Helle Samuli, Helama Samuli
Section of Ecology, Department of Biology, University of Turku, FI-20014 Turku, Finland.
Am J Hum Biol. 2007 Nov-Dec;19(6):844-53. doi: 10.1002/ajhb.20650.
Our current knowledge on climate-mediated effects on human population dynamics is based on preindustrial agrarian societies where climate-induced crop failures had a major impact on fertility and mortality rates. However, because most of the human evolutionary history has been shaped by hunter-gatherer lifestyle relying on diverse plant and animal food sources, it is also important to understand how climate affected the population dynamics of hunter-gatherers. We thus studied whether climate, measured as a reconstructed annual mean temperature, had concurrent or delayed effects on the key components of population dynamics, annual births and deaths, in three historical (1722-1850) Sami populations of Northern Finland that depended mainly on fishing, hunting, and reindeer herding for their livelihood. We found only weak concurrent effects of mean temperature on annual births and deaths, although in general warm years correlated with increased birth and reduced mortality rates. Likewise, temperature-mediated delayed effects were mainly absent: in one population only, a warm previous year tended to reduce the number of births. By contrast, annual numbers of births and deaths were more closely associated, as indicated by negative correlations between births and deaths up to three previous years. To summarize, in contrast to historical agrarian societies, the population dynamics of historical Sami seemed to be only weakly associated with annual mean temperature, which may indicate that these populations, probably due to their dietary breadth, were rather unaffected by climatic variation.
我们目前关于气候对人类人口动态影响的知识，是基于工业化前的农业社会，在这些社会中，气候引发的作物歉收对生育率和死亡率产生了重大影响。然而，由于人类进化史的大部分时间是由依赖多种动植物食物来源的狩猎采集生活方式塑造的，了解气候如何影响狩猎采集者的人口动态也很重要。因此，我们研究了以重建的年平均温度衡量的气候，是否对芬兰北部三个历史时期（1722 - 1850年）主要依靠捕鱼、狩猎和驯鹿放牧为生的萨米人口的人口动态关键组成部分，即年出生和死亡，产生了同时期或延迟的影响。我们发现平均温度对年出生和死亡的同时期影响很微弱，尽管总体而言温暖年份与出生增加和死亡率降低相关。同样，温度介导的延迟影响也基本不存在：仅在一个群体中，前一年温暖往往会减少出生数量。相比之下，年出生和死亡数量的关联更为紧密，前三年出生和死亡之间的负相关表明了这一点。总之，与历史上的农业社会不同，历史上萨米人的人口动态似乎与年平均温度的关联较弱，这可能表明这些人群，可能由于其饮食的多样性，受气候变化的影响较小。
