Here are some interesting recent papers.
Leakey et al. (2012) report two contemporary species of Homo during the Pleistocene of eastern Africa.
http://www.nature.com/nature/journal/v488/n7410/full/nature11322.html?WT.ec_id=NATURE-20120809
Elderfield et al. (2012) report on a potential cause for the mid Pleistocene transition from 41 thousand to 100 thousand year cycles.
http://www.sciencemag.org/content/337/6095/704.short
