19 - 19/02/2008 10:34:00 Haviland Chap. 5 8 million years...

Info iconThis preview shows pages 1–6. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: 19/02/2008 10:34:00 Haviland Chap. 5 8 million years of evolution outline macroevolution and the process of specialization hominid evolution human evolution o anatomically modern peoples and the upper Paleolithic Macroevolution and Specialization Formation of a new species Species concept is fuzzy Speciation in Fossil record Only Phenotype in fossil record Genotype someday Speciation Inferred in fossil record when species changes over time or different forms appear Anagenesis (evolution within species) Cladogenesis (evolution into more than one species) Anagenesis Sustained shift in a populations average characteristics May lead to speciation from ancestor population Factors in anagenesis o Random mutation o Gene flow o Natural selection o Genetic drift Random changes in the gene pool Population bottleneck Gamete sampling Genes are passed to new generations in frequencies unlike those of past generations Recessive genes not masked Founder effect Fission of a population from leads to two or more genetically distinct separate populations Cladogenesis An ancestral population gives rise to two or more descendent population (branching) Isolating Mechanisms Factors that can separate breeding flow and lead to new species Speciation in fossil record Rapid change or slow Transitional forms show both Darwinian gradualism Speciation through adaptation (long periods of transition) Punctuated equilibrium Stephen Jay Gould and Niles Eldredge: o Macroevolution occurs via long periods of stability or stasis punctuated by periods of rapid change The Cenozoic Era 200,000 ya anatomically moderns humans 8-5 mya humans, chimps, gorillas separate lines 23 mya: first hominoids(ape-like) 40 mya: old world/new world types split 65 mya: first primates Hominids Hominids are those hominoids in the fossil record that are bipedal Not all hominids are necessarily human ancestors(but may share common ancestor) Hominids Bipedalism preceded brain expansion, and played a pivotal role in setting us apart from apes Piltdown Man (fraud) 1912, Sussex England big brain ape jaw 1950s hoax uncovered (but many were already skeptical) Piltdown Exposed prejudice and preconceived notions about human evolution A lesson learned Bipedalism Why? o Must have had important evolutionary advantage o Reduces heat stress o Frees the hands o Efficiency of movement o Advantageous in mixed savanna forest environments Disadvantages of bipedalism o Not fast o Visibility to predators o Cant change direction very quickly o Exposes soft underbelly o Climbing Difficult o injury to leg devastating o Other health problems 19/02/2008 10:34:00 2/21/08 From last time Macroevolution, speciation Anagenesis/cladogenesis Isolating mechanisms Gradualism/punctuated EQ Hominoids vs. Hominids o Hominids are Bipedal Earliest Hominids...
View Full Document

Page1 / 27

19 - 19/02/2008 10:34:00 Haviland Chap. 5 8 million years...

This preview shows document pages 1 - 6. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online