Ontological commitment and essence
There are at least three related reasons:
Being born too soon, after only nine months is vital in our acquisition by language. Giraffes and elephants are born only after a much longer period of gestation. And they are able to stand up and walk at birth. It is the human’s prolonged helplessness, extended by his premature birth that work to increase the vacuum or space in which the variable meanings of language and culture can take root. The roots of the symbolic, which includes language need time to establish their space.
In other organisms things are very different. They either have a relatively comprehensive set of instincts, that is a repertoire of vital behaviours and signs of fixed meanings rather than the absent set of instincts found in humans, or they have far less helplessness for a shorter period. So the so called ‘social insects’, bees and ants communicate with signs of fixed meanings: they never use their signs as variable meanings to make a joke or as a metaphor. That is they are not afflicted with the plague of indeterminacy that the Bible marks with the Tower of Babel. Instincts are genetically determined behaviours: being born after some nine months is genetically determined and in most cases leads to the creation of the subject of language.
The variability of meaning or its indeterminacy is the essence of trauma – the not knowing.
Lacan argued that language is a universal trauma, or wound, taking a unique form for every person. People are radically different from all other organisms because we speak, and one word, phrase or sentence can mean a confusingly indeterminate number of different things. Animals and plants communicate but with a lot less trouble than people: plants and animals use signs with relatively fixed meanings, not confusing signifiers whose meanings are highly variable.