Vol 3 Mammals of Africa ... Introduction ... Separation of the mammal groups
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Introduction

Separation of the mammal groups

Mammal groups in the different continents are often similar if the continents were joined together after the groups evolved.
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The separation of Africa from the other continents over time is reflected in the similarities and differences between mammal groups in the different continents. As North America and Asia separated from Africa early on, species that are found in these regions should not be found in Africa, if they evolved after the separation. This is true - there are no bears, wolves or racoons in Africa.

But why are there no marsupials in Africa? If Africa was joined to Australia after it separated from North America, you might expect African mammals to be more similar to Australian mammals. The answer lies in Antarctica! If you look at the separation of the land masses in the late Cretaceous period, you'll see that Africa is separated from Australia, but South America is still joined to Australia via Antarctica. This may explain why marsupials are found in North and South America and in Australia, but not in Africa, Asia or Europe.

Another interesting evolutionary story is that of the camel. We associate camels with North Africa and Asia, but in fact the ancestors of the camel first evolved in North America around 40-45 millon years ago. North America was separated from South America at this time, and by the time it rejoined South America, Africa had long ago disappeared across the Atlantic Ocean, so how did the camel get to Africa?

Migrations of members of the camel family (the llamas and alpacas) took place into South America, and more recently in the far north across the Bering Strait into Asia. After this time, the North American camels died out, and all that remained were the Asiatic, or Bactrian two-humped camels and the South American llamas. As recently as 6,000 years ago there may have been no camels in Africa! It is thought that African (one-humped) camels may be a domesticated form of Bactrian camel, because the two readily interbreed, with the offspring having two humps. In any case, camels could not have arrived in Africa until Asia and Africa joined, around 5 million years ago.

It is interesting to note that the camel, one of the last of the mammal species to arrive in Africa, is a desert animal. Because the only way for an animal to migrate into Africa in the present day is by air, sea or by the Sinai desert, it is unlikely that a non-desert animal could establish itself in Africa, unless it were brought in by man.