  We examine model independent constraints on the high redshift and
prerecombination expansion history from cosmic microwave background
observations, using a combination of principal component analysis and other
techniques. This can be translated to model independent limits on early dark
energy and the number of relativistic species $N_{\rm eff}$. Models such as
scaling (Doran-Robbers), dark radiation ($\Delta N_{\rm eff}$), and barotropic
aether fall into distinct regions of eigenspace and can be easily distinguished
from each other. Incoming CMB data will map the expansion history from
$z=0$--$10^5$, achieving subpercent precision around recombination, and enable
determination of the amount of early dark energy and valuable guidance to its
nature.
