Explanation And Thought Experiments In History

Although interest in them is clearly growing, most professional historians do not accept thought experiments as appropriate tools. Advocates of the deliberate use of thought experiments in history argue that without counterfactuals, causal attributions in history do not make sense. Whereas such arguments play upon the meaning of causation in history, this article focuses on the reasoning processes by which historians arrive at causal explanations. First, we discuss the roles thought experiments play in arriving at explanations of both facts and contrasts. Then, we pinpoint the functions thought experiments fulfill in arriving at weighted explanations of contrasts.     

An improved PCR method for endogenous DNA retrieval in contaminated Neandertal samples based on the use of blocking primers

Neandertal skeletal remains are usually contaminated with modern human DNA derived from handling and washing of the specimens during excavation. Despite the fact that the distinct Neandertal haplotypes allow the design of specific primer pairs, for instance in most of the mitochondrial DNA (mtDNA) hypervariable region 1 (HVR1), the human contaminants can often outnumber the endogenous DNA, thus preventing a successful retrieval of Neandertal sequences. We have developed a novel PCR method, based on the use of blocking primers that preferentially bind to modern human contaminant DNA and block their amplification, and greatly improve the efficiency of Neandertal DNA retrieval. We tested the method in four El Sidrón Neandertal samples (two teeth and two bone fragments) with different contamination levels and taphonomic conditions, and we have been able to significantly increase the Neandertal yield from figures around 25.23% (5–69.6%) up to 90.18% (75.3–100%).