Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the

correct answer to each of the questions from 40 to 47.

Hobbit-like Species of Humans

On the tiny island of Flores, east of Bali and midway between Asia and Australia, the scientists have discovered the remains of a small, hobbit-like species of humans. These people grew no larger than the modern three-year-old child. They lived about 18,000 years ago and are completely different species of human.

This discovery has taught scientists a lot about the human species. This remarkable discovery shows that the human species is more varied and flexible in its ability to adapt than previously thought. These hobbit-like people join a short list of other type of humans that lived with modern humans.

The researchers believe that these hobbits evolved from a normal size, human population that reached Flores around 840,000 years ago. One likely explanation is that, over thousands of years, the species became smaller because the environmental conditions favored a smaller body size. The dwarfing of mammals on islands occurs frequently. Islands limit food supply and predators and species compete for the same environmental space. Survival would depend on minimizing energy requirements.

Which is the main topic of this passage?