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96

Brain architecture suggests the following evolutionary pathway for monkeys and apes

This evolutionary pathway describes a sequential development of the brain associated with the addition of layers of brain tissue - predominantly on the dorsal part of the cerebral cortex. It can be seen that at least four layers of white matter have been added between the weasel type brain and the human brain.

The African monkeys, although genetically very similar to the apes, appear to have undergone reversion of their brain morphology to a slightly more primitive type. Highly evolved brains are expensive on energy requirements and the baboon way of life may not require such intelligence.  

From a cranial morphology point of view, this evolutionary tree is consistent with a gradual and progressive development of a basal mammal’s skull such as a mustelid.

The chromosome number for each stage presents a less clear pattern.

The diploid number of chromosomes for each mammal type are listed below.

Human (Homo sapiens )               2n = 46

Chimpanzee (Pan troglodytes)      2n = 48

Other apes    ........................    2n = 48

African Monkeys ....................    2n = 42

Extinct Intermediate monkey/ape 2n = ?

Extinct Tree Canid .................    2n = ?

Extinct Predatory Canid ..........    2n = ?

Wild Dog (Lycaon pictus ).........   2n = 78

Fennec Fox (Vulpes zerda) .....     2n = 64

Red Fox (Vulpes vulpes) .........    2n = 34 + B

Weasel  (Mustela erminia)........    2n = 38

 

 

 

 

 

 

 

 

 

 

 

 

 

 

                                                                                                      

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Senegal Bushbaby                   East African Brown Galago                Madagascan Mongoose Lemur     
Galago senegalensis                   Otelemur crassicaudatus                     Lemur mongoz
Ring-tailed Lemur
  Lemur catta
AFRICA                                                       MADAGASCAR