[Sanddancer]

Depends on the test. Full-life trials, like this one, tend to have many more than that because you need to take into consideration a lot of the random factors of being alive. However, there other things to keep in mind here. The breed of rat used has a predisposition to get cancer in a real short time; more than half of Sprague-Dawley rats will get cancer within two years. As a result, they're used much more often in research centered around having cancer than getting cancer. Finally, the rats were allowed to eat food whenever they wanted, and however much they wanted. So, there's the possibility that one or more of the groups through chance just had particularly gluttonous rats. Because of this, you have a lot of questions as to what could have led to the problem -- was it the GMO corn/roundup, or did the rats feeding on GMO/Roundup corn eat more, or was it just (un)luck of the draw, etc?