Fig. 4: Estimating Nτ in the human long-term HSC compartment.

a, Trajectory of Nτ for human long-term (LT)-HSCs in the four adult donors aged over 65 years, estimated using Bayesian phylodynamics. The black line represents the estimated mean trajectory of LT-HSC Nτ, with the shaded grey area on either side representing the 95% credibility interval. The solid blue line is the time of birth. The dashed blue lines enclose the region of time in each individual where the trajectory is at the late childhood–young adult level. The shaded region of the plots represents the period of time before sampling over which it is likely that short-term (ST)-HSC/MPPs are contributing to the observed Nτ. The trajectory line is shaded dark grey in the time period where coalescent events are occurring and the trajectory probably represents the combined Nτ of both long-term HSC and short-term HSC/MPP compartments. The trajectory line is shaded light grey where there is a complete absence of coalescent events and the estimates are therefore inaccurate. The red line shows the Bayesian (maximum posterior density) estimate of Nτ. b, Results from approximate Bayesian inference of population size over the first (non-shaded) part of life for each individual. The blue line represents the prior density of Nτ and the red line represents the posterior density. The vertical grey line denotes the peak Nτ for each donor; values are shown above each plot.