What is the Wallace Line?
The Wallace Line is an imaginary boundary between the islands of Asia and Australia, proposed by Alfred Russel Wallace in the 19th century.
It marks a dramatic shift in the types of animals found on either side of the line, with Asia on one side and Australia/New Guinea on the other.
Wallace used this line to explain the differences in biodiversity between these two regions.
What did Wallace find on Sulawesi?
Wallace was surprised by the diversity of species on Sulawesi, an island between Borneo and Australia, where distinct species from both Asia and Australia were found.
Sulawesi had animals like tarsiers (Asian) and marsupials like the dwarf cuscus (Australian), creating confusion about whether the island belonged to Asia or Australia.
Wallace eventually acknowledged that the species distribution was influenced by past geological events.
What does the ancient past say?
The Wallace Line is part of the Malay archipelago, a region with over 25,000 islands.
Wallace suggested that the islands had once been connected to Asia and had broken apart over time, leading to the evolution of distinct species.
Millions of years ago, Australia separated from Antarctica, leading to the formation of new landmasses and the current distribution of species.
As Australia moved north, environmental changes influenced species’ adaptations and migrations.
Does the Line Matter?
New studies have helped refine Wallace’s theory by showing how ancient climate, geography, and species’ migrations shaped the biodiversity we see today.
The Wallace Line is seen as a "mirage" because its existence is better explained by deeper ecological and evolutionary factors rather than a simple boundary.
The concept remains useful, but the focus is now on how species will adapt to modern challenges like habitat destruction and climate change, not just the historical line.
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