Megan H. MacKenzie undermines the foundation of the case against women joining infantry units:
The cohesion hypothesis remains as the most significant set of arguments against GI Janes. There are two main premises to the cohesion hypothesis: 1. cohesion is causally linked to group (in this case military unit) performance; 2. women negatively impact cohesion and thereby negatively impact troop effectiveness. The trouble with these two premises is that they both have been largely discounted by researchers.
In her 1998 article on the Don't Ask Don't Tell policy in International Security, Elizabeth Kier concludes that "the results from more than five decades of research in group dynamics, organizational behaviour, small-group research, sports psychology, social psychology, military history, and military sociology challenge the proposition that primary group unit cohesion enhances military performance." Some research even indicates that high levels of cohesion can be detrimental to military performance as it results in conformity, groupthink, and a lack of adaptability.
The parallels with DADT are obvious. MacKenzie previously discussed the issue here. Previous Dish debate over women in combat and the Lioness Program (explained in the above video) here, here, here and here.