From that which has been established in
    the Sharee'ah (prescribed law) is that mankind was - in the beginning - a single
    nation upn true Tawheed, then Shirk (directing any part or form of worship,
    or anything else that is solely the right of Allah, to other than Allah) gradually
    overcame them. The basis for this is the saying of Allah - the Most Blessed, the Most
    high:
"Mankind was one Ummah, then Allah sent prophets bringing good news and
    warnings."
    (Surah Baqarah 2:213)
Ibn 'Abbas - 
 radiallaahu 'anhu - said:
"Between Nooh (Noah) and Adam were ten generations, all of them were upon Sharee'ah
    (law) of the truth, then they differed. So Allah sent prophets as bringers of good news
    and as warners"(1)
Ibn 'Urwah al-Hanbalee (d.837 H) said:
"This saying refutes those historians from the People of the Book who claim that
    Qaabil (Cain) and his sons were fire-worshippers"(2)
I say: In it is also a refutation of some of the philosophers and athists who claim that
    the (natural) basis of man is Shirk, and that Tawheed evolved in man! The
    preceeding aayah (verse) falsifies this claim, as do the two following authentic hadith:
Firstly:His (the 
prophet  (sallallaahu `alaihi wasallam) ) saying that he related from his Lord (Allah) :
    "I created all my servants upon the true Religion (upon Tawheed, fre from Shirk).
    Then the devils came to them and led them astray from their true Religion. They made
    unlawful to people that which I had made lawful for them, and they commanded them to
    associate in worship with Me, that which I had sent down no authority."(3)
Secondly:His (the prophet  (sallallaahu `alaihi wasallam) ) saying: " Every child is born upon the
    Fitrah(4) but his parents make him a jew
    or a christian or a magian. It is like the way an animal gives birth to a natural
    offspring. have you noticed any born mutilated, before you mutilate them."
Abu Hurayrah said: Recite if you wish: "Allah's
    fitrah with which He created mankind. There is to be no change to the creation (Religion)
    of Allah."(Surah ar-Rum 30:30)(5)
After this clear explanation, it is of the upmost importance for the Muslim to know how Shirk
    spread amongst the believers, after they were muwahhideen (people upon Tawheed)
Concerning the saying of Allah - the 
most perfect - about the people of Nooh:
"And they have said : You shall not forsake your gods, nor shall you forsake
    Wadd, nor Suwaa', nor Yaghooth, nor Ya'ooq, nor Nasr."
(Surah Nooh 71:23)
It has been related by a group from the Salaf (Pious Predecessors), in many narrations,
    that these five deities were righteous worshippers. However, when they died, Shaytaan
    (Satan) whispered into their people to retreat and sit at their graves. Then Shaytaan
    whispered to those who came after them that they should take them as idols, beautifying to
    them the idea that you will be reminded of them and thereby follow them in righteous
    conduct. Then Shaytaan suggested to the third generation that they should worship these
    idols besides Allah - the most high - and he whispered to them that this is what their
    forefathers used to do!!!
So Allah sent to them Nooh (as),
    commanding them to worship Allah alone. However none responded to hiscall except a few.
    Allah - the mighty and majestic - related this whole incident in surah Nooh
Ibn 'Abbas relates:
"Indeed these five names of righteous men from the people of Nooh. When they died
    Shataan whispered to their people to make statues of them and to place these statues in
    their places of gathering as a reminder of them, so they did this.
However, none from amongst them
    worshipped these statues, until when they died and the purpose of the statues was
    forgotten. Then (the next generation) began to worship them."(6)
The likes of this has also been related by Ibn Jareer at-Tabaree and others, from a number
    of the salaf (Pious Predecessors) - radiallaahu 'anhum.
In 
 ad-Durral-Manthoor (6/269):
'Abdullaah ibn Humaid relates from Abu Muttahar, who said: Yazeed ibn al-Muhallab was
    mentioned to Abu Ja'far al-Baaqir (d.11H), so he said: He was killed at the place where
    another besides Allah was first worshipped. Then he mentioned Wadd and said: