (comfort, obtaining food, warfare) These can be passed on within a social group or family.

Note: The whole process of the increase in hominid cranial capacity was through natural selection. - over-production of offspring - variation in a population so some offspring had bigger brains - bigger brains could have meant better problem solving skills thus better fitness due to an ability to find food and shelter more successfully - better fitness would increase the chances of survival - those who survived passed on their genes to the next generation

D.3.10: Discuss the relative importance of genetic and cultural evolution in the recent evolution of humans As brain size increased, so did the quality of tool-making – Genetic evolution preceded cultural evolution Genetic evolution was really important up until Homo sapiens After that, cultural evolution increased in importance – For the last several thousand years, humans have altered the environment so much that we dont need to genetically evolve We evolve tools (cultural) to better solve problems