Complex sentence: A conception that fails to meet this condition cannot assign or deny spandrel status to a linguistic entity in a non-ad hoc and non-arbitrary way, thus we do not at this day know how much of language arose as a spandrel.
Split into simpler sentences: A conception that fails to meet this condition cannot assign or deny spandrel status to a linguistic entity in a non-ad hoc and non-arbitrary way. Thus we do not currently know how much of language arose as a spandrel.