Sorry, you misunderstood me.
I'm not saying that there is contrary evidence.
I'm just saying that there is no evidence at all that could support such an interpretation.
'Prehistory' is an extremely long period depending on the definition, of about 2 million years.
Even if we cut this to the times when we can expect social systems that might support 'slavery' whatever definition we want to use, let's say from Chalkolithic onward, there are still about 6 or 7 thousand years left.
Now, in this period, there are 'massgraves' in many regions in the world. With most of them there is no knowledge at all during how long a period people were buried there. So you don't know if it was 20 people who were buried there at once, or 1 every 10 years for a period of 200 years. And in most periods we are not able to detect chronological differences with this exactness.
This said some of the more recent excavations clearly could show that a considerable number of people was violently killed at a given time (Herxheim) and buried without detectable ritual. This would be a mass grave. Recently and very well excavated and very well published. The period 'Linearbandkeramik' seems a bit too early for slavery in my opinion, but we have a mass grave.
Still, it is somewhat problematic to differenciate between males and females, depending on the age of the deceased and how well the skeletons are preserved.
Now we have a mass grave, but we have zero knowledge about the social status of the people in there.
Nobody in all archaeology can give you a method to tell you that a buried person was a 'slave' (and nobody in all cultural sciences could give you a comprehensive definition what a 'slave' is, because the forms of slavery were extremely differnt over the regions and times)
Now, up to the present state of knowledge in archaeology and archaeological sciences there is no, repeat NO, bulletproof method to show that some of these people were local and others were not:
The 'traditional' archaeological method of looking at burial gifts that are not local, must not mean that the objects mean that their owners were not local.
The 'traditional' physical anthropological method of measuring the bones is proven wrong many, many times. I remember an excavation were the physical anthropologist 'clearly' identified two different groups, inevitably the 'gracile' locals and the robust foreigner (naturally from 'the North'). Then there came a palaeo-pathologist and found out that all these robust northerners were just locals, who died from malaria that has the effect of changing the structure of bones.
And today we have wonderful natural sciences, that spend millions of dollars, mostly to find answers were nobody ever had a question. Genetic analysis is perfectly useless to identify the geographical origin of people within close to middle range.
The most recent hype is the strontium analyses of teeth. It's a new method that might proove to be useful in coming years, up to now it is still ridden with uncertainties and technological/methodological problems. Remember the case of the Egtved girl? Two years ago they secured a lot of funding, because they could show that this young woman (of high status most probably) that was buried in Denmark, originally was born in Southwest Germany and before dying even travelled to and fro several times. There were even videos made ... after some months the videos disappeared and you did not here anything any more. Why? Well, the results were, sorry again bullshit, because the samples they analysed were contaminated ...
So, to sum up: according to *present state of research* there is no way to tell whether the remains of a bureid person were a 'slave'or not and there is no way to tell, whether a buried person was of local origin or not.
And that's everything you have to know, to know that evidence prooving " disturbing patterns of female abduction" is simply not existing, because our methods do not allow to identify such patterns.
