You've stumbled across a clever bit of English grammar called the Nominative Absolute. The second half refers back to the 'basic instincts', which is the subject of the main part of the sentence, and adds that other skills ( i.e. other than those basic instincts) are learnt later on. There is no need for the verb 'to be' to be conjugated. This is because it relies for its meaning on the main subject and verb of the sentence; instead of being conjugated, it's in the present participle form 'being'. The second half of the sentence is a kind of adverbial phrase. You can find out more about it here: http://www.english-for-students.com/nominative-absolute.html If all that looks a bit difficult, don't worry about it. It's a complex construction which you'll never need to use.