Monsters We Met - Other causes - page two

	Who were the first people to arrive in North America?

Australia

Environmental changes precipitated by people

Could people have altered the environment, inadvertently causing the demise of the megafauna? The impact of agriculture on habitats and ecosystems is well known, but less familiar is the effect that hunter-gatherers can have on the land. Fire was probably the world's earliest form of land management as burning off forest and scrub encourages the growth of new grass and entices grazing animals into an area.

Fossil pollen and charcoal fragments in soils and sediment from the sea floor show that Aboriginal burning has been altering the Australian environment for at least 40,000 years. Both natural fires and human activity have pushed Australia towards a fire ecology where animals and plants are adapted to coping with regular bushfires. The progressive drying out of the continent as it drifted north has heightened this trend. Some scientists believe that this was what doomed the megafauna. Plants that could not adapt to the frequent fires died out, and the animals that depended on them followed swiftly after.

Many scientists favour a date around 65,000-68,000 years ago for the arrival of Australia's first people. Mungo III was not one of the first arrivals - it probably took people between one and three thousand years to reach New South Wales from their landfalls in the north. There are megafauna skeletons dated at about 25,000-30,000 years old, so no matter what his age, Mungo III demonstrates that people and megafauna shared Australia for a long, long time.

Horrible hitchhikers

Of course, it was often not just people that arrived in these new lands - even stone-age cultures bring domestic animals and other hitchhikers along with them. Often these animals have unexpected impacts on the native fauna. Aboriginal people introduced the dingo to Australia about 3,000-4,000 years ago, and over the next thousand years the species spread across the continent, displacing the marsupial wolf (Thylacinus cynocephalus) until the latter only survived on Tasmania.

	Spear tips in the North American landscape.

New Zealand

Horrible hitchhikers

Polynesian peoples introduced dogs, chickens, pigs and the Polynesian rat to many of the islands they colonised and the dogs, pigs and rats in turn caused the extinction of many birds and reptiles. The Polynesian rat was not an accidental introduction like the brown or ship rats brought by European explorers - it was used as food by the Polynesians.

Today the Polynesian rat, known as the kiore in New Zealand, is an important cultural animal to the Maori. Brown rats brought by Europeans have driven it out of most of New Zealand, so it is only found on certain offshore islands. Debate continues as to whether the Polynesian rat should be eliminated from these islands as a pest that eats tuataras and wetas, or allowed to survive on selected islands as part of the cultural and biological heritage of prehistoric New Zealand.