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Evolution of human intelligence

From: 
F. S.
Question: 

According to the evolution theory, species will gradually become more intelligent, because smarter species will have a higher chance of survival. This is true for all species, intelligence is a trait beneficial to survival for all species. Yet it seems that in comparison intelligence in humans is far more advanced than in any other specie. Human accomplishments, such as flying to the moon or communicating directly with others on the other side of the world, seem far more impressive and remarkable than accomplishments of any other specie. My question is: Even though intelligence is beneficial for all species, how come human intelligence has evolved so much, while intelligence of other species (seemingly) has not?

Response: 

Great question!  But your question comes from a misunderstanding about how Evolution works.  There is nothing in the theory which states that species gradually become more intelligent.  I know it may seem odd,
but intelligence is not what is most important to every species. Evolution serves one purpose: to keep species from going extinct.  A species will adapt to pressures in their environment until their survival is no longer threatened, and then they will stop evolving.

For example, lets say there is a group of mostly hairless animals on an island.  Naturally, some are born with a little hair, but most are completely bald.  Well, if the Earth begins to cool, only those animals with a little hair would survive, or would survive better, and so they would live on to reproduce, and each surviving generation would gain more and more hair, to adapt to the changing environment, to prevent extinction.

No where in there is intelligence required for survival.  It certainly helps, but species will only evolve so far as to meet a threat or pressure, and no further.  For example, A spider is perfectly evolved to hunt flies, but it is not terribly intelligent.

So why are humans intelligent at all?

The leading theories on that basically say that a species' intelligence is directly tied to two things:  the size of the group it lives in, and the need to be able to non-verbally understand the desires and wishes from members of that group.  For example, dolphins which live in groups of 20 or more, and which need to understand each others wishes just from body language (in order to coordinate hunts, for example), would require intelligence.  By itself, a single dolphin would not be able to survive predators or catch enough food to live for long.  It needs the cooperation of other dolphins in order to survive, and therefor it's circumstances select for intelligence.  And it needs more and more intelligence based on how large it's group typically is.

This theory holds true for us primates.  Apes which live in relatively small groups are not as intelligent as those species which live in very large groups.  And of course Humans live in the largest groups of all.

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