usage: ms nsam howmany
  Options:
         -t theta   (this option and/or the next must be used. Theta = 4*N0*u )
         -s segsites   ( fixed number of segregating sites)
         -T          (Output gene tree.)
         -F minfreq     Output only sites with freq of minor allele >= minfreq.
         -r rho nsites     (rho here is 4Nc)
                 -c f track_len   (f = ratio of conversion rate to rec rate. tracklen is mean length.)
                         if rho = 0.,  f = 4*N0*g, with g the gene conversion rate.
         -G alpha  ( N(t) = N0*exp(-alpha*t) .  alpha = -log(Np/Nr)/t
         -I npop n1 n2 ... [mig_rate] (all elements of mig matrix set to mig_rate/(npop-1)
                 -m i j m_ij    (i,j-th element of mig matrix set to m_ij.)
                 -ma m_11 m_12 m_13 m_21 m_22 m_23 ...(Assign values to elements of migration matrix.)
                 -n i size_i   (popi has size set to size_i*N0
                 -g i alpha_i  (If used must appear after -M option.)
           The following options modify parameters at the time 't' specified as the first argument:
         -eG t alpha  (Modify growth rate of all pop's.)
         -eg t i alpha_i  (Modify growth rate of pop i.)
         -eM t mig_rate   (Modify the mig matrix so all elements are mig_rate/(npop-1)
         -em t i j m_ij    (i,j-th element of mig matrix set to m_ij at time t )
         -ema t npop  m_11 m_12 m_13 m_21 m_22 m_23 ...(Assign values to elements of migration matrix.)
         -eN t size  (Modify pop sizes. New sizes = size*N0 )
         -en t i size_i  (Modify pop size of pop i.  New size of popi = size_i*N0 .)
         -es t i proportion  (Split: pop i -> pop-i + pop-npop, npop increases by 1.
                 proportion is probability that each lineage stays in pop-i. (p, 1-p are admixt. proport.
                 Size of pop npop is set to N0 and alpha = 0.0 , size and alpha of pop i are unchanged.
         -ej t i j   ( Join lineages in pop i and pop j into pop j
                  size, alpha and M are unchanged.
          -f filename     ( Read command line arguments from file filename.)
 See msdoc.pdf for explanation of these parameters.

