HON BIO SCI II
HON BIO SCI II BSC 2011
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This 4 page Class Notes was uploaded by Kari Harber Jr. on Thursday September 17, 2015. The Class Notes belongs to BSC 2011 at Florida State University taught by Staff in Fall. Since its upload, it has received 7 views. For similar materials see /class/205431/bsc-2011-florida-state-university in Biological Sciences at Florida State University.
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Date Created: 09/17/15
November 17 2004 NEW YORK TIMES Even Couch Potatoes May Have Been Born to Run By JOHN NOBLE WILFORD The evolution of a physique for longdistance running is what made humans look the way we do now whether winning a marathon nursing a strained Achilles tendon or sitting on an ample gluteus maximus in front of the TV The apparently crucial role of running in human evolution overlooked for the most part in previous research is being proposed today in an article in the journal Nature by two American scientists While walking upright rst set early human ancestors apart from their ape cousins the scientists write it may have been the ability to run long distances with springy step over the African savanna that in uenced the transition to today39s human body form Endurance running unique to humans among primates and uncommon in all mammals other than dogs horses and hyenas apparently evolved at least two million years ago and probably enabled human ancestors to hunt and scavenge for food over large distances And that in turn probably proved decisive in their pursuit of highprotein food for development of larger brains The scientists Dr Dennis M Bramble of the University of Utah and Dr Daniel E Lieberman of Harvard reported that their analysis of the fossil record showed striking anatomical evidence for the capability of prolonged running in the Homo genus as early as two million years ago 39Today endurance running is primarily a form of exercise and recreation but its roots may be as ancient as the origin of the human genusquot the scientists concluded in the article Dr Bramble a professor of biology and a specialist in the biomechanics of animal locomotion said quotRunning made us human at least in an anatomical sensequot adding that he and Dr Lieberman were quotvery confident that strong selection for running was instrumental in the origin of the modern human body formquot Other paleontologists not involved in the research praised the hypothesis as an important insight into the apparent significance of longdistance running in human survival and evolution But they raised questions over what stimulated the physical transition that led to this human capability By two million years ago Dr Bramble and Dr Lieberman noted early species of the Homo family beginning at least with Homo erectus had long slender legs for greater strides They had shorter arms and a narrower ribcage and pelvis Their skulls included features to help prevent overheating A ligament attached to the base of the skull kept their heads steady as they ran Although tissues do not fossilize traces of muscle and tendon attachment points on bones of early species revealed an extensive network of springy tendons along the back of their legs and feet including a welldeveloped Achilles tendon that anchors the calf muscles to the heel bone Tendons served to store and release elastic energy during running but were not needed for ordinary walking And there was the gluteus maximus the muscle of the buttocks Earlier human ancestors like chimpanzees today had pelvises that could support only a modest gluteus maximus nothing like the strong buttocks of Homo quotHave you ever looked at an apequot Dr Bramble said quotThey have no bunsquot Dr Lieberman a paleontologist explained quotYour gluteus maximus stabilizes your trunk as you lean forward in a run A run is like a controlled fall and the buttocks help to control itquot December 10 2006 NEW YORK TIMES Study Detects Recent Instance of Human Evolution By NICHOLAS WADE A surprisingly recent instance of human evolution has been detected among the peoples of East Africa It is the ability to digest milk in adulthood conferred by genetic changes that occurred as recently as 3000 years ago a team of geneticists has found The nding is a striking example of a cultural practice 7 the raising of dairy cattle 7 feeding back into the human genome It also seems to be one of the first instances of convergent human evolution to be documented at the genetic level Convergent evolution refers to two or more populations acquiring the same trait independently Throughout most of human history the ability to digest lactose the principal sugar of milk has been switched off after weaning because there is no further need for the lactase enzyme that breaks the sugar apart But when cattle were first domesticated 9000 years ago and people later started to consume their milk as well as their meat natural selection would have favored anyone with a mutation that kept the lactase gene switched on Such a mutation is known to have arisen among an early cattleraising people the Funnel Beaker culture which ourished some 5000 to 6000 years ago in northcentral Europe People with a persistently active lactase gene have no problem digesting milk and are said to be lactose tolerant Almost all Dutch people and 99 percent of Swedes are lactosetolerant but the mutation becomes progressively less common in Europeans who live at increasing distance from the ancient Funnel Beaker region Geneticists wondered if the lactose tolerance mutation in Europeans first identified in 2002 had arisen among pastoral peoples elsewhere But it seemed to be largely absent from Africa even though pastoral peoples there generally have some degree of tolerance A research team led by Sarah Tishkoff of the University of Maryland has now resolved much of the puzzle After testing for lactose tolerance and genetic makeup among 43 ethnic groups of East Africa she and her colleagues have found three new mutations all independent of each other and of the European mutation which keep the lactase gene permanently switched on The principal mutation found among NiloSaharanspeaking ethnic groups of Kenya and Tanzania arose 2700 to 6800 years ago according to genetic estimates Dr Tishkoff s group is to report in the journal Nature Genetics on Monday This fits well with archaeological evidence suggesting that pastoral peoples from the north reached northern Kenya about 4500 years ago and southern Kenya and Tanzania 3300 years ago Two other mutations were found among the Beja people of northeastern Sudan and tribes of the same language family AfroAsiatic in northern Kenya Genetic evidence shows that the mutations conferred an enormous selective advantage on their owners enabling them to leave almost 10 times as many descendants as people without them The mutations have created one of the strongest genetic signatures of natural selection yet reported in humans the researchers write The survival advantage was so powerful perhaps because those with the mutations not only gained extra energy from lactose but also in drought conditions would have benefited from the water in milk People who were lactoseintolerant could have risked losing water from diarrhea Dr Tishkoff said Diane GiffordGonzalez an archaeologist at the University of California Santa Cruz said the new findings were very exciting because they showed the speed with which a genetic mutation can be favored under conditions of strong natural selection demonstrating the possible rate of evolutionary change in humans The genetic data fitted in well she said with archaeological and linguistic evidence about the spread of pastoralism in Africa The first clear evidence of cattle in Africa is from a site 8000 years old in northwestern Sudan Cattle there were domesticated independently from two other domestications in the Near East and the Indus valley of India Both NiloSaharan speakers in Sudan and their Cushiticspeaking neighbors in the Red Sea hills probably domesticated cattle at the same time since each has an independent vocabulary for cattle items said Dr Christopher Ehret an expert on African languages and history at the University of California Los Angeles Descendants of each group moved southward and would have met again in Kenya Dr Ehret said Dr Tishkoff detected lactose tolerance among both Cushitic speakers and NiloSaharan groups in Kenya Cushitic is a branch of AfroAsiatic the language family that includes Arabic Hebrew and ancient Egyptian Dr Jonathan Pritchard a statistical geneticist at the University of Chicago and the coauthor of the new article said that there were many signals of natural selection in the human genome but that it was usually hard to know what was being selected for In this case Dr Tishkoff had clearly defined the driving force he said The mutations Dr Tishkoff detected are not in the lactase gene itself but a nearby region of the DNA that controls the activation of the gene The finding that different ethnic groups in East Africa have different mutations is one instance of their varied evolutionary history and their exposure to many different selective pressures Dr Tishkoff said There is a lot of genetic variation between groups in Africa re ecting the different environments in which they live from deserts to tropics and their exposure to very different selective forces she said People in different regions of the world have evolved independently since dispersing from the ancestral human population in northeast Africa 50000 years ago a process that has led to the emergence of different races But much of this differentiation at the level of DNA may have led to the same physical result As Dr Tishkoff has found in the case of lactose tolerance evolution may use the different mutations available to it in each population to reach the same goal when each is subjected to the same selective pressure I think it s reasonable to assume this will be a more general paradigm Dr Pritchard said
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