During the 17-plus-months of their virtual voyage, the crew took part in various studies to assess the effect their isolation was having on their psychological and physiological well being.
"We have got to be clear that the requirement for the carriers is part of a joint requirement for defence as a whole, and the effect they provide is a joint effect, not a maritime effect in isolation, " he said.
It is based on a piece of evolutionary theory called the founder effect, which shows how the isolation of small populations from larger ones can accelerate evolutionary change, because a small population's average characteristics are likely to differ from those of the larger group from which it is drawn.