Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings Lectures by Greg Podgorski, Utah State University Current Issues in Biology, Volume 6 Scientific American Traces of a Distant Past

Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings Concept Review Traces of a Distant Past Fifty or sixty thousand years ago, people began migrating out of Africa to ultimately populate the world These travelers were fully modern humans, and over the millennia they came to replace archaic humans living along their routes of migration Fossils and artifacts were long the only way of tracing our ancestor’s travels In the last 20 years, the DNA of peoples spread across the world has offered a new way to peer into the past

Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings Concept Review Traces of a Distant Past On average, any two people share 99.9% of their DNA sequence Within the 0.1% of DNA that sets people apart is the story of how we came to inhabit the planet

Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings Concept Review Traces of a Distant Past Mitochondrial DNA was the first DNA studied to understand human origins Mitochondrial DNA is transmitted only from mother to offspring and changes relatively quickly at a steady rate The number of differences in mitochondrial DNA sequences can be used as a molecular clock

Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings Concept Review Traces of a Distant Past The greater the number of sequence differences between individuals, the greater the time since they last shared a common ancestor The same reasoning holds for any type of DNA analysis

Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings Concept Review Traces of a Distant Past In 1987, Alan Wilson and Rebecca Cann compared mitochondrial DNA sequences among many human populations Wilson and Cann concluded that all people living today descended from a woman who lived in Africa about 200,000 years ago Since this report, many other types of DNAs have been used to examine human origins

Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings Concept Review Traces of a Distant Past The Human Genome Project made it possible to look for DNA sequence variations across the entire genome Three types of DNA sequence differences are used for learning about human origins SNPs

Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings Concept Review Traces of a Distant Past SNPs (single nucleotide polymorphisms) are the most informative type of sequence variant and are used most widely today Analysis of all types of DNA sequence variation points to an out-of-Africa hypothesis for modern human origins

Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings Concept Review Traces of a Distant Past In the out-of-Africa model, a small human population migrated from Africa and grew in size in its new home until another band eventually broke off and moved away This process was repeated again and again until the entire world was settled According to the out-of-Africa hypothesis, modern humans did not interbreed with the archaic humans they encountered and came to replace

Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings Concept Review Traces of a Distant Past A competing idea of human origins is the multiregional hypothesis In this model, populations of archaic humans that were scattered around the world gradually evolved to become modern humans

Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings Concept Review Traces of a Distant Past Because of DNA evidence, few scientists hold to a strict form of the multiregionalism hypothesis There is, however, some new evidence that suggests some interbreeding between migrating modern humans and archaic natives A project is underway to sequence the Neanderthal genome from fossilized DNA The Neanderthal genome sequence should resolve the question of whether modern human migrants and native Neanderthals interbred

Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings Concept Review Traces of a Distant Past DNA evidence shows that humans continue to evolve European populations are derived from a relatively small group of migrants In such a small group, one expects to see a reduced degree of genetic variation and the possibility of finding harmful mutations at high frequency Both expectations are met by European populations

Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings Concept Review Traces of a Distant Past One recent study of DNA variation suggests that the rate of human evolution has increased over the past 40,000 years This investigation and many others indicate that human populations continue to adapt to the regional differences they encountered since leaving Africa

Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings Concept Review Traces of a Distant Past Studies of human DNA variation discount the concept of distinct human races If a race is a population with features that clearly set it apart from any other group, then there is no race At the level of DNA, the frequency of particular sequence variants gradually changes over geographical distance, not in the all-or-none fashion expected if there were truly distinct races

Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings Traces of a Distant Past Testing Your Comprehension Modern humans began migrating from Africa roughly _______ years ago. a) 15,000 b) 50,000 c) 200,000 d) 2 million

Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings Traces of a Distant Past Testing Your Comprehension Modern humans began migrating from Africa roughly _______ years ago. b) 50,000

Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings Traces of a Distant Past Testing Your Comprehension The principle of estimating when two populations last shared a common ancestor is ________, the longer the time since a common ancestor. a) the more similar the DNA sequences b) the less similar the DNA sequences c) the slower the mutation rate d) the faster the mutation rate

Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings Traces of a Distant Past Testing Your Comprehension The principle of estimating when two populations last shared a common ancestor is ________, the longer the time since a common ancestor. b) the less similar the DNA sequences

Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings Traces of a Distant Past Testing Your Comprehension On average, any two people share ________ of their DNA sequence. a) 75% b) 90% c) 98% d) 99.9%

Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings Traces of a Distant Past Testing Your Comprehension On average, any two people share ________ of their DNA sequence. d) 99.9%

Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings Traces of a Distant Past Testing Your Comprehension Mitochondrial DNA allows tracing the line of human descent from: a) fathers to sons b) fathers to all offspring c) mothers to daughters d) mothers to all offspring

Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings Traces of a Distant Past Testing Your Comprehension Mitochondrial DNA allows tracing the line of human descent from: d) mothers to all offspring

Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings Traces of a Distant Past Testing Your Comprehension Modern humans trace their ancestry to a woman living in Africa _____ years ago. a) 20,000 b) 200,000 c) 1 million d) 2 million

Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings Traces of a Distant Past Testing Your Comprehension Modern humans trace their ancestry to a woman living in Africa _____ years ago. b) 200,000

Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings Traces of a Distant Past Testing Your Comprehension A site where the DNA sequence of two individuals differs by a single nucleotide is: a) uninformative for studies of human origins b) a copy number variation c) a microsatellite d) a SNP

Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings Traces of a Distant Past Testing Your Comprehension A site where the DNA sequence of two individuals differs by a single nucleotide is: d) a SNP

Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings Traces of a Distant Past Testing Your Comprehension According to the out-of-Africa hypothesis, migrating modern humans: a) outcompeted populations of archaic humans b) interbred with archaic humans c) were replaced by archaic humans d) arose at many locations as archaic humans evolved into modern forms

Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings Traces of a Distant Past Testing Your Comprehension According to the out-of-Africa hypothesis, migrating modern humans: a) outcompeted populations of archaic humans

Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings Traces of a Distant Past Testing Your Comprehension In a small group that breaks away from a large population, one expects to see: a) reduced genetic variation b) increased genetic variation c) a high mutation rate d) a low mutation rate

Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings Traces of a Distant Past Testing Your Comprehension In a small group that breaks away from a large population, one expects to see: a) reduced genetic variation

Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings Traces of a Distant Past Testing Your Comprehension Studies of human genetic variation indicate that there are ______ races. a) no b) roughly five c) roughly a dozen d) roughly 50

Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings Traces of a Distant Past Testing Your Comprehension Studies of human genetic variation indicate that there are ______ races. a) no

Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings Traces of a Distant Past Thinking About Science In which of the following groups would you expect to find the greatest diversity of genetic markers? a) In a set of native South American populations b) In a set of native European populations c) In a set of East African populations d) In the set of Australian Aborigine populations

Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings Traces of a Distant Past Thinking About Science In which of the following groups would you expect to find the greatest diversity of genetic markers? c) In a set of East African populations

Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings Traces of a Distant Past Biology and Society If more people understood the scientific view of race, racial tensions across the globe would be greatly reduced. Strongly Agree Strongly Disagree A. E. C. B. D.

Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings Traces of a Distant Past Interpreting Charts and Graphs Which of the following statements is NOT supported by the figures? a) In both hypotheses, modern humans (Homo sapiens) evolved from Homo erectus b) In the multiregional hypothesis, modern humans displaced Homo erectus in Asia, Africa, and Europe c) In the multiregional hypothesis, inbreeding occurred between globally distributed populations over long periods of time d) In the out-of-Africa hypothesis, populations of archaic humans in Asia and Europe were replaced relatively recently by modern humans

Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings Traces of a Distant Past Interpreting Charts and Graphs Which of the following statements is NOT supported by the figures? b) In the multiregional hypothesis, modern humans displaced Homo erectus in Asia, Africa, and Europe