A little geological history of the Bering Straits or Land Bridge is available at ( http://archaeology.about.com/bcthroughbl/qt/beringia.html?nl=1 ). Whenever sea levels in the region dropped by 50 metres below the present position the land surfaced. The dates when this happened have been difficult to establish precisely simply because at the moment the region is submerged. In general terms it is thought Beringia was exposed between 60,000 to 25,000 years ago. During the Late Glacial Maximum, 25,000 to 18,000 years ago, it is thought Beringia was cut off both in the east and in the west. This indicates Beringia was virtually an island – but it is assumed that it was ice that blocked the way. The latter marks the end of the Ice Age, as such, and pollen analysis has shown that between then and the end of the Pleistocene, at the Younger Dryas event 13,000 years ago, Alaska was cold – grasses, herbs and willows dominated the vegetation in summer. It is assumed the climate was cold earlier than 18,000 years ago but this is unclear from what is said as the period where pollen analysis was available also seems to include the cold spike of the Younger Dryas. It is thought Beringia was drowned by 11,000 years ago – during early Holocene, following the end of the Younger Dryas period. However, sea levels did not reach the 50 metre mark until 7000 years ago, indicating this was associated with the 6000BC event (8000 years ago). The status of the Bering land bridge is essential in understanding the colonisation of the Americas by people with an origin in northern Siberia. Archaeologists tie themselves in knots to get the migrants moving through what is an extremely small window of time. Speculation and theory is all we really have. For instance, was Beringia an island between the end of the Ice Age and the end of the Pleistocene (18,000 to 11,500 years ago)? Might it be more expedient to have an ice free Arctic Ocean in the vicinity of Alaska and northern Siberia – with free movement of people in boats. They may therefore have moved southwards when it got colder – during the period after the end of the Ice Age 18,000 years ago. This might upset the whole basis of the Ice Age theory but there is little evidence of glaciation east of Finland between 30,000 and 18,000 years ago, and observation should really outweigh conviction.