The Antarctic of the Past

At http://io9.com/5626068/new-evidence-that-it-was-once-possible-to-sail-across-antarctica/ is a strange title as it gives the impression a paper with a lead author from the British Antarctic Survey was referring to the continent of Antarctica dissected by a waterway – when in fact they were saying no such thing. The occurrence of closely related tiny sea creatures known as bryozoans in the coast off the West Antarctic peninsular and in the Weddell Sea, 1500 miles apart and separated by an ice sheet, suggests they must have travelled across the continent not so long ago – on a massive Antarctic seaway. I thought this was a spoof at first but the next day the story is repeated at www.physorg.com/print202449319.html where all becomes clear as muck. What the paper is suggesting is that the West Antarctic ice sheet (which covers only the peninsular and not the continent) has in the fairly recent past collapsed, and clear water existed between both colonies of bryozoans which accounts for their close similarity (living on continental shelves of the Ross and Weddell seas). It is published in Global Change Biology and has an obvious AGW angle as it has been alleged the West Antarctic ice sheet is fragile. When the seaway was open is not clear but they suggest a suitably distant period such as the last Interglacial period, 125,000 years ago. Why not the Mid Holocene Warm Period?