Are we among the final generations of humans to walk the earth? One Australian scientist says yes, and he's not just another 2012 doomsday believer. Professor Frank Fenner, who announced the eradication of smallpox to the World Health Assembly in 1980, says overpopulation and climate change are just two of many reasons why humans won't survive much more than a century into the future.

In fact, Fenner declines to speak about climate change because he believes there's no use — our fate is sealed.

"Homo sapiens will become extinct, perhaps within 100 years," he said in an interview with The Australian. "A lot of other animals will, too. It's an irreversible situation. I think it's too late. I try not to express that because people are trying to do something, but they keep putting it off."

Thanks to the population explosion and “unbridled consumption”, Fenner says food wars and global droughts will intensify problems like malnutrition and poverty.

"Mitigation would slow things down a bit, but there are too many people here already," he says.

An expert on microbiology, virology and evolution, Fenner was responsible for reducing the population of rabbits in the 1950s with a specially developed virus.

His position on the fate of the human species is shared by many other ecologists, but there are others who believe he's overly pessimistic.

One example is a paper published by researchers in the journal Futures last year entitled “Human Extinction: How Could it Happen?

Investigating various scenarios, the scientists came to the conclusion that no single event is likely to wipe out the species, with small pockets of humans remaining and adapting through successions of catastrophes like pandemics and nuclear wars.

The authors also believe extinction scenarios would involve some kind of intent, malicious or not, among world leaders — though Fenner points to the lack of concerted action on global warming as evidence that this is already happening.

At the very least, says Fenner, "The grandchildren of today's generations will face a much more difficult world."

Humans could go extinct within 100 years, says renowned scientist
Microbiologist Frank Fenner believes it's already too late to save the human species from overpopulation and climate change.