The transition from the Middle to the Upper Palaeolithic, approximately 40,000-35,000 radiocarbon years ago, marks a turning point in the history of human evolution in Europe. Many changes in the archaeological and fossil record at this time have been associated with the appearance of anatomically modern humans. Before this transition, the Neanderthals roamed the continent, but their remains have not been found in the northernmost part of Eurasia. It is generally believed that this vast region was not colonized by humans until the final stage of the last Ice Age some 13,000-14,000 years ago. Here we report the discovery of traces of human occupation nearly 40,000 years old at Mamontovaya Kurya, a Palaeolithic site situated in the European part of the Russian Arctic. At this site we have uncovered stone artefacts, animal bones and a mammoth tusk with human-made marks from strata covered by thick Quaternary deposits. This is the oldest documented evidence for human presence at this high latitude; it implies that either the Neanderthals expanded much further north than previously thought or that modern humans were present in the Arctic only a few thousand years after their first appearance in Europe.

Decompaction routines are used in basin modelling packages to calculate sediment thickness and material properties such as thermal conductivity. However, compaction in nature is dependent on initial porosity, composition, and effective stress, and a considerable range of porosity-depth trends exists. Simple thermal modelling demonstrates that significant uncertainties (up to VRE ± 0.5) arise in predicted maturities due to this variation. Furthermore, the validity of using porosity loss as a measure of compaction is questionable because changes in solid volume can occur. Chemical reaction may increase or decrease porosity without changing sediment thickness, although an apparently smooth transition occurs from dominantly mechanical processes of porosity loss (e.g. grain rearrangement) at shallow levels to dominantly chemical processes (e.g. grain dissolution/cementation) at depth. That compaction and porosity loss are processes dependent upon effective stress, time and temperature is illustrated by the observation of overpressuring in the subsurface, comparison of experimental and natural compaction rates and analysis of porosity-depth trends for sediments of different ages. Mechanistic models of the processes involved in compaction (e.g. pressure solution) also indicate time dependency. Time-dependent models of compaction can be constructed, but these are difficult to incorporate into basin models as they cannot be run in a simple backstripping mode.

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