Eventually, humans invented agriculture, which could be understood as a way of turning the natural world into a tool for our use. There's evidence that we have been domesticating crops and animals for at least 15,000 years, adapting ecosystems to our preferred way of life.

We have converted huge swaths of land and ocean into human habitats where we live and grow food and harvest energy. But there's been a sea change in the past century.

Survivor species tend to have huge populations, so they can afford to lose many individuals and still survive as a species. They also tend to be small. If you're small, you need less food - which is great in a situation where famine is everywhere.

The early Triassic was a period when the planet was recovering from the worst mass extinction it had ever known - that was the end Permian extinction, where climate change caused in part by mega-volcanic eruptions wiped out ninety-five percent of life on Earth. It took about ten or twenty million years for the planet's ecosystems to stabilize. During that time you saw a lot of weird, out-of-balance ecosystems where, for example, crocodile-like predators ripped the crap out of each other along the coasts.

Some time ago we discovered the carbon cycle - a long-term set of chemical reactions that govern climates based on how much carbon is free in the atmosphere. At that point, it became clear that humans were affecting our environments far more profoundly than we realized. By releasing so much carbon and greenhouse gas into the environment, we're making long-term changes to every aspect of the natural world.

So science alone cannot solve this problem [mass extinction of humans]. It's something that we can only tackle by bringing science together with culture, economics, and even politics.

My first goal would be to reduce the perturbation in the carbon cycle. That would mean using carbon neutral sources of energy, and changing our agricultural practices to be less disruptive and polluting. I'm not talking about a policy here so much as changing the way our infrastructure works. That's why I'm so fascinated with changing the way we build cities, because they are the most developed forms of physical infrastructure for human habitation.