In this paper versions of the abstract NKC model are used to examine the conditions under which two significant evolutionary phenomena -multicellularity and eusociality -are likely to occur and why. Firstly, comparisons in evolutionary performance are made between simulations of unicellular organisms and very simple multicellular-like organisms, under varying conditions. The results show that such multicellularity without differentiation appears selectively neutral, but that differentiation to

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... oma (non-reproductives) proves beneficial as the amount of epistasis in the fitness landscape increases. This is explained by considering mutations in the generation of daughter cells and their subsequent effect on the propagule's fitness. This is interpreted as a simple example of the Baldwin effect. Secondly, the correspondences between multicellularity and eusociality are highlighted, particularly that both contain individuals who do not reproduce. The same process is then used to explain the emergence of eusocial colonies. Indeed, it is this similarity that has been used to explain why selection at the level of the individual does not disrupt integration at the higher level in both cases ([19] and [11] respectively). The emergence of multicellularity and eusociality meant that individuals surrendered their ability to reproduce in favour of a close social existence and it is this phenomenon which is investigated here using an abstract model of (coupled) fitness landscapes. Kauffman's [16] genetics-based NKC model, which allows the systematic alteration of various aspects of an evolving environment, is used to show that non-reproduction can prove beneficial when the complexity of the fitness landscape is increased. It is shown that multicellular-like individuals without differentiation appear to be selectively neutral in comparison to equivalent unicellular individuals, but that simple differentiation to non-reproduction (i.e. soma) can prove beneficial in terms of mean performance. One explanation for these results may be found by considering the Baldwin effect [2] . If the multicellular-like individuals are each considered as a selective whole, reproducing cells (gametes) can have their "true" genetic fitness altered by producing daughter cells which are slightly different to them, via the background mutation. In this way natural selection can be guided towards better genetic combinations than those which already exist in the reproducing population -the Baldwin effect. That is, less fit mothers connected to fitter daughters can stand a higher chance of selection than equivalent mothers on their own when the differences between mother and daughter are produced by unavoidable mutations. Further, it is shown that the reasoning used to explain the emergence of non-reproduction in such multicellular individuals can be used to explain the emergence of eusociallike colonies, since it is found that a simplified form of eusociality proves beneficial over sociality with reproduction as the (inter) organism complexity increases; the Baldwin-effect can be used to suggest why individuals surrendered their ability to reproduce in early eusocial colonies.