Evolution Problem Drill 10: Human Evolution

Transcription

1 Evolution Problem Drill 10: Human Evolution Question No. 1 of 10 Question 1. Which of the following statements is true regarding the human phylogenetic relationship with the African great apes? Question #01 (A) Humans evolved from the African great apes. (B) Humans and the African great apes most recent common ancestor was a hominid. (C) Humans are most closely related to chimpanzees, with the split happening approximately 5.4 mya. (D) Humans are most closely related to chimpanzees, with the split happening approximately 200,000 ya. Humans did not evolve from the African great apes, but share a common ancestor with the African great apes. Hominids include species in the modern human lineage AFTER the split from the African great apes. This does not include the most recent common ancestor of the two lineages. C. Correct! Humans and chimpanzees are the most closely related, with the split happening approximately 5.4 mya. Humans and chimpanzees are the most closely related, however, the split between the two lineages occurred much longer ago. Humans and the African great apes share a common ancestor. The human lineage is made up of what we call Hominids and includes all species, extinct and extant, since the split from the African great apes. Morphological and molecular evidence suggests that modern humans are most closely related to chimpanzees and secondly to gorillas. Humans, chimps, and gorillas share approximately 98% of their DNA while humans and chimps share %98.4.

2 Question No. 2 of 10 Question 2. Which of the following statements is not correct regarding Hominids? Question #02 (A) Homo sapiens are the only extant species of Hominid. (B) The first Hominid lived approximately 5.4 mya. (C) The Hominid family contains the African great apes. (D) The Australopithecine known as Lucy is classified as a Hominid species. This statement is correct. There is only one currently living species from the Hominid lineage and it is Homo sapiens, or humans. This statement is correct. The split between humans and chimps occurred approximately 5.4 mya, and Hominids are the family of species that contains humans and the human ancestral species since the split from the apes. C. Correct! This statement is not correct. The Hominid family does not contain the African great apes, but the primates within the human lineage since the split from the African great apes. This statement is correct. Lucy is classified in the genus Australopithecus, which is part of the Hominid family, and a human ancestral species. Note that this question is asking for which statement is NOT correct regarding Hominids. Hominids are the family of primates that include humans and the human ancestral species since the split from the African great apes approximately 5.4 mya. Therefore, Hominids do not include any of the extant African great apes and only have one extant, or currently living, species humans, or Homo sapiens. Within the Hominid lineage are several Genera of species that lived and went extinct, including Australopithecus and several Homo species.

3 Question No. 3 of 10 Question 3. Neanderthals are classified as a Hominid and more specifically as a Homo species. Both molecular and genetic evidence suggest that humans did not evolve from Neanderthals. However, Neanderthals and modern humans lived at the same time. Scientists have questioned whether gene exchange occurred between the species before modern humans replaced the Neanderthals. What evidence listed below suggests that no interbreeding occurred? Question #03 (A) Genetic comparison of nuclear DNA between a Neanderthal fossil and modern humans indicates a split long before modern humans evolved. (B) Genetic comparison of mtdna between a Neanderthal fossil and modern humans indicates a split long before modern humans evolved. (C) Genetic comparison of mtdna between an extant Neanderthal and modern humans indicates a split long before modern humans evolved. (D) Genetic comparison of mtdna between a Neanderthal fossil and modern humans indicates that there in fact was gene flow between the two species. A genetic comparison suggests a split long before modern humans evolved, but the genetic material used was not nuclear DNA. B. Correct! mtdna was extracted from a Neanderthal fossil and compared to modern human mtdna. The result was that these two lineages split long before Neanderthals and modern humans were in contact. There are no extant Neanderthals. There is no evidence of gene flow between the two species, although they lived during the same time. Neanderthals are thought to have lived as little as 34,000 ya, which means that they lived at the same time as modern humans. However, it is unlikely that there was any gene exchange between Neanderthals and modern humans. There is both morphological and molecular evidence to support this assertion. For one, the ear canal is morphologically very different from other hominids, and genetically a comparison of mtdna from a Neanderthal fossil to human mtdna suggests a split long before modern humans evolved. Together this evidence suggests that modern humans did not evolve from Neanderthals and that Neanderthals were a separate species displaced by modern humans

4 Question No. 4 of 10 Pick the answer (4) Go back to review the core concept tutorial as needed. Question 4. The Hominid lineage became progressively more and more complex over the last 4 my. All of the following characters are unique to the Hominid lineage except which of the following? Question #04 (A) An increase in brain size that occurred faster than the increase in body size. (B) A reduction in the size of the upper and lower jaws. (C) An increase in efficiency in bi-pedal walking. (D) Enlarged ovaries and mammary glands. This character is unique to Hominids and probably resulted in the evolution of intelligence. This character is unique to Hominids and may have been due to morphological constrains accompanying increased brain size. This character is unique to Hominids and is not shared by the African great apes. D. Correct! This character is not unique to the Hominid lineage because it is also shared by the African great apes, which are not Hominids. Hominids became progressively more complex over the last 4 million years. They had an increase in brain size that was faster than an increase in body size, which resulted in the evolution of intelligence. There was a reduction in size of the upper and lower jaws, which was possibly due to a change in diet or morphological constraints accompanying increased brain size. There was also an increased efficiency in bi-pedal walking and in manual dexterity and tool use. All of these characters are unique to Hominids and are not normally found in the African great apes.

5 Question No. 5 of 10 Question 5. More and more Hominid fossils are being found throughout Africa, Europe, Asia and even Australia. This fossil evidence, and especially where this evidence is found, tells us what about the dispersal and evolution of modern humans. Choose the correct answer from the statements below. Question #05 (A) Pre-modern humans evolved in Africa, Europe, and Asia and than dispersed into Australia. (B) Pre-modern humans evolved in Africa and than dispersed into Europe, Asia and then Australia, in that order. (C) This Hominid fossil evidence tells us the time at which pre-modern humans dispersed. (D) Australopithecines are thus named because they are the only fossil remains found in Australia. This evidence suggests that pre-modern humans evolved in Africa, not simultaneously in Africa, Europe and Asia. B. Correct! Hominid fossil evidence suggests that pre-modern humans evolved in Africa and then dispersed to the other continents, eventually replacing existing species. The fossil evidence does not indicate the timing of pre-modern human dispersal, but rather the pattern of dispersal. Australopithecine fossils have not been found in Australia and their respective names have nothing in common. Only more recent pre-modern human hominid fossil remains have been found in Europe, Asia and Australia. However, ancient, pre-modern human and modern human fossil remains have all been found in Africa. This evidence indicates that pre-modern humans evolved in Africa and than dispersed into Europe, Asia and then Australia, in that order. It also suggests that pre-modern humans evolved in Africa once and not simultaneously on multiple continents. However, this evidence does not indicate when pre-modern humans dispersed, but only the pattern of dispersal.

6 Question No. 6 of 10 Question 6. Which of the following is the correct timeline within the Hominid lineage from the most ancient living species to the most recent? Question #06 (A) Australopithecus afarensis; Homo erectus; Homo habilis; Homo sapiens. (B) Australopithecus afarensis; Homo habilis; Homo sapiens Homo erectus. (C) Australopithecus afarensis; Homo habilis; Homo erectus; Homo sapiens. (D) Australopithecus afarensis; Homo erectus; Homo sapiens; Homo habilis. Homo erectus lived after Homo habilis. Homo sapiens lived after Homo erectus. C. Correct! This is the correct order of Hominid species. Homo habilis lived before Homo erectus and Homo sapiens. The split between chimpanzees and the human lineage occurred around 5.4 mya. From this point forward all species within the human lineage are considered hominids. Note that there are many more species within the Hominid lineage that are not presented here in this question. However, given these four species, the following order, from oldest to most recent, is correct. Australopithecus afarensis lived from between mya. Homo habilis lived between 1.6 and 2.4 mya and was one of the first forms of modern humans. Homo erectus is the next species on the timeline and lived between 400,000 ya and 1.2 mya. Lastly on this timeline is the species Homo sapiens, which is thought to have lived from 120,000 to the present. Homo sapiens are the only extant species of hominids.

7 Question No. 7 of 10 Question 7. Which of the following statements is not correct with respect to mtdna and the Eve theory? Question #07 (A) Because mtdna is only inherited from the mother, a direct genetic line is created, which is easier to follow. (B) mtdna has a higher rate of substitution compared to nuclear DNA, resulting in better resolution when studying closely related species, or populations within the same species. (C) mtdna normally does not recombine, so there is no change from parent to offspring, allowing scientists to follow the line of descent. (D) mtdna was used to determine the mitochondrial Eve of modern humans, who is one woman that gave rise to all modern humans. This statement is correct mtdna represents a direct genetic line. This statement is correct mtdna provides better resolution when determining phylogenetic relationships. This statement is correct mtdna does not recombine. D. Correct! This statement is not correct. Although mtdna was used to determine the mitochondrial Eve, mitochondrial Eve is not ONE woman. The Eve theory suggests that all mtdna can be traced back to one mitochondrial Eve. This is possible because mtdna is only inherited maternally and does not recombine reflecting only one historical line. In contrast, nuclear DNA is recombined among individuals through sexual reproduction and reflects several different lines. It is important to note that mitochondrial Eve is not one woman but a representation of many women who lived at the same time as the mitochondrial Eve. mtdna supports the Eve theory and the Out of Africa model of human origination and migration.

8 Question No. 8 of 10 Question 8. All of the following statements are true regarding the dating of human migration out of Africa using the molecular clock except which of the following statements? Question #08 (A) The date of migration was determined to be no more than 200,000 ya using the evolution rate of human nuclear DNA. (B) The rate of mtdna evolution in humans was determined using the date of human-chimp divergence. (C) Fossil evidence was used to determine the date of human and chimp divergence. (D) The date of migration was determined to be no more than 200,000 ya using the evolution rate of human mtdna. A. Correct! This statement is not correct. Although the migration rate was determined to be no more than 200,000 ya, it was not determined using human nuclear DNA. This statement is correct. The rate of mtdna evolution was determined using the date of human-chimp divergence. This statement is correct. Fossil evidence was used to determine the human-chimp divergence date. This statement is correct. Using the molecular clock and the evolution rate of mtdna, the migration rate was determined to be no more than 200,000 ya. The date of modern human migration out of Africa was determined using the molecular clock method. The first step in this process was to determine date of speciation between humans and chimpanzees using fossil evidence. In turn, the rate of human mtdna evolution was determined, using this date. The separation times between the mtdna lines in different human populations were then determined using this human mtdna evolution rate. Finally, the timing of separation was determined to be no more then 200,000 ya.

9 Question No. 9 of 10 Question 9. Which populations of humans should have the most genetic diversity if the Out of Africa model is the correct model explaining the migration of modern humans? Question #09 (A) Asian populations. (B) European populations. (C) North American populations. (D) African populations. Think about the genetic consequences of the founder effect. According to the Out of Africa model, modern humans evolved in Africa and then a sub-population migrated to Europe, resulting in reduced genetic variation compared to the original African population. The Americas were populated long after Africa, Europe, and Asia. D. Correct! There should be more genetic diversity within African populations compared to Non-African populations. The Out of Africa model of modern human migration, or the Replacement model, states that Homo sapiens evolved only in Africa and then migrated to Europe and Asia, replacing local Homo species with little or no interbreeding. If the Out of Africa model is correct, then Non-African populations should have reduced genetic diversity compared to African populations because of the founder effect that occurred when a sub-population of the original African population migrated out of Africa. The founding populations would not contain all of the genetic variation that existed in the original African populations.

10 Question No. 10 of 10 Question 10. If modern humans evolved only 200,000 ya, which is what the genetic evidence suggests, then why do we see such large differences in modern human skin color? Question #10 (A) Because skin color in modern humans is geographically adaptive to local light intensity conditions. (B) Because populations of modern humans with different skin colors represent different evolutionary lineages. (C) Because populations of modern humans with different skin colors are genetically very different. (D) Because skin color in modern humans a local adaptation to diet and exercise. A. Correct! Skin color in modern humans is a result of local adaptation to different light intensities. All modern humans come from the same evolutionary lineage regardless of skin color. Populations with different skin colors are not very different genetically. Skin coloration is a local adaptation, but it is not in response to different diet and exercise patterns. Modern human skin coloring is an example of local adaptation. Skin pigmentation follows a predictable geographic pattern dark skin is most common in hot tropical climates and light skin in cold northern climates. Skin color is a local adaptation to the conditions that exist in these respective climates. Dark skin protects the body from UV radiation and cancer in the intense sunlight of the tropics, but is still able to absorb enough sunlight for adequate vitamin D production, which is important for the absorption of calcium and proper bone development. Light skin absorbs more sunlight in the north where light intensity is lower and cancer is less of a risk, allowing adequate light absorption in order to produce enough vitamin D.

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