New step in evolutionary process |
http://www.sina.com.cn 2003/04/03 11:16 Shanghai Daily |
New step has been added to the four-step hypothesis on the evolution of vertebrates, which includes human beings. Chinese paleontologist Shu Degan said the step was taken after it was determined that fossilized ancient worms found in Yunnan Province represented the "first step" of the evolutionary process. The new hypothesis, raised by Chinese scientists in partnership with scholars from Britain and Japan, was revealed in the US-based Science magazine earlier this year. The theory depicted in the prestigious scientific journal outlined the evolutionary process of deuterostomes, one of the basic two pedigrees on the "crown" of the fauna's evolutionary tree. It concluded that vertebrates originated in at least five steps. According to the four-step theory, vertebrates on the top of the deuterostomes pedigree had no relationship with protostomes, and vertebrates stemmed from echinoderms, which were the lowest deuterostomes, and hemichordates. "This hypothesis is based on modern zoological information," said Professor Shu, who works with Northwest China University in Xi'an, capital of Shaanxi Province. "Whether the hypothesis is reliable or not should be tested, revised and reinforced with authentic historic data," Shu said. Shu believes that effective research on the origins of vertebrates in paleological terms should search for fossil evidences in line with clues provided by modern information. Such evidence was discovered at Chengjiang Lagersttat, a county known for its bountiful wealth of fauna fossils in Yunnan Province. The evidence included fossilized jawless Kunming and Haikou fishes, which were believed to be the most primitive vertebrates living 530 million years ago, and ancient worms and Yunnan worms, which reportedly lived in the same geologic age as the Haikou fish or the previous period. "The serial finds of the early deuterostomes not only add evidence to the four-step theory but also help add the 'first step ' to the evolutionary process of the vertebrates," Shu said. According to Shu, the ancient worms and Yunnan worms, which are believed to be the origins of deuterostomes, and thus the "first step" of the evolutionary process of vertebrates, might be regarded as real deuterostomes in terms of such metabolic forms as food absorbing and breathing, although their bodies retained some characteristics of their ancestors. |
【英语学习论坛】【评论】【大 中 小】【打印】【关闭】 |