Source: Arizona State University
Date: 20 February 2009
Genetics Research Sheds Light On Evolution Of The Human Diet
Diet – and how it has shaped our genome – occupies much of an evolutionary scientist's time. Anne Stone, associate professor of anthropology in Arizona State University's School of Human Evolution and Social Change, will discuss how diet holds keys to understanding who we are, how we live and form societies, and how we evolved from hunter-gatherers to agriculturists, all the way to modern urban dwellers, at the American Association for the Advancement of Science annual meeting.
Researchers like Stone look to our closest relatives – the chimpanzee and other primates – for comparisons to humans in order to understand the unique development of the human body and how it is impacted by diseases and the environment.
"One area we look at is starch consumption, something prominent in both agriculturalists and hunter-gatherers," says Stone. A study she and graduate student George "P.J." Perry led on the amalyse gene (AMY1) copy number variation – the gene responsible for starch hydrolysis – produced one of the first examples of positive selection on a copy number variable gene in the human genome. The results show how different levels of AMY1 copy number differentiation is unusual in a population, and that individuals with high starch diets have more copies than those with traditionally low starch diets. Digestion of starches is critically important for energy absorption – especially during episodes of diarrhea. This research gives insight into why certain populations may weather diarrheal diseases better than others.
"To gain an even better understanding of this process in humans, we analyzed patterns of AMY1 copy number variation in chimpanzees and bonobos. We discovered that the average human has about three times more AMY1 copies than chimpanzees, which eat mostly fruit and far less starch than humans. And bonobos may not have any," says Stone. "This human-specific increase may have occurred with a dietary shift early in hominin evolutionary history. We know that starch-rich root plants were a critical food for early hominins, and may even have facilitated the initial spread of Homo erectus out of Africa."
Other genetic research on copy number variants in humans and primates includes examining the TAS2R gene family, the gene responsible for taste sensitivity to the bitter compound phynylthiocarbamide (PTC). "Sensitivity to bitter taste is an important means for animals to interact with their environment. These variants may be very significant from an evolutionary perspective, and they're important to study and understand," says Perry. "We talk about genetic diseases and cures, but first you have to find out what genetic differences are there so you can study what they're involved with and what they mean from a morphological variation and disease standpoint."
Identifying unusual patterns between species, such as copy number differences between humans and chimpanzees, can lead to identifying those that were involved in producing the evolution of human-specific traits. "This research not only illustrates the importance of studying genetic variation in other primates to understand our own genome better, but also sheds light on the diversity and adaptations of our nearest relatives," adds Stone.
“You wait till Larry comes and I tell him my theory!” The bids, duly sealed, were given into the keeping of the commissary officer to be put in his safe, and kept until the day of judgment, when all being opened in public and in the presence of the aspirants, the lowest would[Pg 188] get the contract. It was a simple plan, and gave no more opportunity for underhand work than could be avoided. But there were opportunities for all that. It was barely possible—the thing had been done—for a commissary clerk or sergeant, desirous of adding to his pittance of pay, or of favoring a friend among the bidders, to tamper with the bids. By the same token there was no real reason why the commissary officer could not do it himself. Landor had never heard, or known, of such a case, but undoubtedly the way was there. It was a question of having the will and the possession of the safe keys. "Well, I believe our boys 's all right. They're green, and they're friskier than colts in a clover field, but they're all good stuff, and I believe we kin stand off any ordinary gang o' guerrillas. I'll chance it, anyhow. This's a mighty valuable train to risk, but it ought to go through, for we don't know how badly they may need it. You tell your engineer to go ahead carefully and give two long whistles if he sees anything dangerous." "Fine-looking lot of youngsters," he remarked. "They'll make good soldiers." "That's just what he was, the little runt, and we had the devil's own time finding him. What in Sam Hill did the Captain take him for, I'd like to know? Co. Q aint no nursery. Well, the bugler up at Brigade Headquarters blowed some sort of a call, and Skidmore wanted to know what it meant. They told him that it was an order for the youngest man in each company to come up there and get some milk for his coffee tomorrow morning, and butter for his bread. There was only enough issued for the youngest boys, and if he wanted his share he'd have to get a big hustle on him, for the feller whose nose he'd put out o' joint 'd try hard to get there ahead o' him, and get his share. So Skidmore went off at a dead run toward the sound of the bugle, with the boys looking after him and snickering. But he didn't come back at roll-call, nor at tattoo, and the smart Alecks begun to get scared, and abuse each other for setting up a job on a poor, innocent little boy. Osc Brewster and Ol Perry, who had been foremost in the trick had a fight as to which had been to blame. Taps come, and he didn't get back, and then we all became scared. I'd sent Jim Hunter over to Brigade Headquarters to look for him, but he came back, and said they hadn't seen anything of him there. Then I turned out the whole company to look for him. Of course, them too-awfully smart galoots of Co. A had to get very funny over our trouble. They asked why we didn't get the right kind of nurses for our company, that wouldn't let the members stray out of their sight? Why we didn't call the children in when the chickens went to roost, undress 'em, and tuck 'em in their little beds, and sing to 'em after they'd said 'Now I lay me down to sleep?' I stood it all until that big, hulking Pete Nasmith came down with a camp-kettle, which he was making ring like a bell, as he yelled out, 'Child lost! Child lost!' Behind him was Tub Rawlings singing, 'Empty's the cradle, baby's gone.' Then I pulled off my blouse and slung it into my tent, and told 'em there went my chevrons, and I was simply Scott Ralston, and able to lick any man in Co. A. One o' their Lieutenants came out and ordered them back to their quarters, and I deployed the company in a skirmish-line, and started 'em through the brush toward Brigade Headquarters. About three-quarters o' the way Osc Brewster and Ol Perry, when going through a thicket, heard a boy boo-hooing. They made their way to him, and there was little Skidmore sitting on a stump, completely confused and fagged out. He'd lost his way, and the more he tried to find it the worse he got turned around. They called out to him, and he blubbered out: 'Yes, it's me; little Pete Skidmore. Them doddurned fools in my company 've lost me, just as I've bin tellin' 'em right along they would, durn 'em.' Osc and Ol were so tickled at finding him that they gathered him up, and come whooping back to camp, carrying him every step of the way." And the rush stopped. Cadnan waited for a second, but there was no more. "Dara is not to die," he said. Then he saw Orion hanging over him, very low in the windy sky, shaking with frost. His eyes fixed themselves on the constellation, then gradually he became aware of the sides of a cart, of the smell of straw, of the movement of other bodies that sighed and stirred beside him. The physical experience was now complete, and soon the emotional had shaped itself. Memory came, rather sick. He remembered the fight, his terror, the flaming straw, the crowd that constricted and crushed him like a snake. His rage and hate rekindled, but this time without focus—he hated just everyone and everything. He hated the wheels which jolted him, his body because it was bruised, the other bodies round him, the stars that danced above him, those unknown footsteps that tramped beside him on the road. Farewell to Jane and Caroline!" HoME大香蕉色人阁
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