泥河湾盆地1.8-0.8 Ma古人类生存环境背景的软体动物化石组合研究

The presence and evolution of early humans is thought to be closely related to the environment they lived. However, what kind of environment favorable for the origin and evolution of early humans remains highly debated. The Nihewan Basin is one of the best regions for the understanding of the environment that early humans had lived. As comprehensive studies of the environmental evolution in the Nihewan Basin are sparse, we know very little about the environment that early humans in East Asia had lived. In this project, four high-resolution fossil freshwater mollusk sequences will be established from the Nihewan Basin, covering the period of 1.8-0.8 Ma. Three objectives of the project are as follows: 1) to investigate the preservation conditions, species composition and ecological groups of the freshwater mollusk assemblages; 2) to examine the ecological significance of the modern mollusk species through investigating about 150 water bodies covering the region from Northeast China to middle Southeast China as well as based on the results provided by previous studies; 3) to reconstruct the history of ecological environmental changes in the Nihewan Basin during the time interval from 1.8 to 0.8 Ma based on ecological significance of the fossil mollusk species from the Nihewan Basin, discuss the characteristic of ecological environment and climate change during this period, and decipher the evolution of the Nihewan paleolake based on fossil mollusks and lithological changes. All of these efforts would provide environmental context when early humans lived in this basin. This project would be a significant contribution of freshwater mollusks to the understanding of ecological environmental changes related to the evolution of early humans in East Asia. It would also be of importance to the development of mollusk studies in China.

早期人类起源演化的环境背景是国际上有很大争议的重大科学问题。泥河湾盆地是研究东亚人类演化与环境关系的理想地区之一，但该区古人类生存的气候环境背景、古湖的演化及其与古人类活动具有怎样的联系等因系统研究不足而不明确。本项目拟以该盆地有很好年代学基础、构成南-北向断面的4个剖面（从北到南；马圈沟、小长梁、红崖、花豹沟）为研究对象，建立旧石器遗址集中分布时段（1.8-0.8 Ma）较高分辨率的软体动物组合序列，研究软体动物化石保存状况和种类组成；通过现生种类的调查并参考前人资料，明确优势种类的生态环境意义，根据软体动物化石组合，结合岩性岩相变化，探讨该时期古湖的演化与古人类活动的联系；揭示软体动物组合的演替过程与气候变化特点，并与旧石器文化序列对比，重点研究古人类在泥河湾盆地生存的气候环境背景。本项目有望为人类演化的环境背景研究提供来自泥河湾盆地的新的生物学证据，有望促进我国古软体动物学科的发展。

早期人类演化的环境背景是国际上存在很大争议的重大科学问题。泥河湾盆地是研究东亚人类演化与环境关系的理想地区之一。本项目研究发现该盆地不同剖面软体动物保存有很大差异，软体动物在遗址所在的剖面上分布很不连续，在湖滨相地层中较丰富，在深水相地层中保存很少。为从更大区域上揭示重点时期气候环境变化过程，增加了黄土高原该时期软体动物组合及其卵化石的研究工作。采集了泥河湾盆地遗址及石铺地面50余个层位的软体动物组合样品，完成了洛川剖面1.3-0.6 Ma蜗牛组合样品400余个，表土蜗牛组合样品新采集32个，表土蜗牛卵组合样品200余个，发表论文3篇，待投稿1篇，另有2篇在写。取得的主要成果有：1) 1.3-0.6 Ma期间气候变化过程及其对早期人类演化环境背景的指示。这期间，古人类在泥河湾活动的时期主要是冰期，且可能季节性突发气候事件频发，气候变率增强，支持人类演化的气候变率假说。2）我国间齿螺（Metodontia）的数量分布及其最适宜的生态因子范围。间齿螺的数量分布和生态因子最适区域缺少系统的研究，限制了对间齿螺古生态古气候意义的深入理解。通过对黄土高原及周边地区356个表土蜗牛组合的研究，揭示出间齿螺及其优势种的数量分布与气候参数的关系，以及与经纬度和海拔高度的关系，定量估算了汉山间齿螺和烟台间齿螺的温度和降水量最适区域，为研究古人类演化的环境背景提供了新的定量证据。3）32年来中国黄土陆生蜗牛化石与东亚季风环境变化研究回顾。中国黄土陆生蜗牛化石的研究已经有超过百年的历史，最近二、三十年是黄土蜗牛化石研究最为快速发展的时期。项目组成员参与完成了中国黄土蜗牛研究的历史、进展及其未来的发展趋势的回顾总结。4）基于33个释光年龄点、23个蜗牛壳体14C年龄点，建立了4万年来黄土高精度年代序列，为获得其他黄土剖面的年代标尺提供了对比基准。此外项目积极开展科普工作，在《中国国家地理》和中国科学院地质与地球物理研究所公众号发表了黄土微体化石与古环境研究的科普介绍。