Comment by next_xibalba

The costs and benefits faced by ancient humans were very, very different. Maybe a different way to frame the question would be "At what probability of additional death, injury, or suffering (to you or other tribe members) would you abandon your injured/disabled?" Humans of that era did not have anything even remotely approaching modern medicine and most lived at subsistence levels with starvation always at their doorstep. A huge portion of ancient peoples energy and time was dedicating to obtaining calories. That means caring for the injured/disabled imposes a huge cost and risk. We can just as easily find examples of ancient peoples murdering or abandoning their injured, disabled, and weak. I don't think it would be right or fair to judge them through a modern lens. Of course they cared for their loved ones and mourned their deaths. But they were faced with much harsher circumstances to which their cultures and beliefs were suited.