1.- Take a look at the graph. What does it show? What conclusions can you get from this information?

2.- Read the article and answer these questions in your own words: BBC News online

a) Who started the research and why?

b) What conclusion did he draw from the information?

c) How does he explain the anomaly?

3.- Critical thinking: Do you agree with the conclusions in the article? Why/Why not? (consider the sources, the references and the context).

Source: Gateway 2nd Edition B2+. Student's Book. Macmillan. Pages 48 and 49.