The Earth's land moves. The bit you are sitting on right now is sliding very slowly, about as fast as your fingernails grow. Over millions of years, that adds up. The whole map of the world changes shape.
Long ago, all of today's southern continents were stuck together in one giant supercontinent that scientists call Gondwana. South America, Africa, India, Australia, Antarctica and Madagascar were all touching. Slowly, they pulled apart. Madagascar was one of the first pieces to break off.
When the island drifted away, the animals on it could not get back. They could not swim across the ocean to Africa, and very few animals could float across from Africa to them. So whatever was on Madagascar at the time was stuck there - and over millions of years, those animals evolved in their own direction.
That is why Madagascar's wildlife is so weird and wonderful. There are no lions, no zebras, no elephants. Instead there are lemurs, fossas, aye-ayes and tomato frogs - animals that exist nowhere else. The island is like a giant nature experiment that has been running for 88 million years.