Considering what we know about the key ingredients for life's formation on Earth, here are three explanations for how this process may have occurred on our sister planet.
The rapid invasion is a major threat to the environment and rural people’s livelihoods.
Scientists and soldiers deal with alien invaders in the new Predator movie, but how does the science stack up? With brains and brawn you'd think they'd know how to keep an alien tied down to a table.
Developing countries have been slow to react to the alien species problem. Its impact can be massively reduced if policies are developed to deal with the issue.
Many alien plants and animals have been introduced to Africa from other regions and spread from country to country, often having devastating effects.
We continue to search for intelligent life elsewhere in the universe. But if we find ET there are those who question whether we should make contact or not.
Keeping non-native reptiles as pets is against the law – with good reason. Alien species traded on the black market can potentially establish themselves in the wild if they are released or escape.