If a civilization as old as the Sumerians and Egyptians was to arise in the western fringes of the Mediterranean (Portugal, Morocco essentially), how would the Ancient world be changed.
From what I can gather, such a civilization would dominate the trade of tin into the Mediterranean and thus they would likely set up colonies in the British Isles and along the French and Spanish coast to maintain trade routes. They would also likely travel down the African coast due to their maritime nature. How long would it take before they accidentally (or purposely maybe) discover the Americas?
I could imagine the Berbers eventually developing their own kingdoms through the influence of this civilization (assuming it isn't in Morocco).
In summary, how would a civilization in Portugal/Morocco (founded in 4000-3000 BC) affect the rest of the world?
Morocco is quite a good base for a western Mediterranean thalassocracy. It has a good climate, plenty warm most of the year, thick snowfall in winter. Taking a coastal city like Casablanca, for example, the average high is 26 degrees C in the height of summer, and the coldest months are between December and February where average daily highest temperatures range from 17 degrees C to 19 degrees C. That's on the coast, but further inland, it is colder in winter, especially in the mountains at places like Ifrane, where heavy snowfall is common and ski resorts exist.
The landscape has plenty of natural woodland available for timber, with pine trees and lakes common in the mountains. With access to both the Mediterranean and the Atlantic, Morocco is well placed to act as a link between the ancient civilisations of the Near East, like Egypt and Persia, as well as the Greeks, Italic peoples and western Europe. If a civilisation in Morocco can control the straights of Gibraltar, it can levy taxes on ships coming and going, potentially leading to good profits.
The people living there at this time (and still today) are mostly Berber, an ethnic group that originates in the Near East and which is also genetically closely linked with the inhabitants of Spain since ancient times. They arrived sometime after the last Ice Age (around 10,000BC) and have always inhabited the area since. A fairly typical Mediterranean population group, they would be well placed to develop agriculture and trade and go on to dominate the area.
The only slight downside with Morocco is its geographical distance from the centre of ancient civilisation, in the Fertile Crescent region (Iraq/Iran through Anatolia and Syria to Egypt). This geographical distance may not help the spread of technology in earliest times. On the other hand, agriculture arose independently in several places in antiquity, including the Indus, Mesoamerica, China, as well as the famous examples in the Nile and the Mesopotamia. So it's not out of the question it could arise here too, possibly around the river Sebou, which supports irrigation in Morocco's most fertile region. There are accounts from antiquity of the extreme abundance of wild animals and flora here, of every imaginable variety. The north African forest elephant lived here in antiquity, as did the famous Barbary lion and many other species.
Morocco is also reasonably safe from attack, as the only threat as long as they control the coasts would be to the east, from other, similar tribes located nearby along the coast. This means they would usually only have to defend from a single direction, and if they can extend their power some way to the east, they might find themselves virtually unchallenged. A promising base for an empire, indeed.