Follow up. What defines a civilisation? Simple population density? So many mammals have 'culture' could not those earlier hominid populations have township levels of density?

For the Sumerians et al. The difference is the have writing, meaning its history and not prehistory. And also 1st (?) agriculture. I believe agriculture may be the single thing which brought most change to humankind; but that being agrarian may not have been wholly better for those involved. So is there a consensus definition on a civilisation? Thanks