Alfred Russell Wallace's words

In June of 1858 Wallace, having been in the Malay and Indonesian archipelagoes, sent a long manuscript based on his studies there to Charles Darwin in England.

"On the Tendency of Varieties to depart indefinitely from the Original Type."

This was written at Ternate, Indonesia in

February 1858.

1. "Struggle for existence"

2. The Law of Population of Species  

3. The perfect adaptation to the conditions of existence

His Method

Wallace in 1903.

Describe "useful variation"

"varieties in a state of domesticity"

The imaginary but definitive line initially pointed out by Alfred Russell Wallace of the observed differences in species that exist and are appreciably different between Indonesia's islands of Bali and Lombok; separating Australia and New Guinea flora and fauna from South East Asian species.

For example there are Rhinoceros on Sumatra, but not on New Guinea to the east. Similarly the marsupials of Australia, such as the kangaroo, are not found in Malaya or Indonesia. Such striking divergences between these tropical flora especially led Wallace to conceive of natural selection as a means of explaining how such separate plant and animal associations could thrive in rather climatically similar, but separated island groups.