Consider a dynamical many-body system with a random initial state subsequently evolving through stochastic dynamics. What is the relative importance of the initial state (nature) vs. the realization of the stochastic dynamics (nurture) in predicting the final state? We examined this question for the two-dimensional Ising ferromagnet following an initial deep quench from $T=infty$ to $T=0$. We performed Monte Carlo studies on the overlap between identical twins raised in independent dynamical environments, up to size $L=500$. Our results suggest an overlap decaying with time as $t^{-theta_h}$ with $theta_h = 0.22 pm 0.02$; the same exponent holds for a quench to low but nonzero temperature. This heritability exponent may equal the persistence exponent for the 2D Ising ferromagnet, but the two differ more generally.
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