 So the long history over millions of years is basically progressive drying of the climate. You know I mentioned the rainforest trees three million years ago around Lake George. When the rainfall was probably three times more than the present, so the present annual rainfall around Lake George is pretty similar to Canberra. So 650mm a year or something, so three million years ago it might have been 2,000mm, but slowly over time, and this is related to changes in global climate as well. The development of the Pleistocene ice ages and the growth of ice caps or periodic growth and decay of ice caps around the world affects global climate on timescales of hundreds of thousands of years to millions of years, and so it's well known indeed in other parts of Australia that there's been a progressive drying over the last several million years and we see that here. As we come closer to the present and the vegetation becomes much more like what it was immediately prior to Europeans arriving in this area, then we start to see, well the common species we see eucalyptus and we see casuarina pollen preserved in the sediments, whereas three million years ago you're getting pollen from trees that are more like trees growing up post the day for it. The big picture is progressive drying of the landscape and it fits in with what's happening elsewhere in Australia.