  To evaluate the feasibility of long duration, manned spaceflights, it is of
critical importance to consider the selection and survival of
multi-generational crews in a confined space. Negative effects, such as
infertility, overpopulation and inbreeding, can easily cause the crew to either
be wiped out or genetically unhealthy, if the population is not under a strict
birth control. In this paper, we present a Monte Carlo code named HERITAGE that
simulates the evolution of a kin-based crew. This computer model, the first of
its kind, accounts for a large number of free human-based parameters to be
investigated proactively in order to ensure a viable mission. We show the
reliability of HERITAGE by examining three types of population based on
previously published computations. The first is a generic model where no
birth/population control has been set up, quickly leading to fatal
overcrowding. The second is the model presented by Moore (2003), that succeeds
to bring settlers to another Earth under a 200 year-long flight, but the final
crew is largely diminished (about a third of the initial crew) and about 20% of
them show inbreeding of various levels. The third scenario is the model by
Smith (2014) that is more successful in maintaining genetic diversity for the
same journey duration. We find that both the Moore and Smith scenario would
greatly benefit from coupling a kin-based crew together with a cryogenic bank
of sperm/eggs/embryos to ensure a genetically healthy first generation of
settlers. We also demonstrate that if initial social engineering constraints
are indeed needed to maintain an healthy crew alive for centuries-long
journeys, it is necessary to reevaluate those principles after each generation
to compensate for unbalanced births and deaths, weighted by the inbreeding
coefficient and a need for maximizing genetic diversity.
