In many archaeologist's opinion the term 'complex' is a poor word when used in relation to hunter gatherers. All cultures can be considered 'complex'. I think what archaeologists are trying to describe is that elaboration of some features of societies make them appear relatively more complex than others.
So what do archaeologists mean whaen they use the term 'complex hunter gatherers'?.
Complex hunter gathers are generally limited by geography.
They have relatively high population densities.
Complex hunter gatherers have a more specialized diverse diet than hunter gatherers.
They employ a system of food storage and preservation.
Complex hunter gatherers use more specialized hunting, fishing, and food processing equipment.
They have divisions in labour, not only by age and sex but by activity.
Trade with neighbouring groups.
Elaborate practices and belief systems.
Cemetaries and burial customs.
The above features represent complex hunter gather characteristics. It differs from the image of normal hunter gathers - mobile groups with few possessions. With all this in mind we can review the evidence from southern Scandinavia and discuss wether their mesolithic communities could be described as comples hunter gatherers.
The Ertebolle were the people of southern Scandinavia (Denmark and Sweden) around 5400 - 3900 B.C. Here we have one of the most understanding of any European mesolithic societies. These sites have been researched exstensively. As with many mesolithic communities the retreat of the glaciers and sea - level change is very important.
There is a wealth of evidence from these sites which gives us much information. Mesolithic industries are usually distinguished by the presence of very small flint blades. Here however, we see a very specialized high quality blade industry with high quality stone working. Also there is an enormous range of bone and antler artefacts preserved in waterlogged contexts or middens.