Here's an extract from an article I wrote:
The Nuchal Ligament (Fig. 1 )

With his mention of the ligament of the neck Bowen, interestingly a professor of sports physiology, touched upon what has lately become a substantial theory in human evolution. Up until recently this ligament had been relegated to a vestige of some earlier evolution:
In man it is merely the rudiment of an important elastic ligament, which, in some of the lower animals serves to sustain the weight of the head. (Gray, Henry (1918), Anatomy of the Human Body, Twentieth Edition, Lea and Febiger, New York, page 291)
Writing in Nature, Bramble and Lieberman on their theory that we evolved to endurance run:
Another possible structural modification relevant to running is the nuchal ligament, a convergent feature in Homo (first evident in KNM-ER 1813) and other mammals that are either cursorial (for example, dogs, horses, hares) or have massive heads (elephants). Interestingly, a nuchal ligament is absent in chimpanzees4,31 and apparently in australopithecines (as evinced by the absence of a median nuchal line). (Bramble DM and Lieberman, DE (2004) Endurance running and the Evolution of Homo. Nature. 432: 345-352. )
In a later publication they state quite confidently:
That said, the available evidence suggests that Australopithecus lacked many, if not most, of the derived features of Homo that improve [endurance running] performance. Some of these derived features, such as relatively large anterior and posterior semicircular canals, and the nuchal ligament, are specific to running. ( Daniel E. Lieberman, Dennis M. Bramble, David A. Raichlen and John J. Shea (2007), Brains, brawn, and the evolution of human endurance running capabilities in The First Humans -Origin and Early Evolution of the Genus Homo, Grine, Frederick E.; Fleagle, John G.; Leakey, Richard E. (Eds.), page 88)
Why is the nuchal ligament important in running? What has it to do with performance in the arts? Let me put two and two together for you. As Irene Samuel observed (and any performer could tell you) tensions in the neck are preponderantly reported as symptoms of stage fright. The neck extensor’s role, as I’m sure Bowen was aware, is to tighten the nuchal ligament as it does in other cursorial animals; this allows it to hold the head steady during running. Pigs haven’t got this ligament – ever seen a pig run? Its head bobs all over the place, which makes running for any significant distance impossible. Take into account the real nature of stage fright – adrenaline caused by the fight or flight mechanism, and you have your answer. A tense neck is the body preparing to run!
so i just ignore my surroundings? 
As far as ignoring your surroundings - you can't it's the non-conscious brain paying attention to what's going on around you,
you can't control it. Eventually though it gets more used to it. My advice is to have the right posture and
know where and why tension will creep in so it's not such a concern.
Anyway, look on the bright side - without it you'd be hugging every wild bear you saw
and funfairs just wouldn't be any fun!