资料来源: Barry Roal Carlsen, University of Wisconsin-Madison
据11月20日的《科学》杂志报道说，有关如猛犸象、乳齿象以及地懒等大型动物是如何灭绝的，以及它们的消失是如何影响北美的生态系统等问题终于在其粪便中得到了解答。 在一项阐明那些大约在1万3000年前在最后的冰川期结束时灭绝的动物的研究中，Jacquelyn Gill及其同僚分析了从印地安纳州Appleman Lake的远古沉积层中获取的花粉、木炭以及Sporormiella (小荚孢腔菌) [这是一种生长在大型食草动物粪便中的特殊真菌]。 由于Sporormiella 的量为人们提供了有关当时大型食草动物所产生的生物质的一种指标，因此研究人员能够将此数据与有关植被及来自花粉和木炭的火烧情况进行相关联系。
研究发现，这些巨型动物（称作巨型动物群）的种群数在Clovis人的出现、大规模植物群落变化以及火烧增加的1000多年之前就已开始下降。 因此，尽管研究人员过去认为，Clovis狩猎者及其/或这些环境的变迁导致了北美巨型动物群的衰减；但现在看来，所发生的情况完全倒转了过来：发生在1万4800年至1万3700年之前的巨型动物群的缓慢的灭绝发生在Clovis人出现之前；而且它是植被改变和火烧增加的一个原因而非其结果。 这一发现还排除了人们提出的发生在1万2900年前的来自地球外的撞击事件的可能性。 一篇由Christopher Johnson所撰写的Perspective对这一新的时间轴进行了更为详尽的解释。（生物谷Bioon.com）
生物谷推荐原始出处：
Science 20 November 2009:DOI: 10.1126/science.1179504
Pleistocene Megafaunal Collapse, Novel Plant Communities, and Enhanced Fire Regimes in North America
Jacquelyn L. Gill,1,2 John W. Williams,1,2 Stephen T. Jackson,3 Katherine B. Lininger,1 Guy S. Robinson4
Although the North American megafaunal extinctions and the formation of novel plant communities are well-known features of the last deglaciation, the causal relationships between these phenomena are unclear. Using the dung fungus Sporormiella and other paleoecological proxies from Appleman Lake, Indiana, and several New York sites, we established that the megafaunal decline closely preceded enhanced fire regimes and the development of plant communities that have no modern analogs. The loss of keystone megaherbivores may thus have altered ecosystem structure and function by the release of palatable hardwoods from herbivory pressure and by fuel accumulation. Megafaunal populations collapsed from 14,800 to 13,700 years ago, well before the final extinctions and during the B?lling-Aller?d warm period. Human impacts remain plausible, but the decline predates Younger Dryas cooling and the extraterrestrial impact event proposed to have occurred 12,900 years ago.
1 Department of Geography, University of Wisconsin, Madison, WI 53706, USA.
2 Center for Climatic Research, University of Wisconsin, Madison, WI 53706, USA.
3 Department of Botany, University of Wyoming, Laramie, WY 82071, USA.
4 Department of Natural Science, Lincoln Center Campus, Fordham University, New York, NY 10023, USA.
