Tim Lowe

In my book, Where Song Began, I drew a connection between infertile soil and bird aggression.

It doesn't involve intelligence.

The reasoning goes like this.

Australia is the most geologically stable of all continents and the end result has been a flat, infertile land.

Now the plants have adapted to that infertility with specialised root systems and associations with soil fungi.

But soil fertility, it fluctuates from place to place.

It's not the same over vast areas.

You've got soil eroding off rock outcrops.

You've got soil moved around by water and wind.

So you get variation.

Now think through time.

Over the past two million years, you've had ice ages coming and going.

Plants in the northern hemisphere, they often moved around to stay within the climatic zone that suited them.

That was easy in glaciated landscapes because the glaciers had crushed rocks into soil and pushed this around, creating large areas of similar soil.

This fresh soil was fairly fertile, so the plants didn't need special adaptations to grow in it.

They had seeds that were moved around by animals and flowers pollinated by insects or wind.

Now Australia was never as cold during the ice ages because the southern hemisphere has more ocean than land and ocean currents have always brought warm equatorial waters southwards.

That means less pressure on plants to move.

Now the plants adapted to infertile soil, they don't want to move.

Instead of having mobile seeds, they have mobile pollen.