Concept explainers
We might be able to more easily distinguish between the African replacement and multiregional origin hypotheses (and to answer a host of other unanswered questions about the origin and early evolution of H. sapiens) if we had access to DNA sequences from the earliest representatives of our genus. Is it possible that researchers will one day extract useable DNA from, say. early H. erectus? Perhaps, but the odds of success are not great. H. erectus fossils are up to 1.8 million years old, but the oldest ancient genome so far obtained is from a 700,000-year-old fossil horse. What’s more, the fossil horse was found in northern Canada, where the cold climate is excellent for preserving DNA. H. erectus. however, inhabited warmer regions where DNA degrades more quickly. Nonetheless, some evolutionary biologists hold out hope that useable DNA might be found in early H. erectus bones that fossilized in an environment conducive to preservation, perhaps in a deep cave or in oxygen-depleted underwater sediments. Could DNA survive for more than a million years under the right conditions? Current evidence says no, but then it wasn’t too long ago that recovering Neanderthal DNA seemed like an impossible dream.
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Biology: Life on Earth with Physiology (11th Edition)
- Some people think that many of our uniquely human traits arose by sexual selection. Over thousands of years, women attracted to charming, witty men perhaps prompted the development of human intellect beyond what was necessary for mere survival. Men attracted to women with juvenile features may have shifted the species as a whole to be less hairy and softer featured than any of our simian relatives. Can you think of a way to test these hypotheses?arrow_forwardhttps://evolution.berkeley.edu/evolibrary/news/110301_pcbresistantcod (ARTICLE LINK) QUESTIONS: 1. Review the process of natural selection. Use the steps to explain how PCB resistance became so common among tomcod in the Hudson. Be sure to include the terms mutation, fitness, selective pressure, and adaptation in your explanation. 2. In this blog post, the author describes the tomcod as "a quick learner" because of the population's adaptation to PCBs. Is "learning" an accurate way to describe the change in the Hudson River tomcod population? Why or why not? 3. The data shown on the map above support the hypothesis that natural selection for PCB resistance has occurred among tomcod in the Hudson. What sort of evidence regarding gene frequencies in different populations would argue against this hypothesis (i.e., imagine what the scientists would have observed in this study if natural selection on the AHR gene had not occurred among Hudson River tomcod)? 4. Why is it not accurate to…arrow_forwardOnce nuclear DNA sequencing became fast and able to handle sequencing ancient DNA, living humans were found to have some Neanderthal genes. Is this finding clear evidence that some early modern humans did indeed hybridize with Neanderthals? Why?arrow_forward
- A fossil believed to be the most recent common ancestor between housecats and lions is radio-dated to about 11 million years ago (mya). An analysis of a neutral section of mitochondrial DNA in both species finds 15 DNA base pair differences between the two cats today. Meanwhile, an analysis of housecats and pumas shows 4 DNA base pair differences between them, which are believed to have diverged around 3 mya. Using this data, what is the best estimate of the time since divergence of housecats and lynx, which have 11 DNA base pair differences in this mitochondrial DNA region? 5 mya O6 mya O 7 mya O8 mya 9 myaarrow_forwardWhen I first studied hominin evolution, they had found "Lucy", an Australopithecus afarensis, and everyone thought her species was an early ancestor of Homo sapien. The picture is much more complicated, with lots of hominins living in close proximity for millions of years...much different than our now singular species. Look at the phylogenetic tree and use it as a guide to briefly describe hominin lines in Africa up to Homo. Do not discuss Homo.Just discuss a sense that you generally can grasp what was going on in Africa with our Genus for 6 or 7 million years!arrow_forwardReferring to the phylogenetic tree shown above, answer the following questions: 1. How many OTUs are included in the phylogenetic analysis? 2. How many clades are there? 3. What is an autapomorphic trait of the domestic cat? Explain why? 4. What is the shared derived trait (synapomorphy) in the Family Felidae? Explain why?arrow_forward
- The Out of Africa hypothesis (also called the African Replacement hypothesis) proposes that Homo sapiens arose in Africa and evolved there for several hundred thousand years. Then, some 85,000 years ago, a small band of Homo sapiens migrated out of Africa and populated the remainder of the world. Based on this hypothesis, what predictions would you make about worldwide human variation in mtDNA?arrow_forwardThe figure shows a phylogenetic tree of various members of the order Proboscidea, which includes modern elephants. Which of the following claims is best supported by the information in the figure ? a.The mastodon and the Stegodon diverged from their common ancestor 22 million years ago. b.The common ancestor of the African elephant and the mastodon is the Palaeomastodon. c.The mammoth diverged from its most recent common ancestor with African elephants before the mastodon diverged from its most recent common ancestor with Stegodons. d.The Asian and African elephants are the most closely related species shown on the tree.arrow_forwardRadiometric dating and the cranial capacity measurements are back from the paleolab for the specimen you discovered at the site you were excavating in South Africa. Lab results indicate that the cranial capacity is 520 cubic centimeters and it dates to about 1.5 million years ago. After having identified the cranial traits present, you can now take this new information and provide, at least, the genus to which you think it may belong. Based on this information, choose from the options below, the category to which you think it most likely belongs. -Pre-australopith -Premodern Human -Gracile Australopithecine -Early Genus Homo -Robust Australopithecine -Late Genus Homoarrow_forward
- Radiometric dating and the cranial capacity measurements are back from the paleolab for the specimen you discovered at the site you were excavating in South Africa. Lab results indicate that the cranial capacity is 520 cubic centimeters and it dates to about 1.5 million years ago. After having identified the cranial traits present, you can now take this new information and provide, at least, the genus to which you think it may belong. Based on this information, choose from the options below, the category to which you think it most likely belongs. Group of answer choices Pre-australopith Premodern Human Gracile Australopithecine Early Genus Homo Robust Australopithecine Late Genus Homoarrow_forwardThe second step to calculate the evolutionary rate is based on the values of p obtained above. The relationship between the evolutionary rate, 1 (i.e., changes in sequence per number of years), the proportion of different sites, p, and divergence time in years between the two species, t, is approximately: 21t=p 6. We are assuming that the average value of l applies to all lineages and that each pair of species shares a common ancestor. Given that, why does the formula have a factor of 2 on the left hand side? Hint: think about what happens at a divergence.arrow_forwardDenisovans are ancient humans. What would you least expect? A. They would have a larger brain than H. floresiensis. B. Fusion of chromosome 2a and 2b would not have occurred. C. Their mtDNA would show more similarity to Neanderthals than to H. sapiens. D. They probably did not have a spoken language. E. There would be evidence of them interbreeding with Homo sapiens and Neanderthals.arrow_forward
- Human Heredity: Principles and Issues (MindTap Co...BiologyISBN:9781305251052Author:Michael CummingsPublisher:Cengage Learning