To answer that i will first quote an article from theoretical structural archaeology blog:
Longhouse 6 from Olszanica in Poland  has a doorway 2.20m wide, and it is dated to 5000 BC. So what is that all about?
In 1976, an excavation at Bronocice in SW Poland uncovered parts of a pot with incised decoration depicting two carts with yokes. [left] 
The site was occupied during the Funnel Beaker or TBR culture phase, one of a complex group of cultures that succeeded the LBK in northern Europe, in the Fifth and Fourth Millennia BC.
Bones from the pit in which the pot was found gave radiocarbon dates of around 3635--3370 BC, which, as the excavators pointed out, is earlier than dates for pictograms of wheels from the Samarian Uruk Period.
There a two other main lines of evidence in this period, both from graves associated with the Baden culture that is found in central Europe in the period 3600--2800BC.
In cemeteries like Budakalász on the Danube in Hungary, pottery models of carts have been found. The example, from Grave 177, was painted and is incised with zigzag decoration. [Left]  Some models with handles, which may be drinking cups, have been found on the earliest Baden cultures sites like Boglarelle on Lake Balaton.
What was also found at Budakalász was a grave containing two humans with the bodies of a pair of cattle laid out at right angles to them. Double cattle burials occur in other Baden cemeteries dated to the middle of the Fourth Millennium.
It would clearly be unwise to argue for a cart shed in a late LBK building -- it simply does not fit with the other evidence. Irritatingly, it is not actually 'impossible', as the building is roughly contemporary with the earliest wheel-made pottery.
There are two important points about wheels and animal traction. Firstly, they are two separate technologies; and secondly, they are difficult ideas to keep secret [compared with metallurgy, for example.] We could also consider sledges, or some other form transport dragged by an animal. I have always tacitly assumed that the several hundred pieces of timber required for building a longhouse could be dragged by an animal, presumably an ox.
So first wheeled vehicles appear in the fourth millennium central Europe. But houses with wide doors and space wide and big enough for a car appear much earlier, a whole millennium earlier. The only explanation is that first cars or carts did not have wheels but sleighs.
Now here is a passage from a from folk tale "St Patric and Crom Dubh":
Before St. Patrick came to Ireland there lived a chieftain in the Lower Country1 in Co. Mayo, and his name was Crom Dubh...
When he used to go out about the country he used to send his two sons and his two mastiffs before him, and they announcing to the people according as they proceeded, that Crom Dubh was coming to collect his standing rent, and bidding them to have it ready for him. Crom Dubh used to come after them, and his trickster (?) along with him, and he drawing after him a sort of yoke like a wheelless sliding car, and according as he used to get his standing-rent it used to be thrown into the car, and every one had to pay according to his ability. Anyone who would refuse, he used to be brought next day before Crom Dubh, as he sat beside the fire, and Crom used to pass judgement upon him, and after the judgement the man used to be thrown into the fire....
Crom Dubh had "a sort of yoke like a wheelless sliding car". This kind of description of Crom Dubh vehicle shows that the narrator clearly did not have an idea what that car could have been. Did whoever told the story new what the vehicle was and was that forgotten later? Or was even the first narrator constructing the story based on legends whose meaning was long lost and forgotten?
What kind of vehicle did Crom Dubh have? Well i can actually show you one:
This picture was taken about 10 years ago in south of Serbia in the mountains near the place where i was born. This is me (hi everyone ) sitting on an example of the most common means of transport in the area still to this day: "a sort of yoke like a wheelless sliding car". In this area mountain villages consist of houses strewn across the side of the mountain, so building roads is impossible.
Also even if there were roads connecting houses, local people would still have to get to their fields and forests. They would also have to be able to do that during the winter too, when the whole area is covered with over a meter of snow. The answer to this problem is sledge pulled by oxen. Here is another example from Serbia this time actually being used:
Sledge as means of transportation is perfectly suited for European climate and landscape. In early Ireland, with its hills, mountains, bogs, beaches and no roads, it would have been much easier to transport things using sledge pulled by oxen than using wheeled carts. To use wheeled carts you need hard dry ground, like desert or worm steppe or roads. Unfortunately no desert or worm steppe can be found in Ireland, and no roads were built in Ireland before mid 3rd millennium BC and even then there were only handful of them and they were probably ceremonial:
|There is almost no evidence that large roads were constructed in Ireland during the Stone Age. However, a very large oval henge enclosure, thought to date from c. 2500 BC (the Neolithic period) may possibly have had an ancient roadway associated with it.|
So stone age people in Ireland used oxen pulled sledges for transport. So did Crom Dubh. Did sledges disappear from Ireland with the introduction of wheeled vehicles? I doubt it considering they are still used in Serbia today. But did Crom Dubh arrive on one of these sledges from Central Europe with first wheat farmers way back in 5th or 4th millennium BC? Probably, considering that he not only had sledge pulled by oxen, but he also brought on them the first wheat and the knowledge of wheat cultivation:
|Using the magic artifacts the sons of Tuireann have gathered, Lugh leads the Tuatha Dé Danann in the Second Battle of Mag Tuireadh against the Fomorians. Nuada is killed in the battle by Balor. Lugh faces Balor, who opens his terrible, poisonous eye that kills all it looks upon, but Lugh shoots a sling-stone that drives his eye out the back of his head, wreaking havoc on the Fomorian army behind. After the victory Lugh finds Bres, the half-Fomorian former king of the Tuatha Dé Danann, alone and unprotected on the battlefield, and Bres begs for his life. If he is spared, he promises, he will ensure that the cows of Ireland always give milk. The Tuatha Dé Danann refuse the offer. He then promises four harvests a year, but the Tuatha Dé Danann say one harvest a year suits them. But Lugh spares his life on the condition that he teach the Tuatha Dé Danann how and when to plough, sow and reap.|
Fomorians, Pomorians, Central Europeans from Pomerania, Pomorje, brought with them both the knowledge of "how and when to plough, sow and reap" and also Dabog, Hromi Daba, Crom Dubh, their main god whose fertility face was known as Crom Cruach, the god of bread.