  The mass ordering of mean transverse momentum $\left<p_T\right>$ and of the
Fourier harmonic coefficient $v_2 (p_T)$ of azimuthally anisotropic particle
distributions in high energy hadron collisions is often interpreted as evidence
for the hydrodynamic flow of the matter produced. We investigate an alternative
initial state interpretation of this pattern in high multiplicity proton-proton
collisions at the LHC. The QCD Yang-Mills equations describing the dynamics of
saturated gluons are solved numerically with initial conditions obtained from
the Color Glass Condensate based IP-Glasma model. The gluons are subsequently
fragmented into various hadron species employing the well established Lund
string fragmentation algorithm of the PYTHIA event generator. We find that this
ab initio initial state approach reproduces characteristic features of bulk
spectra, in particular the particle mass dependence of $\left<p_T\right>$ and
$v_2 (p_T)$.
